The goal of this clinical trial is to learn how older adults respond to power training when the level of fatigue during exercise is different. Power training means performing fast movements with moderate loads to improve strength, power and mobility. The main questions the study aims to answer are: * How does the level of fatigue during power training acutely affect strength, movement, and muscle function? * How does it affect recovery, muscle soreness, and how hard the exercise feels? Researchers will compare three power-training sessions with different fatigue levels to see which approach may be safest and most effective for older adults. Participants will be healthy older adults aged 65 to 85 years. Each participant will complete three supervised exercise sessions on a leg press machine. The sessions will take place about one week apart. During the study, participants will: * Perform power training on a pneumatic leg press machine * Complete strength and mobility tests before and after exercise * Provide small blood samples to measure body responses to exercise * Rate how hard the exercise feels * Report muscle soreness for up to two days after exercise The results may help researchers design safer and more effective power-training programs to improve strength, mobility, and recovery in older adults.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
NONE
Enrollment
42
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.
REVAL - Faculty of Rehabilitation Sciences
Diepenbeek, Flanders, Belgium
RECRUITINGMaximum Voluntary Contraction (MVC)
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.
Time frame: Measurements will be taken before exercise (baseline), 5 minutes after each training session, and 24 hours after each session.
Rate of Torque Development (RTD)
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).
Time frame: Measurements will be taken before exercise (baseline), 5 minutes after each training session, and 24 hours after each session.
Muscle Activity
Muscle activity will be assessed by recording the electrical signals of the leg muscles during the leg press exercise using surface electromyography (sEMG; Delsys EMG system). This method enables quantification of muscle activation and fatigue-related changes in neuromuscular function. Surface electrodes will be placed on three key thigh muscles: the vastus lateralis, vastus medialis, and biceps femoris. Metric: EMG amplitude (µV), derived from the recorded electrical signals, representing the level of muscle activation during exercise.
Time frame: Measurements will be taken before exercise (baseline), during exercise session (mean value across the full session), 5 minutes post exercise, and 24 hours post exercise (3 exercise sessions, 1 week apart)
Strength Training Data: Mean Movement Velocity
Mean concentric movement velocity (meter per second (m/s)) recorded during each leg press (exercise) repetition using the Keiser A400 Leg Press.
Time frame: During each exercise session (mean values across the full session) (3 Sessions ; ~1 week apart)
Strength Training Data: Power
Mean mechanical power (Watts (W)) produced during each leg press repetition recorded by the Keiser A400 Leg Press.
Time frame: During each exercise session (mean value across the full session) (3 Sessions ; ~1 week apart)
Strength Training Data: Total Number of Repetitions
Total number of repetitions (count) completed during each exercise session on the leg press.
Time frame: During each exercise session (mean value across the full session) (3 Sessions ; ~1 week apart)
Muscle Oxygenation
Muscle oxygenation will be assessed to determine oxygen availability in the thigh muscle (vastus lateralis) during and after exercise using near-infrared spectroscopy (NIRS). In addition, a vascular occlusion test will be performed to evaluate muscle oxygen extraction and the recovery kinetics of oxygenation following transient blood flow restriction. Metric: Muscle oxygen saturation (%; e.g., SmO₂), as well as reoxygenation rate and amplitude following occlusion.
Time frame: Baseline (pre-exercise), continuously during each exercise session, 5 minutes post-exercise, and 24 hours post-exercise (for each of the 3 sessions, 1 week apart)
Blood Lactate
Small blood sample will be taken to measure lactate, in millimoles per liter analysed through standard laboratory tests, including Enzyme-Linked Immunosorbent Assay (ELISA).
Time frame: Measurements will be taken at baseline and immediately post exercise session (3 sessions, 1 week apart)
Blood Gas
A Small blood sample will be taken to measure blood gas levels (blood oxygen/carbon dioxide levels) using standard laboratory tests, including Enzyme-Linked Immunosorbent Assay (ELISA).
Time frame: Measurements will be taken at baseline and immediately post exercise session (3 sessions, 1 week apart).
Creatine Kinase (CK)
Small blood samples will be taken to measure creatine kinase (CK), an enzyme that increases in the blood when muscles are damaged or stressed. Metric: CK concentration in units per liter (U/L).
Time frame: Measurements will be taken at Baseline and 24 hours after each exercise session.
Functional Performance: Five-Repetition Sit-to-Stand Test
Five-Repetition Sit-to-Stand (5xSTS) test: Participants stand up from a chair repeatedly. An inertial measurement unit (DynaPort MoveTest, McRoberts, The Hague, NL) measures speed (meters per second (m/s)), movement duration (s) , and power (W).
Time frame: Measurements will be taken at Baseline, immediate post exercise and 24 hours after each exercise session.
Functional Performance: Counter Movement Jump
Countermovement Jump (CMJ): Participants jump vertically from a standing position. Jump height (cm), force (Nm), and power (W) are measured using KINVENT force plates.
Time frame: Measurements will be taken at Baseline, immediate post exercise and 24 hours after each exercise session.
Functional Performance: Stair Ascent test
Stair Ascent Test (SA): Participants climb a set of stairs while wearing an inertial measurement unit (DynaPort MoveTest, McRoberts, The Hague, NL), which measures speed (m/s), movement duration (s), distance (cm), and power (W).
Time frame: Measurements will be taken at Baseline, immediate post exercise and 24 hours after each exercise session.
Functional Performance: 30-s Sit-to-Stand Test
30-Second Sit-to-Stand (30sSTS) Tests: Participants stand up from a chair repeatedly. An inertial measurement unit (DynaPort MoveTest, McRoberts, The Hague, NL) measures speed (m/s), movement duration (s), and power (W).
Time frame: Measurements will be taken at Baseline, immediate post exercise and 24 hours after each exercise session.
Perceived Exertion
Perceived exertion will be assessed using the OMNI Resistance Exercise Scale (OMNI-RES). Participants will rate their level of effort after each exercise set during the leg press sessions. The scale ranges from 1 (no exertion at all) to 10 (maximum effort), with higher scores indicating greater perceived exertion.
Time frame: Assessed after each exercise set during each exercise session (mean value across the full session) (3 Sessions ; ~1 week apart)
Delayed Onset Muscle Soreness (DOMS)
Delayed onset of muscle soreness (DOMS) will be assessed using a Visual Analog Scale (VAS). Participants will rate perceived soreness in the leg muscles on a scale from 0 (no soreness) to 10 (worst possible soreness), with higher scores indicating greater muscle soreness.
Time frame: Ratings will be collected at baseline, 24 hours after exercise, and 48 hours after exercise using a remote survey.
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