Flywheel resistance training promotes unique muscle architectural and performance-related adaptations in young adults

Abstract

The purpose of this study was to examine the skeletal muscle hypertrophic, architectural, and performance-related adaptations in response to volume-matched, total-body flywheel versus traditional resistance training in a randomized, non-exercise controlled study in physically active young adults. Thirty-one healthy young adults (24 ± 3 y) were randomized to 10 weeks of traditional resistance training (TRT; n = 7F/5M), flywheel training (FWRT; n = 7F/4M), or a habitual activity control (CON; n = 5F/3M). Maximal voluntary isometric torque (MVIT), one repetition-maximum (1RM) for the free weight squat and bench press, three repetition work maximum (3W_max) for the flywheel squat and bench press, countermovement jump height, and broad jump distance, as well as site-specific muscle hypertrophy, fascicle length (FL), and pennation angle, were measured. Both TRT and FWRT increased MVIT (p ≤ 0.021) and FFM (p ≤ 0.032) compared to CON. However, TRT promoted superior improvements in free weight squat and bench 1RM (p < 0.001), and FWRT improved flywheel 3W_max squat and bench (p < 0.001). FWRT increased the FL and cross-sectional area of the distal VL, countermovement jump height, and broad jump distance (p ≤ 0.048), whereas TRT increased the pennation angle and cross-sectional area of the proximal VL. Therefore, 10 weeks of volume-matched, total-body traditional, and flywheel resistance training similarly increased maximal isometric strength and fat-free mass. However, FWRT promoted unique skeletal muscle architectural adaptations that likely contributed to region-specific VL hypertrophy and jump performance improvements. Thus, FWRT provides a novel training stimulus that promotes architectural adaptations that support improved athletic performance in a manner that is not provided by traditional resistance exercise training.

Keywords: countermovement jump; isoinertial exercise; muscle hypertrophy; muscle plasticity; resistance exercise.

FIGURE 1

Data from training sessions held during the 10‐week intervention period for the traditional resistance training (TRT) and flywheel resistance training (FWRT) groups. Panel A: Average weekly weight lifted, expressed in kg for TRT and kg·m² for FWRT; Panel B: Total (left) and average (right) weekly volume load; Panel C: Total (left) and average (right) weekly readiness, which was asked before every training session on a 0–10 scale, with 10 indicating maximal self‐perceived readiness; Panel D: Total (left) and average (right) weekly session rating of perceived exertion (RPE), which was asked immediately following each training session on a 0–10 scale with 10 representing maximal self‐perceived session exertion. Panel E: Total (left) and average (right) weekly reps completed. *, between‐group difference within the corresponding week (p < 0.05).

FIGURE 2

Group changes in individual muscle size measured using ultrasonography before and after 10 weeks of traditional resistance training (TRT), flywheel resistance training (FWRT), or a control period (CON); * = p < 0.05 when comparing the pre‐ to post‐training within‐group changes between groups using a one‐way linear model; BB, biceps brachii; BF, biceps femoris; Gas, gastrocnemius; Lat, lateral; mCSA, muscle cross‐sectional area; Med, medial; RF, rectus femoris; TB, triceps brachii; VL_DIST, the distal portion of the vastus lateralis; VL_MID, the middle portion of the vastus lateralis; VL_PROX, the proximal portion of the vastus lateralis.

FIGURE 3

Group changes in fascicle length and pennation angle derived from ultrasonography before and after either 10 weeks of traditional resistance training (TRT), flywheel resistance training (FWRT), or a habitual activity, non‐exercise control period (CON); * = p < 0.05 when comparing the pre‐ to post‐training within‐group changes between groups using a one‐way linear model.

FIGURE 4

The multicomponent training distress scale was utilized to assess weekly levels of depression (Panel A), vigor (Panel B), physical symptoms (Panel C), sleep disturbances (Panel D), stress (Panel E), and fatigue (Panel F). *, significant group difference; &, significant difference in CON compared to Week 0; #, significant difference in EX compared to week 0.