Abstract
The aim of the study was to investigate the relationships between vastus lateralis muscle fiber length and fiber type composition in individuals with minimal exposure to systematic resistance/power training. In sixty female physical education students (age: 21.03 ± 2.1 years, body weight: 59.8 ± 9.7 kg, body height: 166.2 ± 6.5 cm), with no experience in systematic training, lean body mass, VL muscle architecture and fiber composition type, countermovement jumping (CMJ) performance, and isometric leg press rate of force development were evaluated. Data were analyzed for all participants, as well as two equally numbered groups assigned according to their maximum countermovement jumping power (High-Power or Low-Power group). Significant but low correlations were found between type II muscle fiber percentage and fascicle length (N = 60, p < 0.05). Significant correlations were found between type IIa and IIx muscle fiber percentage cross-sectional area (%CSA) and fascicle length (N = 60; r = 0.321, and r = 0.378; respectively, p < 0.05). These correlations were higher for the High-Power group (r = 0.499, and r = 0.522; respectively, p < 0.05), and lower, and nonsignificant, for the Low-Power group. The best predictor of strength/power performance was the lean body mass of the lower extremities (r = 0.389–0.645, p < 0.05). These results suggest that in females with minimal exposure to systematic training, fascicle length may be weakly linked with type II fiber areas, only in females with high-power profiles.
Highlights
Muscle power depends on several biological attributes, including muscle fiber composition and muscle fascicle length
Significant differences were found between participants of the High- and Low-Power groups, for total and lower extremity lean body mass (LBM), vastus lateralis (VL) thickness, fascicle length, and fiber type composition (η2 : 0.119–0.239; p < 0.01; Table 1)
When all participants were considered as one group (N = 60), significant correlations were found between lower extremity LBM, VL thickness–pennation angle and countermovement jumping (CMJ) power, MIF, RFD after 150 ms from the onset of muscle contraction, and half squat maximum strength (r: 0.267–0.595; p < 0.01; Table 2 and Supplementary Material Table S1)
Summary
Muscle power depends on several biological attributes, including muscle fiber composition and muscle fascicle length. An increased proportion and size of fast contracting type. II muscle fibers has been linked with higher power performance [1,2], due to the intrinsic contractile characteristics of these muscle fibers [3]. Muscle and tendon morphology and tendon compliance have a significant contribution to muscle strength and power. Tendon stiffness is associated with increased power performance [4]. Muscle thickness is closely linked with the size and anatomical cross-sectional area of muscles, and it can be used to evaluate the size and/or the training induced hypertrophy of muscle [5]
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