Plasma Volume Shifts and Acid–Base Balance After a Single Bout of Resistance Training

Changes in plasma volume (PV), acid–base status and ventilation have rarely been investigated in relation to resistance training (RT). This study aimed to investigate the effect of a single set of exhaustive leg press exercise on these basic physiological parameters in an integrated manner.

Twenty-seven male individuals (27.1 ± 4.1 years, 1.82 ± 0.62 m, 84.4 ± 12.5 kg, BMI: 25.4 ± 3.0 k/gm²) performed a single set leg press exercise during which hemoglobin concentration ([Hb]), hematocrit (Hct), pH, oxygen (pO₂) and carbon dioxide partial pressures (pCO₂), hydrogen carbonate concentration ([HCO₃⁻]), standard base excess (SBE) and lactate concentration ([La⁻]) were determined. Total buffer capacity was calculated based on pH, [HCO₃⁻] and pCO₂.

Mean PV decreased by 559 ± 230 mL (13.7%). As a result, arterial oxygen content was significantly increased due to hemoconcentration (P < 0.001). At exhaustion, pH (7.30 ± 0.06), [HCO₃⁻] (18.6 ± 2.0 mmol/L) and SBE (− 6.6 ± 2.4 mmol/L) were all significantly decreased (P < 0.0001). The pCO₂ first remained unchanged (39.4 ± 4.3 mm Hg) but demonstrated a significant decrease one-minute post-exercise (34.4 ± 4.2 mmHg), indicating metabolic acidosis with respiratory compensation, which was maintained until t₊₁₅. Non-bicarbonate buffering remained constant during recovery while the respiratory component steadily increased until 15-min post-exercise (50.2 mmol/L per pH).

PV shifts following a single set of leg press exercise improve post-exercise arterial oxygen content. The moderate metabolic acidosis was not compensated during exercise because of restricted breathing but partly compensated during the following 15-min recovery period. The respiratory compensation as part of the bicarbonate buffering made up 50% of total buffer capacity in the course of recovery.