Discover the most talked about and latest scientific content & concepts.

Journal: Journal of applied physiology (Bethesda, Md. : 1985)


Carbohydrate (CHO) ingestion is an established strategy to improve endurance performance. Race fuels should not only sustain performance, but also be readily digested and absorbed. Potatoes are a whole-food based option that fulfills these criteria yet their impact on performance remains unexamined. We investigated the effects of potato purée ingestion during prolonged cycling on subsequent performance versus commercial CHO gel or a water-only condition. Twelve cyclists (70.7 ± 7.7 kg, 173 ± 8 cm, 31± 9 years, 22 ± 5.1 % body fat; mean ± SD) with average peak oxygen consumption (VO2PEAK)of 60.7 ± 9.0 mL/kg/min performed a 2 h cycling challenge (60-85%VO2PEAK) followed by a time trial (TT, 6kJ/kg body mass) while consuming potato, gel, or water in a randomized-crossover design. The race fuels were administered with U-[13C6]glucose for an indirect estimate of gastric emptying rate. Blood samples were collected throughout the trials. Blood glucose concentrations were higher (P<0.001) in potato and gel conditions when compared to water condition. Blood lactate concentrations were higher (P=0.001) after the TT completion in both CHO conditions when compared to water condition. TT performance was improved (P=0.032) in both potato (33.0 ± 4.5 min) and gel (33.0 ± 4.2 min) conditions when compared to the water condition (39.5 ± 7.9 min). Moreover, no difference was observed in TT performance between CHO conditions (P=1.00). In conclusion, potato and gel ingestion equally sustained blood glucose concentrations and TT performance. Our results support the effective use of potatoes to support race performance for trained cyclists.


Cross education (CE) occurs after unilateral training whereby performance of the untrained contralateral limb is enhanced. A few studies have shown that CE can preserve or “spare” strength and size of an opposite immobilized limb, but the specificity (i.e., trained homologous muscle and contraction type) of these effects is unknown. The purpose was to investigate specificity of CE “sparing” effects with immobilization. The nondominant forearm of 16 participants was immobilized with a cast, and participants were randomly assigned to a resistance training (eccentric wrist flexion, 3 times/week) or control group for 4 weeks. Pre- and posttesting involved wrist flexors and extensors eccentric, concentric and isometric maximal voluntary contractions (via dynamometer), muscle thickness (via ultrasound), and forearm muscle cross-sectional area (MCSA; via peripheral quantitative computed tomography). Only the training group showed strength preservation across all contractions in the wrist flexors of the immobilized limb (training: -2.4% vs. control: -21.6%; P = 0.04), and increased wrist flexors strength of the nonimmobilized limb (training: 30.8% vs. control: -7.4%; P = 0.04). Immobilized arm MCSA was preserved for the training group only (training: 1.3% vs. control: -2.3%; P = 0.01). Muscle thickness differed between groups for the immobilized (training: 2.8% vs. control: -3.2%; P = 0.01) and nonimmobilized wrist flexors (training: 7.1% vs. control: -3.7%; P = 0.02). Strength preservation was nonspecific to contraction type ( P = 0.69, [Formula: see text] = 0.03) yet specific to the trained flexors muscle. These findings suggest that eccentric training of the nonimmobilized limb can preserve size of the immobilized contralateral homologous muscle and strength across multiple contraction types. NEW & NOTEWORTHY Unilateral strength training preserves strength, muscle thickness, and muscle cross-sectional area in an opposite immobilized limb. The preservation of size and strength was confined to the trained homologous muscle group. However, strength was preserved across multiple contraction types.

Concepts: Muscle, Muscle contraction, Strength training, Forearm, Upper limb, Wrist, Isometric exercise, Preservation


The purpose of this study was to examine the effects of lifelong aerobic exercise (LLE) on VO2max and skeletal muscle metabolic fitness in trained females (n=7, 72±2y) and males (n=21, 74±1y), and compare them to old healthy non-exercisers (OH; females: n=10, 75±1y; males: n=10, 75±1y), and young exercisers (YE; females: n=10, 25±1y; males: n=10, 25±1y). LLE males were further subdivided based on intensity of lifelong exercise and competitive status into performance (LLE-P, n=14) and fitness (LLE-F, n=7). On average, LLE exercised 5d/wk for 7h/wk over the past 52±1y. Each subject performed a maximal cycle test to assess VO2max and had a vastus lateralis muscle biopsy to examine capillarization and metabolic enzymes (citrate synthase, β-HAD, and glycogen phosphorylase). VO2max had a hierarchical pattern (YE>LLE>OH, P<0.05) for females (44±2>26±2>18±1 ml•kg-1•min-1) and males (53±3>34±1>22±1 ml•kg-1•min-1), and was greater (P<0.05) in LLE-P (38±1 ml•kg-1•min-1) than LLE-F (27±2 ml•kg-1•min-1). LLE males, regardless of intensity, and females had similar capillarization and aerobic enzyme activity (citrate synthase and β-HAD) as YE, which were 20-90% greater (P<0.05) than OH. In summary, these data show a substantial VO2max benefit with LLE that tracked similarly between the sexes, with further enhancement in performance trained males. For skeletal muscle, 50+ years of aerobic exercise fully preserved capillarization and aerobic enzymes, regardless of intensity. These data suggest that skeletal muscle metabolic fitness may easier to maintain with lifelong aerobic exercise than more central aspects of the cardiovascular system.


We reported, using a unilateral resistance training (RT) model, that training with high or low loads (mass per repetition) resulted in similar muscle hypertrophy and strength improvements in RT-naïve subjects. Here we aimed to determine whether the same was true in men with previous RT experience using a whole-body RT program and whether post-exercise systemic hormone concentrations were related to changes in hypertrophy and strength. Forty-nine resistance-trained men (mean ± SEM, 23 ± 1 y) performed 12 wk of whole-body RT. Subjects were randomly allocated into a higher-repetition (HR) group who lifted loads of ~30-50% of their maximal strength (1RM) for 20-25 repetitions/set (n=24) or a lower-repetition (LR) group (~75-90% 1RM, 8-12 repetitions/set, n=25), with all sets being performed to volitional failure. Skeletal muscle biopsies, strength testing, DXA scans, and acute changes in systemic hormone concentrations were examined pre- and post-training. In response to RT, 1RM strength increased for all exercises in both groups (p < 0.01), with only the change in bench press being significantly different between groups (HR: 9 ± 1 vs. LR: 14 ±1 kg, p = 0.012). Fat- and bone-free (lean) body mass, type I and type II muscle fibre cross sectional area increased following training (p < 0.01) with no significant differences between groups. No significant correlations between the acute post-exercise rise in any purported anabolic hormone and the change in strength or hypertrophy were found. In congruence with our previous work, acute post-exercise systemic hormonal rises are not related to or in any way indicative of RT-mediated gains in muscle mass or strength. Our data show that in resistance-trained individuals load, when exercises are performed to volitional failure, does not dictate hypertrophy or, for the most part, strength gains.

Concepts: Metabolism, Hormone, Cardiac muscle, Glycogen, Myosin, Muscular system, Strength training, Acetylcholine


Aim: To investigate physiological adaptation with two endurance training periods differing in intensity distribution. Methods: In a randomised cross-over fashion, separated by 4-weeks of detraining, 12 male cyclists completed two 6-week training periods: (1) a polarised model (6.4(±1.4)hrs.week(-1); 80%, 0%, 20% of training time in low, moderate and high intensity zones); and (2) a threshold model (7.5(±2.0)hrs.week(-1); 57%, 43%, 0% training intensity distribution). Before and after each training period, following 2 days of diet and exercise control, fasted skeletal muscle biopsies were obtained for mitochondrial enzyme activity and monocarboxylate transporter (MCT1/4) expression, and morning first void urine samples collected for NMR spectroscopy based metabolomics analysis. Endurance performance (40km time trial), incremental exercise, peak power output, and high-intensity exercise capacity (95% Wmax to exhaustion) were also assessed. Results: Endurance performance, peak power output, lactate threshold, MCT4, and high-intensity exercise capacity all increased over both training periods. Improvements were greater following polarised than threshold for peak power output (Mean (±SEM) change of 8(±2)% vs. 3(±1)%, P<0.05), lactate threshold (9(±3)% vs. 2(±4)%, P<0.05), and high-intensity exercise capacity (85(±14)% vs. 37(±14)%, P<0.05). No changes in mitochondrial enzyme activities or MCT1 were observed following training. A significant multi-level partial least squares-discriminant analysis model was obtained for the threshold model but not the polarised model in the metabolomics analysis. Conclusion: A polarised training distribution results in greater systemic adaptation over 6 weeks in already well-trained cyclists. Markers of muscle metabolic adaptation are largely unchanged but metabolomics markers suggest different cellular metabolic stress that requires further investigation.

Concepts: Metabolism, Enzyme, Exercise, Training, Population genetics, Polymorphism, Adaptation, High intensity training


This study tested the hypothesis that chronic aerobic and resistance exercise (AE+RE) would elicit greater muscle hypertrophy than resistance exercise only (RE). Ten men (25 ± 4 yr) performed 5 wk unilateral knee extensor AE+RE. The opposing limb was subjected to RE. AE completed 6 hr prior to RE consisted of ∼45 min one-legged cycle ergometry. RE comprised 4 × 7 maximal concentric-eccentric knee extensions. Various indexes of in vivo knee extensor function were measured before and after training. Magnetic resonance imaging (MRI) assessed m. quadricep femoris (QF) cross-sectional area (CSA), volume, and signal intensity (SI). Biopsies obtained from m. vastus lateralis determined fiber CSA, enzyme levels, and gene expression of myostatin, atrogin-1, MuRF-1, PGC-1α, and VEGF. Increases (P < 0.05) in isometric strength and peak power, respectively, were comparable in AE+RE (9 and 29%) and RE (11 and 24%). AE+RE showed greater increase (14%; P < 0.05) in QF volume than RE (8%). Muscle fiber CSA increased 17% after AE+RE (P < 0.05) and 9% after RE (P > 0.05). QF SI increased (12%; P < 0.05) after AE+RE, but not RE. Neither AE+RE nor RE showed altered mRNA levels. Citrate synthase activity increased (P < 0.05) after AE+RE. The results suggest that the increased aerobic capacity shown with AE+RE was accompanied by a more robust increase in muscle size compared with RE. Although this response was not carried over to greater improvement in muscle function, it remains that intense AE can be executed prior to RE without compromising performance outcome.

Concepts: Muscle, Exercise, Magnetic resonance imaging, Knee, Strength training, Weight training, Exercise physiology, Isometric exercise


In sport, high training load required to reach peak performance push human adaptation to their limits. In that process, athletes may experience general fatigue, impaired performance and may be identified as overreached (OR). When this state lasts for several months, an overtraining syndrome is diagnosed (OT). Until now, no variable per se can detect OR, a requirement to prevent the transition from OR to OT. It encouraged us to further investigate OR using a multivariate approach including physiological, biomechanical, cognitive and perceptive monitoring. Twenty-four highly trained triathletes were separated into an overload group and a normo-trained group (NT) during three weeks of training. Given the decrement of their running performance, eleven triathletes were diagnosed as OR after this period. A discriminant analysis showed that the changes of eight parameters measured during a maximal incremental test could explain 98.2% of the OR state (lactataemia, heart rate, biomechanical parameters and effort perception). Variations in heart rate and lactataemia were the two most discriminating factors. When the multifactorial analysis was restricted to these variables, the classification score reached 89.5%. Catecholamines and creatine kinase concentrations at rest did not change significantly in both groups. Running pattern was preserved and cognitive performance decrement was observed only at exhaustion in OR subjects. This study showed that monitoring various variables is required to prevent the transition between NT and OR. It emphasized that an OR index, which combines heart rate and blood lactate concentration changes after a strenuous training period, could be helpful to routinely detect OR.

Concepts: Perception, Supercompensation


Resistance training-induced muscle anabolism and subsequent hypertrophy occur most rapidly during the early phase of training and become progressively slower over time. Currently, little is known about the intracellular signaling mechanisms underlying changes in the sensitivity of muscles to training stimuli. We investigated the changes in the exercise-induced phosphorylation of hypertrophic signaling proteins during chronic resistance training and subsequent detraining. Male rats were divided into 4 groups: 1 bout (1B), 12 bouts (12B), 18 bouts (18B), and detraining (DT). In the DT group, rats were subjected to 12 exercise sessions, detrained for 12 days, and then were subjected to 1 exercise session before being sacrificed. Isometric training consisted of maximum isometric contraction was produced by percutaneous electrical stimulation of the gastrocnemius muscle every other day. Muscles were removed 24 h after the final exercise session. Levels of total and phosphorylated p70S6K, 4E-BP1, rpS6, and p90RSK levels were measured, and phosphorylation of p70S6K, rpS6, and p90RSK was elevated in the 1B group compared to control muscle (CON) after acute resistance exercise, while repeated bouts of exercise suppressed those phosphorylation in both 12B and 18B groups. Interestingly, these phosphorylation levels were restored following 12 days of detraining in the DT group. On the contrary, phosphorylation of 4E-BP1 was not altered with chronic training and detraining, indicating that with chronic resistance training, anabolic signaling becomes less sensitive to resistance exercise stimuli, but is restored after a short detraining period.

Concepts: Metabolism, Exercise, Muscle contraction, Muscular system, Strength training, Resistance training, Isometric exercise, Bodybuilding


We examined whether a mixed lactate and caffeine compound (LC) could effectively elicit proliferation and differentiation of satellite cells or activate anabolic signals in skeletal muscles. We cultured C2C12 cells with either lactate (L) or LC for 6 hours. We found that L significantly increased myogenin and follistatin protein levels and phosphorylation of P70S6K while decreasing the levels of myostatin relative to Control (Con). LC significantly increased protein levels of Pax7, MyoD and Ki67 in addition to myogenin, relative to Con. LC also significantly increased follistatin expression relative to Con and stimulated phosphorylation of mTOR and P70S6K. In an in vivo study, male F344/DuCrlCrlj rats were assigned to the control (Sed, n = 10), exercise (Ex, n = 12) and LC supplementation (LCEx, n = 13) groups. LC was orally administered daily. The LCEx and Ex groups were exercised on a treadmill, running for 30 min at low intensity every other day for 4 weeks. The LCEx group experienced a significant increase in the mass of the gastrocnemius (GA) and tibialis anterior (TA) relative to both the Sed and Ex groups. Furthermore, the LCEx group showed a significant increase in the total DNA content of TA compared with the Sed group. The LCEx group experienced a significant increase in myogenin and follistatin expression of GA relative to the Ex group. These results suggest that administration of LC can effectively increase muscle mass concomitant with elevated numbers of myonuclei, even with low-intensity exercise training, via activated satellite cells and anabolic signals.

Concepts: DNA, Muscle, Physical exercise, Cellular differentiation, Muscular system, Exercise physiology, MyoD, Muscle hypertrophy


The purposes of this study are to assess whether 7 days of oral glutamine supplementation: (1) reduces exercise induced intestinal permeability; (2) prevents the pro-inflammatory response; and (3) to determine whether these changes are associated with the up-regulation of the heat shock response. On separate occasions, eight human subjects participated in baseline testing, glutamine (GLN), and placebo (PLA) trials followed by a 60-min treadmill run. Intestinal permeability was higher in the PLA trial compared to baseline and GLN (0.0604 ± 0.047 vs. 0.0218 ±0.008 and 0.0272 ± 0.007, respectively, p<0.05). PBMC IκBα expression was higher 240-min post-ex in GLN trial compared to PLA (1.411 ± 0.523 vs. 0.9839 ± 0.343, p<0.05). In vitro (Caco-2) we measured effects of glutamine supplementation (0 mM, 4 mM, and 6 mM) on heat-induced (37° or 41.8°C) HSP70, HSF-1, and occludin expression. HSF-1 and HSP70 levels increased in 6 mM 41ºC compared to 0 mM 41ºC (1.785 ± 0.495 vs. 0.6681 ± 0.290, and 1.973 ± 0.325 vs. 1.133 ± 0.129, respectively, p<0.05). Occludin levels increased after 4 mM 41ºC and 6 mM 41ºC compared to 0 mM 41ºC (1.236 ± 0.219 and 1.849 ± 0.564 vs. 0.7434 ± 0.027, p<0.001, respectively). Glutamine supplementation prevented exercise-induced permeability, possibly through HSF-1 activation.

Concepts: Shock, In vitro fertilisation, In vitro, Heat shock protein, Tight junction protein 1, Occludin