Blood Flow Restriction

This randomized clinical trial will include competitive male and female sprinters aged 16-30 years, recruited through purposive sampling. Participants will be randomly assigned to one of three groups: (A) HL-BFR (70-85% 1RM with BFR during sets), (B) LL-BFR (20-30% 1RM with BFR), or (C) Passive BFR (BFR applied between sets). The intervention will consist of a 6-week sprint-specific resistance training program performed thrice weekly, incorporating resisted sprints, barbell step-ups, hip thrusts, Nordic curls, and bounding exercises. Strength will be measured using 1RM testing, explosive power through countermovement and standing broad jumps, and sprint performance via 10m, 30m, and 100m timed sprints. Subjective exertion will be tracked using the sRPE scale. The study aims to determine whether HL-BFR, LL-BFR, or passive BFR produces superior improvements in sprint performance and neuromuscular strength. It is hypothesized that HL-BFR may yield greater adaptations due to combined mechanical and metabolic stress, though LL-BFR and passive BFR may offer practical, low-impact alternatives.

Aging leads to declines in functional capacity and effort tolerance. Muscle strength remains stable from ages 25 to 50 but declines significantly after age 60, affecting activities like stair climbing and walking, reducing autonomy and independence. While muscle atrophy is a significant factor, macrovascular endothelial dysfunction also impairs skeletal muscle performance in older adults. Nitric oxide (NO), produced by endothelial cells, regulates vascular homeostasis and contractile function. NO enhances muscle fiber shortening velocity, reduces twitch time-to-peak contraction, and increases the rate of force development. Aging-related endothelial dysfunction reduces NO availability, leading to reduced muscle mass and sarcopenia via decreased skeletal muscle perfusion. Increased arterial stiffness disrupts ventricular-vascular coupling, reducing cardiac output and contributing to age-related muscle weakness. Additionally, microvascular function decreases with age, contributing to altered physical work perception and reduced function. Low capillary density is linked to reduced walking speed in older adults and reduced walking time in peripheral arterial disease patients, supporting the microvasculature\'s role in functional performance. Reduced muscle mass also increases central hemodynamic load, impacting arterial stiffness and cardiac function. Resistance training (RT) is recommended to mitigate aging effects like loss of strength and muscle mass and reduce cardiovascular risk and all-cause mortality. Guidelines suggest 1-3 sets of 8-12 repetitions at 60-80% of the individual\'s repetition maximum (1RM), performed at least twice a week. However, older adults with osteoarthritis and cardiovascular conditions often cannot tolerate high mechanical stress and are prescribed lower intensity-resistance training (LIRT) at 40-50% of 1RM, typically yielding negligible muscle hypertrophy or strength gains. Blood flow restriction (BFR) training, which applies pressure bands to restrict blood flow during LIRT, increases muscle volume and strength. While BFR shows promise, it can cause acute increases in arterial stiffness and blood pressure in older adults, necessitating caution in its prescription. This study aims to compare macrovascular and microvascular function responses to acute resistance exercise with and without BFR in young and older adults. We hypothesize that older adults will show a more pronounced increase in macrovascular and microvascular dysfunction following resistance exercise compared to younger participants. In this parallel group randomized controlled trial, participants will be randomly assigned to either LIRT-BFR or high-intensity resistance training (HIRT). Each participant will attend three sessions: a familiarization session and two experimental sessions involving the randomized exercise conditions. Measurements of brachial blood pressure, heart rate, and macrovascular and microvascular function will be taken at rest and during recovery periods post-exercise.