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Biomedical subjects

N A Maffiuletti

Publications and source records attributed to N A Maffiuletti.

At least 19 recordsLinked to original sources
PubMed2006

A follow-up of GH-dependent biomarkers during a 6-month period of the sporting season of male and female athletes.

In order to verify the effects of the sporting season (entailing periods of training, competition, recovery, resting) on GH-dependent parameters in male and female athletes from different sporting disciplines, 47 male and female athletes (3 rowers, 5 swimmers, 7 alpine skiers, 3 soccer players, 7 middle distance runners, 14 sprinters, 4 triathletes, 1 road walker, 3 cyclists) were followed-up for a period of 6 months. Blood samples were taken every two months for the evaluation of IGF-I, N-terminal propeptide of type III procollagen (PIIINP) and C-terminal cross-linked telopeptide of type I collagen (ICTP). Abnormal IGF-I, PIIINP and ICTP levels were observed during the follow-up period in 7/100 (7%), 9/100 (9.0%) and 8/100 (8%) samples of the male group, respectively, and in 9/88 (10.2%), 1/88 (1.1%) and 0/88 (0%) samples of the female group, respectively. Abnormal levels appeared to be randomly distributed over the different periods of the sporting season and within male and female subjects, with the large majority of abnormal values being found in the younger athletes. Taking into account all the tests done during the 6-month period (no. 564), individual markers falling outside the normal range (for age) were observed in a small number of instances (34/564 tests done, 24/300 for males and 10/264 for females). When our method for the detection of exogenous recombinant GH (rhGH) administration, based on the concomitant determination of these three peripheral GH-dependent markers and on the attribution of specific scores, was applied in the same athlete at a given time point of the 6-month period, the prevalence of a positive score was extremely low (ie, 3/188 samples or 1.6%). Total positive scores were actually recorded in only three male athletes (2 swimmers and 1 skier, aged <21 yr) at one occasion during the 6-month period considered. In contrast, no total positive scores were found in female athletes (ie, 0/88 samples). In conclusion, the concentrations of IGF-I, PIIINP and ICTP were stable and not significantly modified during 6 months of a sporting season (entailing periods of training, competition, recovery, resting) in athletes from different sporting disciplines. Therefore our method, based on the concomitant determination of three peripheral GH-dependent biomarkers appears safe, acceptable, relatively inexpensive and repeatable (in case of positive or suspected values) immediately or at different intervals of the sporting season. Further additional studies are requested to precise the cut-off values for narrower age-class subdivisions in both genders in order to improve the proposed method.

Adolescent↗
PubMed2006

Electromyostimulation and plyometric training effects on jumping and sprint time.

This study compared the effects of four-week training periods of electromyostimulation (EMS), plyometric training (P), or combined EMS and P training of the knee extensor muscles on 20 m sprint time (ST), jumping ability (Squat jump [SJ] and Countermovement jump [CMJ]), maximal isometric strength (MVC), and muscle cross-sectional area (CSA). Forty subjects were randomly assigned to one of the four treatment groups: electromyostimulation (EG), plyometric (PG), combined EMG, and P (EPG), that took place 4 times per week, and a control group (CG). Subjects were tested before and after the training program, as well as once more after 2 wk of detraining. A significant improvement (p < 0.05) in ST was observed after training (2.4 %) in EG while a significant slowing (p < 0.05) was observed (- 2.3 %) in EPG. Significant increases in EPG (p < 0.05) were observed in SJ (7.5 %) and CMJ (7.3 %) after training, while no significant changes in both jumps were observed after training and detraining for EG. A significant increase (p < 0.05) in MVC was observed after training (9.1 %) and after detraining (8.1 %) in EG. A significant increase (p < 0.05) in MVC was observed after training (16.3 %) in EPG. A significant increase (p < 0.01) in CSA was observed after training in EG (9.0 %) and in EPG (7.1 %). EMS combined with plyometric training increased the jumping height and sprint run in physically active men. In addition, EMS alone or EMS combined with plyometric training leads to increase maximal strength and to some hypertrophy of trained muscles. However, EMS training alone did not result in any improvement in jumping explosive strength development or even interfered in sprint run.

Adult↗
PubMed2005

Postural instability of extremely obese individuals improves after a body weight reduction program entailing specific balance training.

The purposes of this study were to compare postural stability between obese and lean subjects and to investigate the effect of a 3-week body weight reduction (BWR) program entailing specific balance training on postural stability of extremely obese patients. Time of balance maintenance and mean error on the medial-lateral direction at the trunk and lower limb level were assessed during a single limb stance on a movable platform in 19 non-obese and in 20 extremely obese individuals (age range: 20-40 yr). Time of balance maintenance was shorter (obese: 21.1+/-7.7 vs lean: 27.3+/-3.1 sec) and medial-lateral sway of the trunk was larger in obese (5.4+/-3.2 degrees) than in lean (3.2+/-1.1 degrees) subjects (p<0.05). Two subgroups of obese subjects were also tested after a BWR program (energy-restricted diet, moderate physical exercise, nutritional education and psychological counselling) combined with or without 6 sessions of specific balance training on a movable platform. BWR plus specific balance training enhanced time of balance maintenance (pre: 23.8+/-7.2 vs post: 30.0+/-0.0 sec) and reduced the trunk sway (5.2+/-2.8 degrees vs 2.6+/-0.9 degrees ) more than BWR alone (p<0.05). The present findings indicate that extremely obese individuals have inadequate postural stability (compared to their lean counterparts) that could however be improved by few sessions of specific balance training incorporated into a multidisciplinary BWR program. It was concluded that balance improvement is an important goal of rehabilitation, that would probably reduce the propensity of overweight individuals to fall while performing everyday activities.

Adult↗
PubMed2005

Gender-related changes in body composition, muscle strength and power output after a short-term multidisciplinary weight loss intervention in morbid obesity.

Obese men and women have notably different body composition, which contributes to a different functional motor impairment, but it is unknown whether they respond differently to the same intervention for body weight (BW) reduction and motor capability improvement. The aim of this investigation was to compare changes in body composition, strength production and power output observed in severely obese men and women after a BW reduction intervention, and to test the hypothesis that changes in body composition may be related to changes in motor functionality. Ninety-five obese men and women of the same age (29.3 +/- 7.0 SD yr) and body mass index (41.2 +/- 4.4 kg/m2) participated in a short-term (3 week) mass reduction program (5 days/week) entailing exercise (aerobic and strength training) and energy-restricted diet. BW and body composition, maximum voluntary total isotonic strength (ST), and maximum leg power output (W) were evaluated before and after the program. After the intervention, BW decreased significantly in both men and women, but males lost a significantly higher amount of their initial BW than females (5.12 +/- 0.91 vs 4.27 +/- 1.42%, p<0.01). In men the BW loss was composed by a similar amount of fat mass (FM) and fat-free mass (FFM), whereas women lost FM almost entirely. Both men and women significantly improved ST after the intervention, but no difference in improvement was detected between genders, while W increased significantly in females (p<0.001), and no change was detected in males, although W per unit BW and FFM increased significantly in both genders (p<0.05-0.001). In spite of the positive correlation of ST and W with FFM (p<0.001), there was no detectable relation between the changes in body composition and those in motor performance, the improvement in ST and W being better attributable to factors other than muscle mass change. The present diet/exercise intervention induced significant effects on BW changes and composition as well as on ST and W, with a different impact in males and females.

Adult↗
PubMed2005

Changes in body composition, physical performance and cardiovascular risk factors after a 3-week integrated body weight reduction program and after 1-y follow-up in severely obese men and women.

OBJECTIVE: To investigate the short- and medium-term (ie, at 1-y follow-up) effects of a hospital-based body weight reduction (BWR) program lasting 3 weeks in severely obese individuals. DESIGN: Longitudinal, clinical intervention study entailing energy-restricted diet, tailored aerobic-strength exercise, psychological counselling and nutritional education during a 3-week period followed by 49 weeks of indirect supervision at home. SUBJECTS: In all, 45 women and 19 men aged 30.2 +/- 7.2 y (mean +/- s.d.) with severe obesity (BMI: 41.3 +/- 4.3 kg/m(2)), classified as weight losers (final < initial weight) and regainers (final> or =initial weight). INTERVENTIONS: Body composition, physical performance and cardiovascular risk factors before and after the BWR program and at follow-up. RESULTS: The large majority of the experimental subjects obtained a clinical success after the 1-y period, and the rate was higher in females (n = 37/45, ie, 82.2%) than in males (n = 11/19, ie, 57.9%). At follow-up, weight losers had higher percent fat-free mass, muscle strength, HDL-cholesterol and self-reported physical activity level and lower total cholesterol and glucose levels than weight regainers (P < 0.05-0.01). Males displayed significantly larger fat-free mass losses than females at post-BWR and at follow-up. CONCLUSIONS A 3-week hospital-based integrated BWR program resulted in a high rate of clinical success in severely obese individuals at 1-y follow-up (particularly in females), that was associated with increased levels of self-reported physical activity and improved muscle strength and lipid profile. Further research is needed to establish the long-term effects (ie, at 2-5 y) associated to this treatment.

Adult↗
PubMed2005

Gender variations of body composition, muscle strength and power output in morbid obesity.

BACKGROUND: Motor capabilities are reduced in obese (OB) individuals, and this impairment may result also from quantitative variation of muscle mass due to alterations in body composition. OBJECTIVE: This study aims to evaluate the differences in body mass (BM) and composition, as well as in muscle strength (ST) and power output W(.) between OB and NW males and females, and to test the hypothesis that variations in body composition affect muscle performance in OB subjects. DESIGN AND METHODS: Body composition (determined by BIA with a two-compartment model), upper and lower limb maximum ST (evaluated with isotonic machines) and lower limb maximum anaerobic W(.) (measured with a jumping test) were studied in a group of 95 extremely OB subjects (OB: 28 males, 67 females; mean age+/-s.d.: 29.3+/-7.0 y; BMI: 41.2+/-4.4 kg/m(2)) and in a control group of 18 NW voluntary subjects (NW: eight males, 10 females; age: 30.3+/-5.3 y; BMI: 22.6+/-2.1 kg/m(2)). RESULTS: OB male and female subjects differed significantly with increases in BM being attained by a similar contribution of fat mass (FM) and fat-free mass (FFM) in male subjects, but mainly contributed by FM in female subjects. Compared with NW, both OB men and women had a greater amount of FFM (P<0.001) and, since a general linear correlation was found between ST and FFM (ST (N)=64.4 FFM (kg)-190.0, R(2)=0.612, P<0.001), they developed higher values of ST (P<0.05) than their respective NW counterparts. For the same reason, both OB and NW male subjects had higher ST (P<0.001) than their female counterparts. Correction for FFM eliminated all gender- and obesity-related ST differences. On the contrary, in spite of their higher absolute muscle strength, both OB men and women could develop absolute W(.) similar to that of NW subjects, and were notably less powerful per unit BM than NW subjects (P<0.001), women being most affected among the OB. CONCLUSIONS: Obesity-related variation in body composition differs considerably by gender, and is responsible for differences in muscle performance: the higher muscle strength observed in OB subjects (both men and women) and in male subjects (both OB and NW) is accounted for by a greater amount of FFM. Nonetheless, biomechanical limitations appear to impair muscle power development during jumping in OB individuals.

Adult↗
PubMed2005

Central and peripheral fatigue of the knee extensor muscles induced by electromyostimulation.

The main purpose of this study was to characterise neuromuscular fatigue induced by 30 contractions of the knee extensor muscles evoked by electromyostimulation (EMS). Twelve healthy subjects were tested before and after a typical EMS session (frequency: 75 Hz, on-off ratio: 6.25 s on-20 s off) used for quadriceps femoris muscle strengthening. Surface electromyographic (EMG) activity and torque obtained during maximal voluntary and electrically evoked contractions were analysed to distinguish peripheral from central fatigue. Maximal voluntary torque of the knee extensor muscles decreased approximately 20 % (p < 0.001) following EMS. In the same way, peak torque associated to single (p < 0.05) and paired (p < 0.001) stimuli as well as M-wave amplitude (p < 0.05) significantly decreased as a result of EMS. The raw EMG activity of both vastus lateralis and rectus femoris muscle recorded during maximal voluntary isometric contraction significantly decreased after the session (-17.3 and -14.5 %, respectively) whereas no changes were observed when EMG signals were normalised to respective M-wave amplitudes. Similarly, voluntary activation estimated by using the twitch interpolation technique was unchanged following EMS. In conclusion, a typical session of EMS of the knee extensor muscles mainly induced neuromuscular propagation failure while excitation-contraction coupling and neural mechanisms were not significantly affected. It is recommended to interpret surface EMG data together with the corresponding M wave, at least for the knee extensor muscles, in order to distinguish peripheral from central causes of fatigue.

Adult↗
PubMed2004

Effect of a 3-week body mass reduction program on body composition, muscle function and motor performance in pubertal obese boys and girls.

The aim of this study was to investigate the effects of a multidisciplinary body mass reduction (BMR) program on body composition, muscle function and motor performance in 50 obese [mean body mass index (BMI): 35.9+/-5.8 kg/m2] boys and girls aged 12-17 yr (Tanner stage III, IV and V). The hospital-based BMR program combined an energy-restricted diet (1400-1600 kcal), nutritional education, psychological counselling and moderate physical activity (45-60 min/ session; 5 sessions/week; 60-80% of the maximal heart rate) during a 3-week period. Fat mass, fat-free mass, maximal power during jumping and stair climbing as well as maximal strength of the upper and lower limb muscles were quantified before and after the treatment. Body mass and fat mass significantly decreased following the BMR program, respectively -5.1 and -7.8% (p<0.001), while percent fat-free mass increased 2.3% (p<0.001). The treatment significantly increased both stair climbing and jumping power, respectively 8.2 and 8.9% (p<0.05), and the same was true for maximal strength of the upper and lower limb muscles (p<0.001). For the first time, it was demonstrated that a BMR program entailing diet and physical exercise significantly improved body composition, muscle function and motor performance in obese boys and girls aged 12-17 yr, while gender and pubertal stages had no influence on BMR program-induced changes.

Adolescent↗
PubMed2004

Neural activation of the triceps surae is impaired following 2 weeks of immobilization.

The purpose of this study was to investigate the effect of 2 weeks of ankle joint immobilization on triceps surae neural activation, with particular emphasis on the potential differences between the monoarticular soleus and the biarticular gastrocnemius muscles. Seventeen male volunteers were divided into the immobilized group (IG, n = 8) and the control group (CG, n = 9). Elastic adhesive bandages and an ankle stabilization orthosis were used to immobilize the ankle joint only. The plantar flexor torque obtained during maximal voluntary contractions (MVC) and after single, paired and tetanic stimuli applied at rest was measured. The associated EMG activity from the soleus and gastrocnemius muscles was also recorded, and their activation levels were estimated by means of the twitch interpolation technique. After immobilization, triceps surae maximal voluntary torque significantly decreased by 17% (P < 0.001). Strength losses were accompanied by a decrement in activation level (-6%, average of the three techniques used) and in maximal 100 Hz tetanic force (-11%). A significant decrease in the soleus (-22%, P < 0.05) but not in the gastrocnemius EMG activity, normalized to respective M-waves, was also found. It was concluded that the reduced voluntary torque output after immobilization could be attributed to both muscular and neural alterations. These latter selectively involved the monoarticular soleus muscle, while neural drive to the biarticular gastrocnemii, which had not been immobilized in their function as knee flexors, was preserved.

Adult↗
PubMed2004

Elderly obese women display the greatest improvement in stair climbing performance after a 3-week body mass reduction program.

OBJECTIVE: To investigate whether stair climbing performance and body composition are similarly affected by a body mass reduction (BMR) program in obese individuals of different gender, age and body mass index (BMI) level. DESIGN: Longitudinal, clinical intervention study entailing energy-restricted diet (5023-7535 kJ/day), nutritional education, psychological counselling and moderate physical activity (indoor cycling, outdoor walking, gymnastics routines, five sessions/week) during a 3-week period. SUBJECTS: A total of 466 male and 807 female subjects categorized as a function of gender, age (< vs >/=50 y) and BMI (< vs >/=40 kg/m(2)). MEASUREMENTS: Body mass, stair climbing time and power before and after the BMR program. Fat-free mass and fat mass were also evaluated by bioimpedance analysis, in a representative subgroup of 160 patients, to evaluate the relation between fat-free mass and power output. RESULTS: Body mass, fat-free mass and fat mass significantly decreased following the BMR program (P<0.001), with male subjects reducing body mass and fat-free mass more than and fat mass less than the female subjects. Stair climbing time decreased (P<0.001) and therefore anaerobic power significantly increased 9.7% after the treatment. The greatest improvement in stair climbing performance was observed in obese women aged >/=50 y. Significant inverse correlations were found between initial power or fat-free mass level and respective percent increases (R=-0.35/-0.37, P<0.001) and between BMR-induced percent changes in body mass and power (R=-0.13, P<0.001). CONCLUSION: Subjects with the lowest baseline level in stair climbing performance (and probably with the lowest amount of fat-free mass), that is, obese women aged more than 50 y, obtained the largest enhancement after the 3-week BMR program, likely improving overall functional capacities and resulting in greater independence during daily-living activities in such a population.

Activities of Daily Living↗
PubMed2003

Effect of ageing on the electrical and mechanical properties of human soleus motor units activated by the H reflex and M wave.

This study was designed to investigate the effect of ageing on the mechanical and electromyographic (EMG) characteristics of the soleus motor units (MUs) activated by the maximal Hoffmann reflex (Hmax) and by the direct muscle compound action potential (Mmax). Eleven young (mean age 25 +/- 4 years) and ten elderly (mean age 73 +/- 5 years) males took part in this investigation. The senior group presented lower amplitudes of Mmax (-57 %, P < 0.001) and Hmax (-68 %, P < 0.001) waves compared to the younger population. These were associated with a depression of relative twitch torque of the plantar flexors. The average values of the Hmax/Mmax ratio did not statistically differ between the two populations, despite a tendency for lower values (~23 %) in the senior group. However, the older adults showed a greater relative amplitude of the sub-maximal M wave evoked at Hmax (MatHmax) than did the younger males (young 5 % vs. elderly 29 % of the Mmax, P < 0.01). This finding suggests an increased homogeneity between the excitability threshold of sensory and motor axons. The twitch torque at Hmax (PtH-M) was subsequently calculated by subtraction from the total twitch torque of the mechanical contamination associated with MatHmax. The resulting PtH-M was significantly lower in the elderly (-59 %, P < 0.001). Despite a discrepancy of 20 % between the two groups, the mechanical ratio (PtH-M/PtM; PtM, twitch tension related to the Mmax compound action potential), like the EMG ratio, did not statistically differ between the young and older individuals. Nevertheless, the senior subjects exhibited a higher twitch/EMG ratio for the reflexively activated MUs (PtH-M/Hmax) than the younger individuals (+40 %, P < 0.05). This finding suggests an on-going neuromuscular remodelling, resulting in an increased innervation ratio. The neural rearrangement may be viewed as a compensatory adaptation of the motor system to preserve the mechanical efficiency of the surviving MUs, despite the age-related impairment of the segmental reflex system. This phenomenon is confirmed by the maintenance, with senescence, of the approximately constant values of the twitch/EMG ratio for the entire motor pool (PtM/Mmax).

Action Potentials↗
PubMed2003

Alteration of neuromuscular function after a prolonged road cycling race.

The aim of this study was to characterize neuromuscular fatigue in knee extensor muscles after a prolonged cycling exercise. During the two days preceding a 140-km race (mean +/- SD duration: 278.2 +/- 24.9 min) and 15 to 30 min after, maximal percutaneous electrical stimulations were applied to the femoral nerve of 11 trained cyclists. Electrically evoked superimposed twitches and trains of 6 stimulations were delivered during isometric maximal voluntary contraction (MVC) to determine maximal voluntary activation (% VA). Knee extensors MVC decreased with fatigue from 158.2 +/- 29.6 to 144.2 +/- 30.0 Nm (p < 0.01), but no central activation failure was detected after the race. The average rate of twitch force development increased significantly from 414 +/- 106 to 466 +/- 102 N x m x s-1 (p < 0.05) and a tendency toward higher peak twitch tension (p = 0.052) was found in the fatigued state. Short tetanus at 20 Hz and 80 Hz were also applied to 4 cyclists, but these fused and unfused tetanic forces were not significantly modified with fatigue. From these results, it can be concluded that the small but significant isometric strength loss measured less than 30 min after the end of a long distance road cycling race is not due to central fatigue. It is also suggested that a raise in peak twitch tension is not necessarily associated with enhanced neuromuscular function.

Adult↗
PubMed2002

Central versus peripheral adaptations following eccentric resistance training.

Aim of the present investigation was to study the effects of an eccentric training on the neuromuscular properties of the plantar-flexor muscles. The experiment was carried out on 14 males divided into two groups (eccentric and control). Eccentric training consisted of six sets of six eccentric contractions at 120 % of one maximal concentric repetition and it was performed four times a week during four weeks. Before and after the 4-wk period, the plantar-flexor torque and the associated electromyographic activity were recorded during voluntary contractions (isometric, concentric and eccentric) and electrically induced contractions (twitch and tetanus), in order to distinguish central from peripheral adaptations. For the eccentric group, voluntary torque significantly increased after training independent of the action mode (relative gains 14 - 30 %, p < 0.05). This was associated with an increase in agonist EMG activity during isometric action and a decrease in antagonist coactivation in concentric (-27 %) and eccentric actions (-22 %) (p < 0.05). Voluntary activation level significantly increased from 80 +/- 5 % to 91 +/- 2 % (p < 0.05). Some of the twitch contractile properties (peak torque and maximal rate of twitch tension relaxation) were significantly modified (p < 0.05), but no changes were observed for the tetanus characteristics. These results allowed to conclude that the torque gains observed after the present training were more likely associated to central adaptations, affecting both agonist and antagonist muscles.

Adaptation, Physiological↗
PubMed2002

Alterations of neuromuscular function after an ultramarathon.

Neuromuscular fatigue of the knee extensor (KE) and plantar flexor (PF) muscles was characterized after a 65-km ultramarathon race in nine well-trained runners by stimulating the femoral and tibial nerves, respectively. One week before and immediately after the ultramarathon, maximal twitches were elicited from the relaxed KE and PF. Electrically evoked superimposed twitches of the KE were also elicited during maximal voluntary contractions (MVCs) to determine maximal voluntary activation. MVC and maximal voluntary activation decreased significantly after the ultramarathon (-30.2 +/- 18.0% and -27.7 +/- 13.0%, respectively; P < 0.001). Surprisingly, peak twitch increased after the ultramarathon from 15.8 +/- 6.3 to 19.7 +/- 3.3 N. m for PF (P < 0.01) and from 131.9 +/- 21.2 to 157.1 +/- 35.9 N for KE (P < 0.05). Also, shorter contraction and half-relaxation times were observed for both muscles. The compound muscle action potentials (M wave) were not significantly altered by the ultramarathon with the exception of the soleus, which showed a slightly higher M-wave amplitude after the running. From these results, it can be concluded that 65 km of running 1) severely depressed the maximal voluntary force capacity mainly because of a decrease in maximal voluntary activation, 2) potentiated the twitch mechanical response, and 3) did not change significantly the M-wave characteristics.

Adult↗
PubMed2001

Effect of pedalling rates on physiological response during endurance cycling.

This study was undertaken to examine the effect of different pedalling cadences upon various physiological responses during endurance cycling exercise. Eight well-trained triathletes cycled three times for 30 min each at an intensity corresponding to 80% of their maximal aerobic power output. The first test was performed at a freely chosen cadence (FCC); two others at FCC - 20% and FCC + 20%, which corresponded approximately to the range of cadences habitually used by road racing cyclists. The mean (SD) FCC, FCC - 20% and FCC + 20% were equal to 86 (4), 69 (3) and 103 (5) rpm respectively. Heart rate (HR), oxygen uptake (VO2), minute ventilation (VE) and respiratory exchange ratio (R) were analysed during three periods: between the 4th and 5th, 14th and 15th, and 29th and 30th min. A significant effect of time (P < 0.01) was found at the three cadences for HR, VO2. The VE and R were significantly (P < 0.05) greater at FCC + 20% compared to FCC - 20% at the 5th and 15th min but not at the 30th min. Nevertheless, no significant effect of cadence was observed in HR and VO2. These results suggest that, during high intensity exercise such as that encountered during a time-trial race, well-trained triathletes can easily adapt to the changes in cadence allowed by the classical gear ratios used in practice.

Adult↗
PubMed2001

Isokinetic strength and anaerobic power of elite, subelite and amateur French soccer players.

Information about the influence of different practice levels on physical characteristics of a large number of soccer players is lacking. Therefore we assessed muscular strength and anaerobic power of elite, subelite and amateur soccer players to clarify what parameters distinguish the top players from the less successful. We tested 95 soccer players from the French first division (elite), second division (subelite), and amateurs and determined the isokinetic strength of the knee extensor and flexor muscles at angular velocities from -120 degrees x s(-1) to 300 degrees x s(-1). Vertical jump, 10 m sprint, 30 m sprint and maximum ball speed during shooting were also measured. The elite players had higher knee flexor torque than the amateurs at all angular velocities (p < 0.05), except at 300 degrees x s(-1). The hamstring/quadriceps ratios proposed with two different methods were significantly lower in the amateur group than in the elite group (p < 0.05), except at 300 degrees x s(-1). Maximum ball speed during shooting and speed over 30 m sprint were not different between elite, subelite, and amateur players while speed over a 10 m sprint was significantly slower in amateur players and faster in the elite group (p < 0.05). Although performance in soccer is not determined only by measurable variables, professional players differ from amateurs in terms of knee flexor muscle strength and short-distance sprinting speed. Based on these findings we conclude that hamstring strength is extremely important in soccer players for joint stabilization during various tasks, notably in eccentric action. Further, short-sprinting performance may mirror actual game situations at high level and could be an important determinant of match-winning actions.

Adult↗