Effectiveness of the Copenhagen adduction modified position stage 1: EMG measurements and hand-held dynamometer analysis in young and healthy men.

OBJECTIVES: To verify the effectiveness of the use of a modified position of the Copenhagen Adduction (CA) stage 1 compared to the original position. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: 31 healthy men aged 23.7 ± 1.9 years with no recent or chronic general pathology. MAIN OUTCOME MEASURES: Differences between EMG amplitudes for the adductor longus (AL), rectus femoris (RF) and semi tendinous (ST) during dynamic contractions and adductor maximal isometric voluntary contraction (MIVC) force values between CA stage 1 standard and modified positions were assessed with either Wilcoxon or paired t-test. RESULTS: No significant differences were observed for EMG amplitudes of the AL (p-value = 0.724) and for the RF muscle (p-value = 0.337) and for the adductor force (p-value = 0.361) between the two positions. A significant difference was obtained for the ST (p-value<0.001) mainly explained by the adapted position of the non-dominant leg which unlocked the hip joint and generated less muscle activity in the hamstrings. CONCLUSIONS: Muscle activity of the AL muscle and adductor force being similar in both positions, the CA stage 1 modified position could be of interest for rehabilitation after adductor injury or strengthening of the adductors in elite athletes.

Sex-related differences in motor control strategies during isometric contractions in the Sorensen test posture with different external loading.

BACKGROUND: There is a sex-related difference in strength and endurance in trunk muscles: males have more strength while females have more endurance. OBJECTIVE: Investigate sex-related differences in motor control strategies in back muscles during isometric contractions (IC) in the Sorensen test posture. METHODS: Thirty-six healthy and young volunteers performed different tasks: three maximal voluntary contraction (MVC) tests recorded with a bio-feedback force sensor, and followed by five loaded IC (LIC) tests using bodyweight and loads of 0 to 8 kg with a 2-kg step. Surface electromyography was used to measure the activity of bilateral lumbar paravertebral (LP) and quadratus lumborum (QL) muscles. RESULTS: Sex-related and load-related differences in EMG amplitudes were highlighted during LIC tests. Females showed significantly (p-value = 0.02) greater EMG amplitude for the highest load (8 kg) than males. Besides, significant differences between low (2 and 4 kg) and high (6 and 8 kg) loads for both LP and QL muscles and for both sexes were observed. Finally, for MVC tests, males produced significantly (p-value = 1.02e-4) greater strength during MVC tests (4.25 ± 1.37 N/kg vs 2.60 ± 0.78 N/kg). CONCLUSION: The results were clinically relevant to bring attention to load strategy during rehabilitation, particularly in females who seemed to recruit the QL muscle more.