Participants perform a single supervised session of power training on a pneumatic leg press, consisting of 4 sets. During the exercise, movement speed is continuously monitored. In this arm, the exercise set will be stopped when movement speed decreases by 10% compared with the fastest repetition, which corresponds to a low level of fatigue (small amount of repetitions).

Participants perform a single supervised session of power training on a pneumatic leg press, consisting of 4 sets. During the exercise, movement speed is continuously monitored. In this arm, the exercise set will be stopped when movement speed decreases by 30% compared with the fastest repetition, which corresponds to a moderate level of fatigue (more repetitions, performed closer to muscle failure).

Participants perform a single supervised session of power training on a pneumatic leg press. In this arm, the exercise is organized into 4 cluster sets. A cluster set consists of small groups of repetitions separated by short rest periods within the set. Participants will perform clusters of 3-4 repetitions with 20 seconds of rest between clusters.

During the exercise, movement speed is continuously monitored. Each cluster will be performed within the range of 10% velocity loss compared with the fastest repetition, which corresponds to a low level of fatigue. Clusters will continue until the total number of repetitions matches the training volume (amount of total repetitions) reached in the 30% velocity loss condition.

This design allows participants to complete a similar total training volume as in the moderate fatigue condition, while maintaining lower fatigue, enabling researchers to separate the effects of exercise volume from the effects of fatigue.

Participants perform supervised power-training exercises on a pneumatic leg press. The sessions are designed to test different levels of fatigue:

1. In one session, participants stop the exercise set when their movement speed drops by 10%.
2. In another session, they stop when their movement speed drops by 30%.
3. In a third session, participants perform the same total work as the 30% session, but stop at 10% velocity loss.

Each session lasts a single training bout (4 sets), and is separated from the next session by one week. During and after each session, researchers measure immediate and post 24h responses to the training in neuromuscular function, physiological responses (e.g., blood markers, muscle oxygenation), functional performance, perceived effort, and muscle soreness.

This intervention is different from other exercise studies because it focuses on how varying fatigue levels during power training affect immediate performance and recovery in healthy older adults.

Maximum voluntary contraction (MVC) will be assessed to determine the maximum force-generating capacity of the leg extensors using an isokinetic dynamometer (Humac Norm). Simultaneously, muscle activity will be recorded using surface electromyography (EMG; Delsys EMG system).

Primary outcome metric: Peak torque (Nm) obtained from three maximal isometric trials recorded on the dynamometer, combined with EMG amplitude (µV) to quantify muscle activation. Interpretation: Higher torque values indicate greater knee extensor strength. EMG amplitude reflects the level of muscle activation during maximal voluntary effort.

Interpretation: Higher force values indicate greater leg muscle strength. EMG values indicate the level of muscle activation during the maximal effort.

Rate of torque development (RTD) will be assessed to determine how quickly participants can generate torque with their leg extensors. This will be measured using an isokinetic dynamometer (Humac Norm), which records joint torque, alongside surface electromyography (EMG; Delsys EMG system), which measures muscle activation. This parameter provides insight into neuromuscular responses to different levels of power training-induced fatigue.

Metric: Peak rate of torque development (Nm/s) calculated from three maximal trials, together with EMG amplitude (µV). RTD will be calculated as the slope of the torque-time curve over a specified time interval (e.g., 0-100ms, 100-200 ms).