Leg blood flow and muscle oxygenation are reduced when exercising with loads >=40% 1RM compared to loads <=30% 1RM due to increases in contraction induced intramuscular pressure

Knee extension exercise shows reduced leg blood flow and vastus lateralis oxygenation at loads ≥40% 1RM, coinciding with higher intramuscular pressure.

• Why it matters: The study addresses how contraction-induced intramuscular pressure affects convective oxygen delivery, despite the COT being estimated around 30–40% 1RM.
• What they did: Twelve participants performed knee extension across 20%, 30%, 40%, 50%, and 60% 1RM while vastus lateralis intramuscular pressure, femoral blood flow (Doppler), blood pressure, NIRS oxygenation, and EMG were recorded.
• The result: Mean intramuscular pressure rose with load (e.g., 27.0(8.7) mmHg at 40% 1RM; 41.14(13.8) mmHg at 60% 1RM), and oxygenation was lower at 40%, 50%, and 60% 1RM versus 20% and 30% 1RM (p<0.05).

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