[Influence of age and physical activity on isokinetic characteristics of hamstring and quadriceps muscles of young gymnasts and soccer players]

ISOKINETIC PROFILES AND REFERENCE VALUES OF PROFESSIONAL SOCCER PLAYERS

ABSTRACT Introduction: Isokinetics is a tool commonly used in professional soccer. There is ongoing debate among researchers as to the isokinetic reference values a player should have. Objectives: To determine the absolute peak torque (PT) and average work of professional soccer players in relation to their positions on the field, and to establish the reference values for these variables. Methods: Purposeful sampling was used to select 289 professional soccer players. The sample included 32 goalkeepers, 100 defenders, 98 midfielders, and 59 strikers. The participants were measured preseason. The players were asked to perform a 10-minute warm-up on an exercise bike, and then to perform 5 repetitions at low speed, 10 at medium speed, and 25 at high speed, with 30 to 40-s of rest between each set of repetitions. The contraction method was concentric-concentric in a dynamometer Isomed 2000. Results: The average age, weight, and height of the players was 21.9 years, 74.3 kilograms, and 1.8 meters, respectively. The goalkeepers presented higher PT at the 3 measured speeds, and the higher average work at 180°/s and 240°/s in relation to defenders and midfielders. The strikers presented higher average work at 240°/s in relation to midfielders, and higher PT in relation to the defenders and midfielders. Absolute values were shown and reference values were established. Conclusions: The goalkeepers and strikers were the players that showed the greatest differences in their favor in relation to the other positions. The peak torque values and average work were described in relation to the player's position on the field. This study resulted in the creation of a tool for health professionals working with professional soccer players, providing reference values for these players in relation to their position on the field that can be used as benchmarks, by health professionals, to optimize soccer players’ performance. Level of evidence II, Prospective comparative study.

The relationship between muscle strength and physiological age: a cross-sectional study in boys aged from 11 to 15

OBJECTIVE

To investigate the relationships between isokinetic knee flexor and extensor muscle strength and physiological and chronological age in young soccer players.

MATERIAL AND METHODS

Seventy-nine young, healthy, male soccer players (mean+/-standard deviation age: 12.78+/-2.88, range: 11 to 15) underwent a clinical examination (age, weight, height, body mass index and Tanner puberty stage) and an evaluation of bilateral knee flexor and extensor muscle strength on an isokinetic dynamometer. Participation in the study was voluntary.

RESULTS

The peak torque increased progressively (by 50%) between the ages of 11 and 15 and most significantly between 12 to 14. The knee flexor/extensor ratios only decreased significantly between 14 and 15 years of age. Puberty stage was the most important determinant of the peak torque level (ahead of chronological age, weight and height) for all angular velocities (p<0.0001). Muscle strength increased significantly between Tanner stages 1 and 5, with the greatest increase between stages 2 and 4.

CONCLUSION

The present study showed that isokinetic muscle strength increases most between 12 and 13 years of age and between Tanner stages 2 and 3. There was strong correlation between muscle strength and physiological age.

[Isokinetic, functional and proprioceptive assessment of soccer players two years after surgical reconstruction of the anterior cruciate ligament of the knee]

Injuries to the anterior cruciate ligament (ACL) of the knee are common in sport and are treated routinely in the world of sports medicine. In order to resume competitive sport in safety, it is important to know the actual level of performance achieved by the operated leg some time after the ligament repair.

OBJECTIVES

The objective of this work was to evaluate the recovery of the operated leg in Tunisian sportsmen two years after surgery by using isokinetic testing (60 degrees s(-1)), the one-leg hop distance test (i.e. a functional activity that one often finds in sport) and proprioceptive assessment. A secondary objective was to detect any possible correlations between the various outcomes.

MATERIALS AND METHOD

The ACL group was composed of 26 top-level Tunisian footballers having undergone ACL ligament repair. Two years after surgery, the following assessments were performed: an isokinetic test with an angular velocity of 60 degrees s(-1), a proprioceptive assessment in both active and passive modes and the functional one-leg hop distance test.

RESULTS

Our investigations confirmed a muscle deficit of 16% in the hamstring muscles of the injured leg. In both active and passive modes, normal proprioception is observed at a flexion of 60 degrees and in total extension but not in a mid-way position. The performance level of the operated leg (in terms of distance) had an average symmetry value of 93.40+/-2.7%.

CONCLUSION

Playing football appears to influence the isokinetic strength profile in sportsmen after ACL repair. The repair procedure leads to bilateral proprioceptive disruption at 15 degrees of knee flexion, on average.

[Isokinetic profile of knee flexors and extensors in a population of rugby players]

OBJECTIVE

We aimed to assess the isokinetic profile of the flexor and extensor muscles of the knee within a population of rugby players.

METHODS AND POPULATION

This was a descriptive study. The rugby players underwent bilateral isokinetic assessment of knee flexion and extension on a CON-TREX MJ isokinetic dynamometer functioning at four angular frequencies - 90, 120, 180 and 240 degrees/s - in a concentric manner. The isokinetic parameters were peak torque, mean power, and mean work in relation to weight and femoral bicep: quadriceps ratio. The population included 16 "Federal 1" (semi-professional) rugby players with mean age 25 years (range 20-33 years). The players were divided into two groups: "forward" players (props, hookers, second line, third line) and "back" players (scrum, inside, center, wing, tail).

RESULTS

The values of the isokinetic parameters did not reveal use of a preferred limb. Consequently, peak torque and mean power were higher in forward players than back players, whereas back players showed a higher relative power throughout the isokinetic test.

CONCLUSION

Among rugby players, forward and back players showed differences in several isokinetic parameters. Accurate knowledge of the equilibrium between the knee's effector muscles is important for stability of the joint, to not only minimize articular accidents but also pinpoint force imbalances, thereby preventing muscular lesions during the sports season.