Muscle metabolic, enzymatic and transporter responses to a session of prolonged cycling

Abstract

A single session of prolonged work was employed to investigate changes in selected metabolic, transporter and enzymatic properties in muscle. Ten active but untrained volunteers (weight = 73.9 ± 4.2 kg) with a peak aerobic power [Formula: see text] of 2.95 ± 0.27 l min(-1), cycled for 2 h at 62 ± 1.3% [Formula: see text] Tissue extraction from the vastus lateralis occurred prior to (E1-Pre) and following (E1-Post) exercise and on 3 consecutive days of recovery (R1, R2, R3). The exercise resulted in decreases (P < 0.05) in ATP (-9.3%) and creatine phosphate (-49%) and increases in lactate (+100%), calculated free ADP (+253%) and free AMP (+1,207%), all of which recovered to E1-Pre by R1. Glycogen concentration, which was depressed (P < 0.05) by 75% at E1-Post, did not recover until R3. Compared to E1-Pre, the cycling also resulted in decreases (P < 0.05) in the activities of cytochrome c oxidase, phosphorylase, and hexokinase but not in citrate synthase (CS) or 3-hydroxy-CoA dehydrogenase at E1-Post. With the exception of CS, which was elevated (P < 0.05) at R3, all enzyme activities were not different from E1-Pre during recovery. For the glucose (GLUT1, GLUT4) and monocarboxylate (MCT1, MCT4) transporters, changes in expression levels (P < 0.05) were only observed for GLUT1 at R1 (+42%) and R3 (+33%). It is concluded that the metabolic stress produced by prolonged exercise is reversed by 1 day of recovery. One day of exercise also resulted in a potential upregulation in the citric acid cycle and glucose transport capabilities, adaptations which are expressed at variable recovery durations.

Distinct protein and mRNA kinetics of skeletal muscle proton transporters following exercise can influence interpretation of adaptations to training

“…No change in crude cytosolic MCT1 protein content was reported after 2 h of cycling at 62% (Green et al . ). A reduction in MCT1 protein content from the onset of exercise is probably specific to the membrane fraction, but whether this is attributable to translocation of the protein, an artefact of inconsistent fractionation (Murphy & Lamb, ) or perhaps a failure of the antibody to bind to the MCT1–basigin heterodimer (Xu & Hemler, ), is unknown at this time.…”

“…), but not to change over three consecutive days following a 2 h bout of cycling at 62% (Green et al . ). Although it is likely that both the duration and the intensity of exercise affect postexercise changes in MCT4 expression, an important distinction between those studies and the present data is that we have investigated the response to a bout of accustomed HIIE at the end of a 4 week HIIT intervention, rather than to unaccustomed exercise in untrained populations.…”

“…) increases in induction of both MCT1 and MCT4 protein, or no change at all (Green et al . ), after single bouts of varied exercise stimuli. Those few studies to have described protein kinetics following multiple bouts of exercise demonstrated that the greatest increase in the content of some, but not all, target proteins was after the first bout, with substantial decreases in the magnitude of induction for subsequent bouts (Perry et al .…”

“…This is compounded by the fact that most studies investigating short-term protein responses to single exercise bouts typically involve untrained populations performing unaccustomed exercise. From such studies, there are either rapid (Green et al 2008b) or delayed (Green et al 2002) increases in induction of both MCT1 and MCT4 protein, or no change at all (Green et al 2011), after single bouts of varied exercise stimuli. Those few studies to have described protein kinetics following multiple bouts of exercise demonstrated that the greatest increase in the content of some, but not all, target proteins was after the first bout, with substantial decreases in the magnitude of induction for subsequent bouts (Perry et al 2010;Egan et al 2013).…”

A pilot study to determine whether differences exist in histochemical properties between the trapezius and extensor carpi radialis brevis muscles in women with work-related myalgia

“…One section was dedicated to the measurement of a range of properties involved in excitation-contraction coupling (Green et al 2008(Green et al , 2011a, while a second sample was used for the assessment of muscle metabolites, glucose and monocarboxylate transporters, and a range of enzymes representative of metabolic pathways and segments specific to the mitochondria and the cytosol (Green et al 2011b). The other sample was used for the measurement of a range of histochemical properties (Green et al 1998(Green et al , 2009).…”