Abstract
Background and Objectives: This study investigates the effects of a five-week training program on the medial gastrocnemius muscle, comparing two approaches: blood flow restriction (BFR) training and normobaric hyperoxia (oxygen supplementation). It evaluates three strengthening modalities (dynamic, isometric, and the 3/7 method) analyzing their impact on maximal voluntary contraction (MVC), muscle architecture, and perceived exertion. Methods: A total of 36 young healthy participants (21 females, 15 males) were randomized into six subgroups (n = 6 each) based on the type of contraction and oxygen condition. Training sessions (three per week) were conducted for five weeks at 30% of MVC. Measurements of MVC, muscle circumference, pennation angle, fascicle length, and perceived exertion were taken at baseline (T0), mid-protocol (T1), and post-protocol (T2). Results: All groups demonstrated significant increases in MVC after five weeks, with no notable differences between BFR and oxygen conditions. Structural changes were observed in specific subgroups: the BFR-isometric group showed increased calf circumference (p < 0.05), and the 3/7 groups exhibited significant fascicle length gains (p < 0.05). Perceived exertion was consistently higher in BFR groups compared to oxygen supplementation, particularly in dynamic exercises. Conclusions: Both BFR and oxygen supplementation are effective in enhancing strength with light loads, though they elicit different structural and perceptual responses. Oxygen supplementation may be more comfortable and less strenuous, offering a viable alternative for populations unable to tolerate BFR. Future research should focus on optimizing training parameters and exploring applications tailored to specific athletic or clinical contexts.