Fatigue profoundly affects swimming performance, impacting muscle engagement and stroke efficiency over time. This study used wireless surface electromyography (sEMG) and accelerometers to analyze how different muscle groups respond to fatigue during a 1,000-meter freestyle swim. Two main measures—stroke duration and muscle activation duration—revealed significant insights into fatigue’s effects on swimming dynamics. Using 14 sEMG (MiniX) produced by Cometa srl the researchers were able to register consistent and reliable data underwater. The sensors, being lightweight and wireless, don’t impact the performance and don’t disturb the natural movement of the subjects, ensuring high-quality acquisitions.
Stroke Duration as a Fatigue Indicator
Stroke duration, recorded with accelerometers, served as a direct measure of swimming efficiency:
- Increased Stroke Duration: Some swimmers showed increased stroke duration due to fatigue, signaling a decline in efficiency as stroke cadence slowed. This change typically indicated reduced speed and propulsive power.
- Decreased Stroke Duration: Interestingly, some subjects demonstrated a reduction in stroke duration, suggesting either enhanced fatigue management or compensatory endurance. This swimmer maintained a steady pace despite fatigue, hinting at individual adaptability.
Muscle Activation Duration and Fatigue Adaptation
Wireless sEMG tracked muscle-specific responses to fatigue, providing information on how fatigue affects muscle activation:
- Increased Activation in Key Muscles: Major propulsive muscles, like the Biceps Brachii and Pectoralis Major, showed increased activation time under fatigue. For example, the Biceps Brachii’s activation of a participant rose by over 14%, reflecting compensatory muscle engagement to sustain power output.
- Reduced Activation in Other Muscles: Conversely, the Triceps Brachii in some subjects showed reduced activation duration, possibly indicating an inability to maintain sustained contractions under fatigue. Such changes suggest that different muscles adapt uniquely to prolonged stress.
Variability in Fatigue Response
The study highlighted distinct individual responses to fatigue. For instance, some demonstrated an increase in activation of the Biceps Brachii (up to 80%) and Latissimus Dorsi (53.9%) to counter fatigue, while other muscles, like the Triceps Brachii, showed minimal change. This selective adaptation underlines the diverse muscle fatigue responses and suggests that certain muscle groups can sustain effort under prolonged use better than others.
Applications for Training and Injury Prevention
This research emphasizes the need for targeted training to increase endurance in propulsive muscles, focusing on fatigue resistance. Stabilizing muscles may also benefit from training to handle prolonged activity during competitive distances. By tailoring training to address fatigue’s impact on each muscle, coaches can help athletes sustain technique under fatigue, thereby improving performance and reducing injury risk.
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