Compensatory motor strategies and changes in muscle activity during prolonged alpine skiing: a field-based single-subject case study

Abstract

Alpine skiing imposes substantial neuromuscular and physiological demands due to repeated eccentric and concentric muscle contractions under high mechanical loads. Previous research has examined fatigue-related changes in muscle activity during skiing, yet most studies have relied on short sampling durations, often analyzing only a few turns or a single run. As a result, little is known about changes in neuromuscular responses under cumulative physical load over multiple consecutive days. Therefore, the purpose of this study was to examine changes in muscle activation, compensatory neuromuscular strategies, and performance changes over three consecutive days of alpine skiing in an elite skier. Using surface electromyography (sEMG), heart rate (HR), and ratings of perceived exertion (RPE), this field-based single-subject case study aimed to explore neuromuscular responses to cumulative internal load. A 27-year-old elite female skier performed on-snow standardized measurement protocol across three consecutive days. Each day included two measurement runs and six free runs: measurement run 1, six free-skiing runs to induce internal load, and measurement run 2. sEMG data were collected from seven muscles and analyzed using root mean square (RMS) amplitude. HR and RPE were measured post-run to monitor physiological and perceptual load. EMG data were analyzed using repeated-measures ANOVA with factors Time (Run 1 vs. Run 2) and Day (1-3), conducted separately for each muscle and leg (outside vs. inside). Significant main or interaction effects were followed by Tukey's post hoc tests (p < .05). Paired t-test (p < .01) was used to analyze performance changes. HR and RPE increased within each day, with elevated RPE at baseline on Day 3. EMG activation showed a decrease in outside-leg muscles but increased activation in inside-leg muscles, suggesting a shift in neuromuscular activity. Despite these changes, turn time remained consistent. This implies preserved performance via compensatory neuromuscular strategies. These results suggest that increased internal load may trigger flexible motor adaptations to maintain task performance under cumulative load. Understanding these adaptation patterns is critical for evaluating performance capacity and injury risk in elite athletes.