The aim of this study was to compare the isokinetic strength profile of a simulated arm stroke between junior, senior, and adult recreational swimmers using time-series statistical approaches. Thirty-five swimmers (junior n=8, senior n=12, recreational n=15) performed five maximal voluntary shoulder extension contractions at six angular velocities (60-300°·s*¹) on an isokinetic dynamometer. Torque signals were time-normalized to 0-100% of the movement cycle. Group differences were assessed using statistical parametric mapping (SPM), and functional principal component analysis (fPCA) was used to evaluate global waveform characteristics. SPM revealed significant between-group differences across angular velocities, predominantly between junior and senior swimmers, with differences primarily located in the early phase of the movement cycle. fPCA indicated that the first principal component (PC1) explained most of the variance and differed significantly between groups, whereas no significant group differences were observed in PC2. Multivariate analysis confirmed significant overall between-group differences across most angular velocities. Additional analyses using body-mass-normalized torque demonstrated that these differences persisted after accounting for body size and revealed significant differences between senior and recreational swimmers. These findings suggest that both maturation and long-term training exposure contribute to superior torque production, particularly during the early phase of the movement cycle, which may be associated with differences in neuromuscular capacity and rapid torque generation. The combined use of SPM and fPCA provided complementary insights into strength profiling, highlighting the value of time-series analyses for identifying phase-specific differences that are not captured by traditional discrete variables.
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