Specific muscle adaptations in type II fibers after high‐intensity interval training of well‐trained runners

High‐intensity interval training (HIIT) forms an important component of endurance athletes' training, but little is known on intramuscular metabolic and fiber type adaptations. This study investigated physiological and skeletal muscle adaptations in endurance runners subjected to 6 weeks HIIT. Eighteen well‐trained endurance athletes were subjected to 6 weeks HIIT. Maximal and submaximal exercise tests and muscle biopsies were performed before and after training. Results indicated that peak treadmill speed (PTS) increased (21.0 ± 0.8 vs 22.1 ± 1.2 km/h, P<0.001) and plasma lactate decreased at 64% and 80% PTS (P<0.05) after HIIT. Cross‐sectional area of type II fibers tended to have decreased (P=0.06). No changes were observed in maximal oxygen consumption, muscle fiber type, capillary supply, citrate synthase and 3‐hydroxyacetyl CoA dehydrogenase activities. Lactate dehydrogenase (LDH) activity increased in homogenate (P<0.05) and type IIa fiber pools (9.3%, P<0.05). The change in the latter correlated with an absolute interval training speed (r=0.65; P<0.05). In conclusion, HIIT in trained endurance runners causes no adaptations in muscle oxidative capacity but increased LDH activity, especially in type IIa fibers and in relation to absolute HIIT speed.     

Muscular adaptations after two different volumes of blood flow‐restricted training

This study aimed to gain an insight into the adaptations of muscle strength and skeletal muscle thickness after two different volumes of blood flow restriction training (BFRT), and compare them with high‐intensity training. The sample was divided into four groups: low‐volume, low‐intensity BFRT (BFRT LV); high‐volume, low‐intensity BFRT (BFRT HV); traditional high‐intensity resistance training (HIT); and a control group, which maintained their routine activities (CON). Leg extension one repetition maximum (1RM), isokinetic peak knee extension, and flexion torques at 60°/s and 180°/s as well as muscle thickness of the rectus femoris (RF) and vastus lateralis (VL) were assessed at baseline and after 5 weeks of training BFRT LV (7.03%, P < 0.05), BFRT HV (6.24%, P < 0.05) and HIT (18.86%, P < 0.001) groups increased 1RM performance, while no changes were observed in the CON group. Muscle thickness of the RF and VL was increased irrespective of the training group (7.5%, P < 0.001; and 9.9%, P < 0.001, respectively). We conclude that doubling the exercise volume with BFRT causes no further benefit with muscular size or strength. Although similar increases in muscle thickness were observed between training groups, HIT increased 1RM performance to a greater extent compared to either volume of BFRT.     

Blood flow restricted and traditional resistance training performed to fatigue produce equal muscle hypertrophy

This study investigated the hypertrophic potential of load‐matched blood‐flow restricted resistance training (BFR) vs free‐flow traditional resistance training (low‐load TRT) performed to fatigue. Ten healthy young subjects performed unilateral BFR and contralateral low‐load TRT elbow flexor dumbbell curl with 40% of one repetition maximum until volitional concentric failure 3 days per week for 6 weeks. Prior to and at 3 (post‐3) and 10 (post‐10) days post‐training, magnetic resonance imaging (MRI) was used to estimate elbow flexor muscle volume and muscle water content accumulation through training. Acute changes in muscle thickness following an early vs a late exercise bout were measured with ultrasound to determine muscle swelling during the immediate 0–48 h post‐exercise. Total work was threefold lower for BFR compared with low‐load TRT (P < 0.001). Both BRF and low‐load TRT increased muscle volume by approximately 12% at post‐3 and post‐10 (P < 0.01) with no changes in MRI‐determined water content. Training increased muscle thickness during the immediate 48 h post‐exercise (P < 0.001) and to greater extent with BRF (P < 0.05) in the early training phase. In conclusion, BFR and low‐load TRT, when performed to fatigue, produce equal muscle hypertrophy, which may partly rely on transient exercise‐induced increases in muscle water content.     

l‐arginine modulates inflammation and muscle regulatory genes after a single session of resistance exercise in rats

We investigated the skeletal muscle adaptation to l ‐arginine supplementation prior to a single session of resistance exercise (RE ) during the early phase of muscle repair. Wistar rats were randomly assigned into non‐exercised (Control), RE plus vehicle (RE ); RE plus l ‐arginine (RE +L‐arg) and RE plus aminoguanidine (RE +AG ) groups. Animals received four doses of either vehicle (0.9% NaCl), l ‐arg (1 g/b.w.), or AG (iNOS inhibitor) (50 mg/b.w.). The animals performed a single RE session until the concentric failure (ladder climbing; 80% overload) and the skeletal muscles were harvested at 0, 8, 24, and 48 hours post‐RE . The RE resulted in increased neutrophil infiltrate (24 hours post‐RE ) (3621 vs 11852; P <.0001) associated with enhanced TNF ‐α (819.49 vs 357.02; P <.005) and IL ‐6 (3.84 vs 1.08; P <.0001). Prior, l ‐arginine supplementation attenuates neutrophil infiltration (5622; P <.0001), and also TNF ‐α (506.01; P <.05) and IL ‐6 (2.51, P <.05) levels. AG pretreatment mediated an inhibition of iNOS levels similar to levels found in RE group. RE animals displayed increased of atrogin‐1 (1.9 fold) and MuRF ‐1 (3.2 fold) mRNA levels, reversed by l ‐arg supplementation [atrogin‐1 (0.6 fold; P <.001); MuRF ‐1 (0.8‐fold; P <.001)] at 24 hours post‐RE . MyoD up‐regulated levels were restricted to l ‐arg treated animals at 24 hours (2.8 vs 1.5 fold; P <.005) and 48 hours post‐RE (2.4 vs 1.1 fold; P <.001). AG pretreatment reversed these processes at 24 hours [atrogin‐1 (2.1 fold; P <.0001); MuRF ‐1 (2.5 fold; P <.0001); MyoD (1.4 fold)]. l ‐arginine supplementation seems to attenuate the resolution of RE ‐induced muscle inflammation and up‐regulates MyoD expression during the early phase of muscle repair.     

Adding strength to endurance training does not enhance aerobic capacity in cyclists

The molecular signaling of mitochondrial biogenesis is enhanced when resistance exercise is added to a bout of endurance exercise. The purpose of the present study was to examine if this mode of concurrent training translates into increased mitochondrial content and improved endurance performance. Moderately trained cyclists performed 8 weeks (two sessions per week) of endurance training only (E, n = 10; 60‐min cycling) or endurance training followed by strength training (ES, n = 9; 60‐min cycling + leg press). Muscle biopsies were obtained before and after the training period and analyzed for enzyme activities and protein content. Only the ES group increased in leg strength (+19%, P < 0.01), sprint peak power (+5%, P < 0.05), and short‐term endurance (+9%, P < 0.01). In contrast, only the E group increased in muscle citrate synthase activity (+11%, P = 0.06), lactate threshold intensity (+3%, P < 0.05), and long‐term endurance performance (+4%, P < 0.05). Content of mitochondrial proteins and cycling economy was not affected by training. Contrary to our hypothesis, the results demonstrate that concurrent training does not enhance muscle aerobic capacity and endurance performance in cyclists.     

The soy isoflavone genistein inhibits the reduction in Achilles tendon collagen content induced by ovariectomy in rats

The objective of this study was to evaluate the effects of genistein and moderate intensity exercise on Achilles tendon collagen and cross‐linking in intact and ovariectomized (OVX) female Sprague–Dawley rats. Rats were separated into eight groups (n = 9/group): intact or OVX, treadmill exercised or sedentary, genistein‐treated (300 mg/kg/day) or vehicle. After 6 weeks, tendons were assayed for the collagen‐specific amino acid hydroxyproline and hydroxylyslpyridinoline (HP). Collagen content was not influenced by exercise (P = 0.40) but was lower (P < 0.001) in OVX‐vehicle rats compared with intact vehicle rats (OVX: 894 ± 35 μg collagen/mg dry weight; intact: 1185 ± 72 μg collagen/mg dry weight). In contrast, collagen content in OVX rats treated with genistein was greater (P = 0.010, 1198 ± 121 μg collagen/mg dry weight) when compared with untreated rats and was not different from intact rats (P = 0.89). HP content was lower in OVX genistein‐treated rats when compared with intact genistein‐treated rats, but only within the sedentary animals (P = 0.05, intact‐treated: 232 ± 39 mmol/mol collagen; OVX‐treated: 144 ± 21 mmol/mol collagen). Our findings suggest that ovariectomy leads to a reduction in tendon collagen, which is prevented by genistein. HP content, however, may not have increased in proportion to the addition of collagen. Genistein may be useful for improving tendon collagen content in conditions of estrogen deficiency.     

Exercise for fitness does not decrease the muscular inactivity time during normal daily life

The time spent in sedentary behaviors has been shown to be independent of exercise in epidemiological studies. We examined within an individual whether exercise alters the time of muscular inactivity within his/her normal daily life. Quadriceps and hamstring muscle electromyographic activities and heart rate were measured during 1 to 6 days of normal daily living of ordinary people. Of 84 volunteers measured, 27 (15 men, 12 women, 40.7 years ± 16.5 years) fulfilled the criteria of having at least 1 day with and 1 day without exercise for fitness (total of 87 days analyzed, 13.0 h ± 2.5 h/day). Reported exercises varied from Nordic walking to strength training and ball games lasting 30 min–150 min (mean 83 min ± 30 min). Exercise increased the time spent at moderate‐to‐vigorous muscle activity (6% ± 4% to 9% ± 6%, P < 0.01) and energy expenditure (13% ± 22%, P < 0.05). Muscular inactivity, defined individually below that measured during standing, comprised 72% ± 12% of day without and 68% ± 13% of day with exercise (not significant). Duration of exercise correlated positively to the increase in moderate‐to‐vigorous muscle activity time (r = 0.312, P < 0.05) but not with inactivity time. In conclusion, exercise for fitness, regardless of its duration, does not decrease the inactivity time during normal daily life. This is possible by slight modifications in daily nonexercise activities.     

Reduction in plasma leucine after sprint exercise is greater in males than in females

There is a pronounced gender difference in the accumulation of plasma ammonia after sprint exercise. Ammonia is a key intermediate in amino acid metabolism, which implies that gender‐related differences in plasma and muscle amino acid concentrations after sprint exercise exist. To study this, three bouts of 30‐s sprint exercise were performed by healthy females (n=8) and males (n=6). Blood leucine and muscle leucine were collected over the exercise period. Basal arterial plasma and skeletal muscle leucine were 40% higher in males than females (P<0.010 and P<0.020). Plasma, but not muscle, leucine decreased by sprint exercise and more so in males than females (g × t: P=0.025). Increase in ammonia was higher in males than females in both plasma and muscle (g × t: P<0.001 and P=0.003). An opposite pattern was shown for plasma glutamine, where an increase was found in females (P<0.001), but not in males. In conclusion, the lower plasma ammonia after sprint exercise in females seems to be explained by a lower accumulation of ammonia in skeletal muscle and by a buffering of ammonia in the form of glutamine in females. The greater reduction in plasma leucine in males seems to be related to their greater increase in muscle ammonia after sprint exercise.     

Muscle conduction velocity,strength, neural activity,and morphological changes after eccentric and concentric training

This study compared the effects of concentric and eccentric training on neuromuscular adaptations in young subjects. Twenty‐two men and women were assigned to one of two groups: concentric (CON, n = 11) and eccentric (ECC, n = 11) training. Training consisted of 6 weeks of isokinetic exercise, performed twice weekly, starting with two sets of eight repetitions, and progressing to five sets of 10 repetitions. Subjects were tested in strength variables [concentric, eccentric, and isometric peak torque (PT), and rate of force development (RFD)], muscle conduction velocity (CV), neuromuscular activity, vastus lateralis (VL) muscle thickness, and echo intensity as determined by ultrasonography. There were similar increases in the concentric and eccentric PTs in both the CON and ECC groups (P < 0.01), but only the ECC group showed an increase in isometric PT (P < 0.001). Similarly, both groups exhibited increased VL muscle thickness, CV, and RFD, and reduced VL echo intensity (P < 0.05). Significant correlations were observed among the relative changes in the neuromuscular outcomes and training variables (e.g., total work, average PT) (r = 0.68–0.75, P < 0.05). The results showed that both training types similarly improved dynamic PT, CV, RFD, and muscle thickness and quality during the early weeks of training.     

Expression of genes related to muscle plasticity after strength and power training regimens

The purpose of our study was to compare the effects of 8‐week progressive strength and power training regimens on strength gains and muscle plasticity [muscle fiber hypertrophy and phenotype shift, mammalian target of rapamycin (mTOR), regulatory‐associated protein of mTOR (RAPTOR), rapamycin‐insensitive companion of m‐TOR (RICTOR), calcineurin and calcipressin gene expression]. Twenty‐nine physically active subjects were divided into three groups: strength training (ST), power training (PT) and control (C). Squat 1 RM and muscle biopsies were obtained before and after the training period. Strength increased similarly for both ST and PT groups (P<0.001). Fiber types I, IIa and IIb presented hypertrophy main time effect (P<0.05). Only type IIb percentage decreased from pre‐ to post‐test (main time effect, P<0.05). mTOR and RICTOR mRNA expression increased similarly from pre‐ to post‐test (P<0.01). RAPTOR increased after training for both groups (P<0.0001), but to a greater extent in the ST (P<0.001) than in the PT group. 4EBP‐1 decreased after training when the ST and PT groups were pooled (P<0.05). Calcineurin levels did not change after training, while calcipressin increased similarly from pre‐ to post‐test (P<0.01). In conclusion, our data indicate that these training regimens produce similar performance improvements; however, there was a trend toward greater hypertrophy‐related gene expression and muscle fiber hypertrophy in the ST group.     

Skeletal muscle 1H MRSI before and after prolonged exercise. II. visibility of free carnitine

Carnitine (Car) buffers excess acetyl‐CoA through the formation of acetylCar (AcCar). AcCar's acetyl group (AG‐AcCar) gives rise to a peak at 2.13 ppm in ¹H MR spectra of skeletal muscle, whereas the trimethylammonium (TMA) groups of both, AcCar and Car, are thought to contribute to the TMA peak at 3.23 ppm. Surprisingly, in previous studies both resonances, AG‐AcCar and TMA, increased after exercise. The aim of this study was to assess if the exercise‐related TMA increase correlated with AcCar production. Magnetic resonance spectroscopic imaging (pulse repetition time/echo time = 1200/35 ms) was performed before and after prolonged exercise in the lower leg and thigh of eight runners and eight cyclists, respectively. TMA and AG‐AcCar increased after exercise (P < 0.001). TMA's increase correlated with the AG‐AcCar increase (R² = 0.73, P < 0.001, lower leg; R² = 0.28, P < 0.001, thigh). The correlation of ΔTMA with ΔAG‐AcCar suggests that the TMA increase is due to AcCar formation. As total Car (Car + AcCar) remains unchanged with exercise, these findings suggest that the contribution of free Car to the TMA peak is limited and, therefore, is partly invisible in muscle ¹H MR spectra. This indicates that the biochemically relevant cytosolic content of free Car is considerably lower than the overall concentration determined by radioisotopic assays, a potentially important result with respect to regulation of substrate oxidation. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.     

Influence of tart cherry juice on indices of recovery following marathon running

This investigation determined the efficacy of a tart cherry juice in aiding recovery and reducing muscle damage, inflammation and oxidative stress. Twenty recreational Marathon runners assigned to either consumed cherry juice or placebo for 5 days before, the day of and for 48 h following a Marathon run. Markers of muscle damage (creatine kinase, lactate dehydrogenase, muscle soreness and isometric strength), inflammation [interleukin‐6 (IL‐6), C‐reactive protein (CRP) and uric acid], total antioxidant status (TAS) and oxidative stress [thiobarbituric acid reactive species (TBARS) and protein carbonyls] were examined before and following the race. Isometric strength recovered significantly faster (P=0.024) in the cherry juice group. No other damage indices were significantly different. Inflammation was reduced in the cherry juice group (IL‐6, P<0.001; CRP, P<0.01; uric acid, P<0.05). TAS was ～10% greater in the cherry juice than the placebo group for all post‐supplementation measures (P<0.05). Protein carbonyls was not different; however, TBARS was lower in the cherry juice than the placebo at 48 h (P<0.05). The cherry juice appears to provide a viable means to aid recovery following strenuous exercise by increasing total antioxidative capacity, reducing inflammation, lipid peroxidation and so aiding in the recovery of muscle function.     

Ibuprofen intake increases exercise time to exhaustion: A possible role for preventing exercise‐induced fatigue

Although the intake of nonsteroidal anti‐inflammatory drugs (NSAIDs) intake by athletes prevents soreness, little is known concerning their role in exercise performance. This study assessed the effects of ibuprofen intake on an exhaustive protocol test after 6 weeks of swimming training in rats. Animals were divided into sedentary and training groups. After training, animals were subdivided into two subsets: saline or ibuprofen. Afterwards, three repeated swimming bouts were performed by the groups. Ibuprofen (15 mg/kg) was administered once a day. Pain measurements were performed and inflammatory and oxidative stress parameters were assayed in cerebral cortex and gastrocnemius muscle. Training, ibuprofen administration, or both combined (P < 0.05; 211 ± 18s, 200 ± 31s, and 279 ± 23s) increased exercise time to exhaustion. Training decreased the acetylcholinesterase (AChE) activity (P < 0.05; 149 ± 11) in cerebral cortex. Ibuprofen intake decreased the AChE activity after exhaustive protocol test in trained and sedentary rats (P < 0.05; 270 ± 60; 171 ± 38; and 273 ± 29). It also prevented neuronal tumor necrosis factor‐α (TNF‐α) and interleukin (IL 1β) increase. Fatigue elicited by this exhaustive protocol may involve disturbances of the central nervous system. Additive anti‐inflammatory effects of exercise and ibuprofen intake support the hypothesis that this combination may constitute a more effective approach. In addition, ergogenic aids may be a useful means to prevent exercise‐induced fatigue.     

Effects of concurrent exercise training on muscle dysfunction and systemic oxidative stress in older people with COPD

Oxidative stress is associated with disease severity and limb muscle dysfunction in COPD. Our main goal was to assess the effects of exercise training on systemic oxidative stress and limb muscle dysfunction in older people with COPD. Twenty‐nine outpatients with COPD (66‐90 years) were randomly assigned to a 12‐week exercise training (ET; high‐intensity interval training (HIIT) plus power training) or a control (CT; usual care) group. We evaluated mid‐thigh muscle cross‐sectional area (CSA; computed tomography); vastus lateralis (VL) muscle thickness, pennation angle, and fascicle length (ultrasonography); peak VO₂ uptake (VO_2peak) and work rate (W_peak) (incremental cardiopulmonary exercise test); rate of force development (RFD); maximal muscle power (P_max; force‐velocity testing); systemic oxidative stress (plasma protein carbonylation); and physical performance and quality of life. ET subjects experienced changes in mid‐thigh muscle CSA (+4%), VL muscle thickness (+11%) and pennation angle (+19%), VO_2peak (+14%), W_peak (+37%), RFD (+32% to 65%), P_max (+38% to 51%), sit‐to‐stand time (?24%), and self‐reported health status (+20%) (all P < 0.05). No changes were noted in the CT group (P > 0.05). Protein carbonylation decreased among ET subjects (?27%; P < 0.05), but not in the CT group (P > 0.05). Changes in protein carbonylation were associated with changes in muscle size and pennation angle (r = ?0.44 to ?0.57), exercise capacity (r = ?0.46), muscle strength (r = ?0.45), and sit‐to‐stand performance (r = 0.60) (all P < 0.05). The combination of HIIT and power training improved systemic oxidative stress and limb muscle dysfunction in older people with COPD. Changes in oxidative stress were associated with exercise‐induced structural and functional adaptations.     

Spinal modulations accompany peripheral fatigue during prolonged tennis playing

To examine the time course of alteration in neural process (spinal loop properties) during prolonged tennis playing, 12 competitive players performed a series of neuromuscular tests every 30 min during a 3‐h match protocol. Muscle activation (twitch interpolation) and normalized EMG activity were assessed during maximal voluntary contraction (MVC) of plantar flexors. Spinal reflexes and M‐waves were evoked at rest (i.e., H_max and M_max, respectively) and during MVC (i.e., H_sup, V‐wave, M_sup, respectively). MVC torque declined significantly (P<0.001) across the match protocol, due to decrease (P<0.001) in muscle activation and in normalized EMG activity. The impairment in MVC was significantly correlated (r=0.77; P<0.05) with the decline in muscle activation. H_max/M_max (P<0.001), H_sup/M_sup (P<0.01) and V/M_sup (P<0.05) ratios were depressed with fatigue and decreased by ～80%, 46% and 61% at the end of exercise, respectively. Simultaneously, peak twitch torque and M‐wave amplitude were significantly (P<0.01) altered with exercise, suggesting peripheral alterations. During prolonged tennis playing, the compromised voluntary strength capacity is linked to a reduced neural input to the working muscles. This central activation deficit partly results from a modulation in spinal loop properties.     

Stimulating whole saliva affects the response of antimicrobial proteins to exercise

This study investigated the salivary secretion rates of antimicrobial proteins in response to prolonged, exhaustive exercise in both stimulated (STIM) and unstimulated (UNSTIM) saliva flow sample methods. Twenty‐four trained men cycled for 2.5 h at 60% and then to exhaustion at 75% . Timed collections of whole saliva were made before exercise, mid‐exercise, at the end of the moderate exercise bout and post‐exhaustive exercise. After each UNSTIM collection, a STIM sample was collected following chewing flavored gum for 1 min. Saliva was analysed for lysozyme, α‐amylase and salivary immunoglobulin A (s‐IgA), and secretion rates were calculated. Saliva flow was 156% higher in STIM compared with UNSTIM (P < 0.001) and decreased with exercise in STIM only (P < 0.001). Exercise increased lysozyme and α‐amylase levels and secretion rates were 144% higher and 152% higher in STIM compared with UNSTIM for lysozyme and α‐amylase, respectively (all P < 0.001). S‐IgA concentration (P < 0.05) and secretion rate (P < 0.001) increased with exercise but were both lower in STIM compared with UNSTIM (P < 0.001). In conclusion, a STIM saliva flow collection during exercise by chewing flavored gum increased the quantity of saliva and the secretion of lysozyme and α‐amylase, but had a limited impact on the secretion of s‐IgA.     

Continuous vs interval training on glycemic control and macro‐ and microvascular reactivity in type 2 diabetic patients

To determine the effects of continuous aerobic exercise training (CON) vs interval aerobic exercise training (INT) on glycemic control and endothelium‐dependent vasodilatation, 43 participants with type 2 diabetes were randomly allocated to the sedentary, CON, and INT groups. The CON and INT exercise training programs were designed to yield the same energy expenditure/exercise session and included walking on treadmill for 30 and 40 min/day, 3 times/week for 12 weeks. Body fatness and heart rate at rest decreased and leg muscle strength increased (all P < 0.05) in both the CON and INT groups. Fasting blood glucose levels decreased (P < 0.05) in both exercise groups but glycosylated hemoglobin levels decreased (P < 0.05) only in the INT group. Maximal aerobic capacity, flow‐mediated dilation, and cutaneous reactive hyperemia increased significantly in both exercise groups; however, the magnitude of improvements was greater in the INT group. Only the INT group experienced reductions in erythrocyte malondialdehyde and serum von Willebrand factor and increases in plasma glutathione peroxidase and nitric oxide (all P < 0.05). We concluded that both continuous and interval training were effective in improving glycemic control, aerobic fitness, and endothelium‐dependent vasodilation, but the interval training program appears to confer greater improvements than the continuous training program.     

Exercise and green tea extract stimulate fat oxidation and prevent obesity in mice

INTRODUCTION/PURPOSE: The purpose of the present study was to explore the combined effects of dietary supplementation with green tea extract (GTE) and regular exercise on the development of obesity in high fat-fed C57BL/6J mice. METHODS: Weight and age-matched male mice were divided into 5 groups of 10 mice each. Groups were treated as follows: a low-fat diet and not exercised (LF), a high-fat diet and not exercised (HF), a high-fat diet supplemented with GTE and not exercised (GTE-HF), a high-fat diet and exercised regularly (EX-HF), or a high-fat diet supplemented with GTE and exercised regularly (GTEEX-HF). The exercise modality was treadmill running. RESULTS: After 15 wk, GTE alone and regular exercise alone caused a 47 and 24% reduction in body weight gain induced by the high-fat diet, respectively, and when combined, resulted in an 89% reduction. In visceral fat accumulation, GTE alone, exercise alone, and their combination caused a 58, 37, and 87% reduction, respectively. Indirect calorimetry showed that the GTEEX-HF group had the highest energy expenditure and fat utilization in the sedentary condition after 4 wk. Furthermore, the GTEEX-HF group utilized more fat than the EX-HF group during exercise. GTE supplementation increased hepatic fatty acid oxidation both in the exercised and nonexercised groups. In addition, when combined with regular exercise, GTE supplementation also stimulated skeletal muscle fatty acid oxidation. CONCLUSION: In conclusion, dietary GTE and regular exercise, if combined, stimulate fat catabolism not only in the liver but also in skeletal muscle, and attenuate high-fat diet-induced obesity more effectively than each alone in C57BL/6J mice.     

Increasing skeletal muscle carnitine availability does not alter the adaptations to high‐intensity interval training

Increasing skeletal muscle carnitine availability alters muscle metabolism during steady‐state exercise in healthy humans. We investigated whether elevating muscle carnitine, and thereby the acetyl‐group buffering capacity, altered the metabolic and physiological adaptations to 24 weeks of high‐intensity interval training (HIIT ) at 100% maximal exercise capacity (Watt_max). Twenty‐one healthy male volunteers (age 23±2 years; BMI 24.2±1.1 kg/m²) performed 2 × 3 minute bouts of cycling exercise at 100% Watt_max, separated by 5 minutes of rest. Fourteen volunteers repeated this protocol following 24 weeks of HIIT and twice‐daily consumption of 80 g carbohydrate (CON ) or 3 g l ‐carnitine+carbohydrate (CARN ). Before HIIT , muscle phosphocreatine (PC r) degradation (P <.0001), glycogenolysis (P <.0005), PDC activation (P <.05), and acetylcarnitine (P <.005) were 2.3‐, 2.1‐, 1.5‐, and 1.5‐fold greater, respectively, in exercise bout two compared to bout 1, while lactate accumulation tended (P <.07) to be 1.5‐fold greater. Following HIIT , muscle free carnitine was 30% greater in CARN vs CON at rest and remained 40% elevated prior to the start of bout 2 (P <.05). Following bout 2, free carnitine content, PC r degradation, glycogenolysis, lactate accumulation, and PDC activation were all similar between CON and CARN , albeit markedly lower than before HIIT . VO _2max, Watt_max, and work output were similarly increased in CON and CARN , by 9, 15, and 23% (P <.001). In summary, increased reliance on non‐mitochondrial ATP resynthesis during a second bout of intense exercise is accompanied by increased carnitine acetylation. Augmenting muscle carnitine during 24 weeks of HIIT did not alter this, nor did it enhance muscle metabolic adaptations or performance gains beyond those with HIIT alone.     

Vitamin C and E supplementation blunts increases in total lean body mass in elderly men after strength training

The aim of this study was to investigate the effects of vitamin C and E supplementation on changes in muscle mass (lean mass and muscle thickness) and strength during 12 weeks of strength training in elderly men. Thirty‐four elderly males (60–81 years) were randomized to either an antioxidant group (500 mg of vitamin C and 117.5 mg vitamin E before and after training) or a placebo group following the same strength training program (three sessions per week). Body composition was assessed with dual‐energy X‐ray absorptiometry and muscle thickness by ultrasound imaging. Muscle strength was measured as one‐repetition maximum (1RM). Total lean mass increased by 3.9% (95% confidence intervals: 3.0, 5.2) and 1.4% (0, 5.4) in the placebo and antioxidant groups, respectively, revealing larger gains in the placebo group (P = 0.04). Similarly, the thickness of m. rectus femoris increased more in the placebo group [16.2% (12.8, 24.1)] than in the antioxidant group [10.9% (9.8, 13.5); P = 0.01]. Increases of lean mass in trunk and arms, and muscle thickness of elbow flexors, did not differ significantly between groups. With no group differences, 1RM improved in the range of 15–21% (P < 0.001). In conclusion, high‐dosage vitamin C and E supplementation blunted certain muscular adaptations to strength training in elderly men.