Gotta Go Fast: Intended Concentric Effort Produces Divergent Myoelectric Spectral Profiles During Fatiguing, Load-Equated Resistance Exercise

Abstract

Benitez, B, Kwak, M, Succi, PJ, Mitchinson, CJ, Snell, ER, and Bergstrom, HC. Gotta go fast: Intended concentric effort produces divergent myoelectric spectral profiles during fatiguing, load-equated resistance exercise. J Strength Cond Res XX(X): 000–000, 2026—The aim of this study was to examine how intended concentric velocity, that is, the volitional effort applied to accelerate a load, influences the spectral characteristics of the surface electromyographic (sEMG) signal during fatiguing, load-equated resistance exercise. Twenty recreationally active adults (10 men and 10 women) performed unilateral leg extensions to task failure at 70% 1 repetition maximum under 2 within-participant conditions as follows: maximal intended concentric velocity ( V _max ) and 50% of individualized V _max (50% V _max ). Bipolar sEMG from the vastus lateralis was decomposed into 10 frequency bands using wavelet-based time-frequency analysis. Band-specific spectral intensities were modeled with a lognormal generalized linear mixed-effects model, and Lin's concordance correlation coefficient (ρc) was computed between condition-specific spectral profiles across pairwise time points. The mean propulsive concentric velocity and total repetitions to task failure were secondary outcomes. Significance was set at p ≤ 0.05. The 3-way interaction of condition × frequency × repetition was significant (χ ² (3) = 23.98, p < 0.001). Across the set, V _max redistributed spectral power bidirectionally, increasing the low bands while suppressing the high bands, whereas 50% V _max increased across the entire spectrum without high-frequency suppression. Despite these divergent profiles, the conditions converged at task failure (ρc = 0.98), and the convergence was asymmetric. The fatigued 50% V _max profile approximated the fresh V _max profile (ρc = 0.97) rather than the reverse (ρc = 0.74), indicating that submaximal effort approached the maximal-effort state as fatigue accumulated. The mean propulsive concentric velocity also declined 3.6 times more steeply under V _max despite similar repetitions. Intended concentric velocity appears to shape the spectral profile of muscle excitation under fixed loading.