Tapering is important, too

Owen Anderson

High-quality players survey the field of play for clues about what their opponents will try to do in a manner which varies strikingly from the visual search patterns used by less-experienced performers.To find out exactly how soccer players become skilled at anticipating events on the field, the English scientists studied 15 experienced and 15 inexperienced male soccer players. The experienced athletes had 13 years of playing experience and had played an average of 640 competitive matches, while the inexperienced subjects had played for five years in an average of 73 matches. The experienced players included eight college first-team players and seven professionals; college third-team and recreational players comprised the inexperienced contingent.

('Visual Search Strategies in Experienced and Inexperienced Soccer Players,' Research Quarterly for Exercise and Sport, vol. 65(2), pp. 127-135, 1994)

As long as there are no gale-force winds, chute-users don't become airborne; in fact, their running velocities slow considerably because of the increased air resistance created by the chute. It's a bit like running uphill, except that instead of working against gravity you're fighting against the air hitting the inside of your trailing parachute.But is it really a good idea to use a speed chute during training? Chute proponents claim that the device strengthens leg muscles and leads to more powerful performances, especially over competitive distances of one mile or less. Even chute critics have to admit that the contraption does provide 'specific' training, which is always a hallmark of wise workouts. After all, you do run when you're wearing the chute, and running well is your ultimate goal. In that regard, chute use is a better form of resistance training than, say, lifting a weight with the leg muscles while the body is in a standing or sitting position.

'Effects of Speed Chute Training on Sprint Performance,'Medicine and Science in Sports and Exercise, vol. 26(5), Supplement, p. S 64, 1994

More than 30 referees enrolled in the Serie A and B Italian championships took part in the study. Each referee was observed between one and six times for a total of 96 matches, using sophisticated video analysis equipment. The key results were as follows:

1. the referees stood still for 14.6% of the total time played;

2. the total distance covered over an entire match was 11,469m;

3. this distance was covered in a variety of runs (forward, backward, sideways) and at various intensities from walking to high intensity (18.1-24k/h) and maximal intensity (24k/h) runs.

You may still not be too impressed, but remember that football referees are not professionals and hold down quite separate full time jobs. Despite this and the fact that they are usually older than the players they officiate over, they are still expected to keep up with the run of play no matter what the tempo.

The Italians concluded that refereeing top-flight matches is a demanding activity, which is predominantly aerobic, although the anaerobic system plays an important role at certain times. As the players get fitter so must their refs; it's a tough job but somebody has to do it!
The Journal Of Strength and Conditioning Research 15 (2) 167-171

Nick Grantham

While the average distance covered by a top-class outfield player during a 90-minute match is over 10,000m, at an average speed of over 7km per hour, these figures do not accurately represent the full demands placed on a player. In addition to running, a player must jump, change direction, tackle, accelerate and decelerate, etc, and each of these individual tasks requires an energy input over and above that required simply to cover a similar distance at a constant speed. Scientific investigation has shown that the true demands on a player can be approximated at roughly 70%VO2max. This is based on evidence of heart rate, sweat loss, increase in body temperature, and depletion of carbohydrate stores within the muscles (intramuscular glycogen)

Implications for training should become apparent. Clearly, the midfield players need more of an all-round fitness profile, with an emphasis on both aerobic and anaerobic capacity. Aerobic capacity relates to sustained performance (20-40 minutes), or performance during lengthy repetitions, each of 2-3 minutes in duration. Anaerobic capacity can be related to performance of a repeated nature, but with work/rest intervals of equal length, and not over 30 seconds.

This situation is exactly what the experienced player is trying to avoid when he decides to return more slowly to his main position on the pitch. However, this obviously requires a large degree of teamwork, with team-mates prepared to cover for the defender concerned. If a team can achieve this sort of cooperation, it helps reduce player fatigue and increases performance capacity throughout the match as a whole. Clearly the role of the coach is paramount in organising this sort of team approach in spreading the workload, especially with inexperienced players. Indeed, some younger players may be almost too enthusiastic for the good of their own and the team's subsequent performance

When discussing this subject, it is usual to express the form of the energy consumed as percentages (proportions) eaten as carbohydrate, fat and protein. While the typical diet for the general British population is about 40% carbohydrate, 45% fat and 15% protein, the recommended dietary proportions for a soccer player would be roughly 65% carbohydrate, 20% fat and 15% protein. However, the typical diet of the soccer player is actually very similar to that of the general population - too little carbohydrate and too much fat

The work carried out some years ago by Jacobs and colleagues ('Muscle glycogen and diet in elite soccer players', European Journal of Applied Physiology, 1982, vol. 48, pp297-302) illustrates the potential pitfalls of a low-carbohydrate diet. These researchers studied players in the Malmo soccer team in Sweden - the side had finished as runners-up in the European Cup the previous season. The players consumed just 47 per cent of dietary energy as carbohydrates - well below the recommended values. Muscle glycogen stores were assessed immediately after a national league match (Day 1), and again 24 hours later after no training (Day 2), and 48 hours after the match after a very light training session (Day 3)

Normal muscle glycogen stores of the general population are approximately 70-90 mmol.kg-1 wet weight. The average values for the Malmo team were 46, 69 and 73 mmol.kg-1 wet weight on the three days.

Alun Williams

Training the quadriceps muscles is an integral part of most sports strength programmes. The quadriceps are important for cycling, swimming, running, jumping, sprinting, throwing - in fact, virtually every full-body athletic movement. Three of the most common quadriceps exercises are the squat, the leg press and the knee extension. But although all three exercises target the quads, they all vary in terms of knee joint forces, muscle activity and functionality. There are even variations within an exercise through changes in technique or equipment.

The squat and the leg press are considered to be a different type of exercise from the knee extension. The squat and the leg press are known as closed kinetic chain exercises (CKC), whereas the knee extension is considered an open chain kinetic exercise (OKC). CKC exercises are distinguished by the foot being fixed and the knee joint moving in conjunction with the hip and ankle in a predictable manner. With the squat, for example, the foot is on the floor. and ankle, knee and hip all flex and then extend in sync. OKC exercises, on the other hand, are distinguished by the foot being free to move and the knee joint working independently of any other joints. With the knee extension, the hip joint is fixed and the knee flexes and extends with the foot freely rotating. (Recently, researchers have argued that this classification system of exercises is too simplistic, but for the purposes of this article, the simple distinction is sufficient.)

What the researchers say
Researchers and physiotherapists seem to be agreed that CKC exercises are superior to OKC ones. CKC knee exercises are considered safer and more effective since they place less strain on the anterior cruciate ligament (ACL) and elicit a hamstrings co-contraction together with the quadriceps. Researchers from the Mayo Clinic (New York) showed that leg press placed no strain on the ACL and elicited significant hamstring co-contraction, whereas the knee extension placed strain on the ACL at 30° of flexion. The decreased ACL strain makes CKC knee exercises important for ACL rehabilitation programmes.

The Mayo Clinic team also argue that CKC exercises are superior because they are more functional than OKC exercises. Walking, jumping and running movements all involve the kinetic chain of ankle, knee and hip. Thus it is advantageous to strengthen the quadriceps in a similar manner to real movements - specificity of training is an accepted principle in sports science. During the squat and leg press, the knee and hip extend together. While the knee extends, the rectus femoris shortens and the hamstrings lengthen, but while the hip extends, the rectus femoris lengthens and the hamstrings shorten. The result is a simultaneous concentric and eccentric contraction at the opposite ends of each muscle. This is known as the 'concurrent shift', and is a specific neuromuscular pattern which occurs during all multi-joint leg movements. This concurrent shift does not take place in OKC exercises. Theoretically, training the quadriceps in isolation, without normal muscular recruitment patterns, could lead to inefficient neuromuscular coordination in athletic movements. Training movements that involve the concurrent shift are very important, so CKC knee exercises are recommended.

Other studies have compared the muscle electromyographic (EMG) activity during the squat, leg press and knee extension exercises. EMG activity is an objective measure of the amount of muscle activity during the exercise. This allows exercises to be compared. Joseph Signorile and a team from the University of Miami investigated the EMG activity of the quadriceps during the squat and knee extension. They used experienced lifters and determined the 10-repetition maximum weight for each exercise. This guaranteed that both exercises required the same relative effort. The team found that the squat elicited significantly more quadriceps EMG activity compared to the knee extension. Signorile et al concluded that because of this the squat should be seen as the superior quadriceps exercise, especially as it is a more functional movement.

More support the squat
Kevin Wilk and a team from the American Sports Medicine Institute investigated the EMG activity of the quadriceps and hamstrings during the squat, leg press and knee extension. They also used experienced lifters and determined the 12-repetition maximum weight for each exercise. Like Signorile, they found that the squat produced the most quadriceps activity, peaking at 60 per cent of maximum activity levels. The leg press produced slightly less, peaking at 52 per cent, with the knee extension less still, peaking at 46 per cent.

Wilk's team also investigated the knee joint forces during the exercises. They confirmed the Mayo Clinic findings regarding ACL strain forces. The CKC exercises, the leg press and squat, placed no strain on the ACL, whereas below 40° of flexion the knee extension did place a strain on the ACL. However, the leg press and squat did place a strain on the posterior cruciate ligament (PCL), and should therefore be avoided by PCL injury patients. The leg press and squat also produced significantly greater knee compression forces than the knee extension, with the squat producing the highest. Compression force refers to the vertical force between the surfaces of the femur and tibia, and excessive compressive forces can cause knee injury.

Wilk et al also found that the squat was the only exercise of the three to elicit a significant hamstring co-contraction. During the squat, the hamstring activity peaked at 36 per cent of maximum compared with the leg press and knee extension in which hamstring activity peaked at 12 and 13 per cent respectively. This finding contradicts the Mayo Clinic research which showed a hamstring co-contraction during the leg press. This suggests that just because the leg press is a CKC exercise, it does not guarantee that there will be significant hamstring co-contraction. Other factors, such as body position and angle of force application, affect whether CKC exercises elicit co-contraction of the hamstrings, and are therefore functional to other movements.


The athlete's position is important
In a recent review paper, Wilk and his team summarised findings from research into co-contraction of hamstrings during leg press and squat exercises. The most important factor seems to be the technique used or body position of the athlete when performing the exercise. For example, with the squat performed normally with a bar across the back of the shoulders, as the knee and hip flex, the trunk leans forward. At the bottom of the lowering phase, the bar is positioned in front of the hips. This means that, as well as the quadriceps working to extend the knee, the hamstrings must work to extend the trunk back upright.

By contrast, with the seated leg press, the athlete sits with the body fixed upright and the footplate is level with the hips. Thus when the legs extend, the quadriceps work to extend the knee but the hamstrings need not work, because the trunk is fixed and the weight is in line with the hips. This biomechanical difference explains why Wilk found co-contraction with the squat and not with the leg press.

With a lying leg-press machine, the body position changes once again. The feet are placed above the hips and so the weight is in front of the hips. Thus, when the leg extends, the hamstrings must work to extend the hip along with the quadriceps which are working to extend the knee. So with the lying leg press there is hamstring co-contraction as with the squat. This is the type of leg press the Mayo team used in their study, which showed leg-press hamstrings activity.

Changes in squat technique can reduce the hamstrings co-contraction - for instance, by placing one's back against a support. This change will isolate the quadriceps since the trunk is supported and the hamstrings do not have to work to keep it upright. Other studies have shown that wide-stance squats produce more hamstrings and gluteal activity, and narrow-stance squats more quadriceps activity. Again, changes in technique result in different patterns of muscle activity.

From the research discussed above, we can draw some conclusions about the efficacy of the three quadriceps exercises.


1. The squat
This is probably the best exercise for the quadriceps. Studies have shown that the squat elicits the highest quadriceps EMG activity compared to the leg press and the knee extension. This means that the squat works the quadriceps the hardest. In addition, the squat is a CKC multi-joint exercise which elicits co-contraction of the hamstrings. Researchers have argued that this makes the exercise functional to athletic movements and therefore a sports-specific strength exercise. The co-contraction of the hamstrings means that the squat trains the 'concurrent shift' pattern, which is very important biomechanically. The squat is also safe for ACL patients, although it is not safe for PCL patients.

Variations such as narrowing the stance will concentrate activity on the quadriceps, while widening the stance will allow more gluteal and hamstrings activity. Leaning against a back support will isolate the quadriceps.

The major disadvantage of the squat is that it results in the highest knee-joint compression forces of all the exercises. This may cause problems for those with weak knees because of the extra pressure on the surfaces of the femur and tibia. For this reason, a correct squatting technique is vital to safety. Athletes also need to be strong in the low back and abdominals, because the squat works the low-back muscles hard and a high intra-abdominal pressure is required to support the spine. For heavy squatting, the athlete will need a training partner or a squat frame to train safely.

I conclude from the evidence that the squat is a very effective and sports-specific quadriceps strengthening exercise. However, it is probably best for well-conditioned athletes only.

The major disadvantage of the leg press is that it is not necessarily functional simply because it is a CKC multi-joint exercise. Wilk showed that with the seated leg press there was no hamstrings co-contraction. This means the concurrent shift pattern is not trained as it is with the squat. However, hamstring co-contraction is possible with a lying leg-press position with the feet placed higher than the hips. The lying leg press would be a good sport-specific exercise, just like the squat, only a little safer and easier.

The complication with the lying leg press is that the feet should not be placed too high. Ideally, they should be placed so that they are above the hip but level with the knee when the knee is fully extended. In this position, both the quadriceps and the hamstrings will work. If the feet are too high, the knee can go below them, which means the quadriceps stop working.

I conclude that the lying leg press, with the feet placed correctly, is a good alternative to the squat., potentially not quite as effective but safe and easy to use, making it more suitable for weight-training beginners. The seated leg press with feet low is not as good because it lacks the functional relevance.

The advantage of the knee extension is that compression forces are lower than with the CKC exercises. And, although the knee extension places a strain on the ACL, the level of strain is safe for a healthy knee. The knee extension is therefore a safe quadriceps exercise for athletes without ACL problems, but the fact that it works the quadriceps in isolation makes it much less effective than other exercises. If variation in strength exercises is required, then dumbbell lunges, barbell step ups, and single-leg squats are much better choices since they are CKC multi-joint movements. The only athletic movement the knee extension is functional for is kicking, which requires a powerful isolated quadriceps contraction.

I conclude that the knee extension exercise is the least effective and least functional of the three. However, it is safe (for non-ACL patients) and would be useful for football and rugby players to improve kicking power.

Raphael Brandon

Just to remind you, there are three major systems available for the production of energy in the muscles: the ATP-PC system for high-intensity short bursts; the anaerobic glycolysis system for intermediate bursts of relatively high intensity (this system produces the by-products of lactate ions and hydrogen ions, commonly known as lactic acid); and finally, there is the aerobic system for long efforts of low to moderate intensity.

With sporting events such as cycling, swimming and running, where the intensity is constant for the duration of the event, it is possible to estimate the relative contribution of each energy system. For example, the energy for the 100m sprint is split 50 per cent from the ATP-PC system and 50 per cent from the anaerobic glycolysis sytem, whereas the marathon relies entirely on the aerobic system (Newsholme et al, 1992). By contrast, games such as football are characterized by variations in intensity. Short sprints are interspersed with periods of jogging, walking, moderate-paced running and standing still. This kind of activity has been termed 'maximal intermittent exercise'.

It would seem reasonable to assume that during a football game all three energy systems would be required, as intensity varies from low to very high. However, because it is not obvious just how fast, how many and how long the sprints are, and just how easy and how long the intervening periods are, it is difficult to determine which of the energy systems are most important. Thus most of the football-related research has attempted to tackle this problem.

The pattern of football play has also been expressed in terms of time. Hungarian researcher Peter Apor and the Japanese researchers both describe football as comprising sprints of 3-5 secs interspersed with rest periods of jogging and walking of 30-90 secs. Therefore, the high to low intensity activity ratio is between 1:10 to 1:20 with respect to time. The aerobic system will be contributing most when the players' activity is low to moderate, ie, when they are walking, jogging and running below maximum. Conversely, the ATP-PC and anaerobic glycolysis systems will contribute during high-intensity periods. These two systems can create energy at a high rate and so are used when intensity is high.

The greater the player's aerobic power the quicker he can recover from the high-intensity bursts. These short bursts will be fuelled by the ATP-PC and anaerobic glycolysis systems. Then, during rest periods, a large blood flow is required to replace the used-up phosphate and oxygen stores in the muscles and to help remove any lactate and hydrogen ion by-products. The quicker this is achieved, the sooner a player can repeat the high-intensity sprints, and thus cover more distance and be able to attempt more sprints. So the aerobic system is crucial for fuelling the low to moderate activities during the game, and as a means of recovery between high-intensity bursts.

As the sprints a player makes are mostly 10-25m in length, or 3-5 secs in duration, some researchers have assumed that the ATP-PC system will be the most important. However, since football has an intermittent intensity pattern, just because the sprints are brief does not mean that anaerobic glycolysis does not occur; research has shown that anaerobic glycolysis will begin within 3 seconds.

A specific type of interval training for footballers would be to mimic the demands of an actual game with the correct work-to-rest ratios and distances covered. If players sprint for over 1 km during a game with high to low ratios of 3-5 secs to 30-90 secs, then a session such as two sets of 20 x 25m maximal sprints with 30 secs rest (2 mins between sets), would represent the demands of a tough match, namely, frequently repeatable high power. To focus solely on the ATP-PC system, short maximal sprints of 20-60m with 1-2 mins recovery are best. To train the anaerobic glycolysis system, longer sprints of 15-30 secs, with 45-90 secs recovery, are recommended. Aerobic training involves running continuously, fartleks, long repetitions (eg, 6 x 800m, 1 min rest) or extensive intervals at moderate speeds (eg, 30 x 200m, 30 secs rest). Trainers should be aware that running sessions, intervals and shuttle runs (or doggies) should be carefully planned so that they target the correct energy system. Running speeds, distances and rest periods should be calculated so that the session will target the specific energy system the coach wants to develop.

Raphael Brandon

soccer exercise | aerobic system

Soccer exercise energy demands

Just to remind you, there are three major systems available for the production of energy in the muscles: the ATP-PC system for high-intensity short bursts; the anaerobic glycolysis system for intermediate bursts of quite high intensity (this system produces the by-products of lactate ions and hydrogen ions, commonly known as lactic acid); and finally, there is the aerobic system for long efforts of low to moderate intensity.

With sporting events such as cycling, swimming and running, where the intensity is constant for the duration of the event, it is possible to estimate the relative contribution of each energy system. For example, the energy for the 100m sprint is split 50 per cent from the ATP-PC system and 50 per cent from the anaerobic glycolysis sytem, whereas the marathon relies entirely on the aerobic system (Newsholme et al, 1992). In contrast, games such as soccer are characterized by variations in intensity. Short sprints are interspersed with periods of jogging, walking, moderate-paced running and standing still. This kind of activity has been termed 'maximal intermittent exercise'.

It would seem reasonable to assume that during a soccer game all three energy systems would be used, as intensity varies from low to very high. However, because it is not obvious just how fast, how many and how long the sprints are, and just how easy and how long the intervening periods are, it is difficult to determine which of the energy systems are most important. Thus most of the soccer-related research has attempted to tackle this problem.

The pattern of soccer play has also been expressed in terms of time. Hungarian researcher Peter Apor and the Japanese researchers both describe soccer as comprising sprints of 3-5 secs interspersed with rest periods of jogging and walking of 30-90 secs. So, the high to low intensity activity ratio is between 1:10 to 1:20 with respect to time. The aerobic system will be contributing most when the players' activity is low to moderate, ie, when they are walking, jogging and running below maximum. Conversely, the ATP-PC and anaerobic glycolysis systems will contribute during high-intensity periods. These two systems can create energy at a high rate and so are used when intensity is high.

The above research has described the average patterns of play during soccer and from this we can calculate when each of the energy systems is contributing most. However, now we need to establish just how important each energy system is for soccer success.

Recovering from high-intensity bursts
There is evidence that the aerobic system is very important for soccer. Along with the fact that players can cover over 10 km in a match, Reilly found heart rate to average 157 bpm. This is the equivalent of operating at 75 per cent of your VO2max for 90 minutes, showing that aerobic contributions are significant. This is confirmed by the fact that various studies have shown soccer players to have VO2max scores of 55-65 ml/kg/min. These VO2max scores represent moderately high aerobic power. Reilly and Thomas (1976) showed that there was a high correlation between a player's VO2max and the distance covered in a game. This was supported by Smaros (1980) who also showed that VO2max correlated highly with the number of sprints attempted in a game. These two findings show that a high level of aerobic fitness is very beneficial to a soccer player.

The greater the player's aerobic power the quicker he can recover from the high-intensity bursts. These short bursts will be fuelled by the ATP-PC and anaerobic glycolysis systems. Then, during rest periods, a large blood flow is required to replace the used-up phosphate and oxygen stores in the muscles and to help remove any lactate and hydrogen ion by-products. The faster this is achieved, the sooner a player can repeat the high-intensity sprints, and thus cover more distance and be able to attempt more sprints. So the aerobic system is crucial for fuelling the low to moderate activities during the game, and as a means of recovery between high-intensity bursts.

As the sprints a player makes are mostly 10-25m in length, or 3-5 secs in duration, some researchers have assumed that the ATP-PC system will be the most important. But since soccer has an intermittent intensity pattern, just because the sprints are brief does not mean that anaerobic glycolysis does not occur; research has shown that anaerobic glycolysis will begin within 3 seconds.

To determine whether anaerobic glycolysis is significant during soccer, researchers have analysed blood lactates during matchplay. But results from these studies have varied. Tumilty and colleagues from Australia cite research varying from 2 mmol/l, which is a low lactate score indicating little anaerobic glycolysis, to 12 mmol/l, which is quite a high score. Most studies seem to find values in the 4-8 mmol/l range, which suggests that anaerobic glycolysis has a role.

The contrast in results is probably due to the varying levels of soccer in the different studies. Some use college-level players, others professionals. Some studies test training games, others competitive matches. This is likely to confound results. Ekblom, a researcher from Sweden, clearly showed that the level of play was crucial to the lactate levels found. Division One players showed lactate levels of 8-10 mmol/l progressively down to Division Four players showing only 4 mmol/l. Tumilty and colleagues conclude that the contribution of anaerobic glycolysis remains unclear, but is probably significant. They suggest that the tempo of the game may be vital to whether anaerobic glycolysis is significant or not. As Ekblom noted: 'It seems that the main difference between players of different quality is not the distance covered during the game but the percentage of overall fast-speed distance during the game and the absolute values of maximal speed play during the game'.