Early muscular and metabolic adaptations to prolonged exercise training in humans

Abstract

A short-term training program involving 2 h of daily exercise at 59% of peak O2 uptake (VO2max) repeated for 10-12 consecutive days was employed to determine the significance of adaptations in energy metabolic potential on alterations in energy metabolism and substrate utilization in working muscle. The initial VO2max determined before training on the eight male subjects was 53.0 +/- 2.0 (SE) ml.kg-1.min-1. Analysis of samples obtained by needle biopsy from the vastus lateralis muscle before exercise (0 min) and at 15, 60, and 99 min of exercise indicated that on the average training resulted (P less than 0.05) in a 6.5% higher concentration of creatine phosphate, a 9.9% lower concentration of creatine, and a 39% lower concentration of lactate. Training had no effect on ATP concentration. These adaptations were also accompanied by a reduction in the utilization in glycogen such that by the end of exercise glycogen concentration was 47.1% higher in the trained muscle. Analysis of the maximal activities of representative enzymes of different metabolic pathways and segments indicated no change in potential in the citric acid cycle (succinate dehydrogenase, citrate synthase), beta-oxidation (3-hydroxyacyl CoA dehydrogenase), glucose phosphorylation (hexokinase), or potential for glycogenolysis (phosphorylase) and glycolysis (pyruvate kinase, phosphofructokinase, alpha-glycerophosphate dehydrogenase, lactate dehydrogenase). With the exception of increases in the capillary-to-fiber area ratio in type IIa fibers, no change was found in any fiber type (types I, IIa, and IIb) for area, number of capillaries, capillary-to-fiber area ratio, or oxidative potential with training.(ABSTRACT TRUNCATED AT 250 WORDS)

Left Ventricular Diastolic Filling and Cardiovascular Functional Capacity in Older Men

“…These large functional changes appeared to be directly related to change in the filling dynamics of the left ventricle and may not have been observed in a normal population. Additionally, the magnitude of the changes in ýOµ,max were, in fact, similar to those reported for healthy younger subjects with similar short-term training protocols of 1 or 2 weeks (Green et al 1984(Green et al , 1991Convertino, 1991). Green et al (1991) reported a 250 ml min¢ (±110 ml min¢) increase in ýOµ,max in healthy men aged 19-30 years after 10-12 consecutive days of exercise at 59% of pre-training peak ýOµ,max for 2 h day¢.…”

“…Additionally, the magnitude of the changes in ýOµ,max were, in fact, similar to those reported for healthy younger subjects with similar short-term training protocols of 1 or 2 weeks (Green et al 1984(Green et al , 1991Convertino, 1991). Green et al (1991) reported a 250 ml min¢ (±110 ml min¢) increase in ýOµ,max in healthy men aged 19-30 years after 10-12 consecutive days of exercise at 59% of pre-training peak ýOµ,max for 2 h day¢. Convertino (1991) observed a 340 ml min¢ increase in ýOµ,max in eight young men after 8 consecutive days of exercise -cycling 2 h day¢ at 65% of ýOµ,max.…”

The Effects of Caffeine on the Kinetics of O2Uptake, CO2Production and Expiratory Ventilation in Humans During the On‐Transient of Moderate and Heavy Intensity Exercise

“…The muscle metabolic profile was not examined in this study but the intensity of exercise performed by the subjects was similar to that examined in several previous studies which demonstrated glycogen depletion early in exercise (Gollnick et al 1974;Green et al 1991Green et al , 1992Spriet et al 1992). Also, the caffeine dose used (6 mg (kg BM)¢) and the length of the accommodation (60 min) immediately following caffeine ingestion were similar to those previously showing increased time to fatigue (Graham & Spriet, 1991;Spriet et al 1992).…”

Metabolic, enzymatic, and transporter responses in human muscle during three consecutive days of exercise and recovery

“…Whole blood for glucose and lactate was placed in a prechilled tube containing 0.6 M perchloric acid and neutralized in a 1.25 mM KHCO 3, and centrifuged; the supernatant was then analyzed fluorometrically (24). Plasma epinephrine and norepinephrine were measured by HPLC techniques using electrochemical detection as modified by our laboratory (25). For the measurements of the catecholamines, whole blood was collected in a tube containing ethylene glycol-bis (␤-aminoethyl ether) N,N,N 1 ,N 1 -tetra acetic acid and glutathione as antioxidant.…”