Written by Peter Joffe
Introduction.
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 high-intensity runs, and a decline in player’s involvement in duels and tackles.
The article suggested that anaerobic metabolites are the main reason for temporal fatigue. Simultaneously, the shortage of glycogen in some muscle fibres 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 at the start and 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 EIMD?
Though at first glance, this task is not overcomplicated physical conditioning training in football presents a significant challenge.
First of all, it is a large spectrum of actions which performs footballers. They sprint on distances ranging from several meters to “box to box” runs, make multiple changes of direction, jumps, tackles, and dribbles. The overall distance covered by the players may be up to 14 km. So who are footballers? Endurance runners? Sprinters? Don’t forget that they 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 strength and endurance, may conflict when they are trained together.
Secondly, football demands that significant training time must be devoted to the game’s technical and tactical aspects. This training put a substantial physical load on a player that should be considered when designing the conditioning programme. Furthermore, competitive football season lasts 10 months, with games sometimes played twice a week; thus, players need significant recovery time.
All these make time devoted purely to physical conditioning very limited, and even raise a question about the practicality of generic running exercise. 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, 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 a vital role in endurance training because it can help in three ways.
Firstly, oxygenation is a 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 recovery from the high-intensity work during the game’s less intense periods. A player needs oxygen for metabolite utilisation and energy restoration.
And finally, a person with better aerobic conditions can sustain higher intensity work without substantial anaerobic pathways, thus creating fewer metabolites.
Aerobic fitness depends on two components: central and peripheral. The central component is responsible for oxygen delivery. It includes the 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.
The ability to use an anaerobic energy system and deal with its metabolites is crucial for short-term fatigue tolerance during the game. For convenience, anaerobic capacities can be divided into two components: production and tolerance. The production means the ability to produce energy anaerobically. It depends on fuel availability ( creatine phosphate and glycogen) and their utilisation rate (creatine kinase reaction and anaerobic glycolysis).
The tolerance is of particular interest for fatigue-resistance training. It is the ability to maintain homoeostasis and sustain intensity level despite significant disturbances that arise from 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 specific chapter. Improving the running economy helps an athlete spend less energy on the same amount of work. That makes fuel utilisation more efficient and creates fewer metabolites. Strength can improve the running economy through an enhanced stretch-shortening cycle because a more “solid” body structure prevents wasting energy.
4. Nutrition.
Nutrition is an important and complicated topic, and it is beyond the scope of the presented article to discuss all aspects of nutrition for footballers. I just want to look briefly at the possibility and practicability to increase muscle energy status through nutritional interventions.
Since fat is a practically infinite energy source 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 others doubt that.
Both PCr and glycogen reserves can be increased with appropriate nutritional interventions. I am not sure that it is worth doing 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 leads to weight gain that is highly undesirable for a footballer.
Concerning glycogen, most findings consider it a significant factor in fatigue development. The nutritional strategy helps to have “full tanks” before the game and restore glycogen reserves faster.
Physiological and psychological measures for endurance.
For prescribing training and monitoring progress coaches and sport scientists may use some measurements 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).
VO2 max is one of the most important indicators of aerobic abilities. It measures the ability to deliver oxygen to the working muscles, thus reflecting the lungs, heart, and blood capacities. Also, it tells us about muscle 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 an 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 cars, VO2 max tells us about engine’s volume of the car. However, we know, that car with the bigger engine is not necessary a fastest. The same is true for VO2 max and endurance.
Although VO2 max is a 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.
Blood lactate 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). For more about blood lactate see article.
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). However, it is questionable 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 the 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, studies show that RPE is indeed a robust measure of exercise difficulty (R. Eston, 2012). It is probably more robust than HR measures and offers a good correlation with blood lactate and VO2.
This measure’s advantage is that it is adjusted to individual ability, age, and gender. For example, if a coach prescribes exercise based on the same heart rate to the athletes with different aerobic abilities, it may cause an entirely different physiological response. However, it may be closer if RPE is the base of prescription. The RPE problem 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 favouring 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 of 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 bouts (Dellal, Varliette, Owen, Chirico, & Pialoux, 2012; Hoff, Wisl?ff, Engen, Kemi, & Helgerud, 2002).
Physical conditioning coaches may change the workload by using different team and pitch sizes (Hill-Haas, Dawson, Impellizzeri, & Coutts, 2011). Usually, a smaller team format involves a greater number of intense duels, thus, possibly, more anaerobically demanding. Increasing pitch size without increasing amount of players may increase distances covered, therefore shifting energy production’s pathway towards aerobic. As mentioned above, almost all technical and tactical drills include physical components, and coaches can use their creativity to manipulate them.
So maybe football itself provides all the necessary ingredients for training a perfect fatigue resistance?
It is not so simple. The 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 the player’s physical conditions, 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, the 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 a mean blood lactate level of 6.7 mmol/l in 2 vs 2 game. That tells us that exercise was significantly anaerobically demanding.
However, if we look at the 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, easy for another (2.9 mmol/l). We don’t know anything about the 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 specificity. Though it can be equal to HR in intense running exercises, actually, stroke volume in games is lower than in running. This is perhaps due to variations in muscle pumping function. It facilitates blood movement up to the heart during muscle contraction. Muscle pumping is more consistent during the running than during the game; consequently, heart filling and stroke volume in running are higher (Buchheit & Laursen, 2013). Stroke volume is crucial for better heart adaptation; thus, running may stimulate the 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 combined with the footballer’s physical training, the 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 the 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 and metabolites production or tolerance of anaerobic one. However, it is important to note that completely separating all aspects of training is very difficult, if possible at all.
Reference points.
Usually, the prescription of the training intensity is based on speed or power. It would be worth defining some reference points that may connect different running velocities/power with different physiological thresholds, giving a scientific meaning to the exercise prescription. There are four most important of them. Though these reference points are based on running in the present article, their significance is universal, and they can be used in any sport.
There are two reference points which are connected with the blood lactate. However, it is important to note that lactate itself is not the reason for fatigue. Even its concentration after the workload doesn’t necessarily tell us about an 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 endurance is better, even if his blood lactate concentration 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, the lactate level does not change even if intensity increases. For instance, if the subject’s lactate threshold is 12 km/hour, blood lactate remains the same, independently whether the subject runs at 10, 11, or 11.9 km/hour. Intensities below and at this threshold are considered as easy-moderate.
Theoretically, the person can run infinitely at speed below the lactate threshold. Work can be limited by only mechanical muscle damage, elevated core temperature and mental tiredness. If a coach doesn’t have a lactate analyser, the lactate threshold can be defined using RPE. This level should be around 3 – 4 on 10-grade scale. The lactate threshold usually corresponded with 70-75 % of the 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 kilometre at given, sub-maximal speed).
2. Lactate turn point / anaerobic threshold/ maximal lactate steady state/critical speed.
This threshold marks the upper border in the range of intensities, which starts from the lactate threshold. Within this spectrum, blood lactate increases linearly with exercise intensity. If the subject in the previous example has an anaerobic threshold at 15 km/hour, his /her blood lactate increases linearly with speed rise from 12 to 15 km /hour. It means that both energy production and metabolite clearance work more and more intensely. Generally, however, the clearance system can still cope, and blood lactate production is in equilibrium with lactate removal, so 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, the clearance system becomes overwhelmed, and blood lactate starts to accumulate exponentially (picture 1). It will not stop to rise even if the intensity remains the same. Thus, when our subject runs 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 intensity where blood lactate stops rising in the last 20 min ( or rises 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 a treadmill or cycle ergometer (picture 1). The additional advantage of this method is that both lactate thresholds can be identified. In the field, the trainer can find out speed corresponded with MLSS using a 45 min – 1-hour time trial ( longer time for better-trained athletes) though it is less precise.
Picture 1. Finding individual lactate thresholds during incremental cycle-ergometer test. Power was increased by 30 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 is 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. The 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 trials (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. The 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.
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 athletes use a maximum of their aerobic capacities at vVO2 max. At the same time, they already significantly uses an anaerobic pathway (MLSS is passed). They can run faster using their anaerobic reserves even more, though that decreases time to exhaustion.
Another consideration about vVO2max is that, sometimes, VO2 max can be achieved while running slower than vVO2max if the subject runs relatively long. However, endurance athletes need, at least, the intensity of around 95% of vVO2max to reach maximal oxygen consumption during a single bout. Conversely, if an athlete is running too fast (e.g., 140% of vVO2 max), he/she will be exhausted before reaching VO2 max. The 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 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. The 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, Mo Farah, with his vVO2 max (23.76 km/h) can’t 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 the lactate threshold correlated with a better result in the marathon. The speed at MLSS with half-marathon, CV- 10000 m, and higher vVO2 max predicts better performance in the middle distance events (3000-5000 m).
Considering football, Rampinini et al. have found that vVO2 max positively correlated with the distance covered and the intensity of runs made by professional football players (Rampinini et al., 2007). The higher speed at MLSS also better for a player because it reflects peripheral adaptations in muscles, improved oxygen utilisation, and better metabolite clearance (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 running faster at them is beneficial for a footballer.
Aerobic running training.
Since aerobic capacities are essential qualities for many sports events, training methods are abundant. Practitioners can use infinite combinations of them. Some new techniques become very popular at the expense of the others, and, possibly, their influence might be overestimated. On the other hand, as I already mentioned, in professional football training time is very limited and should be devoted to other physical qualities such as strength, quickness, and agility. That means that aerobic fitness should be developed most effectively. There are a few forms of aerobic conditioning that 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 – about 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 prevalent in the past, now many strength and conditioning specialists started questioning its usefulness. Their main arguments are that a long slow run is time-consuming and does not elicit event-related intensities. Therefore, they argue, it should be replaced by more intense exercises.
However, it would be worth noting that running below and at aerobic threshold continues to occupy around 75% of training volume for contemporary elite running athletes, even in the events performed at significantly higher intensities (e.g., 3000, 5000, and 10000 meters). However, it worth noting that 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 to weight management, improving glucose transport and fat oxidation, increasing 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 contractions. In simple words: if you need to move for 1.5 hours, you should be used to run 1.5 hours.
Year 1981. English captain Kevin Keegan running Great North Run half-marathon. In the wrong shoes actually. He got blisters, borrowed another shoes from his fan after mile 10-th, and still finished 490-th from 12,264. Good old times…
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 a competitive football season is difficult. In my opinion, this training should be implemented during a 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 the coach should be patient and consistent. That might be another argument favouring that long aerobic runs should be implemented during a player’s development when more training time is available.
And the last consideration about long runs is that it slows athletes down. This notion is widespread among coaches. I will address this problem in the 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 systems. That demands the removal and utilisation metabolites and some muscle’s buffering capacity. As long as metabolite’s production and clearance are in equilibrium, work can be performed theoretically infinitely. However, in practice, it lasts around one hour at the upper border of this range because our ability to deal with metabolites and acidosis is not infinite.
Continuous run within this range can develop both energy production and metabolite’s utilisation abilities, thus moving the upper border of this spectrum higher. At the same time, though being already psychologically demanding, this running does not reach intensities that tax production and clearance 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 utilisation, muscle 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 a 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 into 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 trendy now not only among the professional athlete’s community but amateurs as well. This method is 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 already been 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 training efficiency 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 us 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 in 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, making 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, the reason for that is that the time to achieve VO2max is about 2 min, so these intervals should be at least 3 min long.
Prolonged rest is needed to maintain high speed; otherwise, an athlete may not recover for the next run. Passive rest, possibly, is preferable because it allows better recovery and, some authors also showed that it helps to achieve higher stroke volume. Others, however, prefer active rest for better metabolites removal. If the rest is active, it should be longer. Speed at work should be maintained at 90-95 % of vVO2 max because well-trained athletes might not achieve VO2 max at the lower speed. Volume: 4-8 reps, one set.
It is necessary to note that this exercise type usually ends up with a high blood lactate concentration because the 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 to use 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 readers 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 the 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, the athlete won’t achieve VO2 max. It shouldn’t be near maximal, nevertheless, because an athlete will be fatigued very quickly. If the rest is too long, oxygen consumption will return to the base level after each sprint, and the athlete may not achieve VO2 max or accumulate enough time at VO2 max.
One of the examples may be 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 and result 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 aerobic training session’s efficiency 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 of 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 an athlete already adapted to a high-intensity workload. It is an excellent stimulus for central adaptations. Though it may trigger the same adaptations as long runs, interval training does it differently through other physiological pathways (Laursen, 2010). It helps to overcome stagnation in an 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. Intensity may be higher than vVO2 max. It is worth remembering that blood lactate already starts to build up exponentially after MLSS, which may be at 80-85% vVO2 max.
Two main ways may be suggested for developing anaerobic capacities in team sports: speed endurance development (lactate production) and speed endurance maintenance (lactate tolerance).
The 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, allowing 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 a 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 the next effort while not fully recovered from the previous one, thus developing metabolite clearance, muscle buffering capacities, and fatigue tolerance.
Example: sprint 20-sec maximal effort, 10-sec rest, 6-12 reps.
For team sports, the 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. The rest is active at 50-60% of vVO2 max. Active and relatively intense rest is needed to prevent PCr restoration and metabolite clearance, thus maintaining high glycolytic rate, blood lactate, and metabolite accumulation.
Generally, the same idea is behind circuit training. The player maintains high aerobic level doing a continuous run at 50-70% of vVO2 max and “on a top” of it he/she adds (every 30 sec ) explosive 10-sec bouts: one or two legs high knee jumps and short (3-5 m) maximal shuttles. It is important that the “base run” between explosive bouts should be intense enough to tax significantly aerobic system; thus the 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 fibres to be recruited, leading to increased 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 run much slower than on a flat surface, thus may lose the 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.
After anaerobic (MLSS) threshold 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 are the main accepted criteria of training efficiency 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 the aerobic threshold and MLSS) continue to develop aerobic capacity while simultaneously tax an ability to transport and utilise lactate and muscle buffering capacities. They build up the basis for anaerobic capabilities.
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 the 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 less anaerobic.
5. The same format of work-rest intervals but with more intense sprints (90% of maximal speed) and 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 is the ability to sustain maximal speed inside a 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, may 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 the consequences of high impact forces during the game. Since eccentric contraction is considered the leading cause of EIMD (Byrne, Twist, & Eston, 2004), it would probably be useful to be accustomed to such a 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 for having a protective effect, though some minimal amount and intensity are needed.
Often, when doing a usual strength exercise, athletes focus more on concentric contractions (e.g., how many kilos they can squat) and do not pay a lot of attention to the eccentric phase (e.g., how many kilos they may control when squatting down. It is important to remember that the eccentric maximal force is 20-30 % higher than concentric for the same exercise. Thus, doing both phases with the same load, as it usually happens, may provide an inadequate stimulus for eccentric strength development. One way to overcome this limitation is assistance during the concentric phase, which allows more load, while the eccentric phase is performed unassisted.
Plyometric exercises provide a 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 the former’s volume, intensity, and frequency (Wilson et al., 2012).
A footballer is not a marathon runner; hence player does not need to run as much as runner needs. Even in the aerobic basis development stage, performing endurance sessions three times per week should be sufficient, and they may be less frequent in the other periods. General recommendations are to perform endurance sessions not more than three times per week if strength/speed is trained simultaneously 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 the necessary time for anabolic hormones to increase muscle mass. Since the long runs result in muscle damage and neuro-fatigue, it would be better not to combine them with the training qualities that demand “fresh” muscles such as power, speed, and maximal strength.
However, a coach can successfully combine long runs with strength tonus and strength endurance training. Some studies found that strength exercise immediately after endurance training may be beneficial for endurance (Baar, 2014). However, if strength development is the primary focus, it is better to take a break. If high intensity (more than 80% VO2 max) endurance session is scheduled before strength training on the same day, at least 3 hours break between them is needed to avoid interference-effect.
Summary for concurrent training:
1. Separate long runs from sessions that aim for muscle hypotrophy, absolute strength, and power.
2. Identify your priority in a particular training period. If these are power and speed development, it is important to be non-fatigued before the session.
3. Tonus strength exercises after endurance session help improve endurance, but if strength/power is a 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 the New York marathon in 2014 with a good result (under 5 min/km) and played in U.S. Open final two months 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 do a lot of running as part of her usual training. Look at the 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.
The importance of endurance.
When I am writing this article, five games remaining to play in the 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 an unlikely source of football tactics revelations as “The Economist”.
They made some statistics and found out that, in the last season, if the pace of your attack was high (counterattack), the chances were high that you shoot far from the goal. It means that you were gambling with the lonely striker, who had no support hence was forced to shoot from a distance. This tendency is changing, however, in this season (2015-16). Even if the pace of attacks is high, teams still can deliver the ball close to the goal. That probably, indicates that counterattacking teams now, often, have enough players for support.
Where they came from? They came from the deep runs of the supportive players, whereas their opponents are not willing or able to follow them. It was precisely the case in the 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, the German team convincingly showed us that perfect teamwork, universality, and excellent physical preparation are superior to individuals’ brilliance, even if these individuals are players from “another planet,” like Messi. German attacking players showed a lot of skills and enthusiasm in defence, whereas their midfielders and defenders were excellent in attack.
Interestingly, German star players actually do not shine as brightly as they did in the national team when they were taken out from their perfect system. Perhaps, though they are high-class players, they are not geniuses and cannot make a big difference when the team’s philosophy is not suitable for them. The example, performance of Bastian Schweinsteiger in Man United and Tony Croos in Real Madrid is a strong argument to support the notion that the German team’s strongest asset is their teamwork, not an individual genius of their players.
I tend to 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 a 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 training response are different. Though we are pursuing the same goal (perfect and universally-developed player), we have to choose the individual and most effective way for every footballer.
Conclusion.
It is time to conclude a 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 a too vague definition. However, despite the lack of understanding, it is critical to find ways to train endurance better. Without a doubt, footballers have not achieved their endurance limit and even didn’t come close to it yet, like that, probably, did athletes in track and field events.
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 approaches while monitoring and prescribing physical workload, whether inside technical and tactical drills or generic running exercises.
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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