Abstract
Research into flywheel (FW) resistance training and force–velocity–power (F–v–P) profiling has recently gained attention. Ground reaction force (GRF) and velocity (v) during FW squats can be predicted from shaft rotational data. Our study aimed to compare the inter-set reliability of GRF, v, and F–v–P relationship output variables calculated from force plates and linear encoder (presumed gold-standard) and rotary encoder data. Fifty participants performed two sets of FW squats at four inertias. Peak and mean concentric and eccentric GRF, v, and F–v–P outcomes from mean variables during the concentric phase of the squat were calculated. Good to excellent reliability was found for GRF and v (ICC > 0.85), regardless of the measure and the variable type. The F–v–P outcomes showed moderate to good reliability (ICC > 0.74). Inter-measure bias (p < 0.05) was found in the majority of GRF and v variables, as well as for all the calculated F–v–P outcomes (trivial to large TEs) with very large to perfect correlations for v (r 0.797–0.948), GRF (r 0.712–0.959), and, finally, F–v–P outcomes (ICC 0.737–0.943). Rotary encoder overestimated the force plates and linear encoder variables, and the differences were dependent on the level of inertia. Despite high reliability, FW device users should be aware of the discrepancy between the measures.
Highlights
Flywheel (FW) inertial resistance training has gained attention in recent years due to all the positive acute [1,2] and short-term [3] neuromuscular performance effects, and longterm effects derived from FW training interventions on strength, power (P), performancerelated variables [4,5,6,7,8,9,10,11], and clinical outcomes [12,13,14]
Average values and standard deviations of peak and mean ground reaction force (GRF) and v variables at four different inertias can be found in Appendix A and Appendix B
The main finding of our study is that GRF and v variables at different inertias and F–v–P relationship variables can be calculated from the rotational data of the FW shaft
Summary
Flywheel (FW) inertial resistance training has gained attention in recent years due to all the positive acute [1,2] and short-term [3] neuromuscular performance effects, and longterm effects derived from FW training interventions on strength, power (P), performancerelated variables [4,5,6,7,8,9,10,11], and clinical outcomes [12,13,14]. FW resistance exercise is independent of gravity when the exercise is performed in the horizontal plane rather than the vertical plane In the latter, the gravity acceleration of the body mass contributes to a common loading condition (e.g., squat). Recent studies of the FW squat have found near-perfect linear regression fits between incremental inertias and velocity (v) [16] and between ground reaction force (GRF) and v [17] under incremental inertial conditions. This is in agreement with weight-based exercises—squat jumps and countermovement jumps [18,19,20]. The applicability of training based on the change in F–v curve properties has been validated [21], but not by using FW loads
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