The molecular bases of training adaptation

[Resistive training reduces inflammation in skeletal muscle and improves the peripheral insulin sensitivity in obese rats induced by hyperlipidic diet]

OBJECTIVE

To determine if resistive exercise protocol can modulate Tnf-α, SOCS3 and glucose transporter GLUT4 genes expression in skeletal muscle, and peripheral insulin sensitivity in obese rats induced by hyperlipidic diet.

MATERIALS AND METHODS

Wistar obese rats induced by hyperlipidic diet were subjected a resistive exercise protocol as jump squat. Insulin sensitivity and mRNA content of Tnf-α, SOCS3 and GLUT4 were assayed and compared among the groups: obese sedentary (OS) and exercised (OE), control sedentary (CS) and exercised (CE).

RESULTS

The mRNA content of Tnf-α and SOCS3 has increased in skeletal muscle from OS and has decreased in OE group. The protein and GLUT4 mRNA contents were correlated but they did not change among the groups. Peripheral insulin sensitivity has increased in the OE compared to OS group.

CONCLUSION

The resistive exercise reverses the peripheral insulin resistance and the inflammatory state in skeletal muscle from diet-induced obese rats.

Exercise and melatonin in humans: reciprocal benefits

The aim of this review is to update the reader as to the association between physical exercise and melatonin, and to clarify how the melatonin rhythm may be affected by different types of exercise. Exercise may act as a zeitgeber, although the effects of exercise on the human circadian system are only now being explored. Depending on the time of the day, on the intensity of light, and on the proximity of the exercise to the onset or decline of the circadian production of melatonin, the consequence of exercise on the melatonin rhythm varies. Moreover, especially strenuous exercise per se induces an increased oxidative stress that in turn may affect melatonin levels in the peripheral circulation because indole is rapidly used to combat free radical damage. On the other hand, melatonin also may influence physical performance, and thus, there are mutually interactions between exercise and melatonin production which may be beneficial.

Low-level laser (light) therapy (LLLT) on muscle tissue: performance, fatigue and repair benefited by the power of light

The use of low level laser (light) therapy (LLLT) has recently expanded to cover areas of medicine that were not previously thought of as the usual applications such as wound healing and inflammatory orthopedic conditions. One of these novel application areas is LLLT for muscle fatigue and muscle injury. Since it is becoming agreed that mitochondria are the principal photoacceptors present inside cells, and it is known that muscle cells are exceptionally rich in mitochondria, this suggests that LLLT should be highly beneficial in muscle injuries. The ability of LLLT to stimulate stem cells and progenitor cells means that muscle satellite cells may respond well to LLLT and help muscle repair. Furthermore the ability of LLLT to reduce inflammation and lessen oxidative stress is also beneficial in cases of muscle fatigue and injury. This review covers the literature relating to LLLT and muscles in both preclinical animal experiments and human clinical studies. Athletes, people with injured muscles, and patients with Duchenne muscular dystrophy may all benefit.

The effects of active and passive stretching on muscle length

Active stretch is necessary for regulating muscle fiber length (ie, the number of series sarcomeres). Elevated cytoplasmic calcium is the proposed component of contractile activity required to activate signaling pathways for sarcomere number regulation. Passive stretch reduces muscle tissue stiffness, most likely by signaling connective tissue remodeling via fibroblasts. Passive stretch may induce sarcomere addition if the muscle fibers are lengthened sufficiently to raise cytoplasmic calcium through stretch-activated calcium channels. The magnitude of stretch in vivo is limited by the physiologic range of movement and stretch pain tolerance. The greatest effect of stretching muscle fibers is expected when the lengthening exceeds the optimum fiber length (Lo).

Muscle fatigue and excitation-contraction coupling responses following a session of prolonged cycling

AIM

The mechanisms underlying the fatigue that occurs in human muscle following sustained activity are thought to reside in one or more of the excitation-contraction coupling (E-C coupling) processes. This study investigated the association between the changes in select E-C coupling properties and the impairment in force generation that occurs with prolonged cycling.

METHODS

Ten volunteers with a peak aerobic power (VO(2peak)) of 2.95 ± 0.27 L min(-1) (mean ± SE), exercised for 2 h at 62 ± 1.3%. Quadriceps function was assessed and tissue properties (vastus lateralis) were measured prior to (E1-pre) and following (E1-post) exercise and on three consecutive days of recovery (R1, R2 and R3).

RESULTS

While exercise failed to depress the maximal activity (V(max) ) of the Na(+) ,K(+) -ATPase (P = 0.10), reductions (P < 0.05) were found at E1-post in V(max) of sarcoplasmic reticulum Ca(2+) -ATPase (-22%), Ca(2+) -uptake (-26%) and phase 1(-33%) and 2 (-38%) Ca(2+) -release. Both V(max) and Ca(2+) -release (phase 2) recovered by R1, whereas Ca(2+) -uptake and Ca(2+) -release (phase 1) remained depressed (P < 0.05) at R1 and at R1 and R2 and possibly R3 (P < 0.06) respectively. Compared with E1-pre, fatigue was observed (P < 0.05) at 10 Hz electrical stimulation at E1-post (-56%), which persisted throughout recovery. The exercise increased (P < 0.05) overall content of the Na(+), K(+)-ATPase (R1, R2 and R3) and the isoforms β2 (R1, R2 and R3) and β3 (R3), but not β1 or the α-isoforms (α1, α2 and α3).

CONCLUSION

These results suggest a possible direct role for Ca(2+)-release in fatigue and demonstrate a single exercise session can induce overlapping perturbations and adaptations (particularly to the Na(+), K(+)-ATPase).

Similar changes of gene expression in human skeletal muscle after resistance exercise and multiple fine needle biopsies

Repeated biopsy sampling from one muscle is necessary to investigate muscular adaptation to different forms of exercise as adaptation is thought to be the result of cumulative effects of transient changes in gene expression in response to single exercise bouts. In a crossover study, we obtained four fine needle biopsies from one vastus lateralis muscle of 11 male subjects (25.9 ± 3.8 yr, 179.2 ± 4.8 cm, 76.5 ± 7.0 kg), taken before (baseline), 1, 4, and 24 h after one bout of squatting exercise performed as conventional squatting or as whole body vibration exercise. To investigate if the repeated biopsy sampling has a confounding effect on the observed changes in gene expression, four fine needle biopsies from one vastus lateralis muscle were also taken from 8 male nonexercising control subjects (24.5 ± 3.7 yr, 180.6 ± 1.2 cm, 81.2 ± 1.6 kg) at the equivalent time points. Using RT-PCR, we observed similar patterns of change in the squatting as well as in the control group for the mRNAs of interleukin 6 (IL-6), IL-6 receptor, insulin-like growth factor 1, p21, phosphofructokinase, and glucose transporter in relation to the baseline biopsy. In conclusion, multiple fine needle biopsies obtained from the same muscle region can per se influence the expression of marker genes induced by an acute bout of resistance exercise.

Effects of low-level laser therapy (808 nm) on isokinetic muscle performance of young women submitted to endurance training: a randomized controlled clinical trial

Low-level laser therapy (LLLT) has shown efficacy in muscle bioenergetic activation and its effects could influence the mechanical performance of this tissue during physical exercise. This study tested whether endurance training associated with LLLT could increase human muscle performance in isokinetic dynamometry when compared to the same training without LLLT. The primary objective was to determine the fatigue index of the knee extensor muscles (FIext) and the secondary objective was to determine the total work of the knee extensor muscles (TWext). Included in the study were 45 clinically healthy women (21 ± 1.78 years old) who were randomly distributed into three groups: CG (control group), TG (training group) and TLG (training with LLLT group). The training for the TG and TLG groups involved cycle ergometer exercise with load applied to the ventilatory threshold (VT) for 9 consecutive weeks. Immediately after each training session, LLLT was applied to the femoral quadriceps muscle of both lower limbs of the TLG subjects using an infrared laser device (808 nm) with six 60-mW diodes with an energy of 0.6 J per diode and a total energy applied to each limb of 18 J. VT was determined by ergospirometry during an incremental exercise test and muscle performance was evaluated using an isokinetic dynamometer at 240°/s. Only the TLG showed a decrease in FIext in the nondominant lower limb (P = 0.016) and the dominant lower limb (P = 0.006). Both the TLG and the TG showed an increase in TWext in the nondominant lower limb (P < 0.001 and P = 0.011, respectively) and in the dominant lower limb (P < 0.000 and P < 0.000, respectively). The CG showed no reduction in FIext or TWext in either lower limb. The results suggest that an endurance training program combined with LLLT leads to a greater reduction in fatigue than an endurance training program without LLLT. This is relevant to everyone involved in sport and rehabilitation.

Strategies to optimize concurrent training of strength and aerobic fitness for rowing and canoeing

During the last several decades many researchers have reported an interference effect on muscle strength development when strength and endurance were trained concurrently. The majority of these studies found that the magnitude of increase in maximum strength was higher in the group that performed only strength training compared with the concurrent training group, commonly referred to as the 'interference phenomenon'. Currently, concurrent strength and endurance training has become essential to optimizing athletic performance in middle- and long-distance events. Rowing and canoeing, especially in the case of Olympic events, with exercise efforts between 30 seconds and 8 minutes, require high amounts of maximal aerobic and anaerobic capacities as well as high levels of maximum strength and muscle power. Thus, strength training, in events such as rowing and canoeing, is integrated into the training plan. However, several studies indicate that the degree of interference is affected by the training protocols and there may be ways in which the interference effect can be minimized or avoided. Therefore, the aim of this review is to recommend strategies, based on research, to avoid or minimize any interference effect when training to optimize performance in endurance sports such as rowing and canoeing.

Passing the anaerobic threshold is associated with substantial changes in the gene expression profile in white blood cells

High and moderate intensity endurance exercise alters gene expression in human white blood cells (WBCs), but the understanding of how this effect occurs is limited. To increase our knowledge of the nature of this process, we investigated the effects of passing the anaerobic threshold (AnT) on the gene expression profile in WBCs of athletes. Nineteen highly trained skiers participated in a treadmill test with an incremental step protocol until exhaustion (ramp test to exhaustion, RTE). The average total time to exhaustion was 14:40 min and time after AnT was 4:50 min. Two weeks later, seven of these skiers participated in a moderate treadmill test (MT) at 80% peak O(2) uptake for 30 min, which was slightly below their AnTs. Blood samples were obtained before and immediately after both tests. RTE was associated with substantially greater leukocytosis and acidosis than MT. Gene expression in WBCs was measured using whole genome microarray expression analysis before and immediately after each test. A total of 310 upregulated genes were found after RTE, and 69 genes after MT of which 64 were identical to RTE. Both tests influenced a variety of known gene pathways related to inflammation, stress response, signal transduction and apoptosis. A large group of differentially expressed previously unknown small nucleolar RNA and small Cajal body RNA was found. In conclusion, a 15-min test to exhaustion was associated with substantially greater changes of gene expression than a 30-min test just below the AnT.

Performance and physiological responses during a sprint interval training session: relationships with muscle oxygenation and pulmonary oxygen uptake kinetics

The purpose of this study was to examine the cardiorespiratory and muscle oxygenation responses to a sprint interval training (SIT) session, and to assess their relationships with maximal pulmonary O(2) uptake [Formula: see text], on- and off- [Formula: see text] kinetics and muscle reoxygenation rate (Reoxy rate). Ten male cyclists performed two 6-min moderate-intensity exercises (≈90-95% of lactate threshold power output, Mod), followed 10 min later by a SIT session consisting of 6 × 30-s all out cycling sprints interspersed with 2 min of passive recovery. [Formula: see text] kinetics at Mod onset ([Formula: see text]) and cessation ([Formula: see text]) were calculated. Cardiorespiratory variables, blood lactate ([La](b)) and muscle oxygenation level of the vastus lateralis (tissue oxygenation index, TOI) were recorded during SIT. Percentage of the decline in power output (%Dec), time spent above 90% of [Formula: see text] (t > 90% [Formula: see text]) and Reoxy rate after each sprint were also recorded. Despite a low mean [Formula: see text] (48.0 ± 4.1% of [Formula: see text]), SIT performance was associated with high peak [Formula: see text] (90.4 ± 2.8% of [Formula: see text]), muscle deoxygenation (sprint ΔTOI = -27%) and [La](b) (15.3 ± 0.7 mmol l(-1)) levels. Muscle deoxygenation and Reoxy rate increased throughout sprint repetitions (P < 0.001 for both). Except for t > 90% [Formula: see text] versus [Formula: see text] [r = 0.68 (90% CL, 0.20; 0.90); P = 0.03], there were no significant correlations between any index of aerobic function and either SIT performance or physiological responses [e.g., %Dec vs. [Formula: see text]: r = -0.41 (-0.78; 0.18); P = 0.24]. Present results show that SIT elicits a greater muscle O(2) extraction with successive sprint repetitions, despite the decrease in external power production (%Dec = 21%). Further, our findings obtained in a small and homogenous group indicate that performance and physiological responses to SIT are only slightly influenced by aerobic fitness level in this population.

Chronic CaMKII inhibition blunts the cardiac contractile response to exercise training

Activation of the multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) plays a critical role modulating cardiac function in both health and disease. Here, we determined the effect of chronic CaMKII inhibition during an exercise training program in healthy mice. CaMKII was inhibited by KN-93 injections. Mice were randomized to the following groups: sham sedentary, sham exercise, KN-93 sedentary, and KN-93 exercise. Cardiorespiratory function was evaluated by ergospirometry during treadmill running, echocardiography, and cardiomyocyte fractional shortening and calcium handling. The results revealed that KN-93 alone had no effect on exercise capacity or fractional shortening. In sham animals, exercise training increased maximal oxygen uptake by 8% (p < 0.05) compared to a 22% (p < 0.05) increase after exercise in KN-93 treated mice (group difference p < 0.01). In contrast, in vivo fractional shortening evaluated by echocardiography improved after exercise in sham animals only: from 25 to 32% (p < 0.02). In inactive mice, KN-93 reduced rates of diastolic cardiomyocyte re-lengthening (by 25%, p < 0.05) as well as Ca(2+) transient decay (by 16%, p < 0.05), whereas no such effect was observed after exercise training. KN-93 blunted exercise training response on cardiomyocyte fractional shortening (63% sham vs. 18% KN-93; p < 0.01 and p < 0.05, respectively). These effects could not be solely explained by the Ca(2+) transient amplitude, as KN-93 reduced it by 20% (p < 0.05) and response to exercise training was equal (64% sham and 47% KN-93; both p < 0.01). We concluded that chronic CaMKII inhibition increased time to 50% re-lengthening which were recovered by exercise training, but paradoxically led to a greater increase in maximal oxygen uptake compared to sham mice. Thus, the effect of chronic CaMKII inhibition is multifaceted and of a complex nature.

Exercise-induced angiogenesis correlates with the up-regulated expression of neuronal nitric oxide synthase (nNOS) in human skeletal muscle

The contribution of neuronal nitric oxide synthase (nNOS) to angiogenesis in human skeletal muscle after endurance exercise is controversially discussed. We therefore ascertained whether the expression of nNOS is associated with the capillary density in biopsies of the vastus lateralis (VL) muscle that had been derived from 10 sedentary male subjects before and after moderate training (four 30-min weekly jogging sessions for 6 months, with a heart-rate corresponding to 75% VO(2)max). In these biopsies, nNOS was predominantly expressed as alpha-isoform with exon-mu and to a lesser extent without exon-mu, as determined by RT-PCR. The mRNA levels of nNOS were quantified by real-time PCR and related to the capillary-to-fibre ratio and the numerical density of capillaries specified by light microscopy. If the VL biopsies of all subjects were co-analysed, mRNA levels of nNOS were non-significantly elevated after training (+34%; P > 0.05). However, only five of the ten subjects exhibited significant (P ≤ 0.05) elevations in the capillary-to-fibre ratio (+25%) and the numerical density of capillaries (+21%) and were thus undergoing angiogenesis. If the VL biopsies of these five subjects alone were evaluated, the mRNA levels of nNOS were significantly up-regulated (+128%; P ≤ 0.05) and correlated positively (r = 0.8; P ≤ 0.01) to angiogenesis. Accordingly, nNOS protein expression in VL biopsies quantified by immunoblotting was significantly increased (+82%; P ≤ 0.05) only in those subjects that underwent angiogenesis. In conclusion, the expression of nNOS at mRNA and protein levels was statistically linked to capillarity after exercise suggesting that nNOS is involved in the angiogenic response to training in human skeletal muscle.

Training for intense exercise performance: high-intensity or high-volume training?

Performance in intense exercise events, such as Olympic rowing, swimming, kayak, track running and track cycling events, involves energy contribution from aerobic and anaerobic sources. As aerobic energy supply dominates the total energy requirements after ∼75s of near maximal effort, and has the greatest potential for improvement with training, the majority of training for these events is generally aimed at increasing aerobic metabolic capacity. A short-term period (six to eight sessions over 2-4 weeks) of high-intensity interval training (consisting of repeated exercise bouts performed close to or well above the maximal oxygen uptake intensity, interspersed with low-intensity exercise or complete rest) can elicit increases in intense exercise performance of 2-4% in well-trained athletes. The influence of high-volume training is less discussed, but its importance should not be downplayed, as high-volume training also induces important metabolic adaptations. While the metabolic adaptations that occur with high-volume training and high-intensity training show considerable overlap, the molecular events that signal for these adaptations may be different. A polarized approach to training, whereby ∼75% of total training volume is performed at low intensities, and 10-15% is performed at very high intensities, has been suggested as an optimal training intensity distribution for elite athletes who perform intense exercise events.

Effects of tai chi training on antioxidant capacity in pre- and postmenopausal women

The risk of oxidative stress-related metabolic diseases increases with menopause and physical inactivity. We hypothesized that an 8-week Tai Chi (TC) training program (2 sessions in class; 2 sessions at home; 1-1:15/session) would improve antioxidant capacity and reduce cardiovascular risks in both pre- (n = 8) and postmenopausal (n = 7) sedentary women. Selected measures of physical fitness and blood parameters were analyzed before and after the program. Besides the well-known effects of TC on balance, flexibility, and maximum leg extensor strength, TC (1) increased erythrocyte glutathione peroxidase activity—an aerobic training-responsive antioxidant enzyme—and plasma total antioxidant status and (2) decreased plasma total homocysteine, a cardiovascular risk marker. In addition to being a low-velocity, low-impact, and relatively safe, TC is a suitable physical activity design for pre- and postmenopausal women to increase antioxidant defenses. Investigating breathing effects during TC movements would be an interesting area for further research in diseases prevention.

An acute bout of high-intensity interval training increases the nuclear abundance of PGC-1α and activates mitochondrial biogenesis in human skeletal muscle

Low-volume, high-intensity interval training (HIT) increases skeletal muscle mitochondrial capacity, yet little is known regarding potential mechanisms promoting this adaptive response. Our purpose was to examine molecular processes involved in mitochondrial biogenesis in human skeletal muscle in response to an acute bout of HIT. Eight healthy men performed 4 × 30-s bursts of all-out maximal intensity cycling interspersed with 4 min of rest. Muscle biopsy samples (vastus lateralis) were obtained immediately before and after exercise, and after 3 and 24 h of recovery. At rest, the majority of peroxisome proliferator-activated receptor γ coactivator (PGC)-1α, a master regulator of mitochondrial biogenesis, was detected in cytosolic fractions. Exercise activated p38 MAPK and AMPK in the cytosol. Nuclear PGC-1α protein increased 3 h into recovery from exercise, a time point that coincided with increased mRNA expression of mitochondrial genes. This was followed by an increase in mitochondrial protein content and enzyme activity after 24 h of recovery. These findings support the hypothesis that an acute bout of low-volume HIT activates mitochondrial biogenesis through a mechanism involving increased nuclear abundance of PGC-1α.

MicroRNAs in skeletal muscle: their role and regulation in development, disease and function

Maintaining skeletal muscle function throughout the lifespan is a prerequisite for good health and independent living. For skeletal muscle to consistently function at optimal levels, the efficient activation of processes that regulate muscle development, growth, regeneration and metabolism is required. Numerous conditions including neuromuscular disorders, physical inactivity, chronic disease and ageing are associated with perturbations in skeletal muscle function. A loss or reduction in skeletal muscle function often leads to increased morbidity and mortality either directly, or indirectly, via the development of secondary diseases such as diabetes, obesity, cardiovascular and respiratory disease. Identifying mechanisms which influence the processes regulating skeletal muscle function is a key priority. The discovery of microRNAs (miRNAs) provides a new avenue that will extend our knowledge of factors controlling skeletal muscle function. miRNAs may also improve our understanding and application of current therapeutic approaches as well as enable the identification of new therapeutic strategies and targets aimed at maintaining and/or improving skeletal muscle health. This review brings together the latest developments in skeletal muscle miRNA biology and focuses on their role and regulation under physiological and patho-physiological conditions with an emphasis on: myogenesis, hypertrophy, atrophy and regeneration; exercise and nutrition; muscle disease, ageing, diabetes and obesity.

Nutritional modulation of training-induced skeletal muscle adaptations

Skeletal muscle displays remarkable plasticity, enabling substantial adaptive modifications in its metabolic potential and functional characteristics in response to external stimuli such as mechanical loading and nutrient availability. Contraction-induced adaptations are determined largely by the mode of exercise and the volume, intensity, and frequency of the training stimulus. However, evidence is accumulating that nutrient availability serves as a potent modulator of many acute responses and chronic adaptations to both endurance and resistance exercise. Changes in macronutrient intake rapidly alter the concentration of blood-borne substrates and hormones, causing marked perturbations in the storage profile of skeletal muscle and other insulin-sensitive tissues. In turn, muscle energy status exerts profound effects on resting fuel metabolism and patterns of fuel utilization during exercise as well as acute regulatory processes underlying gene expression and cell signaling. As such, these nutrient-exercise interactions have the potential to activate or inhibit many biochemical pathways with putative roles in training adaptation. This review provides a contemporary perspective of our understanding of the molecular and cellular events that take place in skeletal muscle in response to both endurance and resistance exercise commenced after acute and/or chronic alterations in nutrient availability (carbohydrate, fat, protein, and several antioxidants). Emphasis is on the results of human studies and how nutrient provision (or lack thereof) interacts with specific contractile stimulus to modulate many of the acute responses to exercise, thereby potentially promoting or inhibiting subsequent training adaptation.

Single-leg cycle training is superior to double-leg cycling in improving the oxidative potential and metabolic profile of trained skeletal muscle

Single-leg cycling may enhance the peripheral adaptations of skeletal muscle to a greater extent than double-leg cycling. The purpose of the current study was to determine the influence of 3 wk of high-intensity single- and double-leg cycle training on markers of oxidative potential and muscle metabolism and exercise performance. In a crossover design, nine trained cyclists (78 ± 7 kg body wt, 59 ± 5 ml·kg(-1)·min(-1) maximal O(2) consumption) performed an incremental cycling test and a 16-km cycling time trial before and after 3 wk of double-leg and counterweighted single-leg cycle training (2 training sessions per week). Training involved three (double) or six (single) maximal 4-min intervals with 6 min of recovery. Mean power output during the single-leg intervals was more than half that during the double-leg intervals (198 ± 29 vs. 344 ± 38 W, P < 0.05). Skeletal muscle biopsy samples from the vastus lateralis revealed a training-induced increase in Thr(172)-phosphorylated 5'-AMP-activated protein kinase α-subunit for both groups (P < 0.05). However, the increase in cytochrome c oxidase subunits II and IV and GLUT-4 protein concentration was greater following single- than double-leg cycling (P < 0.05). Training-induced improvements in maximal O(2) consumption (3.9 ± 6.2% vs. 0.6 ± 3.6%) and time-trial performance (1.3 ± 0.5% vs. 2.3 ± 4.2%) were similar following both interventions. We conclude that short-term high-intensity single-leg cycle training can elicit greater enhancement in the metabolic and oxidative potential of skeletal muscle than traditional double-leg cycling. Single-leg cycling may therefore provide a valuable training stimulus for trained and clinical populations.

Exercise-induced regulation of muscular Na+-K+ pump, FXYD1, and NHE1 mRNA and protein expression: importance of training status, intensity, and muscle type

It is investigated if exercise-induced mRNA changes cause similar protein expression changes of Na(+)-K(+) pump isoforms (α(1), α(2), β(1), β(2)), FXYD1, and Na(+)/K(+) exchanger (NHE1) in rat skeletal muscle. Expression was evaluated (n = 8 per group) in soleus and extensor digutorum longus after 1 day, 3 days, and 3 wk (5 sessions/wk) of either sprint (4 × 3-min sprint + 1-min rest) or endurance (20 min) running. Two hours after exercise on day 1, no change in protein expression was apparent in either training group or muscle, whereas sprint exercise increased the mRNA of soleus α(2) (4.9 ± 0.8-fold; P < 0.05), β(2) (13.2 ± 4.4-fold; P < 0.001), and NHE1 (12.0 ± 3.1-fold; P < 0.01). Two hours after sprint exercise, protein expression normalized to control samples was higher on day 3 than day 1 for soleus α(1) (41 ± 18% increase vs. 15 ± 8% reduction; P < 0.05), α(2) (64 ± 35% increase vs. 37 ± 12% reduction; P < 0.05), β(1) (17 ± 21% increase vs. 14 ± 29% reduction; P < 0.05), and FXYD1 (35 ± 16% increase vs. 13 ± 10% reduction; P < 0.05). In contrast, on day 3, soleus α(1) (0.1 ± 0.1-fold; P < 0.001), α(2) (0.2 ± 0.1-fold; P < 0.001), β(1) (0.4 ± 0.1-fold; P < 0.05), and β(2)-mRNA (2.9 ± 1.7-fold; P < 0.001) expression was lower than after exercise on day 1. After 3 wk of training, no change in protein expression relative to control existed. In conclusion, increased expression of Na(+)-K(+) pump subunits, FXYD1 and NHE1 after 3 days exercise training does not appear to be an effect of increased constitutive mRNA levels. Importantly, sprint exercise can reduce mRNA expression concomitant with increased protein expression.

Different molecular and structural adaptations with eccentric and conventional strength training in elderly men and women

Reprogramming of gene expression contributes to structural and functional adaptation of muscle tissue in response to altered use. The aim of this study was to investigate mechanisms for observed improvements in leg extension strength, gain in relative thigh muscle mass and loss of body and thigh fat content in response to eccentric and conventional strength training in elderly men (n = 14) and women (n = 14; average age of the men and women: 80.1 ± 3.7 years) by means of structural and molecular analyses. Biopsies were collected from m. vastus lateralis in the resting state before and after 12 weeks of training with two weekly resistance exercise sessions (RET) or eccentric ergometer sessions (EET). Gene expression was analyzed using custom-designed low-density PCR arrays. Muscle ultrastructure was evaluated using EM morphometry. Gain in thigh muscle mass was paralleled by an increase in muscle fiber cross-sectional area (hypertrophy) with RET but not with EET, where muscle growth is likely occurring by the addition of sarcomeres in series or by hyperplasia. The expression of transcripts encoding factors involved in muscle growth, repair and remodeling (e.g., IGF-1, HGF, MYOG, MYH3) was increased to a larger extent after EET than RET. MicroRNA 1 expression was decreased independent of the training modality, and was paralleled by an increased expression of IGF-1 representing a potential target. IGF-1 is a potent promoter of muscle growth, and its regulation by microRNA 1 may have contributed to the gain of muscle mass observed in our subjects. EET depressed genes encoding mitochondrial and metabolic transcripts. The changes of several metabolic and mitochondrial transcripts correlated significantly with changes in mitochondrial volume density. Intramyocellular lipid content was decreased after EET concomitantly with total body fat. Changes in intramyocellular lipid content correlated with changes in body fat content with both RET and EET. In the elderly, RET and EET lead to distinct molecular and structural adaptations which might contribute to the observed small quantitative differences in functional tests and body composition parameters. EET seems to be particularly convenient for the elderly with regard to improvements in body composition and strength but at the expense of reducing muscular oxidative capacity.

Early time course of Akt phosphorylation after endurance and resistance exercise

PURPOSE

The aim of this study was to determine the early time course of exercise-induced signaling after divergent contractile activity associated with resistance and endurance exercise.

METHODS

Sixteen male subjects were randomly assigned to either a cycling (CYC; n = 8, 60 min, 70% V˙O2peak) or resistance (REX; n = 8, 8 x 5 leg extension, 80% one-repetition maximum, 3-min recovery) exercise group. Serial muscle biopsies were obtained from vastus lateralis at rest before, immediately after, and after 15, 30, and 60 min of passive recovery to determine early signaling responses after exercise.

RESULTS

There were comparable increases from rest in Akt(Thr308/Ser473) and mTOR(Ser2448) phosphorylation during the postexercise time course that peaked 30-60 min after both CYC and REX (P < 0.05). There were also similar patterns in p70S6K(Thr389) and 4E-BP1(Thr37/46) phosphorylation, but a greater magnitude of effect was observed for REX and CYC, respectively (P < 0.05). However, AMPK(Thr172) phosphorylation was only significantly elevated after CYC (P < 0.05), and we observed divergent responses for glycogen synthase(Ser641) and AS160 phosphorylation that were enhanced after CYC but not REX (P < 0.05).

CONCLUSIONS

We show a similar time course for Akt-mTOR-S6K phosphorylation during the initial 60-min recovery period after divergent contractile stimuli. Conversely, enhanced phosphorylation status of proteins that promote glucose transport and glycogen synthesis only occurred after endurance exercise. Our results indicate that endurance and resistance exercise initiate translational signaling, but high-load, low-repetition contractile activity failed to promote phosphorylation of pathways regulating glucose metabolism.

Neuromuscular electrical stimulation training induces atypical adaptations of the human skeletal muscle phenotype: a functional and proteomic analysis

The aim of the present study was to define the chronic effects of neuromuscular electrical stimulation (NMES) on the neuromuscular properties of human skeletal muscle. Eight young healthy male subjects were subjected to 25 sessions of isometric NMES of the quadriceps muscle over an 8-wk period. Needle biopsies were taken from the vastus lateralis muscle before and after training. The training status, myosin heavy chain (MHC) isoform distribution, and global protein pattern, as assessed by proteomic analysis, widely varied among subjects at baseline and prompted the identification of two subgroups: an "active" (ACT) group, which performed regular exercise and had a slower MHC profile, and a sedentary (SED) group, which did not perform any exercise and had a faster MHC profile. Maximum voluntary force and neural activation significantly increased after NMES in both groups (+∼30% and +∼10%, respectively). Both type 1 and 2 fibers showed significant muscle hypertrophy. After NMES, both groups showed a significant shift from MHC-2X toward MHC-2A and MHC-1, i.e., a fast-to-slow transition. Proteomic maps showing ∼500 spots were obtained before and after training in both groups. Differentially expressed proteins were identified and grouped into functional categories. The most relevant changes regarded 1) myofibrillar proteins, whose changes were consistent with a fast-to-slow phenotype shift and with a strengthening of the cytoskeleton; 2) energy production systems, whose changes indicated a glycolytic-to-oxidative shift in the metabolic profile; and 3) antioxidant defense systems, whose changes indicated an enhancement of intracellular defenses against reactive oxygen species. The adaptations in the protein pattern of the ACT and SED groups were different but were, in both groups, typical of both resistance (i.e., strength gains and hypertrophy) and endurance (i.e., a fast-to-slow shift in MHC and metabolic profile) training. These training-induced adaptations can be ascribed to the peculiar motor unit recruitment pattern associated with NMES.

Effects of low level laser therapy (808 nm) on physical strength training in humans

Recent studies have investigated whether low level laser therapy (LLLT) can optimize human muscle performance in physical exercise. This study tested the effect of LLLT on muscle performance in physical strength training in humans compared with strength training only. The study involved 36 men (20.8±2.2 years old), clinically healthy, with a beginner and/or moderate physical activity training pattern. The subjects were randomly distributed into three groups: TLG (training with LLLT), TG (training only) and CG (control). The training for TG and TLG subjects involved the leg-press exercise with a load equal to 80% of one repetition maximum (1RM) in the leg-press test over 12 consecutive weeks. The LLLT was applied to the quadriceps muscle of both lower limbs of the TLG subjects immediately after the end of each training session. Using an infrared laser device (808 nm) with six diodes of 60 mW each a total energy of 50.4 J of LLLT was administered over 140 s. Muscle strength was assessed using the 1RM leg-press test and the isokinetic dynamometer test. The muscle volume of the thigh of the dominant limb was assessed by thigh perimetry. The TLG subjects showed an increase of 55% in the 1RM leg-press test, which was significantly higher than the increases in the TG subjects (26%, P = 0.033) and in the CG subjects (0.27%, P < 0.001). The TLG was the only group to show an increase in muscle performance in the isokinetic dynamometry test compared with baseline. The increases in thigh perimeter in the TLG subjects and TG subjects were not significantly different (4.52% and 2.75%, respectively; P = 0.775). Strength training associated with LLLT can increase muscle performance compared with strength training only.

Cellular responses in skeletal muscle to a season of ice hockey

We hypothesized that a season of ice hockey would result in extensive remodeling of muscle. Tissue sampled from the vastus lateralis of 15 players (age = 20.6 ± 0.4 years; mean ± SE) prior to (PRE) and following (POST) a season was used to characterize specific adaptations. Measurement of representative metabolic pathway enzymes indicated higher maximal activities in POST than in PRE (p < 0.05) for succinic dehydrogenase (3.26 ± 0.31 vs. 3.91 ± 0.11 mol mg protein(-1) min(-1)), citrate synthase (7.26 ± 0.70 vs. 8.70 ± 0.55 mol mg protein(-1) min(-1)), and phosphofructokinase (12.8 ± 1.3 vs. 14.4 ± 0.96 mol mg protein(-1) min(-1)) only. The season resulted in an increase in Na+-K+-ATPase concentration (253 ± 6.3 vs. 265 ± 6.0 pmol g(-1) wet weight), a decrease (p < 0.05) in maximal activity of the sarcoplasmic reticulum Ca2+-ATPase (107 ± 4.2 micromol g protein(-1) min(-1) vs. 92.0 ± 4.6 micromol g protein(-1) min(-1)), and no change in the distribution (%) of fibre types. A smaller (p < 0.05) cross-sectional area (CSA) for both type I (-11.7%) and type IIA (-18.2%) fibres and a higher (p < 0.05) capillary count/CSA for type I (+17.9%) and type IIA (+17.2%) were also found over the season. No changes were found in peak oxygen consumption (51.4 ± 1.2 mL kg(-1) min(-1) vs. 52.3 ± 1.3 mL kg(-1) min(-1)). The results suggest, based on the alterations in oxidative and perfusion potentials and muscle mass, that the dominant adaptations are in support of oxidative metabolism, which occurs at the expense of fibre CSA and possibly force-generating potential.

Regulation of skeletal muscle transcriptome in elderly men after 6 weeks of endurance training at lactate threshold intensity

A compromised muscle function due to aging, sarcopenia and reduced level of physical activity can lead to metabolic complications and chronic diseases. Endurance exercise counters these diseases by inducing beneficial adaptations whose molecular mechanisms remain unclear. We have investigated the transcriptomic changes following mild-intensity endurance training in skeletal muscle of elderly men. Seven healthy subjects followed an exercise program of cycle ergometer training at lactate threshold (LT) level for 60 min/day, five times/week during six weeks. Physiological and transcriptomic changes were analyzed before and after training. LT training decreased percentage body fat and fasting levels of plasma glucose, while increasing high-density lipoprotein cholesterol and lecithin-cholesterol acyltransferase levels. Transcriptomic analysis revealed fast-to-slow fiber type transition, increased amount of mtDNA encoded transcripts and modulation of 12 transcripts notably related to extracellular matrix (ECM), oxidative phosphorylation (OXPHOS), as well as partially characterized and novel transcripts. The training simultaneously induced the expression of genes related to slow fiber type transition, OXPHOS and ECM, which might contribute to the improvement of glucose and lipid metabolisms and whole body aerobic capacity.

What is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes?

Successful endurance training involves the manipulation of training intensity, duration, and frequency, with the implicit goals of maximizing performance, minimizing risk of negative training outcomes, and timing peak fitness and performances to be achieved when they matter most. Numerous descriptive studies of the training characteristics of nationally or internationally competitive endurance athletes training 10 to 13 times per week seem to converge on a typical intensity distribution in which about 80% of training sessions are performed at low intensity (2 mM blood lactate), with about 20% dominated by periods of high-intensity work, such as interval training at approx. 90% VO2max. Endurance athletes appear to self-organize toward a high-volume training approach with careful application of high-intensity training incorporated throughout the training cycle. Training intensification studies performed on already well-trained athletes do not provide any convincing evidence that a greater emphasis on high-intensity interval training in this highly trained athlete population gives long-term performance gains. The predominance of low-intensity, long-duration training, in combination with fewer, highly intensive bouts may be complementary in terms of optimizing adaptive signaling and technical mastery at an acceptable level of stress.

Effects of resistance training on the inflammatory response

Resistance training (RT) is associated with reduced risk of low grade inflammation related diseases, such as cardiovascular disease and type 2 diabetes. The majority of the data studying cytokines and exercise comes from endurance exercise. In contrast, evidence establishing a relationship between RT and inflammation is more limited. This review focuses on the cytokine responses both following an acute bout, and after chronic RT. In addition, the effect of RT on low grade systemic inflammation such as individuals at risk for type 2 diabetes is reviewed. Cytokines are secreted proteins that influence the survival, proliferation, and differentiation of immune cells and other organ systems. Cytokines function as intracellular signals and almost all cells in the body either secrete them or have cytokine receptors. Thus, understanding cytokine role in a specific physiological situation such as a bout of RT can be exceedingly complex. The overall effect of long term RT appears to ameliorate inflammation, but the specific effects on the inflammatory cytokine, tumor necrosis factor alpha are not clear, requiring further research. Furthermore, it is critical to differentiate between chronically and acute Interleukin-6 levels and its sources. The intensity of the RT and the characteristics of the training protocol may exert singular cytokine responses and as a result different adaptations to exercise. More research is needed in the area of RT in healthy populations, specifically sorting out gender and age RT acute responses. More importantly, studies are needed in obese individuals who are at high risk of developing low grade systemic inflammatory related diseases. Assuring adherence to the RT program is essential to get the benefits after overcoming the first acute RT responses. Hence RT could be an effective way to prevent, and delay low grade systemic inflammatory related diseases.

Mitochondrial gene expression in elite cyclists: effects of high-intensity interval exercise

Little is known about the effect of training on genetic markers for mitochondrial biogenesis in elite athletes. We tested the hypothesis that low-volume sprint interval exercise (SIE) would be as effective as high-volume interval exercise (IE). Ten male cyclists competing on national elite level (W (max) 403 ± 13 W, VO(2peak) 68 ± 1 mL kg(-1) min(-1)) performed two interval exercise protocols: 7 × 30-s "all-out" bouts (SIE) and 3 × 20-min bouts at ~87% of VO(2peak) (IE). During IE, the work was eightfold larger (1,095 ± 43 vs. 135 ± 5 kJ) and the exercise duration 17 times longer (60 vs. 3.5 min) than during SIE. Muscle samples were taken before and 3 h after exercise. The mRNA of upstream markers of mitochondrial biogenesis [peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1α), PGC-1α-related coactivator (PRC) and peroxisome proliferator-activated receptor δ (PPARδ)] increased to the same extent after SIE and IE (6-, 1.5- and 1.5-fold increase, respectively). Of the downstream targets of PGC-1α, mitochondrial transcription factor A (Tfam) increased only after SIE and was significantly different from that after IE (P < 0.05), whereas others increased to the same extent (pyruvate dehydrogenase kinase, PDK4) or was unchanged (nuclear respiratory factor 2, NRF2). We conclude that upstream genetic markers of mitochondrial biogenesis increase in a similar way in elite athletes after one exercise session of SIE and IE. However, since the volume and duration of work was considerably lower during SIE and since Tfam, the downstream target of PGC-1α, increased only after SIE, we conclude that SIE might be a time-efficient training strategy for highly trained individuals.

The degree of p70 S6k and S6 phosphorylation in human skeletal muscle in response to resistance exercise depends on the training volume

Regular performance of resistance exercise induces an increase in skeletal muscle mass, however, the molecular mechanisms underlying this effect are not yet fully understood. The purpose of the present investigation was to examine acute changes in molecular signalling in response to resistance exercise involving different training volumes. Eight untrained male subjects carried out one, three and five sets of 6 repetition maximum (RM) in leg press exercise in a random order. Muscle biopsies were taken from the vastus lateralis both prior to and 30 min after each training session and the effect on protein signalling was studied. Phosphorylation of Akt was not altered significantly after any of the training protocols, whereas that of the mammalian target of rapamycin was enhanced to a similar extent by training at all three volumes. The phosphorylation of p70S6 kinase (p70(S6k)) was elevated threefold after 3 × 6 RM and sixfold after 5 × 6 RM, while the phosphorylation of S6 was increased 30- and 55-fold following the 3 × 6 RM and 5 × 6 RM exercises, respectively. Moreover, the level of the phosphorylated form of the gamma isoform of p38 MAPK was enhanced three to fourfold following each of the three protocols, whereas phosphorylation of ERK1/2 was unchanged 30 min following exercise. These findings indicate that when exercise is performed in a fasted state, the increase in phosphorylation of signalling molecules such as p70(S6k) and the S6 ribosomal protein in human muscle depends on the exercise volume.

New horizons for the methodology and physiology of training periodization

The theory of training was established about five decades ago when knowledge of athletes' preparation was far from complete and the biological background was based on a relatively small amount of objective research findings. At that time, traditional 'training periodization', a division of the entire seasonal programme into smaller periods and training units, was proposed and elucidated. Since then, international sport and sport science have experienced tremendous changes, while the traditional training periodization has remained at more or less the same level as the published studies of the initial publications. As one of the most practically oriented components of theory, training periodization is intended to offer coaches basic guidelines for structuring and planning training. However, during recent decades contradictions between the traditional model of periodization and the demands of high-performance sport practice have inevitably developed. The main limitations of traditional periodization stemmed from: (i) conflicting physiological responses produced by 'mixed' training directed at many athletic abilities; (ii) excessive fatigue elicited by prolonged periods of multi-targeted training; (iii) insufficient training stimulation induced by workloads of medium and low concentration typical of 'mixed' training; and (iv) the inability to provide multi-peak performances over the season. The attempts to overcome these limitations led to development of alternative periodization concepts. The recently developed block periodization model offers an alternative revamped approach for planning the training of high-performance athletes. Its general idea proposes the sequencing of specialized training cycles, i.e. blocks, which contain highly concentrated workloads directed to a minimal number of targeted abilities. Unlike the traditional model, in which the simultaneous development of many athletic abilities predominates, block-periodized training presupposes the consecutive development of reasonably selected target abilities. The content of block-periodized training is set down in its general principles, a taxonomy of mesocycle blocks, and guidelines for compiling an annual plan.

Electric pulse stimulation of cultured murine muscle cells reproduces gene expression changes of trained mouse muscle

Adequate levels of physical activity are at the center of a healthy lifestyle. However, the molecular mechanisms that mediate the beneficial effects of exercise remain enigmatic. This gap in knowledge is caused by the lack of an amenable experimental model system. Therefore, we optimized electric pulse stimulation of muscle cells to closely recapitulate the plastic changes in gene expression observed in a trained skeletal muscle. The exact experimental conditions were established using the peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha) as a marker for an endurance-trained muscle fiber. We subsequently compared the changes in the relative expression of metabolic and myofibrillar genes in the muscle cell system with those observed in mouse muscle in vivo following either an acute or repeated bouts of treadmill exercise. Importantly, in electrically stimulated C2C12 mouse muscle cells, the qualitative transcriptional adaptations were almost identical to those in trained muscle, but differ from the acute effects of exercise on muscle gene expression. In addition, significant alterations in the expression of myofibrillar proteins indicate that this stimulation could be used to modulate the fiber-type of muscle cells in culture. Our data thus describe an experimental cell culture model for the study of at least some of the transcriptional aspects of skeletal muscle adaptation to physical activity. This system will be useful for the study of the molecular mechanisms that regulate exercise adaptation in muscle.

Changes in skeletal muscle mitochondria in response to the development of type 2 diabetes or prevention by daily wheel running in hyperphagic OLETF rats

The temporal changes in skeletal muscle mitochondrial content and lipid metabolism that precede type 2 diabetes are largely unknown. Here we examined skeletal muscle mitochondrial fatty acid oxidation (MitoFAOX) and markers of mitochondrial gene expression and protein content in sedentary 20- and 40-wk-old hyperphagic, obese Otsuka Long-Evans Tokushima fatty (OLETF-SED) rats. Changes in OLETF-SED rats were compared with two groups of rats who maintained insulin sensitivity: age-matched OLETF rats given access to voluntary running wheels (OLETF-EX) and sedentary, nonobese Long-Evans Tokushima Otsuka (LETO-SED) rats. As expected, glucose tolerance tests revealed insulin resistance at 20 wk that progressed to type 2 diabetes at 40 wk in the OLETF-SED, whereas both the OLETF-EX and LETO-SED maintained whole body insulin sensitivity. At 40 wk, complete MitoFAOX (to CO(2)), beta-hydroxyacyl-CoA dehydrogenase activity, and citrate synthase activity did not differ between OLETF-SED and LETO-SED but were significantly (P < 0.05) higher in OLETF-EX compared with OLETF-SED rats. Genes controlling skeletal muscle MitoFAOX (PGC-1alpha, PPARdelta, mtTFA, cytochrome c) were not different between OLETF-SED and LETO-SED at any age. Compared with the OLETF-SED, the OLETF-EX rats had significantly (P < 0.05) higher skeletal muscle PGC-1alpha, cytochrome c, and mtTFA mRNA levels at 20 and 40 wk and PPARdelta at 40 wk; however, protein content for each of these markers did not differ between groups at 40 wk. Limited changes in skeletal muscle mitochondria were observed during the transition from insulin resistance to type 2 diabetes in the hyperphagic OLETF rat. However, diabetes prevention through increased physical activity appears to be mediated in part through maintenance of skeletal muscle mitochondrial function.

Combining hypoxic methods for peak performance

New methods and devices for pursuing performance enhancement through altitude training were developed in Scandinavia and the USA in the early 1990s. At present, several forms of hypoxic training and/or altitude exposure exist: traditional 'live high-train high' (LHTH), contemporary 'live high-train low' (LHTL), intermittent hypoxic exposure during rest (IHE) and intermittent hypoxic exposure during continuous session (IHT). Although substantial differences exist between these methods of hypoxic training and/or exposure, all have the same goal: to induce an improvement in athletic performance at sea level. They are also used for preparation for competition at altitude and/or for the acclimatization of mountaineers. The underlying mechanisms behind the effects of hypoxic training are widely debated. Although the popular view is that altitude training may lead to an increase in haematological capacity, this may not be the main, or the only, factor involved in the improvement of performance. Other central (such as ventilatory, haemodynamic or neural adaptation) or peripheral (such as muscle buffering capacity or economy) factors play an important role. LHTL was shown to be an efficient method. The optimal altitude for living high has been defined as being 2200-2500 m to provide an optimal erythropoietic effect and up to 3100 m for non-haematological parameters. The optimal duration at altitude appears to be 4 weeks for inducing accelerated erythropoiesis whereas <3 weeks (i.e. 18 days) are long enough for beneficial changes in economy, muscle buffering capacity, the hypoxic ventilatory response or Na(+)/K(+)-ATPase activity. One critical point is the daily dose of altitude. A natural altitude of 2500 m for 20-22 h/day (in fact, travelling down to the valley only for training) appears sufficient to increase erythropoiesis and improve sea-level performance. 'Longer is better' as regards haematological changes since additional benefits have been shown as hypoxic exposure increases beyond 16 h/day. The minimum daily dose for stimulating erythropoiesis seems to be 12 h/day. For non-haematological changes, the implementation of a much shorter duration of exposure seems possible. Athletes could take advantage of IHT, which seems more beneficial than IHE in performance enhancement. The intensity of hypoxic exercise might play a role on adaptations at the molecular level in skeletal muscle tissue. There is clear evidence that intense exercise at high altitude stimulates to a greater extent muscle adaptations for both aerobic and anaerobic exercises and limits the decrease in power. So although IHT induces no increase in VO(2max) due to the low 'altitude dose', improvement in athletic performance is likely to happen with high-intensity exercise (i.e. above the ventilatory threshold) due to an increase in mitochondrial efficiency and pH/lactate regulation. We propose a new combination of hypoxic method (which we suggest naming Living High-Training Low and High, interspersed; LHTLHi) combining LHTL (five nights at 3000 m and two nights at sea level) with training at sea level except for a few (2.3 per week) IHT sessions of supra-threshold training. This review also provides a rationale on how to combine the different hypoxic methods and suggests advances in both their implementation and their periodization during the yearly training programme of athletes competing in endurance, glycolytic or intermittent sports.

Contraction-induced changes in TNFalpha and Akt-mediated signalling are associated with increased myofibrillar protein in rat skeletal muscle

Resistance training results in skeletal muscle hypertrophy, but the molecular signalling mechanisms responsible for this altered phenotype are incompletely understood. We used a resistance training (RT) protocol consisting of three sessions [day 1 (d1), day 3 (d3), day 5 (d5)] separated by 48 h recovery (squat exercise, 4 sets x 10 repetitions, 3 min recovery) to determine early signalling responses to RT in rodent skeletal muscle. Six animals per group were killed 3 h after each resistance training session and 24 and 48 h after the last training session (d5). There was a robust increase in TNFalpha protein expression, and IKK(Ser180/181) and p38MAPK(Thr180/Tyr182) phosphorylation on d1 (P < 0.05), which abated with subsequent RT, returning to control levels by d5 for TNFalpha and IKK(Ser180/181). There was a trend for a decrease in MuRF-1 protein expression, 48 h following d5 of training (P = 0.08). Notably, muscle myofibrillar protein concentration was elevated compared to control 24 and 48 h following RT (P < 0.05). Akt(Ser473) and mTOR(Ser2448) phosphorylation were unchanged throughout RT. Phosphorylation of p70S6k(Thr389) increased 3 h post-exercise on d1, d3 and d5 (P < 0.05), whilst phosphorylation of S6(Ser235/236) increased on d1 and d3 (P < 0.05). Our results show a rapid attenuation of inflammatory signalling with repeated bouts of resistance exercise, concomitant with summation in translation initiation signalling in skeletal muscle. Indeed, the cumulative effect of these signalling events was associated with myofibrillar protein accretion, which likely contributes to the early adaptations in response to resistance training overload in the skeletal muscle.

Prevalência de alterações posturais em praticantes de musculação

INTRODUÇÃO: Atualmente, as academias de musculação são centros de promoção de saúde procurados por um número cada vez maior de pessoas. A execução adequada dos exercícios resistidos em academia depende de um bom alinhamento postural. OBJETIVO: Verificar quantitativamente as principais alterações posturais em praticantes de exercício resistido sistematizado (musculação). MÉTODOS: Foram realizadas avaliações posturais em 306 indivíduos, de ambos os sexos e faixa etária entre 14 e 73 anos. As avaliações foram realizadas por acadêmicos de fisioterapia devidamente treinados e padronizadas de modo que os dados fossem coletados da maneira mais objetiva possível. RESULTADOS: Os resultados são apresentados de maneira geral (total da amostra), além de subdivididos conforme os gêneros masculino (n = 113) e feminino (n = 193) e de acordo com a faixa etária, adotando-se as seguintes categorias: alunos menores de 21 anos (n = 74); entre 21 e 30 anos (n = 127); entre 31 e 50 anos (n = 40); e maiores de 50 anos (n = 65). Dentre os resultados, destacam-se as alterações na coluna vertebral (aumento da curvatura ou retificação): 43,4% na região cervical, 55,2% na torácica e 73,8% na lombar. Além disso, 48,0% apresentaram atitude escoliótica, sendo que em 37,0% foi observado presença de gibosidade. CONCLUSÕES: A principal conclusão do presente estudo é de que os praticantes de musculação apresentam consideráveis índices de desvios posturais, enfatizando a necessidade de maior atenção sobre essa crescente população.

Ammonia metabolism, the brain and fatigue; revisiting the link

This review addresses the ammonia fatigue theory in light of new evidence from exercise and disease studies and aims to provide a view of the role of ammonia during exercise. Hyperammonemia is a condition common to pathological liver disorders and intense or exhausting exercise. In pathology, hyperammonemia is linked to impairment of normal brain function and the onset of the neurological condition, hepatic encephalopathy. Elevated blood ammonia concentrations arise due to a diminished capacity for removal via the liver and lead to increased exposure of organs, such as the brain, to the toxic effects of ammonia. High levels of brain ammonia can lead to deleterious alterations in astrocyte morphology, cerebral energy metabolism and neurotransmission, which may in turn impact on the functioning of important signalling pathways within the neuron. Such changes are believed to contribute to the disturbances in neuropsychological function, in particular the learning, memory, and motor control deficits observed in animal models of liver disease and also patients with cirrhosis. Hyperammonemia in exercise occurs as a result of an increased production by contracting muscle, through adenosine monophosphate (AMP) deamination (the purine nucleotide cycle) and branched chain amino acid (BCAA) deamination prior to oxidation. Plasma concentrations of ammonia during exercise often achieve or exceed those measured in liver disease patients, resulting in increased cerebral uptake. In this article we propose that exercise-induced hyperammonemia may lead to concomitant disturbances in brain function, potentially through similar mechanisms underpinning pathology, which may impact on performance as fatigue or reduced function, especially during extreme exercise.

Changes of gene expression in electrically stimulated and contralateral rat soleus muscles

In this study we investigate the effect of a single session of high-intensity contractions on expression of pleiotropic genes and, in particular, those genes associated with metabolism in soleus muscle from electrically stimulated (ES) and contralateral (CL) limbs. The right limbs of male Wistar rats were submitted to contractions by 200-ms trains of electrical stimulation at 100-HZ frequency with pulses of 0.1 ms (voltage 24 +/- 3 V) delivered each second for 1 hour. Soleus muscles were isolated 1 hour after contraction, and gene expression was analyzed by a macroarray technique (Atlas Toxicology 1.2 Array; Clontech Laboratories). Electrical stimulation increased expression in 92 genes (16% of the genes present in the membrane). Sixty-six genes were upregulated in both ES and CL soleus muscles, and expression of 26 genes was upregulated in the ES muscle only. The most altered genes were those related to stress response and metabolism. Electrical stimulation also raised expression of transcription factors, translation and posttranslational modification of proteins, ribosomal proteins, and intracellular transducers/effectors/modulators. The results indicate that a single session of electrical stimulation upregulated expression of genes related to metabolism and oxidative stress in soleus muscle from both ES and CL limbs. These findings may indicate an association with tissue hypertrophy and metabolic adaptations induced by physical exercise training not only in the ES but also in the CL non-stimulated muscle, suggesting a cross-education phenomenon.

Effect of consecutive repeated sprint and resistance exercise bouts on acute adaptive responses in human skeletal muscle

We examined acute molecular responses in skeletal muscle to repeated sprint and resistance exercise bouts. Six men [age, 24.7 ± 6.3 yr; body mass, 81.6 ± 7.3 kg; peak oxygen uptake, 47 ± 9.9 ml·kg−1·min−1; one repetition maximum (1-RM) leg extension 92.2 ± 12.5 kg; means ± SD] were randomly assigned to trials consisting of either resistance exercise (8 × 5 leg extension, 80% 1-RM) followed by repeated sprints (10 × 6 s, 0.75 N·m torque·kg−1) or vice-versa. Muscle biopsies from vastus lateralis were obtained at rest, 15 min after each exercise bout, and following 3-h recovery to determine early signaling and mRNA responses. There was divergent exercise order-dependent phosphorylation of p70 S6K (S6K). Specifically, initial resistance exercise increased S6K phosphorylation (∼75% P < 0.05), but there was no effect when resistance exercise was undertaken after sprints. Exercise decreased IGF-I mRNA following 3-h recovery (∼50%, P = 0.06) independent of order, while muscle RING finger mRNA was elevated with a moderate exercise order effect ( P < 0.01). When resistance exercise was followed by repeated sprints PGC-1α mRNA was increased (REX1-SPR2; P = 0.02) with a modest distinction between exercise orders. Repeated sprints may promote acute interference on resistance exercise responses by attenuating translation initiation signaling and exacerbating ubiquitin ligase expression. Indeed, repeated sprints appear to generate the overriding acute exercise-induced response when undertaking concurrent repeated sprint and resistance exercise. Accordingly, we suggest that sprint-activities are isolated from resistance training and that adequate recovery time is considered within periodized training plans that incorporate these divergent exercise modes.

mTOR function in skeletal muscle: a focal point for overnutrition and exercise

The mammalian target of rapamycin (mTOR) is a highly conserved atypical serine–threonine kinase that controls numerous functions essential for cell homeostasis and adaptation in mammalian cells via 2 distinct protein complex formations. Moreover, mTOR is a key regulatory protein in the insulin signalling cascade and has also been characterized as an insulin-independent nutrient sensor that may represent a critical mediator in obesity-related impairments of insulin action in skeletal muscle. Exercise characterizes a remedial modality that enhances mTOR activity and subsequently promotes beneficial metabolic adaptation in skeletal muscle. Thus, the metabolic effects of nutrients and exercise have the capacity to converge at the mTOR protein complexes and subsequently modify mTOR function. Accordingly, the aim of the present review is to highlight the role of mTOR in the regulation of insulin action in response to overnutrition and the capacity for exercise to enhance mTOR activity in skeletal muscle.