Résumé
Dupeyron, A, Hertzog, M, Micallef, JP, and Perrey, S. Does an abdominal strengthening program influence leg stiffness during hopping tasks? J Strength Cond Res 27(8): 2129-2133, 2013According to the spring mass model, leg stiffness (characterized by the measure of k(leg)) behavior is theoretically dependent on lower limb joint and trunk stiffness. Yet, the influence of the trunk as a possible regulator of k(leg) is unknown. This study investigated the influence of abdominal training on k(leg) during hopping tasks. Fourteen young male (age 18.5 +/- 0.5 years, height 176.4 +/- 4.3 cm, weight 69.9 +/- 5.5 kg) soccer players (national level) participated in the study. Two groups (bracing B group, n = 7 vs. hollowing transversus abdominis [TrA] H group, n = 7) with identical training load followed an 8-week training program for abdominal strengthening. Contact time, flight time, jump height, and k(leg) were measured with an OptoJump system during a standardized hopping task (2.2 Hz) before and after the training program. Results for each group showed that only the H group increased k(leg) after the intervention (+15.7%) compared with the B group (+5.9%). This difference was explained by a 6.5% decrease in contact time in H group (-2.4% in B) with increased flight time (+8.8% in H vs. +2% in B). A large increase was found for jump height in H (+16.9%) compared with B group (+4.4%). This study showed that TrA strengthening improves leg stiffness in hopping tasks. Our findings suggest the potential role of abdominal muscles in controlling lumbopelvic stiffness as a part of the spring according to the spring mass model, and thus influencing k(leg) by reduced ground contact phase.