Acute and chronic response of skeletal muscle to resistance exercise

Exercise induces tissue-specific adaptations to enhance cardiometabolic health

The risk associated with multiple cancers, cardiovascular disease, diabetes, and all-cause mortality is decreased in individuals who meet the current recommendations for physical activity. Therefore, regular exercise remains a cornerstone in the prevention and treatment of non-communicable diseases. An acute bout of exercise results in the coordinated interaction between multiple tissues to meet the increased energy demand of exercise. Over time, the associated metabolic stress of each individual exercise bout provides the basis for long-term adaptations across tissues, including the cardiovascular system, skeletal muscle, adipose tissue, liver, pancreas, gut, and brain. Therefore, regular exercise is associated with a plethora of benefits throughout the whole body, including improved cardiorespiratory fitness, physical function, and glycemic control. Overall, we summarize the exercise-induced adaptations that occur within multiple tissues and how they converge to ultimately improve cardiometabolic health.

Proteomic features of skeletal muscle adaptation to resistance exercise training as a function of age

Resistance exercise training (RET) can counteract negative features of muscle ageing but older age associates with reduced adaptive capacity to RET. Altered muscle protein networks likely contribute to ageing RET adaptation; therefore, associated proteome-wide responses warrant exploration. We employed quantitative sarcoplasmic proteomics to compare age-related proteome and phosphoproteome responses to RET. Thigh muscle biopsies were collected from eight young (25 ± 1.1 years) and eight older (67.5 ± 2.6 years) adults before and after 20 weeks supervised RET. Muscle sarcoplasmic fractions were pooled for each condition and analysed using Isobaric Tags for Relative and Absolute Quantification (iTRAQ) labelling, tandem mass spectrometry and network-based hub protein identification. Older adults displayed impaired RET-induced adaptations in whole-body lean mass, body fat percentage and thigh lean mass (P > 0.05). iTRAQ identified 73 differentially expressed proteins with age and/or RET. Despite possible proteomic stochasticity, RET improved ageing profiles for mitochondrial function and glucose metabolism (top hub; PYK (pyruvate kinase)) but failed to correct altered ageing expression of cytoskeletal proteins (top hub; YWHAZ (14-3-3 protein zeta/delta)). These ageing RET proteomic profiles were generally unchanged or oppositely regulated post-RET in younger muscle. Similarly, RET corrected expression of 10 phosphoproteins altered in ageing, but these responses were again different vs. younger adults. Older muscle is characterised by RET-induced metabolic protein profiles that, whilst not present in younger muscle, improve untrained age-related proteomic deficits. Combined with impaired cytoskeletal adhesion responses, these results provide a proteomic framework for understanding and optimising ageing muscle RET adaptation.

ANALYSIS OF STUDENTS' HEALTH INDICATORS IN THE COURSE OF PHYSICAL EDUCATION CLASSES WITH A SPORTS FOCUS

OBJECTIVE

The aim: To conduct a comparative analysis of the health indicators of students who were engaged in various types of sports during physical education classes (using the example of power sports).

PATIENTS AND METHODS

Materials and methods: The research was conducted in 2019-2021 when the male students (n=96) were studying at the 1st and 2nd years in Kharkiv State Academy of Physical Culture. We examined the health indicators of 17-19-year-old students, who were engaged in various power sports: powerlifting, kettlebell lifting, armsport and CrossFit. Students' health was assessed by indicators of body weight, cardiovascular, respiratory and muscular systems.

RESULTS

Results: It was found that during the study period, the most pronounced changes in the activity of the cardiovascular (Robinson's index) and respiratory systems (vital index) were found among students who were engaged in CrossFit and kettlebell lifting. In the indicators that characterize the muscular system (power index), the greatest increase was found among students who were engaged in powerlifting and armsport.

CONCLUSION

Conclusions: It has been revealed that classes in any power sport positively affect the improvement of certain indicators of students' health, which, in general, will positively contribute to mastering the skills and abilities to independently use the means of physical culture and sports in everyday life to maintain high performance both during academic and future professional activities.

Prediction of muscle fiber composition using multiple repetition testing

Direct determination of muscle fiber composition is invasive and expensive, with indirect methods also requiring specialist resources and expertise. Performing resistance exercises at 80% 1RM is suggested as a means of indirectly estimating muscle fiber composition, though this hypothesis has never been validated against a direct method. The aim of the study was to investigate the relationship between the number of completed repetitions at 80% 1RM of back squat exercise and muscle fiber composition. Thirty recreationally active participants’ (10 females, 20 males) 1RM back squat load was determined, before the number of consecutive repetitions at 80% 1RM was recorded. The relationship between the number of repetitions and the percentage of fast-twitch fibers from vastus lateralis was investigated. The number of completed repetitions ranged from 5 to 15 and was independent of sex, age, 1RM, training frequency, training type, training experience, BMI or muscle fiber cross-sectional area. The percentage of fast-twitch muscle fibers was inversely correlated with the number of repetitions completed (r = –0.38, P = 0.039). Participants achieving 5 to 8 repetitions (n = 10) had significantly more fast-twitch muscle fibers (57.5 ± 9.5 vs 44.4 ± 11.9%, P = 0.013) than those achieving 11–15 repetitions (n = 11). The remaining participants achieved 9 or 10 repetitions (n = 9) and on average had equal proportion of fast- and slow-twitch muscle fibers. In conclusion, the number of completed repetitions at 80% of 1RM is moderately correlated with muscle fiber composition.

The Effects of Multiple Sets of Squats and Jump Squats on Mechanical Variables

Rossetti, ML, Munford, SN, Snyder, BW, Davis, SE, and Moir, GL. The effects of multiple sets of squats and jump squats on mechanical variables. J Strength Cond Res 34(4): 1017-1023, 2020-The mechanical responses to 2 nonballistic squat and 2 ballistic jump squat protocols performed over multiple sets were investigated. One protocol from each of the 2 nonballistic and ballistic conditions incorporated a pause between the eccentric and concentric phases of the movements in order to determine the influence of the coupling time on the mechanical variables and postactivation potentiation (PAP). Eleven men (age: 21.9 ± 1.8 years; height: 1.79 ± 0.05 m; mass: 87.0 ± 7.4 kg) attended 4 sessions where they performed multiple sets of squats and jump squats with a load equivalent to 30% 1-repetition maximum under one of the following conditions: (a) 3 × 4 repetitions of nonballistic squats (30N-B); (b) 3 × 4 repetitions of nonballistic squats with a 3-second pause between the eccentric and concentric phases of each repetition (30PN-B); (c) 3 × 4 repetitions of ballistic jump squats (30B); (d) 3 × 4 repetitions of ballistic jump squats with a 3-second pause between the eccentric and concentric phases of each repetition (30PB). Force plates were used to calculate variables including average vertical velocity, average vertical force (GRF), and average power output (PO). Vertical velocities during the ballistic conditions were significantly greater than those attained during the nonballistic conditions (mean differences: 0.21-0.25 m·s, p < 0.001, effect sizes [ES]: 1.70-1.89) as were GRFs (mean differences: 478-526 N, p < 0.001, ES: 1.61-1.63), and PO (mean differences: 711-869 W, p < 0.001, ES: 1.66-1.73). Moreover, the increase in PO across the 3 sets in 30B was significantly greater than the changes observed during 30N-B, 30PN-B, and 30PB (p ≤ 0.015). The pause reduced the mechanical variables during both the nonballistic and ballistic conditions, although the differences were not statistically significant (p > 0.05). Ballistic jump squats may be an effective exercise for developing PO given the high velocities and forces generated in these exercises. Furthermore, the completion of multiple sets of jump squats may induce PAP to enhance PO. The coupling times between the eccentric and concentric phases of the jump squats should be short in order to maximize the GRF and PO across the sets.

Acute resistance exercise induces Sestrin2 phosphorylation and p62 dephosphorylation in human skeletal muscle

Sestrins (1, 2, 3) are a family of stress-inducible proteins capable of attenuating oxidative stress, regulating metabolism, and stimulating autophagy. Sequestosome1 (p62) is also a stress-inducible multifunctional protein acting as a signaling hub for oxidative stress and selective autophagy. It is unclear whether Sestrin and p62^Ser403 are regulated acutely or chronically by resistance exercise (RE) or training (RT) in human skeletal muscle. Therefore, the acute and chronic effects of RE on Sestrin and p62 in human skeletal muscle were examined through two studies. In Study 1, nine active men (22.1 ± 2.2 years) performed a bout of single-leg strength exercises and muscle biopsies were collected before, 2, 24, and 48 h after exercise. In Study 2, 10 active men (21.3 ± 1.9 years) strength trained for 12 weeks (2 days per week) and biopsies were collected pre- and post-training. Acutely, 2 h postexercise, phosphorylation of p62^Ser403 was downregulated, while there was a mobility shift of Sestrin2, indicative of increased phosphorylation. Forty-eight hours postexercise, the protein expression of both Sestrin1 and total p62 increased. Chronic exercise had no impact on the gene or protein expression of Sestrin2/3 or p62, but Sestrin1 protein was upregulated. These findings demonstrated an inverse relationship between Sestrin2 and p62 phosphorylation after a single bout of RE, indicating they are transiently regulated. Contrarily, 12 weeks of RT increased protein expression of Sestrin1, suggesting that despite the strong sequence homology of the Sestrin family, they are differentially regulated in response to acute RE and chronic RT.

Comparison of fatigue responses and rapid force characteristics between explosive- and traditional-resistance-trained males

PURPOSE

To compare maximal and rapid force characteristics, as well as fatigability, between traditional (TRT) and explosive (ERT) resistance-trained men.

METHODS

Fourteen TRT (mean age = 25 years) and twelve ERT (mean age = 22 years) men performed rapid maximal contractions followed by an isokinetic fatigue protocol consisting of 50 maximal knee extension (KE) and flexions (KF) at a moderate speed (180° s^-¹). Baseline measures included: isokinetic peak torque (PT), isometric rate of torque development (RTD_0-50), peak acceleration (ACC_max), and peak velocity (V_max). Changes in torque with fatigue were used to calculate a fatigue index (FI%).

RESULTS

The ERT group (M ± SD; 1199.05 ± 404.12) displayed a significantly higher isometric RTD_0-50 (p = 0.049) during KE than the TRT group (931.73 ± 244.75). No other significant differences in the dependent variables (PT, FI%, ACC_max, V_max; all p ≥ 0.05) were observed between groups (TRT vs. ERT) for either of the muscle groups (KE and KF).

CONCLUSIONS

The results of the present study indicated that only knee extension RTD was able to discriminate between the two groups. These findings suggest that rapid force production may be more sensitive at distinguishing training-specific muscular adaptations than peak acceleration or velocity.

Prior acetaminophen consumption impacts the early adaptive cellular response of human skeletal muscle to resistance exercise

Resistance exercise (RE) is a powerful stimulus for skeletal muscle adaptation. Previous data demonstrate that cyclooxygenase (COX)-inhibiting drugs alter the cellular mechanisms regulating the adaptive response of skeletal muscle. The purpose of this study was to determine whether prior consumption of the COX inhibitor acetaminophen (APAP) alters the immediate adaptive cellular response in human skeletal muscle after RE. In a double-blinded, randomized, crossover design, healthy young men ( n = 8, 25 ± 1 yr) performed two trials of unilateral knee extension RE (8 sets, 10 reps, 65% max strength). Subjects ingested either APAP (1,000 mg/6 h) or placebo (PLA) for 24 h before RE (final dose consumed immediately after RE). Muscle biopsies (vastus lateralis) were collected at rest and 1 h and 3 h after exercise. Mammalian target of rapamycin (mTOR) complex 1 signaling was assessed through immunoblot and immunohistochemistry, and mRNA expression of myogenic genes was examined via RT-qPCR. At 1 h p-rpS6Ser240/244 was increased in both groups but to a greater extent in PLA. At 3 h p-S6K1Thr389 was elevated only in PLA. Furthermore, localization of mTOR to the lysosome (LAMP2) in myosin heavy chain (MHC) II fibers increased 3 h after exercise only in PLA. mTOR-LAMP2 colocalization in MHC I fibers was greater in PLA vs. APAP 1 h after exercise. Myostatin mRNA expression was reduced 1 h after exercise only in PLA. MYF6 mRNA expression was increased 1 h and 3 h after exercise only in APAP. APAP consumption appears to alter the early adaptive cellular response of skeletal muscle to RE. These findings further highlight the mechanisms through which COX-inhibiting drugs impact the adaptive response of skeletal muscle to exercise.

NEW & NOTEWORTHY The extent to which the cellular reaction to acetaminophen impacts the mechanisms regulating the adaptive response of human skeletal muscle to resistance exercise is not well understood. Consumption of acetaminophen before resistance exercise appears to suppress the early response of mTORC1 activity to acute resistance exercise. These data also demonstrate, for the first time, that resistance exercise elicits fiber type-specific changes in the intracellular colocalization of mTOR with the lysosome in human skeletal muscle.

The effect of warm-ups with stretching on the isokinetic moments of collegiate men

Performing warm-ups increases muscle temperature and blood flow, which contributes to improved exercise performance and reduced risk of injuries to muscles and tendons. Stretching increases the range of motion of the joints and is effective for the maintenance and enhancement of exercise performance and flexibility, as well as for injury prevention. However, stretching as a warm-up activity may temporarily decrease muscle strength, muscle power, and exercise performance. This study aimed to clarify the effect of stretching during warm-ups on muscle strength, muscle power, and muscle endurance in a nonathletic population. The subjects of this study consisted of 13 physically active male collegiate students with no medical conditions. A self-assessment questionnaire regarding how well the subjects felt about their physical abilities was administered to measure psychological readiness before and after the warm-up. Subjects performed a non-warm-up, warm-up, or warm-up regimen with stretching prior to the assessment of the isokinetic moments of knee joints. After the measurements, the respective variables were analyzed using nonparametric tests. First, no statistically significant intergroup differences were found in the flexor and extensor peak torques of the knee joints at 60°/sec, which were assessed to measure muscle strength. Second, no statistically significant intergroup differences were found in the flexor and extensor peak torques of the knee joints at 180°/sec, which were assessed to measure muscle power. Third, the total work of the knee joints at 240°/sec, intended to measure muscle endurance, was highest in the aerobic-stretch-warm-ups (ASW) group, but no statistically significant differences were found among the groups. Finally, the psychological readiness for physical activity according to the type of warm-up was significantly higher in ASW. Simple stretching during warm-ups appears to have no effect on variables of exercise physiology in nonathletes who participate in routine recreational sport activities. However, they seem to have a meaningful effect on exercise performance by affording psychological stability, preparation, and confidence in exercise performance.

Aerobic training but no resistance training increases SIRT3 in skeletal muscle of sedentary obese male adolescents

In recent years, prevalence of obesity in children and adolescents has increased. A strategy for prevention and management of obesity is aerobic training (AT) due to its effectiveness to decrease fat mass. AT increases the content of SIRT3, a mitochondrial protein that increases the expression of PGC-1α and NFR1, thereby enhances mitochondrial function and metabolic health. Resistance training (RT) provides metabolic benefits but its effect on SIRT3 content is unknown. To compare the effect of AT and RT on SIRT3, PGC-1α and NRF-1 protein levels in skeletal muscle of sedentary obese adolescents. Twenty-seven sedentary obese male adolescents (age: 16.7 ± 0.9 years; BMI: 33.7 ± 4.3 kg/m²) completed a 1-month control period prior to randomization to one of two supervised exercise protocols: AT (3 days/week, 40 min/day, 70-80% peak heart rate) or RT (3 days/week, 11 exercises, 2 sets/exercise, 12 repetitions/set) for 12 weeks. Biopsies were obtained from the vastus lateralis muscle before and after 12 weeks to analyse SIRT3, PGC-1α and NRF-1 proteins content. Peak oxygen consumption (VO_2peak) and anthropometric variables were evaluated before and after training. AT increased SIRT3 content, which was associated with improvements in PGC-1α content and body fat percentage. RT did not affect SIRT3 or PGC-1α. VO_2peak increased only in AT. The increase in muscle mitochondrial SIRT3 was observed only following AT. In contrast, RT increased muscle mass without improving SIRT3 in obese male adolescents.

Transcriptional profiling of rat skeletal muscle hypertrophy under restriction of blood flow

Blood flow restriction (BFR) under low-intensity resistance training (LIRT) can produce similar effects upon muscles to that of high-intensity resistance training (HIRT) while overcoming many of the restrictions to HIRT that occurs in a clinical setting. However, the potential molecular mechanisms of BFR induced muscle hypertrophy remain largely unknown. Here, using a BFR rat model, we aim to better elucidate the mechanisms regulating muscle hypertrophy as induced by BFR and reveal possible clinical therapeutic targets for atrophy cases. We performed genome wide screening with microarray analysis to identify unique differentially expressed genes during rat muscle hypertrophy. We then successfully separated the differentially expressed genes from BRF treated soleus samples by comparing the Affymetrix rat Genome U34 2.0 array with the control. Using qRT-PCR and immunohistochemistry (IHC) we also analyzed other related differentially expressed genes. Results suggested that muscle hypertrophy induced by BFR is essentially regulated by the rate of protein turnover. Specifically, PI3K/AKT and MAPK pathways act as positive regulators in controlling protein synthesis where ubiquitin-proteasome acts as a negative regulator. This represents the first general genome wide level investigation of the gene expression profile in the rat soleus after BFR treatment. This may aid our understanding of the molecular mechanisms regulating and controlling muscle hypertrophy and provide support to the BFR strategies aiming to prevent muscle atrophy in a clinical setting.

Contractile properties of motor units and expression of myosin heavy chain isoforms in rat fast-type muscle after volitional weight-lifting training

Dynamic resistance training increases the force and speed of muscle contraction, but little is known about modifications to the contractile properties of the main physiological types of motor units (MUs) that contribute to these muscle adaptations. Although the contractile profile of MU muscle fibers is tightly coupled to myosin heavy chain (MyHC) protein expression, it is not well understood if MyHC transition is a prerequisite for modifications to the contractile characteristics of MUs. In this study, we examined MU contractile properties, the mRNA expression of MyHC, parvalbumin, and sarcoendoplasmic reticulum Ca²⁺ pump isoforms, as well as the MyHC protein content after 5 wk of volitional progressive weight-lifting training in the medial gastrocnemius muscle in rats. The training had no effect on MyHC profiling or Ca²⁺-handling protein gene expression. Maximum force increased in slow (by 49%) and fast (by 21%) MUs. Within fast MUs, the maximum force increased in most fatigue-resistant and intermediate but not most fatigable MUs. Twitch contraction time was shortened in slow and fast fatigue-resistant MUs. Twitch half-relaxation was shortened in fast most fatigue-resistant and intermediate MUs. The force-frequency curve shifted rightward in fast fatigue-resistant MUs. Fast fatigable MUs fatigued less within the initial 15 s while fast fatigue-resistant units increased the ability to potentiate the force within the first minute of the standard fatigue test. In conclusion, at the early stage of resistance training, modifications to the contractile characteristics of MUs appear in the absence of MyHC transition and the upregulation of Ca²⁺-handling genes.

Expanding Instrumental Options for Dysphagia Diagnosis and Research: Ultrasound and Manometry

Diagnostic assessment of swallowing in routine clinical practice relies heavily on the long-standing techniques of videofluoroscopic swallowing study (VFSS) and videoendoscopic evaluation of swallowing (VEES). These complementary and sophisticated techniques provide a real-time visualization of biomechanical movements of the structures involved in swallowing and consequent effects on bolus flow. Despite the sophistication of this instrumentation, interpretation relies heavily on subjective clinical judgement and temporal resolution is limited, limitations that may influence patient management. Adjunctive diagnostic assessments may be utilized to compensate for the limitations posed by VFSS and VEES. Ultrasound and pharyngeal manometry do not represent the latest in technological advances, with both emerging in swallowing research over 20 years ago. However, both have resisted integration into routine clinical practice, despite the fact that they offer quantitative metrics of swallowing that are not available using standard techniques. The aim of this review is to present recent research on these two less frequently used modalities in clinical swallowing assessment, discuss potential applications in clinical practice and review supportive data on test-retest reliability, rater reliability and validity. The paper will conclude with a case report that exemplifies the unique contribution of these modalities in executing and revising therapeutic approaches for a patient with neurogenic dysphagia.

Aerobic and resistance training dependent skeletal muscle plasticity in the colon-26 murine model of cancer cachexia

PURPOSE

The appropriate mode of exercise training for cancer cachexia is not well-established. Using the colon-26 (C26) mouse model of cancer cachexia, we defined and compared the skeletal muscle responses to aerobic and resistance training.

METHODS

Twelve-month old Balb/c mice were initially assigned to control, aerobic training (AT; wheel running), or resistance training (RT; ladder climbing) (n=16-17/group). After 8weeks of training, half of each group was injected with C26 tumor cells, followed by 3 additional weeks of training. Body composition and neuromuscular function was evaluated pre- and post-training. Muscles were collected post-training and analyzed for fiber cross-sectional area (CSA), Akt-mTOR signaling, and expression of insulin-like growth factor-I (IGF-I) and myogenic regulatory factors.

RESULTS

Total body mass decreased (p<0.05) in C26 (-8%), AT+C26 (-18%), and RT+C26 (-15%) but not control. Sensorimotor function declined (p<0.05) in control (-16%), C26 (-13%), and RT+C26 (-23%) but not AT+C26. Similarly, strength/body weight decreased (p<0.05) in control (-7%), C26 (-21%), and RT+C26 (-10%) but not AT+C26. Gastrocnemius mass/body weight tended to be greater in AT+C26 vs. C26 (+6%, p=0.09). Enlargement of the spleen was partially corrected in AT+C26 (-27% vs. C26, p<0.05). Fiber CSA was lower in all C26 groups vs. control (-32% to 46%, p<0.05); however, the effect size calculated from C26 and AT+C26 was large (+24%, d=1.04). Phosphorylated levels of mTOR in AT+C26 exceeded C26 (+32%, p<0.05). RT+C26 showed greater mRNA expression (p<0.05) of IGF-IEa (+79%) and myogenin (+126%) with a strong tendency for greater IGF-IEb (+127%, p=0.069) vs.

CONCLUSIONS

Aerobic or resistance training was unable to prevent tumor-induced body weight loss. However, aerobic training may have preserved function, reduced the inflammatory response of the spleen, and marginally rescued muscle mass possibly through activation of mTOR. Aerobic training may therefore have therapeutic value for patients with cancer cachexia. In contrast, resistance training induced the expression of genes associated with muscle damage and repair. This gene response may be supportive of excessive stress generated by high resistance loading in a tumor-bearing state.

Role of Ingested Amino Acids and Protein in the Promotion of Resistance Exercise-Induced Muscle Protein Anabolism

The goal of this critical review is to comprehensively assess the evidence for the molecular, physiologic, and phenotypic skeletal muscle responses to resistance exercise (RE) combined with the nutritional intervention of protein and/or amino acid (AA) ingestion in young adults. We gathered the literature regarding the translational response in human skeletal muscle to acute exposure to RE and protein/AA supplements and the literature describing the phenotypic skeletal muscle adaptation to RE and nutritional interventions. Supplementation of protein/AAs with RE exhibited clear protein dose-dependent effects on translational regulation (protein synthesis) through mammalian target of rapamycin complex 1 (mTORC1) signaling, which was most apparent through increases in p70 ribosomal protein S6 kinase 1 (S6K1) phosphorylation, compared with postexercise recovery in the fasted or carbohydrate-fed state. These acute findings were critically tested via long-term exposure to RE training (RET) and protein/AA supplementation, and it was determined that a diminishing protein/AA supplement effect occurs over a prolonged exposure stimulus after exercise training. Furthermore, we found that protein/AA supplements, combined with RET, produced a positive, albeit minor, effect on the promotion of lean mass growth (when assessed in >20 participants/treatment); a negligible effect on muscle mass; and a negligible to no additional effect on strength. A potential concern we discovered was that the majority of the exercise training studies were underpowered in their ability to discern effects of protein/AA supplementation. Regardless, even when using optimal methodology and large sample sizes, it is clear that the effect size for protein/AA supplementation is low and likely limited to a subset of individuals because the individual variability is high. With regard to nutritional intakes, total protein intake per day, rather than protein timing or quality, appears to be more of a factor on this effect during long-term exercise interventions. There were no differences in strength or mass/muscle mass on RET outcomes between protein types when a leucine threshold (>2 g/dose) was reached. Future research with larger sample sizes and more homogeneity in design is necessary to understand the underlying adaptations and to better evaluate the individual variability in the muscle-adaptive response to protein/AA supplementation during RET.

Effect of cluster set configurations on mechanical variables during the deadlift exercise

The purpose of the present study was to investigate the effects of different configurations of repetitions within a set of deadlifts on the mechanical variables of concentric force, concentric time under tension, impulse, work, power, and fatigue. Eleven resistance trained men (age: 21.9 ± 1.0 years; deadlift 1 repetition maximum: 183.2 ± 38.3 kg) performed four repetitions of the deadlift exercise with a load equivalent to 90% of 1 repetition maximum under three different set configurations: Traditional (continuous repetitions); Doubles cluster (repetitions 1 and 2, and 3 and 4 performed continuously with a 30 s rest inserted between repetitions 2 and 3); Singles cluster (30 s rest provided between repetitions). The order of the sessions was counterbalanced across the subjects and the mechanical variables were calculated during each repetition from the synchronized signals recorded from force platforms and a motion analysis system. Relative to the Traditional set, the insertion of rest periods in the cluster set configurations resulted in greater time under tension (p < 0.001) and therefore, greater impulse (p < 0.001) during the repetitions. Reductions in power were observed during the cluster sets compared to the Traditional set (p = 0.001). The Doubles cluster set resulted in greater fatigue scores for power compared to the Traditional set (p = 0.04). The influence of cluster sets on mechanical variables appears to be mediated by the mechanical characteristics of the exercise (i.e. stretch-shortening cycle) and the competing physiological mechanisms of fatigue and potentiation.

The heat shock protein response following eccentric exercise in human skeletal muscle is unaffected by local NSAID infusion

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely consumed in relation to pain and injuries in skeletal muscle, but may adversely affect muscle adaptation probably via inhibition of prostaglandin synthesis. Induction of heat shock proteins (HSP) represents an important adaptive response in muscle subjected to stress, and in several cell types including cardiac myocytes prostaglandins are important in induction of the HSP response. This study aimed to determine the influence of NSAIDs on the HSP response to eccentric exercise in human skeletal muscle. Healthy males performed 200 maximal eccentric contractions with each leg with intramuscular infusion of the NSAID indomethacin or placebo. Biopsies were obtained from m. vastus lateralis before and after (5, 28 hrs and 8 days) the exercise bout from both legs (NSAID vs unblocked leg) and analysed for expression of the HSPs HSP70, HSP27 and αB-crystallin (mRNA and protein). NSAID did not affect the mRNA expression of any of the HSPs. Compared to pre values, the mRNA expression of all HSPs was increased; αB-crystallin, 3.6- and 5.4-fold; HSP70, 26- and 3.4-fold; and HSP27: 4.8- and 6.5-fold at 5 and 28 hrs post-exercise, respectively (all p < 0.008). Immunohistochemical stainings for αB-crystallin and HSP70 revealed increased staining in some samples but with no differences between legs. Changes in force-generating capacity correlated with both αB-crystallin and HSP70 mRNA and immunohistochemisty data. Increased expression of HSPs was observed on mRNA and protein level following eccentric exercise; however, this response was unaffected by local intramuscular infusion of NSAIDs.

The Yo-Yo IR2 test: physiological response, reliability, and application to elite soccer

The purpose of this study was to compare the effects of resistance training performed on either a stable or unstable surface on performance tests in female soccer players. Nineteen National Collegiate Athletic Association Division II female soccer players were assigned to either an unstable training group (UST: 19.0 ± 0.47 years; 1.69 ± 6.4 m; 67.8 ± 7.7 kg) or a stable training group (ST: 19.6 ± 0.49 years; 1.64 ± 3.2 m; 62.7 ± 6.27 kg). Player positions were distributed evenly between the groups. Both the groups followed a 5-week periodized resistance training program designed to develop maximum muscular strength. The groups performed the same exercises during each workout, with the UST performing 2 of the exercises in each session on an unstable surface. Pretraining and posttraining measures of straight-line sprint speed, planned and reactive agility, aerobic capacity, and countermovement vertical jump (CMJ) were taken. Significant main effects for time were reported for straight-line sprint speed, planned agility, and reactive agility with both groups demonstrating improvements during the posttraining testing session. The ST demonstrated a significant increase in CMJ during the posttraining session (change in mean: 0.04 m) in contrast to the decline demonstrated by the UST (change in mean: -0.01 m). Performing resistance training exercises on an unstable surface confers no advantage over traditional resistance training exercises for improving the speed, agility, and aerobic capacity of female soccer players. Furthermore, the use of an unstable surface may inhibit the effects of resistance training on vertical jump height, an important variable in soccer performance.

Early activation of rat skeletal muscle IL-6/STAT1/STAT3 dependent gene expression in resistance exercise linked to hypertrophy

Cytokine interleukin-6 (IL-6) is an essential regulator of satellite cell-mediated hypertrophic muscle growth through the transcription factor signal transducer and activator of transcription 3 (STAT3). The importance of this pathway linked to the modulation of myogenic regulatory factors expression in rat skeletal muscle undergoing hypertrophy following resistance exercise, has not been investigated. In this study, the phosphorylation and nuclear localization of STAT3, together with IL-6/STAT3-responsive gene expression, were measured after both a single bout of resistance exercise and 10 weeks of training. Flexor Digitorum Profundus muscle samples from Wistar rats were obtained 2 and 6 hours after a single bout of resistance exercise and 72 h after the last bout of either 2, 4, or 10 weeks of resistance training. We observed an increase in IL-6 and SOCS3 mRNAs concomitant with phosphorylation of STAT1 and STAT3 after 2 and 6 hours of a single bout of exercise (p<0.05). STAT3-dependent early responsive genes such as CyclinD1 and cMyc were also upregulated whereas MyoD and Myf5 mRNAs were downregulated (p<0.05). BrdU-positive satellite cells increased at 2 and 6 hours after exercise (p<0.05). Muscle fiber hypertrophy reached up to 100% after 10 weeks of training and the mRNA expression of Myf5, c-Myc and Cyclin-D1 decreased, whereas IL-6 mRNA remained upregulated. We conclude that the IL-6/STAT1/STAT3 signaling pathway and its responsive genes after a single bout of resistance exercise are an important event regulating the SC pool and behavior involved in muscle hypertrophy after ten weeks of training in rat skeletal muscle.

Protein supplementation augments the adaptive response of skeletal muscle to resistance-type exercise training: a meta-analysis

BACKGROUND

Protein ingestion after a single bout of resistance-type exercise stimulates net muscle protein accretion during acute postexercise recovery. Consequently, it is generally accepted that protein supplementation is required to maximize the adaptive response of the skeletal muscle to prolonged resistance-type exercise training. However, there is much discrepancy in the literature regarding the proposed benefits of protein supplementation during prolonged resistance-type exercise training in younger and older populations.

OBJECTIVE

The objective of the study was to define the efficacy of protein supplementation to augment the adaptive response of the skeletal muscle to prolonged resistance-type exercise training in younger and older populations.

DESIGN

A systematic review of interventional evidence was performed through the use of a random-effects meta-analysis model. Data from the outcome variables fat-free mass (FFM), fat mass, type I and II muscle fiber cross-sectional area, and 1 repetition maximum (1-RM) leg press strength were collected from randomized controlled trials (RCTs) investigating the effect of dietary protein supplementation during prolonged (>6 wk) resistance-type exercise training.

RESULTS

Data were included from 22 RCTs that included 680 subjects. Protein supplementation showed a positive effect for FFM (weighted mean difference: 0.69 kg; 95% CI: 0.47, 0.91 kg; P < 0.00001) and 1-RM leg press strength (weighted mean difference: 13.5 kg; 95% CI: 6.4, 20.7 kg; P < 0.005) compared with a placebo after prolonged resistance-type exercise training in younger and older subjects.

CONCLUSION

Protein supplementation increases muscle mass and strength gains during prolonged resistance-type exercise training in both younger and older subjects.

Peripheral signals of energy homeostasis as possible markers of training stress in athletes: a review

The importance of physical exercise in regulating energy balance and ultimately body mass is widely recognized. There have been several investigative efforts in describing the regulation of the energy homeostasis. Important in this regulatory system is the existence of several peripheral signals that communicate the status of body energy stores to the hypothalamus including leptin, adiponectin, ghrelin, interleukin-6, interleukin-1β, and tumor necrosis factor-α--different cytokines and other peptides that affect energy homeostasis. In certain circumstances, all these peripheral signals may be used to reveal the condition of the athlete as the result of several months of prolonged exercise training. These hormone and cytokine concentrations characterize a physical stress condition in which different hormone and cytokine responses are apparently linked to changes in physical performance. The possibility to use these peripheral signals as markers of training stress (and possible overreaching/overtraining) in elite athletes should be considered. These measured hormone and cytokine levels could also be used to characterize the physical stress of single exercise session, as the hormone and cytokine response to exercise may actually be a response to the concurrent energy deficit. In summary, different peripheral signals of energy homeostasis may be sensitive to changes in specific training stress and may be useful for predicting the onset of possible overreaching/overtraining in athletes.

The mechanisms of muscle hypertrophy and their application to resistance training

The quest to increase lean body mass is widely pursued by those who lift weights. Research is lacking, however, as to the best approach for maximizing exercise-induced muscle growth. Bodybuilders generally train with moderate loads and fairly short rest intervals that induce high amounts of metabolic stress. Powerlifters, on the other hand, routinely train with high-intensity loads and lengthy rest periods between sets. Although both groups are known to display impressive muscularity, it is not clear which method is superior for hypertrophic gains. It has been shown that many factors mediate the hypertrophic process and that mechanical tension, muscle damage, and metabolic stress all can play a role in exercise-induced muscle growth. Therefore, the purpose of this paper is twofold: (a) to extensively review the literature as to the mechanisms of muscle hypertrophy and their application to exercise training and (b) to draw conclusions from the research as to the optimal protocol for maximizing muscle growth.

The Role of Resistance Training in Distance Running

The main determinants of distance running performance include V̇O2max, lactate threshold (LT), and running economy (RE). The conventional way to achieve improvements in these areas is through endurance training due to the principle of training specificity. Some physiologists believe that the addition of resistance training is beneficial to distance running in the form of injury prevention and preparing runners for pace surge and sprint finishes. To date, it is consistent among findings that resistance training does not improve nor compromise V̇O2max in trained distance runners while LT improvements are only found in untrained individuals. RE has been shown to improve significantly post resistance training possibly due to neuromuscular changes including a shortening of the stretch-shortening cycle and an increase in muscle stiffness. The primary purpose of this review is to understand the impact of resistance training on the various factors known to affect distance running performance and to recommend resistance training guidelines for the distance runner to adhere to.

Structural protein alterations to resistance and endurance cycling exercise training

The muscle cytoskeleton is necessary for the effective transmission of forces generated by actin-myosin interactions. We have examined the impact of muscle force and exercise volume on the cytoskeleton by measuring desmin and dystrophin content in human skeletal muscle after 12 weeks of progressive resistance or endurance cycle training. Muscle biopsies of the vastus lateralis were obtained before and after training. Desmin and dystrophin content was determined using immunoblotting techniques. After resistance training, desmin content increased 82 +/- 18% (p < 0.05), whereas there was no change in desmin content with endurance cycling. Dystrophin content did not change in either group. One-repetition maximum and VO2max increased (p < 0.05) in the resistance and endurance groups, respectively. These data demonstrate that a high-tension stimulus impacts the cytoskeleton in contrast to high-volume concentric contractions. The tensile loading and eccentric components of resistance training are implicated in desmin alterations. Indeed, the functional improvements resulting from resistance training may be related in part to the mechanical integration provided by the desmin protein.

EMG changes during graded isometric exercise in pianists: comparison with non-musicians

BACKGROUND

Long-term piano training might induce some biochemical and structural adaptations in the intrinsic muscles of the hand or change the motor strategy of the nervous system. The main purpose of this study was to analyze whether the intrinsic muscles of the hands of pianists and sedentary controls differ in electromyographic characteristics at different strengths.

METHODS

Fifteen college piano students and 15 sedentary controls were asked to sit on an examination bench and perform first dorsal interosseous muscle contractions for 1 minute. The motor unit potentials were recorded during various percentages of maximal voluntary muscle contraction (MVC) by automatic decomposition electromyography.

RESULTS

The pianists demonstrated a significantly higher firing rate, shorter duration, and higher amplitude of motor unit potentials during minimal muscle contractions than the sedentary controls. But when comparing all the parameters at other degrees of contractions, the pianists were found to have significantly higher firing rate only at 25% and 50% of MVC, and higher amplitude at maximal contraction than the control group. The amplitude at maximal control contraction was higher in pianists than in controls.

CONCLUSION

These results imply that high-frequency and highly efficient muscle fibers are recruited in pianists when minimal muscle contractions are performed, which also indicate that by using smaller motor units, pianists may delicately control their fine motor performance.

Results of a diet/exercise feasibility trial to prevent adverse body composition change in breast cancer patients on adjuvant chemotherapy

PURPOSE

Patients with breast cancer on adjuvant chemotherapy can experience weight gain and concurrent losses in muscle mass. Exercise interventions can prevent these changes, but time and travel pose barriers to participation. The Survivor Training for Enhancing Total Health (STRENGTH) trial assessed the feasibility and impact of 2 home-based interventions.

PATIENTS AND METHODS

Ninety premenopausal patients with breast cancer on adjuvant chemotherapy were randomized to a calcium-rich diet (CA) intervention (attention control) or to 2 experimental arms: a CA + exercise (EX) arm or a CA + EX and high fruit and vegetable, low-fat diet (FVLF) arm. Exercise arms included aerobic and strength-training exercises. Body composition, weight status, waist circumference, dietary intake, physical activity, quality of life, anxiety, depression, serum lipids, sex hormone binding globulin, insulin, proinsulin, C-reactive protein, interleukin-1B, and tumor-necrosis factor receptor-II were measured at baseline and at 6-month follow-up.

RESULTS

Accrual targets were achieved and modest attrition was observed (8.8%). Self-reports suggest increased calcium intakes in all arms, and higher fruit and vegetable and lower fat intake in the CA + EX + FVLF arm; no differences in physical activity were observed. While measures of adiposity were generally lower in the CA + EX + FVLF arm, the only significant difference was in percentage of body fat (arms and legs); change in scores (mean +/- standard deviation) were +0.7% +/- 2.3% (CA); +1.2% +/- 2.7% (CA + EX); and +0.1% +/- 2% (CA + EX + FVLF; P = .047). Lean body mass was largely preserved, even in the control arm (net gain of 452 g +/- 2395 g). No differences were observed in other endpoints.

CONCLUSION

Diet and exercise interventions can prevent weight gain and adverse body composition changes, but more research is needed to determine optimally effective interventions that can be implemented during active treatment and that promote adherence.

Strength training improves supramaximal cycling but not anaerobic capacity

This study examined supramaximal cycling performed to exhaustion at 120% of peak O(2) uptake (120% VO(2)peak) before and after 8 weeks of strength training. Eight previously untrained men completed 8 weeks of leg-strength training 3 days week(-1) on a hack-squat machine; four sets, five repetitions at 85% of one repetition maximum each session. Anaerobic capacity was quantified by determining the maximal accumulated O(2) deficit during supramaximal cycling. After 8 weeks of strength training, one repetition maximum for the hack squat significantly increased by 90 +/- 33% when compared to before training. However, 8 weeks of strength training did not increase the maximal accumulated O(2) deficit. Nevertheless, after 8 weeks of strength training, there was a significant increase in time to exhaustion for cycling at 120% VO(2)peak. The increase in time to exhaustion after 8 weeks of strength training was accompanied by a significant increase in accumulated O(2) uptake. In conclusion, 8 weeks of strength training improves supramaximal cycling performance in previously untrained subjects. However, increases in time to exhaustion for supramaximal cycling following strength training are associated with an increase in the contribution of the aerobic energy system rather than an improvement in anaerobic capacity.

Enhancement of isokinetic muscle strength with a combined training programme in chronic heart failure

BACKGROUND

Patients with congestive heart failure (CHF) exhibit an impaired exercised tolerance that dramatically limits their functional capacity and alters their quality of life.

DESIGN

The aim of this study was to compare the effects of two types of training programmes on isokinetic muscle strength and aerobic capacities in patients with CHF.

METHODS

A group of 23 stable CHF patients included consecutively followed an exercise training programme, 3 days a week for 8 weeks. The first group (P1, n=11) exercised on a cycloergometer for 45 min at 65% of peak VO2. The second group (P2, n=12) followed a 45-min combined bicycle and quadricipital strength training. Strength training consisted of 10 series of 10 repetitions at 70% of maximal voluntary force. Incremental maximal cardiopulmonary exercise tests as well as an isokinetic quadricipital dynamometry evaluation were performed before and after training.

RESULTS AND CONCLUSIONS

In P1, peak VO2 increased by 20% (22.3+/-4.9 versus 17.8+/-4.5 ml min(-1) kg(-1); P<0.05) without any significant change in isokinetic muscle strength. In P2, peak VO2 improved within the same range (20.5+/-2.8 versus 18.6+/-3.7 ml min(-1) kg(-1); P<0.01). This last rehabilitation programme significantly increased isokinetic muscle strength at each angular velocities (+10.5+/-13.5%, P<0.04; +5.6+/-7.0%, P<0.03; for 180 degrees s(-1) and 60 degrees s(-1) respectively). Only the combined endurance/strength training programme was associated with an improvement in both peak VO2 and peripheral muscle strength, two significant parameters of outcome and quality of life in CHF.

Coactivation et inhibition musculaire : influences sur la régulation du couple de force développé et les adaptations induites par un entraînement en force

This review aims at analysing the influence of antagonist muscle coactivation and muscle inhibition on the ability of the neuromuscular system to produce an external torque and to account for changes in these two mechanisms with resistance training. Indeed, antagonist muscle coactivation and muscle inhibition occur during muscle contraction in order to preserve joint integrity. The origin of these two mechanisms would be both spinal and supraspinal and would tend to decrease with resistance training, which allows, under certain conditions, increasing the external torque developed. However, antagonist muscle coactivation and muscle inhibition depend on the characteristics of movement. Moreover, the origin and the contribution of supraspinal mechanisms to the antagonist muscle coactivation and muscle inhibition processes have to be specified.

Cross Education

Resistance training can be defined as the act of repeated voluntary muscle contractions against a resistance greater than those normally encountered in activities of daily living. Training of this kind is known to increase strength via adaptations in both the muscular and nervous systems. While the physiology of muscular adaptations following resistance training is well understood, the nature of neural adaptations is less clear. One piece of indirect evidence to indicate that neural adaptations accompany resistance training comes from the phenomenon of 'cross education', which describes the strength gain in the opposite, untrained limb following unilateral resistance training. Since its discovery in 1894, subsequent studies have confirmed the existence of cross education in contexts involving voluntary, imagined and electrically stimulated contractions. The cross-education effect is specific to the contralateral homologous muscle but not restricted to particular muscle groups, ages or genders. A recent meta-analysis determined that the magnitude of cross education is approximately equal to 7.8% of the initial strength of the untrained limb. While many features of cross education have been established, the underlying mechanisms are unknown. This article provides an overview of cross education and presents plausible hypotheses for its mechanisms. Two hypotheses are outlined that represent the most viable explanations for cross education. These hypotheses are distinct but not necessarily mutually exclusive. They are derived from evidence that high-force, unilateral, voluntary contractions can have an acute and potent effect on the efficacy of neural elements controlling the opposite limb. It is possible that with training, long-lasting adaptations may be induced in neural circuits mediating these crossed effects. The first hypothesis suggests that unilateral resistance training may activate neural circuits that chronically modify the efficacy of motor pathways that project to the opposite untrained limb. This may subsequently lead to an increased capacity to drive the untrained muscles and thus result in increased strength. A number of spinal and cortical circuits that exhibit the potential for this type of adaptation are considered. The second hypothesis suggests that unilateral resistance training induces adaptations in motor areas that are primarily involved in the control of movements of the trained limb. The opposite untrained limb may access these modified neural circuits during maximal voluntary contractions in ways that are analogous to motor learning. A better understanding of the mechanisms underlying cross education may potentially contribute to more effective use of resistance training protocols that exploit these cross-limb effects to improve the recovery of patients with movement disorders that predominantly affect one side of the body.

Contralateral effects of unilateral strength training: evidence and possible mechanisms

If exercises are performed to increase muscle strength on one side of the body, voluntary strength can increase on the contralateral side. This effect, termed the contralateral strength training effect, is usually measured in homologous muscles. Although known for over a century, most studies have not been designed well enough to show a definitive transfer of strength that could not be explained by factors such as familiarity with the testing. However, an updated meta-analysis of 16 properly controlled studies (range 15–48 training sessions) shows that the size of the contralateral strength training effect is ∼8% of initial strength or about half the increase in strength of the trained side. This estimate is similar to results of a large, randomized controlled study of training for the elbow flexors (contralateral effect of 7% initial strength or one-quarter of the effect on the trained side). This is likely to reflect increased motoneuron output rather than muscular adaptations, although most methods are insufficiently sensitive to detect small muscle contributions. Two classes of central mechanism are identified. One involves a “spillover” to the control system for the contralateral limb, and the other involves adaptations in the control system for the trained limb that can be accessed by the untrained limb. Cortical, subcortical and spinal levels are all likely to be involved in the “transfer,” and none can be excluded with current data. Although the size of the effect is small and may not be clinically significant, study of the phenomenon provides insight into neural mechanisms associated with exercise and training.

How nutrition and exercise maintain the human musculoskeletal mass

In this article we review some of our recent work concerning the effects of nutrition and exercise on protein synthesis and signal transduction in human musculoskeletal tissues. A great deal of new information is being generated by the application of recently refined techniques for measuring protein turnover. The field remains one that is largely descriptive but increasingly we are beginning to discern mechanisms underlying lean tissue maintenance, growth and wasting especially as multidisciplinary tools are applied to its study. Several types of exercise and nutrition are potent stimuli for protein synthesis in skeletal muscle. By contrast, collagen in the extracellular matrix in muscle and tendon appears to be mechanically but not nutritionally sensitive. The rates of collagen turnover in a variety of tissues are sufficiently high to account for a sizeable proportion of whole body protein turnover. One of the most recent surprises is the high turnover rate of human bone collagen and its anabolic response to feeding. As our understanding of the normal physiology of these processes advances, we become better able to construct testable hypotheses concerning the effects of ageing and disease on the musculoskeletal mass. Current evidence suggests that one of the major problems with loss of muscle during ageing is an inability of the tissue to respond adequately to increased availability of nutrients.

Possible Stimuli for Strength and Power Adaptation

The metabolic response to resistance exercise, in particular lactic acid or lactate, has a marked influence upon the muscular environment, which may enhance the training stimulus (e.g. motor unit activation, hormones or muscle damage) and thereby contribute to strength and power adaptation. Hypertrophy schemes have resulted in greater lactate responses (%) than neuronal and dynamic power schemes, suggesting possible metabolic-mediated changes in muscle growth. Factors such as age, sex, training experience and nutrition may also influence the lactate responses to resistance exercise and thereafter, muscular adaptation. Although the importance of the mechanical and hormonal stimulus to strength and power adaptation is well recognised, the contribution of the metabolic stimulus is largely unknown. Relatively few studies for example, have examined metabolic change across neuronal and dynamic power schemes, and not withstanding the fact that those mechanisms underpinning muscular adaptation, in relation to the metabolic stimulus, remain highly speculative. Inconsistent findings and methodological limitations within research (e.g. programme design, sampling period, number of samples) make interpretation further difficult. We contend that strength and power research needs to investigate those metabolic mechanisms likely to contribute to weight-training adaptation. Further research is also needed to examine the metabolic responses to different loading schemes, as well as interactions across age, sex and training status, so our understanding of how to optimise strength and power development is improved.

Effects of strength, endurance and combined training on myosin heavy chain content and fibre-type distribution in humans

This study investigated the effect of strength training, endurance training, and combined strength plus endurance training on fibre-type transitions, fibre cross-sectional area (CSA) and MHC isoform content of the vastus lateralis muscle. Forty volunteers (24 males and 16 females) were randomly assigned to one of four groups: control (C), endurance training (E), strength training (S), or concurrent strength and endurance training (SE). The S and E groups each trained three times a week for 12 weeks; the SE group performed the same S and E training on alternate days. The development of knee extensor muscle strength was S>SE>E ( P<0.05) and has been reported elsewhere. The reduction in knee extensor strength development in SE as compared to S corresponded to a 6% increase in MHCIIa content ( P<0.05) in SE at the expense of the faster MHCIId(x) isoform ( P<0.05), as determined by electrophoretic analyses; reductions in MHCIId/x content after S or E training were attenuated by comparison. Both S and SE induced three- to fourfold reductions ( P<0.05) in the proportion of type IIA/IID(X) hybrid fibres. S also induced fourfold increases in the proportion of type I/IIA hybrid fibres within both genders, and in a population of fibres expressing a type I/IID(X) hybrid phenotype within the male subjects. Type I/IIA hybrid fibres were not detected after SE. Both S and SE training paradigms induced similar increases (16-19%, P<0.05) in the CSA of type IIA fibres. In contrast, the increase in CSA of type I fibres was 2.9-fold greater ( P<0.05) in S as compared to SE after 12 weeks. We conclude that the interference of knee extensor strength development in SE versus S was related to greater fast-to-slow fibre-type transitions and attenuated hypertrophy of type I fibres. Data are given as mean (SEM) unless otherwise stated.

The impact of resistance training on distance running performance

Traditionally, distance running performance was thought to be determined by several characteristics, including maximum oxygen consumption (VO(2max)), lactate threshold (LT), and running economy. Improvements in these areas are primarily achieved through endurance training. Recently, however, it has been shown that anaerobic factors may also play an important role in distance running performance. As a result, some researchers have theorised that resistance training may benefit distance runners. Because resistance training is unlikely to elicit an aerobic stimulus of greater than 50% of VO(2max), it is unlikely that resistance training would improve VO(2max) in trained distance runners. However, it appears that VO(2max) is not compromised when resistance training is added to an endurance programme. Similarly, LT is likely not improved as a result of resistance training in trained endurance runners; however, improvements in LT have been observed in untrained individuals as a result of resistance training. Trained distance runners have shown improvements of up to 8% in running economy following a period of resistance training. Even a small improvement in running economy could have a large impact on distance running performance, particularly in longer events, such as marathons or ultra-marathons. The improvement in running economy has been theorised to be a result of improvements in neuromuscular characteristics, including motor unit recruitment and reduced ground contact time. Although largely theoretical at this point, if resistance training is to improve distance running performance, it will likely have the largest impact on anaerobic capacity and/or neuromuscular characteristics. The primary purpose of this review is to consider the impact of resistance training on the factors that are known to impact distance running performance. A second purpose is to consider different modes of resistance exercise to determine if an optimal protocol exists.

FL, Navarro F, Uchida MC, Bacurau RFP. Suplementação de carboidrato não reverte o efeito deletério do exercício de endurance sobre o subseqüente desempenho de força

Estudos disponíveis na literatura demonstram que a realização prévia de um exercício de endurance afeta de modo adverso o desempenho no exercício de força subseqüente. Tal ocorrência pode estar relacionada a mudanças metabólicas induzidas pelo exercício de endurance. O objetivo deste trabalho foi verificar se a ingestão de carboidrato (CHO) pode atenuar os efeitos de uma sessão aguda de exercício de endurance sobre o desempenho de força. A fim de testar essa hipótese, seis estudantes universitárias (164 ± 5,9cm; 64,9 ± 7,2kg), com experiência em treinamento de força, foram submetidas a um teste para a determinação do VO2pico (44 ± 4,3ml.min-1) e um teste de 1-RM para o leg press (186 ± 22,5kg) seguido de um teste de repetições máximas (duas séries de leg press realizado a 70% de 1-RM até exaustão 1ª série 21 ± 2,6 e 2ª série 11 ± 1,9 repetições) em dias diferentes. Seguindo um protocolo duplo-cego, os sujeitos foram submetidos a duas condições experimentais, recebendo uma bebida placebo (P) ou outra contendo carboidrato (6% - maltodextrina), antes (500ml) e durante (500ml) a realização de uma sessão de exercício de endurance (corrida em esteira 70% do VO2pico por 45 minutos). Em seguida ao exercício de endurance, os indivíduos realizaram um teste de 1-RM seguido pelo teste de repetições máximas. Não foram observadas mudanças no teste de 1-RM e na concentração plasmática de glicose entre as condições experimentais (P x CHO). O número de repetições máximas a 70%-1RM apresentou decréscimo nas duas situações (P 1ª série 13 ± 2,9 repetições e 2ª série 6 ± 2,1 repetições; CHO 1ª série 15 ± 2,5 repetições e 2ª série 7 ± 1,7 repetições, p < 0,05), não havendo diferença entre ambas. Uma sessão de exercício de endurance (intensidade moderada e longa duração) realizada previamente afeta de modo negativo a capacidade de realizar repetições máximas. Independente do mecanismo envolvido na redução do número de repetições máximas, o consumo de carboidrato foi incapaz de reverter esse efeito prejudicial.

Strength/endurance training versus endurance training in congestive heart failure

PURPOSE

The aim of this study was to compare the effects of endurance training alone (ET) with combined endurance and strength training (CT) on hemodynamic and strength parameters in patients with congestive heart failure (CHF).

METHODS

Twenty male patients with CHF were randomized into one of two training regimens consisting of endurance training or a combination of endurance and resistance training. Group ET had 40-min interval cycle ergometer endurance training three times per week. Group CT combined endurance and strength training with the same interval endurance training for 20 min, followed by 20 min of strength training. Left ventricular function was assessed at baseline and after 40 training sessions by echocardiography and radionuclide ventriculography. Work capacity was measured with cardiopulmonary exercise test (CPX) and lactate determination. Strength was measured with an isokinetic dynamometer.

RESULTS

After 40 sessions, the ET group improved functional class, work capacity, peak torque, and muscular endurance. However, peak O2 remained unchanged. Left ventricular ejection fraction (LVEF) and fractional shortening (FS) decreased, whereas left ventricular end-diastolic diameter (LVED) increased. The CT group improved NYHA score, working capacity, peak O2, and peak lactate; peak torque and muscular endurance, LVEF, and FS increased, whereas LVED decreased. Compared with ET, CT was significantly (P < 0.05) better in improving LV function.

CONCLUSION

Combined endurance/strength training was superior to endurance training alone concerning improvement of LV function, peak VO2, and strength parameters. It appears that for stable CHF patients, a greater benefit can be derived from this training modality.

The sites of neural adaptation induced by resistance training in humans

Although it has long been supposed that resistance training causes adaptive changes in the CNS, the sites and nature of these adaptations have not previously been identified. In order to determine whether the neural adaptations to resistance training occur to a greater extent at cortical or subcortical sites in the CNS, we compared the effects of resistance training on the electromyographic (EMG) responses to transcranial magnetic (TMS) and electrical (TES) stimulation. Motor evoked potentials (MEPs) were recorded from the first dorsal interosseous muscle of 16 individuals before and after 4 weeks of resistance training for the index finger abductors (n = 8), or training involving finger abduction-adduction without external resistance (n = 8). TMS was delivered at rest at intensities from 5 % below the passive threshold to the maximal output of the stimulator. TMS and TES were also delivered at the active threshold intensity while the participants exerted torques ranging from 5 to 60 % of their maximum voluntary contraction (MVC) torque. The average latency of MEPs elicited by TES was significantly shorter than that of TMS MEPs (TES latency = 21.5 +/- 1.4 ms; TMS latency = 23.4 +/- 1.4 ms; P < 0.05), which indicates that the site of activation differed between the two forms of stimulation. Training resulted in a significant increase in MVC torque for the resistance-training group, but not the control group. There were no statistically significant changes in the corticospinal properties measured at rest for either group. For the active trials involving both TMS and TES, however, the slope of the relationship between MEP size and the torque exerted was significantly lower after training for the resistance-training group (P < 0.05). Thus, for a specific level of muscle activity, the magnitude of the EMG responses to both forms of transcranial stimulation were smaller following resistance training. These results suggest that resistance training changes the functional properties of spinal cord circuitry in humans, but does not substantially affect the organisation of the motor cortex.

Muscle strength testing: use of normalisation for body size

Assessment of muscle strength tests has been a popular form of testing muscle function in sports and exercises, as well as in other movement-related sciences for several decades. Although the relationship between muscle strength and body size has attracted considerable attention from researchers, this relationship has been often either neglected or incorrectly taken into account when presenting the results from muscle strength tests. Two specific problems have been identified. First, most of the studies have presented strength data either non-normalised for body size, or normalised using inappropriate methods, or even several different normalisations have been applied on the same sets of data. Second, the role of body size in various movement performances has been neglected when functional movement performance was assessed by muscle strength. As a consequence, muscle function, athletic profiles, or functional movement performance assessed by tested muscle strength have been often confounded by the effect of body size. Differences in the normalisation methods applied also do not allow for comparison of the data obtained in different studies. Using the following allometric formula for obtaining index of muscle strength, S, independent of body size (assessed by body mass, m) should be recommended in routine strength testing procedures: The allometric parameter should be either b = 0.67 for muscle force (recorded by a dynamometer), or b = 1 for muscle torque (recorded by an isokinetic apparatus). We also recommend using body-size-independent indices of both muscle strength and movement performance when assessing functional performance from recorded muscle strength or vice versa.

Neural adaptations to resistance training: implications for movement control

It has long been believed that resistance training is accompanied by changes within the nervous system that play an important role in the development of strength. Many elements of the nervous system exhibit the potential for adaptation in response to resistance training, including supraspinal centres, descending neural tracts, spinal circuitry and the motor end plate connections between motoneurons and muscle fibres. Yet the specific sites of adaptation along the neuraxis have seldom been identified experimentally, and much of the evidence for neural adaptations following resistance training remains indirect. As a consequence of this current lack of knowledge, there exists uncertainty regarding the manner in which resistance training impacts upon the control and execution of functional movements. We aim to demonstrate that resistance training is likely to cause adaptations to many neural elements that are involved in the control of movement, and is therefore likely to affect movement execution during a wide range of tasks. We review a small number of experiments that provide evidence that resistance training affects the way in which muscles that have been engaged during training are recruited during related movement tasks. The concepts addressed in this article represent an important new approach to research on the effects of resistance training. They are also of considerable practical importance, since most individuals perform resistance training in the expectation that it will enhance their performance in related functional tasks.