Impact of exercising muscles to exhaustion on blood markers in weight-training

Abstract

Metabolic markers of physical exhaustion were evaluated in venous blood drawn from 8 men (20-30 years old) with at least 3 years’ experience in weight-lifting training. They were submitted, in the morning, to an overload (exhaustion) test starting at 80% of 1 RM (one repetition maximum) on 8 muscle groups. Heart rate (HR) was measured and samples of venous blood were collected before and immediately after the exhaustion test (ET) and sent to a laboratory for blood gas analysis (pH, lactate, pO2, pCO2 and HCO-3) and measurement of electrolytes (Na+, Cl-, K+ and Ca++) and glycemia. The HR/kg ratios observed were in the following sequence of descending order: arm and hamstrings > shoulder and back > chest > quadriceps > calf. Results for NH4, pH, lactate and HCO-3 levels were changed in all 8 muscle groups, whereas Ca++, K+, Na+, Cl-, and uric acid did not change significantly after the ET. The muscle groups: back, biceps, triceps, chest, and hamstrings exhibited changes in seven to nine indicators while only 4 to 6 biochemical indicators changed in response to shoulder, calf, and quadriceps exercises. Thus, blood markers indicating acidosis, hemoconcentration and hyperglycemia were sensitive markers although with low specificity for the eight muscle groups. Calf and quadriceps had the highest tolerance for weight loading along with the smallest HR increase and lowest number of biochemical indicators changed. Therefore, it appears possible to reach muscle exhaustion with systemic responses in the blood by working out the arm muscles and hamstrings with lighter weights than for quadriceps and calf muscles.