Initiating aerobic exercise with low glycogen content reduces markers of myogenesis but not mTORC1 signaling

Background The effects of low muscle glycogen on molecular markers of protein synthesis and myogenesis before and during aerobic exercise with carbohydrate ingestion is unclear. The purpose of this study was to determine the effects of initiating aerobic exercise with low muscle glycogen on mTORC1 signaling and markers of myogenesis. Methods Eleven men completed two cycle ergometry glycogen depletion trials separated by 7-d, followed by randomized isocaloric refeeding for 24-h to elicit low (LOW; 1.5 g/kg carbohydrate, 3.0 g/kg fat) or adequate (AD; 6.0 g/kg carbohydrate, 1.0 g/kg fat) glycogen. Participants then performed 80-min of cycle ergometry (64 ± 3% VO2peak) while ingesting 146 g carbohydrate. mTORC1 signaling (Western blotting) and gene transcription (RT-qPCR) were determined from vastus lateralis biopsies before glycogen depletion (baseline, BASE), and before (PRE) and after (POST) exercise. Results Regardless of treatment, p-mTORC1Ser2448, p-p70S6KSer424/421, and p-rpS6Ser235/236 were higher (P < 0.05) POST compared to PRE and BASE. PAX7 and MYOGENIN were lower (P < 0.05) in LOW compared to AD, regardless of time, while MYOD was lower (P < 0.05) in LOW compared to AD at PRE, but not different at POST. Conclusion Initiating aerobic exercise with low muscle glycogen does not affect mTORC1 signaling, yet reductions in gene expression of myogenic regulatory factors suggest that muscle recovery from exercise may be reduced.

Functional electrical stimulation‐assisted cycle ergometry-based progressive mobility programme for mechanically ventilated patients: randomised controlled trial with 6 months follow-up

PurposeFunctional electrical stimulation-assisted cycle ergometry (FESCE) enables in-bed leg exercise independently of patients’ volition. We hypothesised that early use of FESCE-based progressive mobility programme improves physical function in survivors of critical care after 6 months.MethodsWe enrolled mechanically ventilated adults estimated to need >7 days of intensive care unit (ICU) stay into an assessor-blinded single centre randomised controlled trial to receive either FESCE-based protocolised or standard rehabilitation that continued up to day 28 or ICU discharge.ResultsWe randomised in 1:1 ratio 150 patients (age 61±15 years, Acute Physiology and Chronic Health Evaluation II 21±7) at a median of 21 (IQR 19–43) hours after admission to ICU. Mean rehabilitation duration of rehabilitation delivered to intervention versus control group was 82 (IQR 66–97) versus 53 (IQR 50–57) min per treatment day, p<0.001. At 6 months 42 (56%) and 46 (61%) patients in interventional and control groups, respectively, were alive and available to follow-up (81.5% of prespecified sample size). Their Physical Component Summary of SF-36 (primary outcome) was not different at 6 months (50 (IQR 21–69) vs 49 (IQR 26–77); p=0.26). At ICU discharge, there were no differences in the ICU length of stay, functional performance, rectus femoris cross-sectional diameter or muscle power despite the daily nitrogen balance was being 0.6 (95% CI 0.2 to 1.0; p=0.004) gN/m2 less negative in the intervention group.ConclusionEarly delivery of FESCE-based protocolised rehabilitation to ICU patients does not improve physical functioning at 6 months in survivors.Trial registration numberNCT02864745.

Exercise Induced Bronchoconstriction and Bronchodilation; investigating the effects of age, sex, airflow limitation and the FEV1

Exercise induced bronchoconstriction (EIBc) is a recognised response to exercise in asthmatics and athletes but is less well understood in an unselected broad population. Exercise induced bronchodilation (EIBd) has received even less attention. The objective of this study was to Investigate the effects of age, sex, forced expiratory volume in 1 s (FEV1), airflow limitation (FEV1/FVC<0.7) on the prevalence of EIBc and EIBd. Incremental CPET on cycle ergometry to symptom limitation was performed between 1988–2012 at McMaster University. The FEV1 was performed before and 10 mins after exercise. EIBc was defined as a % fall in FEV1 post exercise below the 5th percentile, whilst EIBd as % increase in FEV1 above the 95% percentile. 35 258 subjects between age 6–95 were included in the study (mean age 53, 60% male, 10.3% had airflow limitation (AL, FEV1/FVC<0.7). The lowest 5% of subjects demonstrated a >7.6% fall in FEV1 post exercise (EIBc), whilst the top 5% a >11% increase (EIBd). The probability of both EIBc and EIBd increased with age and was highest in females across all ages (OR 1.76(1.60–1.94) p<0.0001). The probability of EIBc increased as the FEV1%predicted declined (<40% OR 4.38(3.04–6.31),p<0.0001), a >2× increased likelihood in females (OR 2.31(1.71–3.113)p<0.0001), with a trend with AL(p=0.06). The probability of EIBd increased as the FEV1%predicted declined, in the presence of AL (OR 1.55 (1.24–0.95) p=0.0001), but sex had no effect. EIBc and EIBd can be demonstrated at the population level and is influenced by age, sex, FEV1%predicted and airflow limitation.