## 2 Methods
### Procedures  
Participants completed a separate familiarization session prior to experimental testing to obtain anthropometric measurements (height, weight, and BMI) and to acclimate to the multi-joint eccentric dynamometer (Eccentron, BTE Technologies, Hanover, MD, USA). During this session, a maximal eccentric strength test was conducted to determine each participant's individualized 40% submaximal training load and this predetermined load was manually input into the Eccentron software for the subsequent exercise session. Descriptive statistics for maximal eccentric strength values are provided in Table 1. Following this, participants engaged in eccentric training at the 40% load for 3 min to simulate the protocol used during the subsequent experimental session.  
Experimental testing for each participant was conducted in a single session, scheduled at least 72 h after the familiarization session. To begin, electrode sites were shaved, cleansed with an alcohol swab, and prepared for placement of adhesive waterproof electrodes over the TA, GM, BF, and VL of the dominant leg (note the dominant leg was selected in accordance with common practice in the literature, as differences in muscle activation between dominant and non-dominant limbs are unlikely, given the absence of limb-related differences observed in our prior work using force-based Eccentron measurements [16]). Electrode placement followed the standardized guidelines of the Surface Electromyography for the Non-Invasive Assessment of Muscles (SENIAM) project [17]. The intrinsic foot muscles were not included in the EMG protocol due to practical electrode placement limitations and the study's focus on larger, extrinsic lower limb muscles primarily engaged by the Eccentron exercise movement. To minimize motion artifacts in the EMG signals, the electrodes were further secured with adhesive, hypoallergenic waterproof wrapping. Leg dominance was determined by asking participants which leg they would use to kick a ball.  
Prior to the eccentric exercise bout, participants completed a 4 min treadmill warm-up at a speed of 2.5 mph (Tandem Treadmill, AMTI, Watertown, MA, USA). This was followed by a 3 min eccentric exercise session on the Eccentron. Exercise intensity was standardized across participants at a 40% submaximal load, based on each individual's  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sex** & \(n\) & **Age (years)** & \begin{tabular}{c} **Height** \\ **(cm)** \\ \end{tabular} & \begin{tabular}{c} **Weight** \\ **(kg)** \\ \end{tabular} & \begin{tabular}{c} **BMI** \\ **(kg\(\cdot\)m\({}^{2}\))** \\ \end{tabular} & \begin{tabular}{c} **Max ECC** \\ **(_n_)** \\ \end{tabular} \\ \hline Female & 8 & 19.9 (2.0) & 174.9 (4.8) & 76.7 (12.1) & 25.1 (3.7) & \
\begin{tabular}{c} 1505.2 \\ (447.2) \\ \end{tabular} \\ Male & 10 & 21.6 (1.9) & 167.2 (31.8) & 74.5 (10.6) & 23.5 (3.2) &
\begin{tabular}{c} 1846.9 \\ (540.0) \\ \end{tabular} \\ \hline \hline \end{tabular} BMI = body mass index; Max ECC = maximal multi-joint lower body eccentric strength. Data are presented as mean (SD).  
\end{table}
Table 1: Participant characteristics.  
maximal eccentric strength. The dynamometer velocity was set to 23 cycles per minute, representing a moderate speed consistent with velocities used in prior studies from our laboratory that have been shown to elicit substantial strength adaptations [3,4]. The seat position on the dynamometer was adjusted to ensure a knee joint angle of 30\({}^{\circ}\) at the most extended position, in accordance with the manufacturer's guidelines. During the 3 min eccentric exercise bout, muscle activity of the TA, GM, BF, and VL was recorded using a 16-channel surface EMG system (Cometa Mini Wave, Cometa SRL, Milan, Italy). Raw EMG signals were sampled at 2000 Hz, in accordance with established recommendations for high-fidelity electromyographic data acquisition [18].