Applied Physiology of Female Soccer Players

REVIEW ARTICLE

Spons Medicine 16 (3): 180-189, 1993 0112-1642/93/0009-0180/$05.00/0 © Adis International Limited. All rights reserved. SP01271

Applied Physiology of Female Soccer Players Jackie A. Davis and John Brewer The Lilleshall Human Performance Centre, LiIleshaIl Hall NSC, Newport, Shropshire, England

Contents 180 181 181 181 181 182 182 182 182 182 183 184 184 185 185 186 186 186 187 187 188

Summary

Summary I. An Historical Perspective 2. Match Analysis 3. Physiological Characteristics

3.1 Heart Rate 3.2 Body Temperature 3.3 Blood Lactate Concentrations

4. Physical Characteristics 4.1 Age, Height and Body Mass 4.2 Body Composition 4.3 Maximal Aerobic Power 4.4 Respiratory System Function 4.5 Hip Flexion 4.6 Knee Extension and Aexion Torques 4.7 Anaerobic Power 4.8 Vertical Jump Performance 4.9 Speed

5. The Menstrual Cycle 6. Haematological Status 7. Training 8. Conclusions

Women's soccer is in its infancy as a sport and research into its physiological demands and the physical characteristics of players is somewhat limited. There is now an increasing demand for scientific investigation of the female game and of the players, match analysis and role vari-ations requiring particular attention.

Current research suggests that the demands of the game for women are similar to those placed on male players. Women are reported to cover a similar distance (mean 8471m) to their male counterparts during a game and much the same proportions of the game appear to be devoted to exercise of varying intensities. Furthermore, female and male players appear to tax the aerobic and anaerobic energy systems to a similar level. The physical and physiological characteristics of female soccer players are comparable with those of other female games players and are more favourable than average for the population. Mean body fat percentages of between 19.7 and 22.0% and V02max values of between 47.1 and 57.6 ml/kg/min have been reported for elite female players, while faster than average sprint times are also characteristic of them.

Physiology of Female Soccer Players

The game of soccer is becoming increasingly popular with women worldwide, with an ever growing number of female players taking part in domestic and international matches. The inaugural World Cup for women was held in 1991, a com-petition which can only serve to elevate the status of the game. In view of the relative infancy of women's soccer, however, research into its phys-iological demands and the physical characteristics of players is limited. There is now an increasing demand for scientific investigation of the female game and of the players, match analysis and role variations requiring particular attention. The pur-pose of this review is to present the research work which has been undertaken so far and to highlight those areas which require further, more detailed study.

1. An Historical Perspective

The game of soccer has traditionally been the preserve of male players, little encouragement and even open hostility having been shown to those women who have participated. Despite this, soccer has become increasingly popular among women worldwide. In England, for example, women have been playing since the early 1900s. 11 000 players are now officially registered, with the most skilful making up 24 teams in the newly formed National League. In Japan, 9647 players were registered with the Japanese Football Association by 1988, the number of women's teams totalling 470 (Kohno et al. 1990). The first European Championships were held in 1982, and in 1991 the United States won the inaugural World Cup, staged in China. Wom-en's soccer has now firmly established itself as a serious sport at the highest level which is open to scientific investigation aimed at enhancing the standards and image of the game.

2. Match Analysis

Match analysis of male games has demonstrated that soccer is a demanding game which is inter-mittent in nature. Players cover a considerable total distance, while frequently having to exercise at a

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high intensity with only limited recovery periods. Few investigations, to date, have undertaken match analysis of women's soccer. The little work which has been done, however, would suggest that the re-quirements are similar for both men and women (Worthington 1980).

Recent match analysis of 7 members of an elite Swedish women's National League squad (Ekblom & Aginger, unpublished data) confirms this view. The women in this investigation covered an av-erage of 8471 ± 2200m during a game and an av-erage of 14.9 ± 5.6m each time they sprinted. The distance covered and average sprint duration were very similar to those observed in male players (Bangsbo et al. 1991; Reilly & Thomas 1976). Reilly and Thomas (1979) found that men cover an av-erage of 8680m during a game, of which the major part of the time (62%) is spent either walking or jogging (25 and 37% of the time, respectively). Men were reported to complete about 62 sprints in total, accounting for 11 % of the time, at an average of 15.6m per sprint.

While further investigation of the female game is required, particularly in terms of positional vari-ations, such results tend to confirm that soccer for both the female and male player requires a similar work pattern and output. To cope with such de-mands, players must have a high level of aerobic endurance while also having the capacity to re-cover rapidly from high intensity exercise if they are to be successful.

3. Physiological Characteristics

Investigation of the physiological demands of soccer for the female player has also been limited. Those observations which have been made so far, however, are of great interest and should serve as a catalyst for further work in the area.

3.1 Heart Rate

Match analysis of a 4-a-side game suggests that the heart rate during a game of soccer is similar for both male and female players (Miles et al. 1992). In their investigation, heart rates for all-female

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teams (x 176 beats/min) and for mixed teams (x 168 beats/min) were similar to those obtained for all-male teams (x 171 beats/min). These data are confirmed by the heart rates of 177.3 ± 10.9, 174.3 ± 10.5 and 172.8 ± 9.9 beats/min recorded in 3 separate full-sided female games (Ekblom & Agin-ger, unpublished data). These results suggest that female players operate at a high exercise intensity for the duration of a game, as do their male coun-terparts. The latter have been found to work at a rate in excess of 85% of their maximum heart rate for about two-thirds of the game (Ekblom 1986).

3.2 Body Temperature

An increase in body core temperature occurred between the start and the end of a game in 7 female members of a Danish National League Squad (Ek-blom & Aginger, unpublished data). Core temper-ature increased on average from 37.5 ± 0.3 to 38.7 ± OSC during each of 3 games. These values are lower than those reported by Ekblom (1986) in male first-division players and in male players from lower divisions. Because of the positive relationship be-tween core temperature and relative exercise in-tensity, these results would tend to contradict the heart rate data, suggesting that female players tend to work at a relatively lower exercise intensity than men during a game. It is possible that female play-ers, although covering a similar distance, actually cover more of the distance at a lower intensity than do their male counterparts. Further match and physiological analysis is required.

3.3 Blood Lactate Concentrations

Blood lactate concentrations at half-time and at the end of the game were 5.1 ± 2.1 and 4.6 ± 2.1 mmol/L, respectively, in the 7 female players in-vestigated by Ekblom and Aginger (unpublished data). This would support the core temperature findings which suggest that while glycolysis makes a significant contribution to the energy pool during a game, female players may not tax the anaerobic energy systems as highly as male players. Average blood lactate concentrations for professional, re-

Sports Medicine 16 (3) 1993

creational and older male players have all been higher than those observed in the women and range from from 8.0 ± 3.6 to 12.0 mmol/L (Ekblom 1986).

4. Physical Characteristics

While studies of the physiological responses of female players to the game of soccer are still very limited, an increasing number of investigations have described their physical characteristics. The findings are discussed below.

4.1 Age, Height and Body Mass

The average age of elite female players ranges from 20.3 to 24.5 years of age. A similar age range has been reported in studies observing male play-ers (Reilly 1990).

A considerable variation in the stature of female players has been observed by different investiga-tors, mean heights ranging from 158.1 to 169.0cm (Colquhoun & Chad 1986; Jensen & Larsson 1992). Such a variation, however, is not uncommon to the male game, and although height may influence playing position (goalkeepers, centre backs and for-wards may benefit from being taller), it does not appear to prohibit a player from becoming suc-cessful (Reilly & Thomas 1980). Further studies, investigating the physical characteristics of female players relative to playing position, should dem-onstrate the extent to which stature influences role selection.

With the exception of the comparatively short Australian players investigated by Colquhoun and Chad (1986), the body mass of players in each of the other studies fell within a very narrow range -between 59.5 and 63.2kg. This is slightly higher than average for the female population. The reference European Caucasian woman having a body mass of 57kg and attaining a height of 163cm (National Coaching Foundation 1992). Table I summarises the results of various investigations.

4.2 Body Composition

A high body fat percentage is associated with a decrement in athletic performance in those sports in which bodyweight must be supported and trans-

Physiology of Female Soccer Players 183

Table I. Mean (± SO) age, height and body mass of female soccer players

Reference Status

Colquhoun & Chad (1986) Australian state international players

Davis & Brewer (1992) English national squad Jensen & Larsson (1992) Danish national squad Rhodes & Mosher (1992) Canadian university players Tumilty & Darby (1992) Australian national squad Withers et al. (1987) Australian representative

players

ferred either horizontally or vertically by individ-uals (Hergenroeder & Klish 1990). Furthermore, health and normal physiological function can be impaired when the body fat percentage is reduced below a certain critical level, about 12% body-weight in females (Katch & Katch 1984). The as-sessment of body composition is therefore im-portant in both performance and health terms. While varying techniques have been used to de-termine the body fat percentage of female soccer players, mean values of between 19.7 and 22.0% have generally been observed.

Colquhoun and Chad (1986), in a study of 10 Australian state and international players at the close of the competitive season, undertook the measurement of body fat percentage using hydro-static weighing techniques. Players had an average of 20.8 ± 4.7% body fat, with a lean body mass of 43.8kg. This is very similar to that observed by Withers and colleagues (1987) using a similar tech-nique, with an average body fat percentage of 22.0 ± 6.8% and a lean body mass of 47.35kg obtained in 11 elite female Australian soccer players. Esti-mates of body fat percentage from skinfold meas-urements have produced comparable results. Davis and Brewer (1992) obtained average values of21.5 and 21.1% body fat in 14 members of the England women's squad assessed before and after a 12-month training programme, respectively.

The values obtained for the elite players in each of these studies compare favourably with those for other female games players including elite lacrosse and field hockey players (Withers et al. 1987). It

No. Age Height Mass (y) (cm) (kg)

10 24.4 ± 4.5 158.1 ± 5.7 55.4 ± 6.5

14 24.5 ± 3.6 166.0 ± 6.1 60.8 ± 5.2 10 23.0 169.0 63.2 12 20.3 164.8 59.5 20 23.1 ± 3.4 164.5 ± 6.1 58.5 ± 5.7 11 22.1 ± 4.1 164.9 ± 5.6 61.2 ± 8.6

might be inferred, therefore, that performance at the elite level in women's soccer requires a body fat percentage below average for the population (a mean of 29% body fat for females between the ages of20 and 29 was determined by Durnin and Wom-ersley 1974), while values as low as those observed in female endurance athletes (Wilmore & Brown 1974) and rhythmic gymnasts (Alexander 1991) will not necessarily enhance performance. On the other hand, it is likely that the fairly low body fat per-centages observed in female soccer players, relative to the average for the population, is a consequence of the training which they undertake.

Further investigation is needed to determine variations between players in different playing po-sitions. Male outfield players have been found to be a somewhat homogeneous group, while signifi-cantly higher body fat percentages are common in goalkeepers (Davis et al. 1992).

4.3 Maximal Aerobic Power

Studies investigating male soccer players have demonstrated a positive correlation between maxi-mal aerobic power (V02max, ml/kg/min) and work rate (Ekblom 1986). Furthermore, V02max values for male players are far higher than the norm for the population, although generally lower than would be observed in elite endurance athletes. A some-what similar trend appears to be emerging in fe-male players, with average V02max values being similar to those observed for females engaged in other team and individual sports (Alexander 1991;

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Kirby & Reilly 1992), above average for the un-trained population (Cooke et al. 1991), but below the average observed in endurance athletes (Pate et al. 1987).

Maximal aerobic power has been determined for female soccer players using both direct and indirect techniques. Rhodes and Mosher (1992) obtained an average V02max value of 47.1 ml/kg/min for 12 elite Canadian university players using direct expired air analysis. This compares favourably with values obtained by Colquhoun and Chad (1986) who observed an average V02max of 47.9 ml/kg/ min for 10 Australian players of a similar age and standard. A slightly higher average value of 49.75 ml/kg/min was observed by Evangelista and col-leagues (1992), in 12 elite Italian players, while Jenssen and Larsson (1992) obtained values of 53.3 and 57.6 ml/kg/min, in 10 Danish national squad players before and after a 15-month training programme, respectively.

Indirect assessment of aerobic power has pro-duced very similar results. Davis and Brewer (1992) implemented the Multistage Fitness Test (Rams-bottom et al. 1988) to estimate maximal aerobic power in 14 members of the England women's squad. Average estimated V02max values in-creased from 4804 to 52.2 ml/kg/min during a 12-month training period. Using the same test, Bal-som (unpublished data) obtained an estimated V02max value of 51.9 ml/kg/min in 9 members of a Swedish national league squad.

Based on these findings and those analysing the demands of the game, it is clear that for the female player, just as for the male, soccer requires a high level of aerobic endurance. As the women's game develops, players may well be required to attain even higher standards of fitness to succeed in the sport.

404 Respiratory System Function

Colquhoun and Chad (1986) observed an av-erage vital capacity (VC) of 3.94 ± lAL and an average forced expiratory volume in 1 sec (FEV I> of 3.7 ± OAL in 10 elite female Australian soccer players. These values compare favourably with


those obtained by Bale and McNaught-Davies (1983) in female hockey players, and are above av-erage for age- and size-matched members of the general population. Studies undertaken on male soccer players (Raven et al. 1976; Reilly 1990) have similarly observed higher than average values for both VC and FEV 1.

While such findings have been attributed to genetic endowment, evidence does suggest that lung capacity and function are enhanced with training. Because of the physical demands of the game of soccer, it is likely that a combination of genetic endowment and training would explain the above average values observed in both male and female players.

4.5 Hip Flexion

Exercises to improve hamstrings and lower back flexibility, in an effort to increase the range ofmo-tion and to reduce the risk of injury, have become an integral part of many soccer training pro-grammes. Male soccer players, particularly those in outfield positions, have consistently achieved below average scores on hip flexion tests and demonstrate poor hamstring flexibility (Oberg et al. 1984; Rhodes et al. 1986). While few studies have re-ported measurements of hip flexion in female soc-cer players, those which have suggest that their scores are similar to those generally observed in other groups of female games players (Davis & Brewer, unpublished data).

Tumilty and Darby (1992), in a study of 14 members of the Australian women's soccer squad, observed hip flexion scores, as measured using the 'sit and reach' flexibility test, of ± 12.8 (± 4.1) cm. This value is higher than the average ± 9 A (± 7.7) cm obtained by Colquhoun and Chad (1986), in their investigation of Australian players, but sim-ilar to that obtained by Davis and Brewer (1992) in the same number of England players before a 12-month training programme. In the latter study an initial mean of ± 12.3 (± 6.9) cm was increased to ± 1504 (± 6.5) cm after training.

With the considerable evidence to suggest that poor flexibility, or imbalances in flexibility, in-


creases the likelihood of injury (Knapik et al. 1991), stretching should continue to be an integral part of the female soccer player's training programme. Furthermore, the specialist requirements of the goalkeeper with regard to this component of fitness warrant further investigation.

4.6 Knee Extension and Flexion Torques

Dynamic muscular strength is essential for the successful execution of soccer skills such as kicking and dribbling, while jumping, tackling and running all require a high degree of muscular strength and endurance. Furthermore, imbalances in lower ex-tremity strength have been observed to increase the risk of injury in both male and female soccer play-ers (Knapik et al. 1991; Oberg et al. 1984).

Considerable research has been undertaken to assess muscular strength in soccer players. Isoki-netic knee extension and flexion torques for female players have been reported in a number of inves-tigations. Costain and Williams (1984) observed peak knee extension torques of 132.0 and 129.0 N • m, and peak flexion torques of 80.4 and 79.1 N • m, in the dominant and nondominant legs of 16 female high school players. These values were observed at an angular velocity of 1.05 rad/sec. At the same angular velocity Balsom (unpublished data), in an investigation of 9 members of the Swedish women's national league squad, observed higher peak extension torques. Since maturity and training status influence muscular strength, lower values in the high school players might be attrib-uted to their age.

Irrespective of speed, peak extension torque is significantly greater than peak flexion torque and as the speed of movement is increased, so the peak torques for both knee extension and flexion de-crease (Balsom, unpublished; Costain & Williams 1984; Davis & Brewer 1992; Tumilty & Darby 1992). Furthermore, ratios of hamstrings to quad-riceps strength are also altered with a change in angular velocity. Knapik et al. (1991) observed a knee flexor/extensor ratio of 0.62 and 0.79 in 138 female collegiate athletes involved in weight-bear-ing varsity sports, including soccer, at angular ve-

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loci ties of 1.05 and 6.27 rad/sec. This is almost identical to the ratios of 0.61 and 0.78 at the same speeds observed by Costain and Williams (1984).

None of the studies observed a significant dif-ference between legs when comparing either exten-sion or flexion torques irrespective of speed. Where imbalances have been found in individual players, however, the tendency has been for an increased likelihood of injury (Knapik et al. 1991). These findings are very much in agreement with those observed for other groups and for male soccer play-ers (Alexander 1990; Oberg et al. 1984; Prietto & Caiozzo 1989). While absolute torque values are lower for female soccer players than they are for males, and also lower than observed in female sprinters (Alexander 1990), female players do ex-hibit a normal response to isokinetic testing and generally have higher peak torque values than the nonathletic population. Given recent evidence to suggest that there is no difference in the peak torques generated between men and women when body mass is accounted for, although there may be between those involved in power as opposed to en-durance sports, further investigation is warranted.

4.7 Anaerobic Power

Soccer has been described as an intermittent ac-tivity in which periods of steady, low intensity ex-ercise are interspersed with shorter periods of high intensity exercise. Consequently, a player must have the ability to produce, sustain and reproduce ex-ercise of a high intensity and to recover rapidly if performance is to be optimised. Maximal anaero-bic power, mean power and fatigue in female soc-cer players have been determined through per-formance on the Wingate Anaerobic Test (Bar-Or et al. 1977). Peak anaerobic power was achieved within the first 5 seconds ofthe 30-second test and averaged 47.8 ± 11.2W for 10 Australian soccer players studied by Colquhoun and Chad (1986). The maintenance of 62.1 % of the peak power out-put at the end of the test suggests that this group of players had a well developed capacity to sustain high intensity exercise.

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4.8 Vertical Jump Performance

A positive correlation has been observed be-tween both vertical jump height and knee extensor strength (Ekblom 1986), and vertical jump height and maximal anaerobic power (relative to body mass) achieved on a bicycle ergometer (Vande-walle et al. 1987). Those individuals who are in-volved in speed/power activities tend to score more highly on the vertical jump test than do those in-volved in other activities. The vertical jump test has been used by a number of researchers to assess explosive leg power in female soccer players.

Jensen and Larsson (1992) observed an increase in jump height from 34.0cm (26.4 to 41.9cm) to 37.8cm (30.7 to 45.7cm) after 15 months of train-ing in 10 Danish national female soccer players. These values were slightly lower than the average of 40.5 ± 4.5cm observed by Tumilty and Darby (1992) in 14 members of the Australian women's soccer squad. None of these values is exceptionally high, however, suggesting that above average per-formance on the vertical jump is not as crucial to success in soccer as it may be in games such as netball which have a greater jumping component (Tumilty & Darby 1992). This would also appear to be true of the men's game, Ekblom (1986) hav-ing found that absolute vertical jump scores were no higher in male players than in untrained con-trols. Since goalkeepers have a very different role from outfield players, and one which requires con-siderable jumping ability, it would be worthwhile to observe the performance of these players on such tests, in isolation.

4.9 Speed

Although players must have the ability to re-produce high intensity exercise, the difference be-tween success and failure is often as small as a frac-tion of a second - the defender who reaches the ball ahead of her opponent may prevent a goal from being scored, while the attacker who outpaces a de-fender can create space and increase the likelihood of scoring. Consequently, players must not only be able to demonstrate a high level of aerobic fitness,


they must also have good leg speed. A mean 20m sprint time of 3.31 ± 0.11 sec was

reported by Tumilty and Darby (1992) for 20 members of the Australian women's soccer squad. While no other literature could be found as a com-parison, the authors observed that this was faster than the average reported for Australian netball players (3.40 sec), rowers (3.65 sec) or hockey play-ers (3.43 sec). Using a photoelectric cell timing de-vice, sprint times for 15m following a rolling start averaged 2.6 ± 0.05 sec for 9 members of the Swedish national league squad (Balsom, unpub-lished data). This compares favourably with a mean time of 2.7 sec for elite female hockey players as-sessed over the same distance by Davis and Brewer (unpublished data). The players in the latter in-vestigation were manually timed from a stationary start.

5. The Menstrual Cycle

A number of investigations of female athletes have suggested that physical performance may be impaired at certain phases in the menstrual cycle, while the prevalence of injury is also greater at cer-tain times (Moller-Nielsen & Hammar 1991; Wearing et al. 1972). Furthermore, menstrual ir-regularities have been linked to intensive training, excessive energy expenditure and inadequate nu-trition. The development of 'athlete's' amenor-rhoea is associated with low estrogen levels, low bone density and an increased risk of stress frac-ture (Burke 1991).

While no investigations into menstrual irregu-larities amongst soccer players could be found, a comprehensive study of the effect of the menstrual cycle on injury was undertaken by Moller-Nielsen and Hammar (1989). They studied 86 female soc-cer players from the Swedish First, Second and Third Divisions over a 12-month period. A sig-nificantly greater risk of traumatic injury was ob-served during the premenstrual and menstrual phases of the cycle than at any other time, partic-ularly in those women experiencing premenstrual or menstrual symptoms of discomfort. Further-


more, women using the contraceptive pill, often prescribed to alleviate such symptoms, sustained significantly fewer traumatic injuries than those us-ing other forms of contraceptive. With consider-able health and performance implications associ-ated with phases of or changes in the menstrual cycle, this is an area which warrants further in-depth investigation, not only for soccer players but for all female athletes.

6. Haematoiogicai Status

Suboptimal haemoglobin levels have been ob-served by numerous investigators in trained ath-letes and in previously sedentary individuals after a period of training (Miller 1990; Watts 1989). Since low haemoglobin concentrations have been asso-ciated with a decrement in performance, several studies have investigated the haematological status of female soccer players.

Perhaps the most comprehensive assessment was made by Douglas (1989) in her 14-week study of college hockey and soccer players. A group of 30 young players (mean age 19.2 years) was compared with a control group of 30 college students (mean age 20.6 years) who were not regular exercisers. Blood samples drawn from the participants before, during and after the competitive season were used to determine haemoglobin, haematocrit, red blood cell count (RBC) and mean corpuscle volume (MCV). Haemoglobin increased from 13.2 ± 0.88 to 14.1 ± 0.90 g/dl, haematocrit from 38.7 ± 2.59 to 40.5 ± 3.59%, RBC from 4.31 ± 0.34 to 4.38 ± 0.28 X 106/mm3 and MCV from 89.7 ± 4.63 to 92.5 ± 5.74m3 over the 14-week period in the soccer and hockey players, while the same trend was observed in the control group. In a less com-prehensive study, Davis and Brewer (1992) also observed an increase in the haemoglobin concen-tration of 14 English players following 12 months of supplemented training. Average values in-creased from 13.8 ± 1.1 to 14.6 ± 1.5 g/dl during this time.

These findings suggest that female games play-ers are able to maintain normal values for all of the haematological parameters with training, and

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training may actually increase each of these para-meters. Consequently, the development of 'sports anaemia' would appear to be relatively unusual in the games player compared with the endurance athlete. Players should be regularly monitored and a more detailed investigation made of those exhib-iting low values.

7. Training

Few studies have been made of specific training involved in the preparation of the elite female soc-cer player. Jensen and Larsson (1992) suggested that on average players in Danish league clubs train 2 to 3 times per week for 90 minutes, although the actual content of the training programme was not discussed. They supplemented this training, for members of the national squad, with 2 to 4 run-ning sessions (20 to 30 minutes in duration) and I to 2 strength training sessions each week over a 15-month period. Improvements in maximal aerobic power, running velocity at a blood lactate concen-tration of 4 mmol/L and jump height were achieved, while a significant decrease in the aver-age body fat percentage of the players was observed (Jensen & Larsson 1992).

Similar results were obtained by Davis and Brewer (1992) for 14 members of the English na-tional squad during 12 months of supplemented training. Most of the English players also trained twice each week with their respective clubs and were prescribed 3 additional training sessions consisting of 30 minutes of running or circuit training. Non-significant improvements were observed in maxi-mal aerobic power and hip flexion, while signifi-cant improvements in peak knee extension torques and torque: weight ratios were achieved.

Unlike many of the male players investigated, female soccer players, even at the elite level, are generally amateurs and have limited time for train-ing. Because of the physical demands of the game of soccer both male and female players require a highly developed aerobic capacity, considerable muscular and speed endurance, speed and flexi-bility. Female players should be encouraged to sup-plement club training in an effort to improve their

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work rate and to maintain a high skill level throughout the duration of a game. A minimum of 3 training sessions each week would help to main-tain fitness levels once higher levels are achieved, while 4 or 5 sessions will result in improvements; I or 2 long, steady runs (20 to 60 minutes in dur-ation) should help to maintain a player's aerobic endurance, while a similar number of higher in-tensity sessions will be required to develop speed endurance and speed. In addition, strengthening and flexibility work also have a place in training programmes.

8. Conclusions

There is considerable scope for further investi-gation of female soccer players. Match analysis work, physiological measurements of players dur-ing matches and more detailed analysis of playing position are particularly relevant at this stage. In-vestigations which have been undertaken to date suggest that the requirements of the female game are very similar to those of the male game. Not surprisingly, high levels of aerobic power, muscu-lar strength and endurance, speed endurance, flex-ibility and speed are required of female players, just as they are of male players. Female soccer players display very similar characteristics to those of other female games players, while demonstrating a level of fitness which is well above average for untrained women of the same age. However, the exceptional levels of aerobic power, and the very low body fat percentage scores of elite female endurance athletes are rarely observed in female soccer players.

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Correspondence and reprints: Jackie A. Davis, The Lilleshall Human Performance Centre, Lilleshall Hall NSC, Nr Newport, Shropshire TFIO 9AT, England.

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Applied Physiology of Female Soccer Players