Training endurance for football: is it enough just to play football?

 

Introduction

Fuballmannschaft

In my previous article, I pointed out that there are two types of fatigue during the game. One of them is temporal, from that player can recover throughout less intense periods of the match. Another is overall (general) fatigue which accumulates towards the end of the match and cannot be overcome during the game. Temporally fatigue manifests an inability to maintain maximal efforts inside short, intense periods, whereas general fatigue leads to the overall decrease in a game ’s intensity, the quantity of moderate and low-intensity runs, as well as decline in player’s involvement in duels and tackles. The article suggested that anaerobic metabolites are the main reason for temporal fatigue, while the shortage of glycogen in some muscle fibers and Exercise-Induced Muscle Damage (EIMD) may be the reasons for overall exhaustion. At the same time, it is impossible to separate these two types of fatigue in real life due to a complex interaction between them. The previous workload influences temporary fatigue; thus it may be different in the beginning and at the end of the game. In turn, general fatigue accumulates quicker when more intense bouts are performing, and more temporally fatigues occur during the game. Following from these conclusions is a need to answer the questions:

1. How to increase fuel reserves and achieve more effective fuel utilisation?

2. How to achieve better metabolite’s clearance and tolerance?

3. How to deal with the EIMD?

Though at first glance, these task is not overcomplicated physical conditioning training in football presents a significant challenge.

First of all, it is a considerable spectrum of actions which performs footballer. He/she sprints on distances ranging from a several meters to “box to box” runs, makes multiple changes of direction, jumps, tackles and dribbles. Overall distance covered by player might be up to 14 km. So who is a footballer? Endurance runner? Sprinter? Don’t forget that he/she should be strong in duels and agile. A football coach cannot just prepare a player for a particular type of activity like it is possible in track and field sports. To make the problem even more complicated, some qualities, needed for a player, like for example, strength and endurance, may conflict with each other when they are trained together.

Secondly, football demands that significant training time has to be devoted to technical and tactical aspects of the game. This training put the substantial physical load on a player that should be taken into account when considering conditioning programme. Furthermore, competitive football season lasts 10 months, with games sometimes played twice a week; thus players need significant time for recovery.

All these make time, devoted purely to physical conditioning, very limited and even raise a question about the expediency of generic running exercise for footballers. Is it possible to train endurance while playing football and inside technical-tactical drills? If it is not, what kind of exercises are better for developing fatigue-resistance in football? Can we train perfect endurance without substantial loss of other physical qualities needed for a player, such as speed, strength, and power? So, there are many things have to be considered, and recommendations are sometimes controversial. Let’s try to shed light on a problem.

Setting the goals

To answer the questions, which were outlined in the previous paragraph, coach, in my opinion, has to design training programme which aims:

1. Improving aerobic abilities

Aerobic conditioning plays an important role in endurance training because it can help in three ways. Firstly, the oxygenation is the more efficient way of extracting energy from glycogen/glucose, and it is the only way for fat metabolism. Secondly, well developed aerobic capacity helps in faster recovering from the high-intensity work during the less intense periods of the game. A player needs oxygen for metabolite utilisation and energy reserves restoration. Moreover, a person with the better aerobic conditions can sustain higher intensity work without a substantial usage of anaerobic pathways, thus creates fewer metabolites.

Aerobic fitness depends on two components: central and peripheral. The central component is responsible for oxygen delivery hence it includes lungs, heart and blood capacities. Peripheral component reflects muscle ability to utilise delivered oxygen which depends on mitochondria properties, oxidative enzymes and capillary density in muscles.

2. Improving anaerobic abilities

Ability efficiently to use anaerobic energy system and to deal with its metabolites is crucial for short term fatigue tolerance during the game. For convenience, anaerobic capacities can be divided on two components: energetic and metabolic. Energetic component means ability to produce energy anaerobically. It depends on fuel availability ( creatine phosphate and glycogen) and on rate of their utilisation (creatine kinase reaction and anaerobic glycolysis) . Metabolic component, is of particular interest for fatigue-resistance training. It is ability to maintain homoeostasis and sustain intensity level despite significant disturbances in internal environment which arises from the work in hypoxia.

3. Increasing Strength.

The two primary applications of strength for endurance are: running economy and EIMD. I will talk about EIMD in a particular chapter. In its turn, improving running economy helps an athlete to spend less energy on the same amount of work. That makes fuel utilisation more efficient and creates fewer metabolites. Strength can improve running economy through an enhanced stretch-shortening cycle because more “solid” body structure prevents wasting energy.

4.  Nutrition.

Nutrition is a significant and complicated topic, and it is beyond the scope of the presented article to discuss all aspects of nutrition for footballers.I would like to look briefly at the possibility and practicability to increase muscles energy status through nutritional interventions.

Since fat is a practically infinite source of energy in our body, the main concern about increasing fuel reserves is creatine phosphate( PCr) and glycogen. Most authors agree that training cannot increase PCr. Some scientists argue that training can increase muscle’s glycogen content up to 20% whereas other doubt that.  Both PCr and glycogen reserves can be increased with appropriate nutritional interventions. I am not sure that it worth to do for PCr. The connection between elevated initial muscle’s PCr content and fatigue during intense exercise remains doubtful. Besides, increasing muscle’s PCr content often accompanies with the weight gain that is highly undesirable for a footballer. Concerning glycogen, most findings consider it a significant factor in fatigue development. Nutritional strategy helps to have “full tanks” before the game and to restore glycogen reserves faster after it.

Physiological and psychological measures for endurance

For prescribing training and monitoring progress coaches and sport scientists may use some measures during tests or directly in training. Most common are:

1. Oxygen uptake / maximal oxygen uptake

2. Blood/muscles lactate concentration

3. Heart rate

4. Rate of perceived exertion.

Maximal oxygen consumption (VO2 max) is one of the most important indicators of aerobic abilities. It indicates the ability to deliver oxygen to the working muscles thus reflects lungs, heart and blood capacities. Also, it tells us about muscles abilities to utilise oxygen which depends on mitochondria amount and size, capillary density and aerobic enzymes. Oxygen uptake measures during training provide information about exercise intensity. However, it is difficult to obtain online oxygen uptake values during real football training or match because it demands relatively complicated equipment. That can be done in a laboratory during incremental test. Additional consideration about VO2 max is that is not directly telling us about endurance capacities. Subjects with the same VO2 max may perform differently. If we make an analogy with the cars, VO2 max tells us how many litters of petrol car can consume. It does not mean, however, that it runs faster than a car which consumes less. The same is for athletes. Though VO2 max is very informative variable for physical conditioning evaluation, other variables such as: running economy, buffering capacities, clearance abilities, etc. play an important role in performance.

Lactic acid is the product of anaerobic glycolysis and its concentration in the blood is an indirect measure of the intensity of anaerobic processes and whether or not metabolite’s clearance is matching its production. Blood lactate is relatively easier to measure than VO2. The problem with this indicator is that it reflects only one of the anaerobic energy production pathways during exercise – anaerobic glycolysis. It doesn’t tell us directly how, for example, PCr utilisation is going, and assumptions about metabolites accumulation based on blood lactate values are not precise. Besides, in intermittent activity, such as football, blood lactate is not strongly correlated with lactate concentration in muscles, which is our primary interest, because some significant amount can be utilised directly in muscle’s cells and does not enter into the blood (Krustrup et al., 2006).

Heart rate (HR)

HR is the most common measure of exercise intensity. It is very easy to obtain even during real matches (though it is not allowed to wear HR monitors during official games). It is questionable, however, how precise it can reflect intensity during intermittent activity, such as football and other sports games. HR has some inertia, and very often it cannot come up with the rapid changes in exercise intensity. Another consideration is that stroke volume may be different during intermittent and continuous activities (see the next chapter) thus HR may not give us exact information about how much blood heart is actually pumping.

Rate of perceived exertion (RPE)

Borg’s scale 1-10, or 6-20 http://www.brianmac.co.uk/borgscale.htm

Though the question “How do you feel ?” doesn’t seem scientific, however, studies show that RPE is indeed robust measure of exercise difficulty (R. Eston, 2012). It is even, probably, more robust than HR measures and shows good correlation with blood lactate and VO2. The advantage of this measure is that it adjusted exercise intensity or volume to individual ability, age, and gender. If a coach, for example, prescribes exercise based on the same heart rate to the athletes with the different aerobic abilities, it may cause an entirely different physiological response. However, it may be closer if RPE is the base of prescription. The problem of the RPE is that it doesn’t provide any information about exercise physiological nature only about its difficulty for a subject.

Training

Football drills

Recently, a “new” approach becomes increasingly popular in contemporary football training. The idea is to combine physical conditioning preparation with tactical and technical drills. Besides saving time and having more fun, the main argument in favour of this approach is that its physical workload is close to the real game thus players receive all necessary stimuli for developing their physical qualities. For example, small-sided games have become widely advertised as an effective way for developing endurance in football. This method has a clear advantage in specificity to the game and is more emotional compared to running. Footballers can simultaneously train endurance and their technical-tactical skills. Some authors argue that psychological and physiological measures (HR ,RPE, blood lactate and VO2) in small-sided games are the same as for high-intensity running programme (Dellal, Varliette, Owen, Chirico, & Pialoux, 2012; Hoff, Wisl?ff, Engen, Kemi, & Helgerud, 2002). Physical conditioning coaches may change workload by using a different number of players and different pitch sizes (Hill-Haas, Dawson, Impellizzeri, & Coutts, 2011). Usually smaller teams format involves greater number of intense duels thus, possibly, more anaerobically demanding. Increasing pitch size without increasing number of players may increase distances covered, therefore shifts energy production’s pathway towards aerobic. As it was mentioned above, almost all technical and tactical drills include physical components and coaches can use their creativity to manipulate with them.

So maybe football itself provides all necessary ingredients for training a perfect fatigue resistance? It is not so simple. Devil hides in details and training physical conditioning inside football drills is not detailed enough for precise and effective intervention. It is,  too non-specific for developing of particular components of endurance. If a coach is not happy with physical conditions of the player, it is necessary to understand where the problem is and start to work on it. It is not enough just to play more football. Also, workload in football drills varies between players and depends on many factors which are difficult to control. Let’s take for example Hill-Haas et al. study (Hill-Haas, Dawson, Coutts, & Rowsell, 2009). In their experiment players achieved mean blood lactate level of 6.7 mmol/l in 2 vs 2 game. Thiat tells us that exercise was significantly anaerobically demanding. However, if we look at data carefully, we can notice that range of lactate concentration among four players was from 2.9 to 11.7 mmol/l . Thus it looks like the game was highly anaerobically challenging, at least for one player (11.7 mmol/l) and, probably, very easy at least for another one (2.9 mmol/l). We don’t know anything about other two players. The same situation was when there were 4 vs 4 and 6 vs 6 games ( 2.3-8.0 and 1.8-9.1 respectively). Can physical conditioning coach be happy with such variations? I don’t think so. HR measure during small-sided games has some specifity. Though it can be equal to HR in intense running exercises, actually, stroke volume in games is lower than in the running. This is due to changes in muscles pumping function which moves blood up to the heart during muscle’s contraction. It is more consistent during the run than during the game, consequently, heart filling and stroke volume in the running are higher (Buchheit & Laursen, 2013). Stroke volume is crucial for better heart adaptation thus running may stimulate heart better than small-sided games.

To conclude, in my opinion,  technical-tactical exercises are a useful addition to generic endurance training however they are no substitution for running. The workload in football drills is non-specific and varies hugely between players. If your training is too general, you train “everything and nothing” thus stagnation will be inevitable. Whereas tactical and technical drills can be and should be combined with the footballer’s physical training, physical conditioning coach has to consider how it can be possible to implement individual and more detailed approach when prescribing and monitoring physical workload inside technical-tactical exercises. It is relatively easier in the individual sports games (e.g. tennis) but not so simple in the team sports. Small-sided games alone cannot be sufficient for developing endurance at the level which demands contemporary and, more importantly, future game. Footballers don’t like to run? Unfortunately, they will have to.

Running

The main reason for prescribing running exercise for footballers instead of just playing football is an attempt to make intervention more precise. First of all, it is a separation between predominantly aerobic and anaerobic training effects of a session. Trying to go further, coaches may target precisely central or peripheral components of aerobic fitness as well as metabolites production or tolerance of anaerobic one. However, it is important to note, that completely to separate all aspects of training is very difficult if possible at all.

Reference points.

Usually, prescription of the training intensity is based on speed or power. It would be worth to define some reference’s points which may connect different running velocities/power with different physiological thresholds, hence giving a scientific meaning to the exercise prescription. There are four most important of them. Though in the present article, these reference points are based on running, their significance is universal, and they can be used in any sport.

There are two reference’s points which are connected with the blood lactate. It is important to note, however, that lactate itself is not the reason for fatigue and even its concentration after the workload doesn’t necessarily tell us about athlete’s endurance abilities. More important is to find out individual lactate concentration thresholds, which reflect the dynamic of its changes, and running speed which can be sustained at these thresholds. If one athlete can run faster at these points than another one, then we can, with some confidence, say that his/her endurance is better, even if blood lactate concentration for the first athlete is higher.

1. Lactate threshold/aerobic threshold marks the upper border of intensities where blood lactate remains stable or slightly elevated (less than 1 mmol/l above the baseline). Below this threshold lactate level does not change even if intensity increases. For instance, if subject’s lactate threshold is 12 km/hour, blood lactate remains the same, independently whether subject runs at 10, 11 or 11.9 km/hour. Intensities below and at this threshold are considered as easy-moderate. Theoretically, a subject can run infinitely at speed below lactate threshold. Work can be limited by only mechanical muscles damage, elevated core temperature and mental tiredness. If a coach doesn’t have lactate analyser, lactate threshold can be defined using RPE. This level should be around 3 – 4 on 10-grade scale. Lactate threshold usually corresponded with 70-75 % of maximal heart rate in trained athletes. Higher speed at lactate threshold tells coaches about better aerobic capacities and better running economy (amount of oxygen per kilometer at given, sub-maximal speed).

2. Lactate turn point / anaerobic threshold/ maximal lactate steady state/critical speed.

This threshold marks upper border in the range of intensities which starts from lactate threshold. Within this spectrum, blood lactate increases linearly with exercise intensity. So if subject in the previous example has an anaerobic threshold at 15 km/hour, his /her blood lactate increases linearly together with speed rise from 12 to 15 km /hour. Actually, it means that both, aerobic and anaerobic systems (including metabolite clearance) are working more and more intense. Generally, however, clearance system still can cope, and blood lactate production is in equilibrium with lactate removal, so it is why this threshold is called Maximum Lactate Steady State (MLSS). If speed increase stops at, let’s say, 13 km /hour, blood lactate stops rising as well. However, above an anaerobic /MLSS threshold, clearance system becomes overwhelmed, and blood lactate starts to accumulate exponentially (picture 1) and will not stop to rise even if intensity remains the same. Thus, when our subject is running at a constant speed above MLSS (for example 16 km/hour) he/she continues to increase his/her blood lactate concentration, and we can predict impending work termination. The gold standard for MLSS determination is conduction, on separate occasions, four 30 min continuous runs at the constant velocities between 50-90% of vVO2 max (for vVO2 max see next paragraph), with blood lactate measurements throughout the tests. The maximal speed when blood lactate stop rising in last 20 min ( or rise less than 1 mmol/L) is MLSS. While blood lactate analysers are not so expensive now, nevertheless this method remains time consuming. More economical is an incremental test on treadmill or cycle ergometer (picture 1). The additional advantage of this method is that both lactate thresholds can be identified. In the field, trainer can find out speed corresponded with MLSS using 45 min – 1 hour time trial ( longer time for better trained) though it is less precise.

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Picture 1. Finding individual lactate thresholds during incremental cycle-ergometer test. Power was increased by 50 W every 3 min. We can see clear difference in the rate of lactate accumulation after first threshold (around 100 W) and after second, lactate turn point/MLSS (200W) .

Another method that can be used is a finding the Critical Velocity (CV). This velocity represents maximal theoretical speed which can be sustained without a continuous usage of anaerobic reserves. Though CV, as many authors argue, is not the same as MLSS (generally higher) and can be sustained only for approximately 30 min, it reflects the same ideas and practitioner can choose it for exercise prescription. In the field, CV can be roughly estimated from two (1500 and 3000 m) time-trial. The slope of the line between these two points on a graph ( y-distance x-time) is a CV (picture 2). Three trails (e.g., 1200, 2400, and 3600m) with the best-fitted line on the graph would be better. A coach can expect 80-90 % of maximal HR at MLSS with RPE around 7 whereas it may be 90-95% and 8 at CV. Higher speed at CV/MLSS tells coaches not only about better aerobic abilities and running economy but about a superior capacity to buffer and clear metabolites that, to some extent, may be considered as anaerobic qualities.

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Picture 2. Theoretical calculation of Critical Speed/Velocity for Mo Farah based on his personal best 1500, 1 mile, 3000, 2 miles and 5000 results.

In his case it is remarkably close to his 10000 m personal best speed (22.406 km/h ) which, according to (Billat, 2001), is a practical CV for high-level runners.

3.Minimal speed correspondent with VO2 max (vVO2max)

The name of this reference point talks for itself. This is a minimum speed which can elicit maximum aerobic capacities from the athlete during relatively short (5-10 min) incremental test with direct oxygen uptake measures. It can be important to note that it is not a maximum speed and it is not “pure aerobic” speed. We assume that at this point athletes use a maximum of their aerobic capacities though at vVO2 max athlete already significantly uses anaerobic pathway (MLSS is passed) as well. He/she can run faster using his/her anaerobic reserves even more, though the more they are used the more limited is time to exhaustion. Another consideration about vVO2max is that, sometimes, VO2 max can be achieved while running slower than vVO2max if subject runs relatively long. However, endurance athletes need, at least, intensity around 95% of vVO2max to reach maximal oxygen consumption during a single bout. In opposite, if an athlete is running too fast (e.g., 140% of vVO2 max), he/she will be exhausted before reaching VO2 max. Intensities domain between MLSS and vVO2 max is severe. On a field, the speed at VO2 max may be found in 5 min time trial or in Montreal University Track Test (Leger & Boucher, 1980) and, of course, the higher it is –the better.

4. Maximum speed (V max) is the fastest speed athlete can run. 40 m sprint with the flying start may be used to find it. Intensity domain between vVO2 max and V max is considered as extreme.

Approximation of the different reference points in relation to vVO2 max

This approximation is just for general reference. Numbers are significantly varied among athletes of different specialisations and levels. For example, it is impossible for Mo Farah with his vVO2 max (23.76 km/h) to have a maximal speed of 45.14 km/h (190% of vVO2 max). At the same time, Usain Bolt, with his top speed of 44.64 km/h, unlikely has 23.50 km/h as his vVO2 max.

Lactate threshold – 70-80 % vVO2 max

MLSS – 80-90% vVO2 max

CV – 90-95 % vVO2 max

vVO2 max- 100 %

Maximum speed- 180-190 % vVO2 max

Another interesting question is how, actually, these reference points are relevant to football. For instance, we know that higher speed at lactate threshold correlated with a better result in marathon, the speed at MLSS with half-marathon, CV- 10000 m and higher vVO2 max predicts better performance in middle distance events (3000-5000 m). In connection with football, Rampinini et al. have found that vVO2 max positively correlated with distance covered and intensity of runs made by professional football players (Rampinini et al., 2007). Higher speed at MLSS also is better for a player because it reflects peripheral adaptations in muscles, improving the ability to utilise oxygen and better to clean metabolites (Silva, Dittrich, & Guglielmo, 2011). That may be beneficial for the ability to repeat high-intensity efforts. And, finally, increasing in speed at lactate thresholds tells coaches about general improvements in aerobic fitness and running economy. Thus, it can be concluded, that all mentioned above reference points are important and to run faster at them is beneficial for a footballer.

Aerobic running training

Since aerobic capacities are essential qualities for many sports events, there is an abundance of methods for training. Practitioners can use infinite combinations of them. Some new techniques become very popular to an expense of the others and, possibly, their influence might be overestimated. On the other hand, as I already mentioned, training time, available for professional football players is very limited and should be devoted to other physical qualities such as strength, quickness and agility as well. That means that aerobic fitness should be developed most effectively. There are a few forms of aerobic conditioning which I would like to discuss.

Continuous running

Continuous run below and at aerobic threshold

around (1-1.5 hour) is a low intensity – high volume work. Indicators: RPE scale – around 3-4, talking during the run – no problem, HR – stable around 70-75 % of maximum, blood lactate – stable around 2 mmol/L

Though this kind of running was very popular in the past, however, now, many strength and conditioning specialists start to question its usefulness. Their main arguments are that a long slow run is time-consuming and it does not elicit event-related intensities. Therefore, they argue, it should be replaced by more intense exercises. However, it would be worth to note that running below and at aerobic threshold continues to occupy around 75% of training volume for contemporary elite running athletes, even in the events which are performed at significantly higher intensities (e.g., 3000, 5000 and 10000 meters). However, for elite runner’s “easy” pace is not the same as for footballers. Some authors argue that long runs provide the necessary basis for aerobic conditioning (Foster, Daniels, & Seiler, 1999). Possible advantages include but not limited by weight management, improving glucose transport and fat oxidation, increasing in mitochondrial amount, size and oxidative capacity, capillary density. Since football matches demand relatively long distances to cover (10-14 km), long runs might provide the valuable ability to tolerate long repeated muscle’s contractions. In simple words: if you need to move during 1.5 hours, you should be used to run 1.5 hours. However, there are few issues connected with the long-running. One of them I have already mentioned; it is time-consuming. Finding time for such training during competitive football season is difficult. In my opinion, this training should be implemented during young athlete’s development, probably in its later phases (14-18 years) when aerobic abilities are being built. For already formed players best time for long runs might be in the first weeks of pre-season training or in-season breaks.

The second issue with the long runs is that results will not come quickly and coach should be patient and consistent. That might be another argument in favour that long aerobic runs should be implemented during player’s development when more training time is available.

And the last consideration about long runs is that it slows athlete down. This notion is widespread among coaches. I will address this problem in Concurrent Training chapter.

There are two other forms of continuous running which may be used for aerobic conditioning.

Continuous run between lactate thresholds

( 30 min -1 hour). Benefits: cardio-respiratory adaptation, temperature regulation, increase in blood volume, lactate transport, and utilisation, muscle’s oxidative adaptation, fast twitch fibres recruitment.

Borg scale 5-7, talking –hard, HR-up to 85-90 % of maximum, blood lactate up to 4 mmol/L

At this range of intensities increasing energy demand taxes more and more aerobic system, however, at the same time, anaerobic contribution starts growing as well. That demands removal and utilisation of anaerobic metabolites and powerful muscle’s buffering system. As long as metabolite’s production and clearance are in equilibrium, work can be performed theoretically infinitely. In practice, however, it lasts around one hour at the upper border of this range because our ability to deal with metabolites and acidosis is not infinitive. Continuous run within this range can develop both aerobic and metabolite’s utilisation/buffering abilities thus to move upper border of this spectrum (MLSS/CV) higher. At the same time, however, this running, though being already psychologically demanding, does not reach intensities which tax aerobic and anaerobic systems at their highest level thus its usefulness may be questioned. Nevertheless, in my opinion, this method can provide some basis for developing anaerobic abilities and, so-called, “lactate tolerance.”

 Continuous run between anaerobic threshold and vVO2 max

( 5-30 min). Benefits: cardio-respiratory adaptations, lactate transport and utilization, muscles buffering capacity, fast twitch fibres recruitment, metabolites tolerance.

Borg scale 8-9, HR-90-100 % Talking- impossible, blood lactate – more than 4 mmol/L.

Continuous running at these intensities can be used for testing aerobic abilities (e.g. 5 min time trial to find out vVO2 max or famous 12 min Cooper test) but not often for training. It is not intense enough if performed at lower border (MLSS/CV) and leads to quick exhaustion if an athlete runs at vVO2 max. Thus, coaches prescribe lower intensities, if they want more volume or separate runs on intervals for achieving more accumulated intensity without complete exhaustion.

High-intensity interval training (HIT)

HIT is a very powerful tool for developing aerobic abilities. It became very popular now not only among professional athlete’s community but amateurs as well. This method is being advertised as an alternative to long continuous running because it is less time-consuming and reaches higher intensities. In my opinion, however, it should be used after some aerobic base has been already built; otherwise, you just don’t reach a necessary intensity of HIT. Time spent at VO2 max is, probably, one of the main criteria for the efficiency of training regarding developing maximum aerobic capacities. Some recommendations are that it should be at least 5-6 min per session for team and racket sports. The main idea behind HIT is that it allows to reach and to spend more time at VO2 max by using the cumulative effect of repetitive bouts. If, for example, an athlete can tolerate speed correspondent with VO2max just 5-6 min from which 2 min are needed to reach VO2 max, then he/she spends at VO2 max only 3-4 min. This run is exhaustive, and it is difficult to repeat it on the same session. When using HIT, athletes can run 4-8 bouts of 4 min runs slower (e.g. 90-95 % of vVO2 max) and use rest intervals (e.g. 2 min) to restore their capacity to maintain this speed. He/she might not reach VO2 max in the first bout but will do that in the next bouts due to elevated oxygen consumption. Time spent at VO2 max would be 6-14 min which makes HIT more efficient than a single exhaustive run.

Athletes can achieve targeted time at VO2 max with the different work-rest intervals. General recommendations are that for better cardio adaptations longer intervals (more than 3-4 min) are preferable with the relatively long passive rest (around 2 min). As was already mentioned, time to achieve VO2max is about 2 min, so it is why these intervals are so long. Long rest is needed to maintain high speed; otherwise, an athlete may not recover for the next run. Passive rest, possibly, is preferable option because it allows better recovery and, also, some authors showed that it helps to achieve higher stroke volume. Others, however, prefer active rest for better metabolites removal. If rest is active, it should be longer. Speed should be maintained at 90-95 % of vVO2 max because at lower speed well-trained athletes might not achieve VO2 max. Volume: 4-8 reps, one set. It is necessary to note that this type of exercise usually ends up with a high blood lactate concentration because intensity is higher than MLSS and overall work is relatively long. Hence coaches, who want to avoid significant lactate accumulation can choose shorter work interval formats while sacrifice benefits from a longer time at VO2 max.

Another way is a usage of shorter and more intense intervals, more typical for sports games, for achieving sufficient time at VO2 max through an accumulated effect of the load with short recovery periods. Speed should be at 100- 120 % of vVO2 max, recovery at 50-70 % or passive.

Examples: work/rest in seconds.

30/30 sprints. Work -110%, active rest – 50 % of vVO2max, 2 sets x 12 reps

15/15 sprints. Work-120%, rest-0% of vVO2max , 2 sets 12-15 reps

As attentive reader noticed in these types of HIT, already multiple sets are used. It helps to achieve more time at VO2 max and, at the same time, rest between sets allows avoiding early exhaustion. For the same reason, working intervals should not be more intense than 120% vVO2 max for 30/30 mode. Otherwise, it, actually, leads to earlier exhaustion and impairs time spent at VO2 max.

Short repeated sprints may be used for aerobic training in team and racket sports.

Repeated sprint mode means that work interval duration is less than 10 sec. rest – less than 60 sec

For increasing oxygen consumption, work intervals longer than 6 sec should be recommended, with relatively short rest (<20 sec). Intensity should be significantly higher than vVO2 max otherwise athlete won’t achieve VO2 max. It shouldn’t be near maximal, nevertheless, because an athlete will be fatigued very quickly. If rest is too long, oxygen consumption will return to the base level after each sprint and athlete may not to achieve VO2 max or may not to accumulate enough time at VO2 max.

One of the examples maybe 10/20 sprints at 120-130% of vVO2 max, 0% rest. Some authors argue that this method can provide a good time at VO2 max while resulted in limited lactate concentration. However, not all players, especially the fittest, may achieve VO2 max with the short, repeated, sub-maximal sprints.

One of the indicators of the efficiency of the aerobic training session is a relationship between time spent at VO2 max and overall session time. In this aspect, long intervals and short intervals with the work/rest ratio more than one are preferable for better time@VO2max/ exercise time ratio.

 What is better for aerobic training; HIT or continuous runs?

It seems that both are necessary. Continuous runs build up the basis for aerobic endurance and promote peripheral adaptations. HIT is more effective when athlete already adapted to high-intensity workload. It is an excellent stimulus for central adaptations. Interval training, though may trigger the same adaptations as long runs, does it differently, through other physiological pathways (Laursen, 2010). It helps to overcome stagnation in athlete’s development. It is closer to the real game intensities, less time-consuming and accumulates less mechanical stress on muscles compare to long runs. Hence, HIT is preferable during tapering and competitive periods.

Anaerobic running training

Anaerobic training is generally more intense, and Intensity may be higher than vVO2 max though it worth to remember that blood lactate already starts to build up exponentially after MLSS which may be at 80-85% vVO2 max .

Two main ways might be suggested for developing anaerobic capacities in team sports: speed endurance development (lactate production) and speed endurance maintaining (lactate tolerance). First way aims to develop an ability to resist fatigue during the single, maximal and relatively long effort. This effort should last not less than 10 sec which allows glycolysis to reach its maximum and, probably, not longer than 1 min to avoid significant aerobic contribution and pace strategy. Rest intervals should be sufficient for full recovery (approximately five times longer than work duration) thus work intervals longer than 30 sec may demand too long rest intervals. Therefore work intervals between 10 and 30 sec with 50 sec-2.5 min rest intervals may be recommended. That allows high glycolysis level with a limited aerobic contribution.

Example: 30/150 sec sprint, maximum effort and passive rest,10-12 repetitions.

Speed endurance maintenance training manipulates with the rest periods. They should be equal to work periods or even shorter. The athlete starts next effort while not fully recovered from previous one, thus developing metabolite clearance, muscle’s buffering capacities and fatigue’s tolerance.

Example: sprint 20 sec maximal effort , 10 sec rest , 6-12 reps.

For team sports accumulated effect of shorter sprints may be used as well. Then a work/rest ratio is an important variable.

Example for team sports: maximum sprints 6 sec, rest-17 sec. It is more game-specific, less mentally difficult. Rest is active at 50-60% of vVO2 max. Active and relatively intense rest is needed for prevention of PCr restoration and metabolite clearance thus maintaining high glycolytic rate, blood lactate, and metabolite accumulation.

Generally, the same idea is behind circuit training. Player maintain high aerobic level doing continuous run at 50-70% of vVO2 max and “on a top” of it he/she adds (every 30 sec ) an explosive 10 sec bouts: one or two legs high knee jumps and/or short (3-5 m) maximal shuttles. It is important that “base run” between explosive bouts should be intense enough to tax significantly aerobic system thus addition of explosive bouts will be taxing heavily anaerobic energy production.

Uphill running is a useful method for endurance development because it allows more muscle’s fibres to be recruited which leads to increase in oxygen consumption and metabolite production. I think it shouldn’t be too long, however. If an uphill run is long, athletes start to use pacing strategy and, actually runs much slower than on a flat surface, thus may lose benefits of uphill training. In my opinion, uphill runs are more useful for anaerobic workouts –speed endurance production. The work interval for uphill runs should be around 30 sec for a footballer, with a full effort and long rest between sprints.

Summary for aerobic and anaerobic training.

Both, aerobic and anaerobic mechanisms are working together thus we can talk only about the relative contribution of each of them.

Time spent at VO2 max and blood lactate is the mainly accepted criteria of the efficiency of training because it is difficult to measure others.

1. Continuous run below/at aerobic threshold allows building up a basis for endurance training.

2. More intense constant runs (between aerobic threshold and MLSS) continue to develop aerobic capacity while simultaneously tax an ability to transport and utilise lactate and muscles buffering capacities. They build up the basis for anaerobic abilities.

3. HIT training with long intervals ( 3-4 min) and passive 2 min or active 3 min recovery is better for cardio adaptations. Intensity – 90-95% of vVO2 max. However, it taxes anaerobic system as well (end lactate can reach 9 mmol/L).

4. The accumulated effect of shorter intervals 10-30 sec with higher intensities at 100-130% of vVO2 max and active recovery (50-70 % vVO2 max) of the same duration taxes more aerobic system and anaerobic- less.

5. The same format of work-rest intervals but with more intense sprints (90% of maximal speed) and with the passive recovery is mainly anaerobic. It trains the ability to maintain high speed during frequently repeated bouts.

6. The same work duration format with maximal sprints and full recovery aims to speed endurance production. That ability to sustain maximal speed inside relatively long individual bout. It is mostly anaerobic.

7. Shorter repeated sprints 4-10 sec with maximal effort and short rest: another way for speed endurance production through accumulated effect.

8. Less intense repeated sprints 140 % of vVO2 max is mostly aerobic. Fitter athletes, however, might not reach VO2 max in this exercise.

EIMD

As I already mentioned EIMD might be one of the main causes of general fatigue in a football match, hence it is important to find a way to train players to be better accustomed to it.

Appropriate strength training can help to alleviate consequences of high impact forces during the game. Since eccentric contraction is considered as the main cause of EIMD (Byrne, Twist, & Eston, 2004), probably, it would be useful to be accustomed to such type of workload. It was found that repeated bouts of eccentric contractions have a protective effect against EIMD (McHugh, Connolly, Eston, & Gleim, 1999). The idea is simple. Perform eccentric contraction exercise, and you will be less damaged when you performed it next time. Interestingly, preliminary eccentric training shouldn’t be necessary damaging to have a protective effect, though some minimal amount and intensity are needed. Another thing is that when doing usual strength exercise athletes focus more on concentric contractions (e.g., how many kilos he/she can squat) and does not pay a lot of attention to eccentric phase (e.g., how many kilos they may control when squatting down. It is important to remember that for the same exercise eccentric maximal force is 20-30 % higher than concentric thus doing both phases with the same load, as it usually happens, may provide inadequate stimulus for eccentric strength development. One of the methods to overcome this limitation is assistance during concentric phase, which allows more load, while the eccentric phase is performed unassisted. Plyometric exercises provide powerful stimulus for EIMD adaptation because they develop eccentric muscle actions during landing. Another interesting method is downhill running (R. G. Eston, Mickleborough, & Baltzopoulos, 1995). When we are running on the surface with the negative gradient, impact forces are significantly higher, thus demand more eccentric work, especially, from the quadriceps muscles. Some authors recommended gradient – 5.7 ° as the most suitable for EIMD adaptation (R. G. Eston, et al., 1995).

Concurrent training

One of the primary considerations about endurance training in football is that it slows a player down. This notion is widespread among coaches. Since speed to a great extent depends on strength and power, the question about the possibility to train these qualities and endurance concurrently receives a lot of attention. The answer, which contemporary sports science gives on that question, is that it is possible with the appropriate periodisation, though it is difficult to avoid interference completely. The negative influence of concurrent endurance sessions on strength and power development depends on volume, intensity, and frequency of the former (Wilson et al., 2012). A footballer is not a marathon runner hence he/she does not need to run as much as runner needs. Even in aerobic basis development stage, to perform endurance sessions for three times per week should be sufficient and they may be less frequent on the other stages. General recommendations are to perform endurance session not more than three times per week if strength/speed is trained at the same period and to allow sufficient time for recovery. If muscle hypertrophy is the aim (which may be important for young footballers), then, at least, 18 hours rest after strength session should be allowed before subsequent endurance session. That allows necessary time for anabolic hormones to increase muscle’s mass. Since the long runs result in muscle’s damage and neuro fatigue, it would be better do not to combine them with the training qualities which demand “fresh” muscles such as power, speed, and maximal strength. However, a coach can successfully combine long runs with strength tonus and endurance. Some studies, actually, found that strength exercise immediately after endurance training may be beneficial for endurance(Baar, 2014). However, if the strength development is the primary focus, it is better to make a break. If high intensity (more than 80% VO2 max) endurance session scheduled before strength training on the same day, then, at least, 3 hours break between them should be allowed to avoid interference effect.

Summary for concurrent training:

1. Separate long runs from sessions which aim muscles hypotrophy, absolute strength and power.

2. Identify your priority in particular training period. If these are power and speed development it is important to be non-fatigued before session.

3. Tonus strength exercises after endurance session help to improve endurance but if strength/powewr is priority, strength exercises should be performed after a rest.

P.S. Recently, I have found an interesting example of concurrent training: Caroline Wozniacki, a tennis star, who had run New York marathon in 2014 with a good result (under 5 min per/km) and played in US Open final two month before (actually during preparation to marathon). Definitely tennis is a very explosive sport and marathon runs are not part of the routine for tennis stars. However, she used to make a lot of running as part of her usual training. Look at fragment from her interview to “thegurdian” “… I run every day – every other day I do a longer run, and then the other day is intervals. So may be anything from 30 minutes to 1 hour 15/20 minutes. It really depends”. Does this make her less explosive? I suppose – no

The future of football

Importance of endurance.

When I am writing this article, five games are remaining to play in English Premier League with Leister City still at the top of the table. I cannot say whether they will win the League or not but what I can say is that their physical preparation for this season was brilliant. Leister City is generally counterattacking team, and there were interesting thoughts about this style of football in such unlikely source of football tactics revelations as The Economist

http://www.economist.com/blogs/gametheory/2015/12/competitive-balance-football .

They made some statistics and found out that, in the last season, If the pace of your attack is high (counterattack), the chances are high that you shoot far from the goal. It means that you are gambling with the lonely striker, who has no support hence is forced to shoot from a distance. This tendency is changing, however, in this season. Now, even if the pace of attacks is high, teams can anyway to deliver ball close to the goal. That, probably, indicates that counter-attacking teams now, often, have enough players for support. Where they come from? They come from the deep runs whereas their opponents are not willing or able following them. It was exactly the case in Manchester City-Leister City Leister city game ( 1-3). Though the monetary value of Leister start eleven was ten times less than Man City players, their physical abilities were so superior that result looks quite logical. Well done Leister City Sports Science department!

Team-work and Universality.

In the last World Cup, German team showed us convincingly that perfect teamwork, universality and excellent physical preparation are superior to the brilliance of individuals, even if these individuals are players from “another planet,” like Messi. German attacking players showed a lot of skills and enthusiasm in defense whereas their midfielders and defenders were excellent in attack. Interestingly, German star’s players, when they were taken from their perfect system, like, for example, national team or Bayern Munich, actually, do not shine as brightly as they did in teams mentioned above. Probably, they, though without doubts being high-class players, are not geniuses and cannot make a big difference when team’s philosophy is not suitable for them. Example of Bastian Schweinsteiger in Man United and Tony Croos in Real Madrid is a strong argument to support the notion that German team’s strongest asset is their teamwork not an individual genius of their players.

I agree with Matt Whitehouse thoughts (Whitehouse, 2014) that universality is the future of Football. Players will be demanded to perform attacking, defensive and play-making functions whatever his/her position formally is. It will require universality in physical preparation too. Footballers will not be either sprinters or endurance runners. They will be complete athletes who can run fast and a lot. Paradoxically, it demands more individual approach in physical preparation than that it is now. We cannot train a group of players in the same manner because their initial level, abilities and response to training are different. We are pursuing the same aim (perfect and universally-developed player), but we have to choose different, individual, most effective ways to it for every footballer.

Conclusion.

It is time to conclude vast and controversial topic about endurance in football. It is evident that fatigue during the game is a multifactorial and interactive process. It is still not completely clear how it develops. Possibly, anaerobic metabolites, EIMD and a shortage of glycogen in some muscle fibres play a crucial role, but it is still too vague definition. However, despite the lack of understanding it is critical to find the ways to train endurance better. Without a doubt, footballers have not achieved their limit of endurance and even didn’t come close to it yet, like that, probably, did athletes in track and field events

(http://www.economist.com/news/international/21657818-everybody-knows-todays-sportsmen-are-better-their-predecessors-working-out-how) . Most often players receive physical conditioning training in a group, with the same exercises and intensities for all footballers. It is not efficient. To improve fatigue- resistant training, coaches have to implement individual approach while monitoring and prescribing physical workload whether it is inside technical and tactical drills or generic running exercise. Furthermore, just playing football is not sufficient for fatigue-resistance training; therefore, more precise and effective methods should be borrowed from endurance events or invented for training footballers. Future football will demand universality and perfectly coordinated team-work. Every player will have to be able to do everything in every part of the pitch. That will request complete athletes. To achieve this, we should train them much more efficiently than we are doing now.

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