Effects of detraining on endurance capacity and metabolic changes during prolonged exhaustive exercise

Abstract

The effects of 4 wk of detraining on maximal O2 uptake (VO2max) and on endurance capacity defined as the maximal time to exhaustion at 75% of VO2max were studied in nine well-trained endurance athletes. Detraining consisted of one short 35-min high-intensity bout per week as opposed to the normal 6-10 h/wk. Detraining had no effect on VO2max (4.57 +/- 0.10 vs. 4.54 +/- 0.08 l/min), but endurance capacity decreased by 21% from 79 +/- 4 to 62 +/- 4 min (P < 0.001). Endurance exercise respiratory exchange ratio was higher in the detrained than in the trained state (0.91 +/- 0.01 vs. 0.89 +/- 0.01; P < 0.01). Muscle [K+] values were unchanged during exercise and were similar in the trained and detrained states. Muscle [Mg2+] values were similar at rest and at minute 40 (30.3 +/- 0.9 vs. 30.8 +/- 0.6 mmol/kg dry wt) but increased significantly at exhaustion to 33.8 +/- 1.0 mmol/kg dry wt in the trained state and to 33.9 +/- 0.9 mmol/kg dry wt in the detrained state. The elevated muscle [Mg2+] at exhaustion could contribute to fatigue in prolonged exercise through an inhibition of Ca2+ release from sarcoplasmic reticulum. It is concluded that the endurance capacity can vary considerably during detraining without changes in VO2max. Altered substrate utilization or changes in electrolyte regulation may account for the reduced endurance capacity.

The Trainability of Adolescent Soccer Players to Brief Periodized Complex Training

“…reduced capillarization of muscle fibers, substrate utilization, mitochondrial energy capacity, electrolyte regulation) even after only 3-4 weeks of detraining. 31 The complex training model adapted by this study did not affect endurance as it did for strength/power measures indicating a specificity effect.…”

Exercise training-induced enhancement in myocardial mechanics is lost after 2 weeks of detraining in rats

“…The improvement due to exercise has been associated with decreases in maximum heart rate (WisløV et al The reason for physical Wtness decline after a period of detraining is unclear; however, the physical capacity is inXuenced by changes in the cardiovascular system and skeletal muscles (Mujika and Padilla 2000). Decrements in cardiac output, arterial-venous diVerences, oxidative enzymes, concentration of blood hemoglobin, mitochondria function, skeletal muscle capillarization and blood Xow contribute to this loss (Convertino et al 1981;Coyle et al 1984;Neufer 1989;Madsen et al 1993),…”

Effects of long-term training cessation in young top-level road cyclists

“…has been reported during periods of reduced training (Hickson, Kanakis, Davis, Moore, & Rich, 1982;Madsen, Pedersen, Djurhuus, & Klitgaard, 1993).…”