Barbell Vs Flywheel Squat: Patellofemoral Joint Kinetics And Muscle Activity In Females

Previous literature has supported flywheel (FW) training with inducing muscular size and strength comparable to resistance training with free weights. However, it remains unclear how the biomechanical demands of these two training methods differ regarding factors related to load-dependent injury risk. PURPOSE: With a growing number of female astronauts, this study aimed to compare patellofemoral joint kinetics and muscle activation when squatting to full depth on the barbell back squat (BBS) and a gravity-independent FW device utilizing technology to be deployed in future long-term space missions. METHODS: Twenty recreationally trained females (22.3 ± 2.7 yrs, 1.6 ± 0.1 m, 59.8 ± 6.8 kg) with at least two years of experience in BBS training participated in this study. Participants attended two sessions: 1) one repetition-maximum testing (1RM) and FW familiarization and 2) experimental session consisting of a set of seven repetitions at 83% of their 1RM on the BBS and a set of seven maximal repetitions on the FW device with an inertial load of 0.100 kg·m2 in randomized order. Three-dimensional motion capture, force platforms, and electromyography were used to calculate peak knee extensor moments (pKEM) and assess muscle activation on the participants' dominant limb. Patellofemoral joint reaction forces (PFJRF) and patellofemoral joint stresses (PFJS) were calculated from biomechanical models incorporating joint moments and angles. Paired t-tests were conducted with a significance set at p ≤ 0.05. RESULTS: The BBS was associated with greater pKEM, PFJRF, and PFJS (Table 1). Mean muscle activity averaged over the set was also greater in the BBS; apart from the rectus femoris, vastus medialis, and tibialis anterior (Table 1). CONCLUSION: Although squatting on the FW device demands less loading on the patellofemoral joint, overall muscle recruitment was greater in the BBS. The data suggests that FW training may reduce the risk of patellofemoral related injury. Table 1. - Patellofemoral Joint kinetics and muscular activity. Means ± standard deviation. Flywheel Squat Barbell Back Squat p d pKEM (Nm/kg) 1.94 ± 0.06 2.14 ± 0.36 0.004* 0.738 PFJRF (BW) 26.55 ± 4.49 30.74 ± 2.63 0.001* 0.855 PFJS (MPa) 29.98 ± 5.55 34.89 ± 5.59 0.001* 0.906 Rectus Femoris (%MVIC) 73.96 ± 30.18 72.32 ± 38.12 0.771 0.066 Vastus Lateralis (%MVIC) 62.76 ± 23.63 68.45 ± 28.59 0.015* 0.595 Vastus Medialis (%MVIC) 85.51 ± 40.41 92.84 ± 51.36 0.107 0.379 Bicep Femoris (%MVIC) 10.18 ± 5.83 14.82 ± 5.38 <0.001* 1.206 Gluteus Maximus (%MVIC) 15.93 ± 10.80 20.60 ± 11.51 0.024* 0.549 Gluteus Medius (%MVIC) 10.57 ± 6.23 13.32 ± 4.46 0.011* 0.631 Gastrocnemius Lateralis (%MVIC) 20.08 ± 12.40 23.17 ± 12.69 0.028* 0.531 Gastrocnemius Medialis (%MVIC) 12.55 ± 9.28 15.03 ± 10.84 0.024* 0.549 Tibialis Anterior (%MVIC) 26.38 ± 13.65 20.82 ± 9.67 0.004* 0.726