Sílvia Ribeiro Santos Araújo

Analysis of lower limb asymmetries by isokinetic and vertical jump tests in soccer players.

Abstract Menzel, H-J, Chagas, MH, Szmuchrowski, LA, Araujo, SRS, de Andrade, AGP, and Resende de Jesus-Moraleida, F. Analysis of lower limb asymmetries by isokinetic and vertical jump tests in soccer players. J Strength Cond Res 27(5): 1370–1377, 2013—Assessment of lower extremity bilateral asymmetries in soccer players is important for both injury prevention and performance. The purpose of this investigation was to compare isokinetic knee extensor assessment of asymmetry with a more specific countermovement jump (CMJ). Forty-six Brazilian male professional soccer players participated in this study. The maximal power, maximal force and impulse were determined during CMJ and the total work and peak torque at 60, 180, and 300°·s−1 during isokinetic leg extension, separately for each leg. Factor analysis was performed for all investigated variables, and the diagnostic concordance between different criteria was analyzed by McNemar’s &khgr;2 test. The factor analysis showed that the isokinetic and CMJ tests were widely independent methods for the assessment of bilateral differences. Concordance of the diagnostic information could only be found between the maximal force during CMJ and the total work and peak torque at 180 and 300°·s−1 during isokinetic leg extension. Impulse and maximal power during CMJ on a double force platform appear to be appropriate additional variables for the identification of bilateral differences. Therefore, it might be pertinent to perform, in addition to isokinetic assessment, a vertical jump test on a force platform to assure widespread and reliable diagnostic information.

USEFULNESS OF THE JUMP-AND-REACH TEST IN ASSESSMENT OF VERTICAL JUMP PERFORMANCE

The objective was to estimate the reliability and criterion-related validity of the Jump-and-Reach Test for the assessment of squat, countermovement, and drop jump performance of 32 male Brazilian professional volleyball players. Performance of squat, countermovement, and drop jumps with different dropping heights was assessed on the Jump-and-Reach Test and the measurement of flight time, then compared across different jump trials. The very high reliability coefficients of both assessment methods and the lower correlation coefficients between scores on the assessments indicate a very high consistency of each method but only moderate covariation, which means that they measure partly different items. As a consequence, the Jump-and-Reach Test has good ecological validity in situations when reaching height during the flight phase is critical for performance (e.g., basketball and volleyball) but only limited accuracy for the assessment of vertical impulse production with different jump techniques and conditions.

Viscoelastic stress relaxation in the hamstrings before and after a 10-week stretching program.

We investigated the viscoelastic stress relaxation response before and after a 10‐week hamstrings static stretch program. Methods: The maximal range of motion (ROMmax) and maximal torque (Torquemax) were assessed before and after a 10‐week stretching program. Six 30‐s static stretches at a predetermined torque were performed, and the relative change in stress relaxation was examined. Results: ROMmax and Torquemax increased by 53% and 82%, respectively (P < 0.001). The relative stress relaxation (RSR) decreased significantly for repetition 1 when comparing the pretest (25%) and posttest (21%) values (P = 0.003). A significant decrease was also observed for repetitions 2 and 3 (P < 0.014), with no significant difference in repetitions 4–6 (P > 0.056). Conclusions: Individuals who participated in a 10‐week hamstrings passive–static stretch program had a reduced RSR response. A higher stretch intensity or longer duration may be necessary to achieve RSRs similar to those reported before the stretch program. Muscle Nerve, 2015 Muscle Nerve 51:761–764, 2015

TEST-retest reliability of kinetic variables measured on campus board in sport climbers

Abstract Sport climbers frequently use campus board (CB) to improve their upper limb strength under similar conditions of high-difficulty sport climbing routes. The objective of this study was to assess the test-retest reliability of peak force and impulse measured using a CB instrumented with two load cells on starting holds. The same evaluator examined 22 climbers on two days with 48 h between the assessments. The participants performed five concentric lunges (CL) and five lunges with stretch-shortening cycle with 1 min intervals between repetitions and 10 min between exercises. All variables were associated with significant intraclass correlation coefficient (ICC) values (p = 0.001), and none variable showed systematic errors (p > 0.05). Peak force ICC was higher than 0.88, and the standard error of measurement (SEM%) was less than 5%. Impulse ICC for the CL was greater than 0.90, and the SEM% was less than 14%. We conclude that the kinetic variables measured using the CB were reliable. The ability of the hands to maintain contact with the holds (peak force) and the abilities of the arms and shoulders vertically move the centre of mass (impulse) should be taken into account by coaches on CB training prescription as well for further research.

IMPACTO DO NÍVEL COMPETITIVO E DA FAIXA ETÁRIA SOBRE FORÇA E ASSIMETRIA DE FUTEBOLISTAS JOVENS

Rev Bras Med Esporte – Vol. 24, No 5 – Set/Out, 2018 ABSTRACT Introduction: Muscular strength is an essential capacity for soccer players; however, the profile of this capacity has not yet been clearly established in young players. Objective: To compare muscular strength performance in the countermovement jump (CMJ) task and the presence of lower limb asymmetry among soccer athletes of the under 15 (U15), under 17 (U17) and under 20 (U20) categories, and between two teams of different competitive levels. Methods: One hundred and fifty one young soccer players of three different categories (U15, U17 and U20) from two teams in the Brazilian first and second divisions performed six vertical jumps in a system of two force plates. Ground reaction force (GRF) was used to calculate jump height and to obtain the variables Peak force (FMAX), Impulse (I) and Peak power (PMAX) with regard to body mass and the respective asymmetry values. Results: No differences were found in the performance and asymmetry variable between the categories (Jump height: p=0.23; FMAX: p=0.15; I: p=0.11; PMAX: p=0.32; FMAX asymmetry: p=0.21; I asymmetry: p=0.58; PMAX asymmetry: p=0.58). The first division club had higher muscle strength and asymmetry values than the second division club (Jump height: p<0.01; I: p<0.01; PMAX: p<0.01; FMAX asymmetry: p<0.01; I asymmetry: p<0.01; PMAX asymmetry: p<0.01), except for FMAX (p=0.63). No variable had an interaction effect (club x category). Conclusion: As categories progress, jump height, relative I, PMAX and FMAX values and their respective asymmetries are stable. The asymmetry and strength performance of the first division club were higher than that of the second division club, except for FMAX, indicating that the competitive level may influence strength performance and the development of asymmetry. Level of Evidence II; Diagnostic study – Investigating a diagnostic test.