The Effect of Complex Training on Muscle Architecture in Rugby League Players

Purpose: To compare the effects of variable-resistance complex training (VRCT) versus traditional complex training (TCT) on muscle architecture in rugby league players during a 6-week mesocycle. Methods: Twenty-four rugby league players competing in the British University & Colleges Sport (BUCS) Premier North Division were randomized to VRCT (n = 8), TCT (n = 8), or control (n = 8). Experimental groups completed a 6-week lower-body complex training intervention (2x/wk), which involved alternating high-load resistance exercise with plyometric exercise in the same session. The VRCT group performed resistance exercises at 70% of 1-repetition maximum (1RM) + 0% to 23% of 1RM from band resistance with a 90-second intracontrast rest interval, whereas the TCT group performed resistance exercise at 93% of 1RM with a 4-minute intracontrast rest interval. Muscle thickness (MT), pennation angle, and fascicle length (L-f) were assessed for the vastus lateralis (VL) and gastrocnemius medialis using ultrasound imaging. Results: Both TCT and VRCT groups significantly improved VL MT and VL L-f compared with control (all P <.05). Standardized within-group changes in MT and L-f (Cohen d(av) +/- 95% CI) were moderate for TCT (d(av) = 0.91 +/- 1.0; d(av) = 1.1 +/- 1.1) and unclear for VRCT (d(av) = 0.44 +/- 0.99; d(av) = 0.47 +/- 0.99), respectively. Differences in change scores between TCT and VRCT were unclear. Conclusions: VRCT and TCT can be utilized during the competitive season to induce favorable MT and L-f muscle architecture adaptations for the VL. TCT may induce greater muscle architecture adaptations of the VL, whereas VRCT may be of more practical value given the shorter intracontrast rest interval between resistance and plyometric exercises.