Arterio-venous metabolite and electrolyte responses to low-load training with and without blood flow restriction...

Low-load resistance training with blood flow restriction (BFR) has gained popularity for eliciting muscular adaptations comparable to high-load resistance training. However, its acute metabolic and electrolyte responses within the exercising limb, particularly under exhaustive conditions, remain insufficiently characterized. This study aimed to assess these responses using simultaneous arterial and venous blood sampling during unilateral elbow flexion to volitional failure under three conditions: low-load (LL-RT, 30%1RM), low-load with BFR (LL-BFR-RT, 30%1RM, 50%LOP), and high-load (HL-RT, 75%1RM).

Ten healthy men (26.8 ± 4.6 years) completed all exercise conditions in a randomized cross-over design. Catheters were placed in the radial artery and antecubital vein of the exercising arm. Serum creatine kinase (CK) and lactate dehydrogenase (LDH) were assessed as indirect muscle damage markers.

LL-RT produced the highest total workload (692 ± 251 kg), exceeding both LL-BFR-RT (378 ± 58.7 kg) and HL-RT (327 ± 65.1 kg, p < 0.001). Muscle pain perception assessed using a visual analog scale increased during exercise, with a highest level in LL-BFR-RT (p < 0.01). LL-BFR-RT also induced the most pronounced venous perturbations (e.g., reduced pH and sO₂, elevated pCO₂ and K⁺), while arterial responses remained modest across conditions. CK increased slightly at 48 h post-exercise across all conditions (p = 0.036), while LDH was highest following HL-RT (p < 0.001).

These findings suggest that LL-BFR-RT to failure induces substantial local metabolic and ionic stress within the exercising limb despite reduced mechanical loading. The marked venous disturbances, alongside minimal increases in systemic damage markers, support its use as a metabolically potent yet mechanically efficient training modality when applied with care.