Changes in mitochondrial function and mitochondria associated protein expression in response to 2-weeks of high intensity interval training.

PURPOSE: High-intensity short-duration interval training (HIT) stimulates functional and metabolic adaptation in skeletal muscle, but the influence of HIT on mitochondrial function remains poorly studied in humans. Mitochondrial metabolism as well as mitochondrial-associated protein expression were tested in untrained participants performing HIT over a 2-week period. METHODS: Eight males performed a single-leg cycling protocol (12 × 1 min intervals at 120% peak power output, 90 s recovery, 4 days/week). Muscle biopsies (vastus lateralis) were taken pre- and post-HIT. Mitochondrial respiration in permeabilized fibers, citrate synthase (CS) activity and protein expression of peroxisome proliferator-activated receptor gamma coactivator (PGC-1α) and respiratory complex components were measured. RESULTS: HIT training improved peak power and time to fatigue. Increases in absolute oxidative phosphorylation (OXPHOS) capacities and CS activity were observed, but not in the ratio of CCO to the electron transport system (CCO/ETS), the respiratory control ratios (RCR-1 and RCR-2) or mitochondrial-associated protein expression. Specific increases in OXPHOS flux were not apparent after normalization to CS, indicating that gross changes mainly resulted from increased mitochondrial mass. CONCLUSION: Over only 2 weeks HIT significantly increased mitochondrial function in skeletal muscle independently of detectable changes in mitochondrial-associated and mitogenic protein expression.

Sex differences in acute translational repressor 4E-BP1 activity and sprint performance in response to repeated-sprint exercise in team sport athletes.

OBJECTIVES: The physiological requirements underlying soccer-specific exercise are incomplete and sex-based comparisons are sparse. The aim of this study was to determine the effects of a repeated-sprint protocol on the translational repressor 4E-BP1 and sprint performance in male and female soccer players. DESIGN: Cross-over design involving eight female and seven male university soccer players. METHODS: Participants performed four bouts of 6 × 30-m maximal sprints spread equally over 40 min. Heart rate, sprint time and sprint decrement were measured for each sprint and during the course of each bout. Venous blood samples and muscle biopsies from the vastus lateralis were taken at rest, at 15 min and 2h post-exercise. RESULTS: While males maintained a faster mean sprint time for each bout (P < 0.05) females exhibited a greater decrement in sprint performance for each bout (P < 0.05), indicating a superior maintenance of sprint performance in males, with no sex differences for heart rate or lactate. Muscle analyses revealed sex differences in resting total (P < 0.05) and phosphorylated (P < 0.05) 4E-BP1 Thr37/46, and 15 min post-exercise the 4E-BP1 Thr37/46 ratio decreased below resting levels in males only (P < 0.05), indicative of a decreased translation initiation following repeated sprints. CONCLUSIONS: We show that females have a larger sprint decrement indicating that males have a superior ability to recover sprint performance. Sex differences in resting 4E-BP1 Thr37/46 suggest diversity in the training-induced phenotype of the muscle of males and females competing in equivalent levels of team-sport competition.

Cytokine mRNA expression responses to resistance, aerobic, and concurrent exercise in sedentary middle-aged men.

Concurrent resistance and aerobic exercise (CE) is recommended to ageing populations, though is postulated to induce diminished acute molecular responses. Given that contraction-induced cytokine mRNA expression reportedly mediates remunerative postexercise molecular responses, it is necessary to determine whether cytokine mRNA expression may be diminished after CE. Eight middle-aged men (age, 53.3 ±1.8 years; body mass index, 29.4 ± 1.4 kg·m(-2)) randomly completed (balanced for completion order) 8 × 8 leg extensions at 70% maximal strength (RE), 40 min of cycling at 55% of peak aerobic workload (AE), or (workload-matched) 50% RE and 50% AE (CE). Muscle (vastus lateralis) was obtained pre-exercise, and at 1 h and 4 h postexercise, and analyzed for changes of glycogen concentration, tumor necrosis factor (TNF)α, TNF receptor-1 and -2 (TNF-R1 and TNF-R2, respectively), interleukin (IL)-6, IL-6R, IL-1ß, and IL-1 receptor-antagonist (IL-1ra). All exercise modes upregulated cytokine mRNA expression at 1 h postexercise comparably (TNFα, TNF-R1, TNF-R2, IL-1ß, IL-6) (p < 0.05). Expression remained elevated at 4 h after RE and AE (p < 0.05), though returned to pre-exercise levels after CE (p > 0.05). Moreover, AE and RE upregulated IL-1ß and IL-1ra expression, whereas CE upregulated IL-1ß expression only (p < 0.05). Only AE reduced muscle glycogen concentration (p < 0.05), whilst upregulating receptor expression the greatest; though, IL-6R expression remained unchanged after all modes (p > 0.05). In conclusion, in middle-aged men, all modes induced commensurate cytokine mRNA expression at 1 h postexercise; however, only CE resulted in ameliorated expression at 4 h postexercise. Whether the RE or AE components of CE are independently or cumulatively sufficient to upregulate cytokine responses, or whether they collectively inhibit cytokine mRNA expression, remains to be determined.

Comparative effects of single-mode vs. duration-matched concurrent exercise training on body composition, low-grade inflammation, and glucose regulation in sedentary, overweight, middle-aged men.

The effect of duration-matched concurrent exercise training (CET) (50% resistance (RET) and 50% endurance (EET) training) on physiological training outcomes in untrained middle-aged men remains to be elucidated. Forty-seven men (age, 48.1 ± 6.8 years; body mass index, 30.4 ± 4.1 kg·m(-2)) were randomized into 12-weeks of EET (40-60 min of cycling), RET (10 exercises; 3-4 sets × 8-10 repetitions), CET (50% serial completion of RET and EET), or control condition. The following were determined: intervention-based changes in fitness and strength; abdominal visceral adipose tissue (VAT), total body fat (TB-FM) and fat-free (TB-FFM) mass; plasma cytokines (C-reactive protein (CRP), tumor necrosis factor-α (TNFα) interleukin-6 (IL-6)); muscle protein content of p110α and glucose transporter 4 (GLUT4); mRNA expression of GLUT4, peroxisome proliferator-activated receptor-γ coactivator-1α-ß, cytochrome c oxidase, hexokinase II, citrate synthase; oral glucose tolerance; and estimated insulin sensitivity. CET promoted commensurate improvements of aerobic capacity and muscular strength and reduced VAT and TB-FM equivalently to EET and RET (p < 0.05), yet only RET increased TB-FFM (p < 0.05). Although TNFα and IL-6 were reduced after all training interventions (p < 0.05), CRP remained unchanged (p > 0.05). EET reduced area under the curve for glucose, insulin, and C-peptide, whilst CET and RET respectively reduced insulin and C-peptide, and C-peptide only (p < 0.05). Notwithstanding increased insulin sensitivity index after all training interventions (p < 0.05), no change presented for GLUT4 or p110α total protein, or chronic mRNA expression of the studied mitochondrial genes (p > 0.05). In middle-aged men, 12 weeks of duration-matched CET promoted commensurate changes in fitness and strength, abdominal VAT, plasma cytokines and insulin sensitivity, and an equidistant glucose tolerance response to EET and RET; despite no change of measured muscle mechanisms associative to insulin action, glucose transport, and mitochondrial function.

Concurrent resistance and aerobic exercise stimulates both myofibrillar and mitochondrial protein synthesis in sedentary middle-aged men.

We determined myofibrillar and mitochondrial protein fractional synthesis rates (FSR), intramuscular signaling protein phosphorylation, and mRNA expression responses after isolated bouts of resistance exercise (RE), aerobic exercise (AE), or in combination [termed concurrent exercise (CE)] in sedentary middle-aged men. Eight subjects (age = 53.3 ± 1.8 yr; body mass index = 29.4 ± 1.4 kg·m(2)) randomly completed 8 × 8 leg extension repetitions at 70% of one repetition-maximum, 40 min of cycling at 55% peak aerobic power output (AE), or (consecutively) 50% of the RE and AE trials (CE). Biopsies were obtained (during a primed, constant infusion of l-[ring-(13)C(6)]phenylalanine) while fasted, and at 1 and 4 h following postexercise ingestion of 20 g of protein. All trials increased mitochondrial FSR above fasted rates (RE = 1.3-fold; AE = 1.5; CE = 1.4; P < 0.05), although only CE (2.2) and RE (1.8) increased myofibrillar FSR (P < 0.05). At 1 h postexercise, phosphorylation of Akt on Ser(473) (CE = 7.7; RE = 4.6) and Thr(308) (CE = 4.4; RE = 2.9), and PRAS40 on Thr(246) (CE = 3.8; AE = 2.5) increased (P < 0.05), with CE greater than AE for Akt Ser(473)-Thr(308) and greater than RE for PRAS40 (P < 0.05). Despite increased phosphorylation of Akt-PRAS40, phosphorylation of mammalian target of rapamycin (Ser(2448)) remained unchanged (P > 0.05), while rpS6 (Ser(235/236)) increased only in RE (10.4) (P < 0.05). CE and AE both resulted in increased peroxisome proliferator receptor-γ coactivator 1-α (PGC1α) expression at 1 h (CE = 2.9; AE = 2.8; P < 0.05) and 4 h (CE = 2.6; AE = 2.4) and PGC1ß expression at 4 h (CE = 2.1; AE = 2.6; P < 0.05). These data suggest that CE-induced acute stimulation of myofibrillar and mitochondrial FSR, protein signaling, and mRNA expression are equivalent to either isolate mode (RE or AE). These results occurred without an interference effect on muscle protein subfractional synthesis rates, protein signaling, or mRNA expression.

The effect of graduated compression stockings on running performance.

The aim of this study was to examine the effects of wearing different grades of graduated compression stockings (GCS) on 10-km running performance. After an initial familiarization run, 9 male and 3 female competitive runners (VO2max 68.7 ± 5.8 ml·kg⁻¹·min⁻¹) completed 4 10-km time trials on an outdoor 400-m track wearing either control (0 mm Hg; Con), low (12-15 mm Hg; Low), medium (18-21 mm Hg; Med), or high (23-32 mm Hg; Hi) GCS in a randomized counterbalanced order. Leg power was assessed pre and postrun via countermovement jump using a jump mat. Blood-lactate concentration was assessed pre and postrun, whereas heart rate was monitored continuously during exercise. Perceptual scales were used to assess the comfort, tightness, and any pain associated with wearing GCS. There were no significant differences in performance time between trials (p = 0.99). The change in pre to postexercise jump performance was lower in Low and Med than in Con (p < 0.05). Mean heart rate (p = 0.99) and blood lactate (p = 1.00) were not different between trials. Participants rated Con and Low as more comfortable than Med and Hi (p < 0.01), Med and Hi were rated as tighter than Low (p < 0.01), all GCS were rated as tighter than Con (p < 0.01), and Hi was associated with the most pain (p < 0.01). In conclusion, GCS worn by competitive runners during 10-km time trials did not affect performance time; however Low and Med GCS resulted in greater maintenance of leg power after endurance exercise. Athletes rated low-grade GCS as most comfortable garments to wear during exercise.

Adaptations to skeletal muscle with endurance exercise training in the acutely fed versus overnight-fasted state.

Minimising carbohydrate (CHO) status in the peri-training period may accelerate the training adaptations normally observed. The aim of this study was to compare adaptations to endurance training undertaken in the acutely CHO fed and overnight-fasted states. Eight female and six male untrained, healthy participants: aged 26.6+/-5.8 years (mean+/-SD); height 174.7+/-7.6 cm; weight 75.3+/-11.4 kg; VO(2max) 3.48+/-0.67 l/min; were randomly divided into two training groups and undertook four weeks of five days per week endurance cycle ergometer training in either the overnight-fasted (FAST) or acutely fed (FED) state. FAST training had no effect on RER or plasma glucose, lactate and FFA concentrations during subsequent submaximal exercise. Training-induced changes in Vastus lateralis citrate synthase (CS) and 3-hydroxy-CoA dehydrogenase (HAD) activities were not different between training groups (P=0.655 and 0.549, respectively), but when the effect of gender was considered, men responded better to FAST and women responded better to FED. The FAST group showed a significantly greater training-induced increase in VO(2max) and resting muscle glycogen concentration than FED (P=0.014 and P=0.047 respectively), but there was no gender interaction. In conclusion, these results suggest that (a) meal ingestion prior to daily exercise can modify some of the exercise training-induced adaptations normally seen with endurance training compared to when daily exercise is undertaken in the overnight-fasted state; and (b) the extent of these adaptations in skeletal muscle differ slightly between men and women.

Physiological effects of wearing graduated compression stockings during running.

This study examined the effect of wearing different grades of graduated compression stockings (GCS) on physiological and perceptual measures during and following treadmill running in competitive runners. Nine males and one female performed three 40-min treadmill runs (80 +/- 5% maximal oxygen uptake) wearing either control (0 mmHg; CON), low (12-15 mmHg; LO-GCS), or high (23-32 mmHg; HI-GCS) grade GCS in a double-blind counterbalanced order. Oxygen uptake, heart rate and blood lactate were measured. Perceptual scales were used pre- and post-run to assess comfort, tightness and any pain associated with wearing GCS. Changes in muscle function, soreness and damage were determined pre-run, immediately after running and 24 and 48 h post-run by measuring creatine kinase and myoglobin, counter-movement jump height, perceived soreness diagrams, and pressure sensitivity. There were no significant differences between trials for oxygen uptake, heart rate or blood lactate during exercise. HI-GCS was perceived as tighter (P < 0.05) and more pain-inducing (P < 0.05) than the other interventions; CON and LO-GCS were rated more comfortable than HI-GCS (P < 0.05). Creatine kinase (P < 0.05), myoglobin (P < 0.05) and jump height (P < 0.05) were higher and pressure sensitivity was more pronounced (P < 0.05) immediately after running but not after 24 and 48 h. Only four participants reported muscle soreness during recovery from running and there were no differences in muscle function between trials. In conclusion, healthy runners wearing GCS did not experience any physiological benefits during or following treadmill running. However, athletes felt more comfortable wearing low-grade GCS whilst running.