Neuromuscular adaptations during the acquisition of muscle strength, power and motor tasks

Age- and sex-dependence of muscle quality: Influence of intramuscular non-contractile tissues

PURPOSE

Muscle quality is explained by the ratio between muscle size and strength. Conventionally, muscle size is evaluated without considering the composition of contractile and non-contractile tissues in muscle, hence the influence of non-contractile tissues on muscle quality is not fully understood, especially within aging muscle. This study investigated the differences in intramuscular non-contractile tissues between different age and sex groups, and investigated their influence on muscle quality.

METHODS

Eighty-two older and 64 young females and males participated. Muscle cross-sectional area (quadriceps and hamstrings), separating contractile and non-contractile areas, was calculated from the magnetic resonance image of the right mid-thigh. Maximal voluntary isometric knee extension and flexion torque was measured. Torque/muscle area and torque/contractile area were calculated for each age and sex group.

RESULTS

Non-contractile/muscle area was higher in older than in young individuals in both muscle groups (p < 0.05), and it was greater in the hamstrings than in the quadriceps. For the hamstrings, torque/muscle area was lower in older than in young individuals in both sexes (p < 0.05). However, torque/contractile area did not show the differences between age groups, only between sexes (males>females) (p < 0.05).

CONCLUSIONS

The results indicate that 1) the presence of non-contractile tissues varies by age and muscle groups, 2) the extensive presence of non-contractile tissues can contribute to the underestimation of its muscle quality, and 3) the sex differences in muscle quality are influenced by factors other than muscle composition.

Effects of physical training combined with transcranial direct current stimulation on maximal strength and lower limb explosive strength in healthy adults

Objective

The purpose of this systematic review and meta-analysis was to investigates whether transcranial direct current stimulation applied during physical training increases muscle strength in comparison with sham tDCS combined with physical training.

Methods

Randomized controlled trials of the effects of tDCS combined physical training intervention on muscle strength and cortical excitability were collected by searching Web of Science, Pubmed, EBSCO, CNKI. The retrieval date ends in April 2024. 11 randomized controlled trials are finally included. The total sample size of the study is 338. The experimental group was subjected to tDCS combined with physical training intervention, and the control group was physical training combined with sham tDCS intervention.

Results

There is a significant increase in maximal strength (SMD = 0.38; 95% CI: 0.09, 0.67; p = 0.01) and lower limb explosive strength (MD = 2.90; 95% CI: 1.06, 4.74; p = 0.002) when physical training was performed with tDCS, but not following physical training combined with sham tDCS. Subgroup analysis of the subject population showed an increase in muscle strength in those with training experience following tDCS combined with physical training (SMD = 0.39; 95% CI: 0.08, 0.70; p = 0.01), but not for those without training experience (SMD = 0.29; 95% CI: -0.06, 0.63; p = 0.10). Motor evoked potential (MEP) wave amplitude increased significantly following physical training with tDCS (SMD = 0.71; 95% CI: 0.18, 1.24; p = 0.008), but was not different between groups (SMD = 0.16; 95% CI: -0.33, 0.65; p = 0.52).

Conclusions

tDCS combined with physical training intervention can improve muscle strength, lower limb explosive strength and cerebral cortex excitability. Compared to tDCS combined with training of small muscle groups, tDCS combined with training of large muscle groups was more effective in improving muscle strength. Muscle strength was more likely to improve after tDCS combined with physical training in people with physical training experience compared with people without physical training experience. The combination of tDCS with physical training intervention and the sham-tDCS with physical training intervention both increased cortical excitability.

Systematic Review Registration

https://www.crd.york.ac.uk/, PROSPERO, identifier (CRD42024550454).

Weak grip strength among persons with multiple sclerosis having minimal disability is not related to agility or integrity of the corticospinal tract

INTRODUCTION

Mobility impairment is common in multiple sclerosis (MS); however, agility has received less attention. Agility requires strength and neuromuscular coordination to elicit controlled propulsive rapid whole-body movement. Grip strength is a common method to assess whole body force production, but also reflects neuromuscular integrity and global brain health. Impaired agility may be linked to loss of neuromuscular integrity (reflected by grip strength or corticospinal excitability).

OBJECTIVES

We aimed to determine whether grip strength would be associated with agility and transcranial magnetic stimulation (TMS)-based indices of corticospinal excitability and inhibition in persons with MS having low disability. We hypothesized that low grip strength would predict impaired agility and reflect low corticospinal excitability.

METHODS

We recruited 34 persons with relapsing MS (27 females; median [range] age 45.5 [21.0-65.0] years) and mild disability (median [range] Expanded Disability Status Scale 2.0 [0-3.0]), as well as a convenience sample of age- and sex-matched apparently healthy controls. Agility was tested by measuring hop length during bipedal hopping on an instrumented walkway. Grip strength was measured using a calibrated dynamometer. Corticospinal excitability and inhibition were examined using TMS-based motor evoked potential (MEP) and corticospinal silent period (CSP) recruitment curves, respectively.

RESULTS

MS participants had significantly lower grip strength than controls independent of sex. Females with and without MS had weaker grip strength than males. There were no statistically significant sex or group differences in agility. After controlling for sex, weaker grip strength was associated with shorter hop length in controls only (r = 0.645, p < .05). Grip strength did not significantly predict agility in persons with MS, nor was grip strength predicted by corticospinal excitability or inhibition.

CONCLUSIONS

In persons with MS having low disability, grip strength (normalized to body mass) was reduced despite having intact agility and walking performance. Grip strength was not associated with corticospinal excitability or inhibition, suggesting peripheral neuromuscular function, low physical activity or fitness, or other psychosocial factors may be related to weakness. Low grip strength is a putative indicator of early neuromuscular aging in persons with MS having mild disability and normal mobility.

Effects of 7-day quercetin intervention on motor unit activity and muscle contractile properties before and after resistance exercise in young adults randomized controlled trials

We investigated whether the alteration of the motor unit recruitment threshold (MURT) caused by quercetin ingestion intervention for 7 days modifies motor unit activation patterns before and after a single session of resistance exercise. Twenty young male and female adults were divided into two groups: ingestion of placebo (PLA) or quercetin glycosides at 200 mg/day (QUE). High-density surface electromyography during submaximal contractions was measured to assess the motor unit firing rate (MUFR) and MURT of the vastus lateralis muscle before (PRE) and after (POST) resistance exercise (DAY1). The same measurements were repeated after 7 days of placebo or quercetin glycoside ingestion (DAY8). In QUE, MURT decreased more from DAY1-PRE to DAY8-PRE (29.1 ± 9.1 to 27.1 ± 9.5% MVC, p < 0.001) but not in PLA (29.8 ± 10.4 to 28.9 ± 9.7% MVC, p < 0.167). For percentage change in MUFR following resistance exercise, there was a significant interaction (day × group, p < 0.001). The degree of changes in MURT from DAY1-PRE to DAY8-PRE was significantly correlated with the percentage change of MUFR from DAY8-PRE to DAY8-POST in QUE (p = 0.014, r = -0.363) but not in PLA (p = 0.518). The study suggests that 7-day quercetin ingestion alters the motor unit recruitment pattern, and this may induce changes in motor unit firing patterns during a single session of resistance training (Trial registration: UMIN000052255, R000059650).

Resistance Training on an Outdoor Exercise Structure Improves Lower-Body Relative Strength in Older Adults

Improving relative strength is important for maintaining functionality with age, and outdoor exercise structures could be useful to facilitate this. A total of 29 adults aged 65+ participated in a non-randomized crossover study with a 6-week control followed by a 6-week resistance training intervention on an outdoor exercise structure (3x/week). Relative strength (predicted maximal leg press/lower body lean mass [Dual-energy X-ray Absorptiometry]) and physical function variables were measured at baseline, post-control, and post-intervention. Represented as median (25th-75th), lower body relative strength improved from 7.91 (7.01-9.35) post-control to 8.50 (7.99-9.72) post-intervention (p = .002) in study completers (n = 17). Maximum leg press (p = .002), 30-second chair stand (p < .001), one-leg stance (p = .011), and maximum chest press (p = .009) also improved significantly during the intervention. There were no significant changes in aerobic activity, grip strength, lean mass, or muscle power. This study demonstrates that there could be potential relative strength benefits associated with the use of outdoor exercise structures in older adults.

Effects of aquatic exercises on physical fitness and quality of life in postmenopausal women: an updated systematic review and meta-analysis

Objective

In the present systematic review and meta-analysis, we aimed to evaluate and update the effects of aquatic exercise on physical fitness and quality of life (QoL) in postmenopausal women.

Methods

The databases Cochrane Library, PubMed, Web of Science, and MEDLINE were searched for randomized controlled trials (RCTs) on the topic from inception to July 2022. The GetData software was used to extract data from the published images. RevMan5.4 software was used for statistical analysis. Data are expressed as standardized mean difference (SMD) with 95% confidence intervals (CI). I² index was employed for heterogeneity. Egger's test was used to assess publication bias. We evaluated the methodological quality of included studies using the Physiotherapy Evidence Database scale.

Results

We included 594 participants in 16 RCTs (19 comparison groups). The results indicated that aquatic exercise can significantly improve lower limb strength (LLS), upper limb strength (ULS), agility, flexibility, and overall QoL. No significant effects were found on aerobic capacity. Subgroup-analysis results indicated that aquatic exercise only significantly improved LLS, ULS, agility, and flexibility in postmenopausal women < 65 years of age. However, aquatic exercise improves the overall QoL both in postmenopausal women < 65 years and ≥ 65 years. Aquatic resistance exercise significantly improves LLS, ULS, agility and flexibility. In addition, aquatic aerobic exercise can effectively increase LLS, and combined aquatic aerobic and resistance exercise can enhance the overall QoL.

Conclusions

Aquatic exercise can effectively improve physical fitness and overall QoL in postmenopausal women, but has limited effects on aerobic capacity; thus, it is highly recommended in postmenopausal women.

From thinking fast to moving fast: motor control of fast limb movements in healthy individuals

The ability to produce high movement speeds is a crucial factor in human motor performance, from the skilled athlete to someone avoiding a fall. Despite this relevance, there remains a lack of both an integrative brain-to-behavior analysis of these movements and applied studies linking the known dependence on open-loop, central control mechanisms of these movements to their real-world implications, whether in the sports, performance arts, or occupational setting. In this review, we cover factors associated with the planning and performance of fast limb movements, from the generation of the motor command in the brain to the observed motor output. At each level (supraspinal, peripheral, and motor output), the influencing factors are presented and the changes brought by training and fatigue are discussed. The existing evidence of more applied studies relevant to practical aspects of human performance is also discussed. Inconsistencies in the existing literature both in the definitions and findings are highlighted, along with suggestions for further studies on the topic of fast limb movement control. The current heterogeneity in what is considered a fast movement and in experimental protocols makes it difficult to compare findings in the existing literature. We identified the role of the cerebellum in movement prediction and of surround inhibition in motor slowing, as well as the effects of fatigue and training on central motor control, as possible avenues for further research, especially in performance-driven populations.

Association between Tongue Pressure and Jaw-Opening Force in Older Adults

Tongue pressure (TP) is used to assess tongue muscle strength and is related to function and frailty. While performing TP, it is necessary to elevate the tongue and oral floor by contracting the suprahyoid muscles. However, the association between TP and suprahyoid muscle strength remains unclear. Accordingly, this study investigated the relationship between TP and jaw-opening force (JOF), an indicator of suprahyoid muscle strength. This cross-sectional study included 88 independent community-dwelling participants aged ≥65 years. Age, sex, and the number of remaining teeth were recorded. Ultrasonography was used to evaluate the cross-sectional area of the tongue and geniohyoid muscle, as representatives of the suprahyoid muscles. Sarcopenia was diagnosed based on appendicular skeletal muscle mass index, handgrip strength, and gait speed. Multiple regression analysis was performed with TP as the dependent variable. TP was significantly associated with JOF (β = 0.371, p = 0.003). This study revealed that decreased TP was associated with a decline in JOF and suprahyoid muscle mass in older adults. Thus, low TP may be associated with decreased JOF. Prevention of the weakness of the suprahyoid muscles and maintaining TP may also contribute to the prevention of frailty associated with TP.

Effect of Leg Half-Squat Training With Blood Flow Restriction Under Different External Loads on Strength and Vertical Jumping Performance in Well-Trained Volleyball Players

Purpose

To examine the effect of blood flow restriction resistance training under different external loads on the muscle strength and vertical jumping performance in volleyball players.

Methods

18 well-trained collegiate male volleyball players were randomly divided into 3 groups: high-load resistance training group (HL-RT, 70% 1RM, n = 6), low-load blood flow restriction resistance training group (LL-BFR-RT, 30% 1RM, 50% arterial occlusion, n = 6), and high-load blood flow restriction resistance training group (HL-BFR-RT, 70% 1RM, 50% arterial occlusion, n = 6). Participants performed leg half-squat exercise 3 times per week for 8 weeks. Measurements of Isokinetic peak torque of knee extension and flexion, 1RM leg half-squat, squat jump, and 3 footed take-off were obtained before and after training. A two-way repeated-measures analysis of variance was used to examine differences among the 3 groups and between the 2 testing time (pre-test vs post-test).

Results

(1) The HL-RT group was significantly greater in muscle strength than that in the LL-BFR-RT group (P < .05), but no improvement in vertical jumping performance (P >.05). (2) Improvement in muscle strength and vertical jumping performance was significantly greater in the HL-BFR-RT group than that in the LL-BFR-RT group (P <.05). (3) The HL-BFR-RT group had greater but not significant improvement in muscle strength and vertical jumping performance than that in the HL-RT group.

Conclusions

Although increases in muscle strength were observed between training groups, HL-BFR-RT increased not only muscle strength but vertical jumping performance to a greater extent compared to LL-BFR-RT and HL-RT.

Upper Limbs Muscle Co-contraction Changes Correlated With the Impairment of the Corticospinal Tract in Stroke Survivors: Preliminary Evidence From Electromyography and Motor-Evoked Potential

Objective

Increased muscle co-contraction of the agonist and antagonist muscles during voluntary movement is commonly observed in the upper limbs of stroke survivors. Much remain to be understood about the underlying mechanism. The aim of the study is to investigate the correlation between increased muscle co-contraction and the function of the corticospinal tract (CST).

Methods

Nine stroke survivors and nine age-matched healthy individuals were recruited. All the participants were instructed to perform isometric maximal voluntary contraction (MVC) and horizontal task which consist of sponge grasp, horizontal transportation, and sponge release. We recorded electromyography (EMG) activities from four muscle groups during the MVC test and horizontal task in the upper limbs of stroke survivors. The muscle groups consist of extensor digitorum (ED), flexor digitorum (FD), triceps brachii (TRI), and biceps brachii (BIC). The root mean square (RMS) of EMG was applied to assess the muscle activation during horizontal task. We adopted a co-contraction index (CI) to evaluate the degree of muscle co-contraction. CST function was evaluated by the motor-evoked potential (MEP) parameters, including resting motor threshold, amplitude, latency, and central motor conduction time. We employed correlation analysis to probe the association between CI and MEP parameters.

Results

The RMS, CI, and MEP parameters on the affected side showed significant difference compared with the unaffected side of stroke survivors and the healthy group. The result of correlation analysis showed that CI was significantly correlated with MEP parameters in stroke survivors.

Conclusion

There existed increased muscle co-contraction and impairment in CST functionality on the affected side of stroke survivors. The increased muscle co-contraction was correlated with the impairment of the CST. Intervention that could improve the excitability of the CST may contribute to the recovery of muscle discoordination in the upper limbs of stroke survivors.

Effects of exercise intensity and duration on a myokine, secreted protein acidic and rich in cysteine

Secreted protein acidic and rich in cysteine (SPARC), an exercise-induced myokine, has been suggested as a potential endogenous factor that suppresses colon tumorigenesis. However, the effects of different exercise protocols on circulating SPARC levels are unclear. The main purpose of this study was to examine the effects of both exercise intensity and duration on circulating SPARC levels. This study also examined the relationship between responsiveness of SPARC levels and physical characteristics, including body composition and skeletal muscle function. Nineteen healthy adult men participated in four experimental interventions: two 30-min exercises at workloads corresponding to 60% (W60) and 40% (W40) peak oxygen uptake (VO_2peak), a 45-min session of W40, and a 30-min session of complete rest. Blood SPARC and lactate concentrations were measured before and after each session. Only W60 significantly increased serum SPARC levels (p < 0.05), and a significant correlation was found between changes in SPARC levels and lactate concentrations (r = 0.411, p < 0.05). The relative changes in SPARC levels during W60 demonstrated significant positive correlations with skeletal muscle mass and knee extensor muscle strength (both p < 0.05). The increase in serum SPARC levels might be mediated by lactate accumulation and might not, hence, be induced during exercise at the intensity of the first ventilatory threshold levels even though the duration is prolonged. Our results provide fundamental insight into exercise prescription of both exercise intensity and duration for SPARC response, leading to a better understanding of the preventive effects of exercise on colon cancer.Highlight This study found that the increase in serum secreted protein acidic and rich in cysteine (SPARC) levels might be mediated by lactate accumulation and might, hence, be influenced by exercise intensity rather than exercise duration.An association was found between SPARC response to exercise and skeletal muscle mass.Our results provide a better understanding of the preventive effects of exercise on colon cancer.

Higher strength gain after hypoxic vs normoxic resistance training despite no changes in muscle thickness and fractional protein synthetic rate

Acute hypoxia has previously been suggested to potentiate resistance training-induced hypertrophy by activating satellite cell-dependent myogenesis rather than an improvement in protein balance in human. Here, we tested this hypothesis after a 4-week hypoxic vs normoxic resistance training protocol. For that purpose, 19 physically active male subjects were recruited to perform 6 sets of 10 repetitions of a one-leg knee extension exercise at 80% 1-RM 3 times/week for 4 weeks in normoxia (FiO₂ : 0.21; n = 9) or in hypoxia (FiO₂ : 0.135, n = 10). Blood and skeletal muscle samples were taken before and after the training period. Muscle fractional protein synthetic rate was measured over the whole period by deuterium incorporation into the protein pool and muscle thickness by ultrasound. At the end of the training protocol, the strength gain was higher in the hypoxic vs the normoxic group despite no changes in muscle thickness and in the fractional protein synthetic rate. Only early myogenesis, as assessed by higher MyoD and Myf5 mRNA levels, appeared to be enhanced by hypoxia compared to normoxia. No effects were found on myosin heavy chain expression, markers of oxidative metabolism and lactate transport in the skeletal muscle. Though the present study failed to unravel clearly the mechanisms by which hypoxic resistance training is particularly potent to increase muscle strength, it is important message to keep in mind that this training strategy could be effective for all athletes looking at developing and optimizing their maximal muscle strength.

Web-Based Exercise Program Increases Cervical Strength in Adolescent Athletes

ABSTRACT

Wilson, JC, Levek, C, Daoud, AK, Brewer, M, Brooks, K, Sochanska, A, Randall, M, and Provance, AJ. Web-based exercise program increases cervical strength in adolescent athletes. J Strength Cond Res 35(4): 1149-1155, 2021-This cohort study aimed to evaluate the efficacy of a web-based 6-week cervical strengthening program on cervical strength in adolescent athletes. It was hypothesized that subjects completing the program would demonstrate significant increase in cervical muscle strength compared with baseline strength. Eighty-three high school soccer athlete subjects were recruited from 2 local nationally competitive soccer clubs. Teams were assigned to either control or intervention groups to minimize information crossover. Fifty subjects were recruited to the intervention group (29 male, 21 female; average age 15.1 years). Thirty-three subjects were recruited to the control group (21 male, 12 female; average age 15.1 years). Intervention group subjects completed a web-based progressive cervical strengthening program over 6 weeks. Cervical strength in flexion, extension, right and left lateral flexion (LLF) was measured in Newton (N) of force at 3 time points during the competitive season for both control and intervention groups. Intervention group subjects significantly increased cervical strength [mean difference (95% confidence interval)] in LLF [24.1 (15.9-32.4)], extension [27.9 (18.4-37.5)], right lateral flexion [18.8 (11.6-26.1)], and flexion [mean ratio: 1.2 (1.1-1.2)] at follow-up testing; whereas control subjects did not see significant changes in strength. A web-based progressive cervical strengthening program improves cervical muscular strength in a population of adolescent athletes over a period of 6 weeks. Such a program could be used by researchers in future studies evaluating the influence on concussion risk and by practitioners as a means of reducing sport-related head and neck injuries.

Effects of Plyometric Jump Training on Physical Fitness in Amateur and Professional Volleyball: A Meta-Analysis

We aimed to examine the effects of plyometric jump training (PJT) on measures of physical fitness in amateur and professional volleyball players. A systematic electronic literature search was carried out in the databases PubMed, MEDLINE, Web of Science, and SCOPUS. Controlled studies including pre-to-post intervention tests of physical fitness and involving healthy volleyball players regardless of age and sex were considered. A random-effects model was used to calculate effect sizes (ES) between intervention and control groups. Moderator analyses considered programme duration, training frequency, total number of training sessions and jumps, participants' sex, age, and expertise level. The Physiotherapy Evidence Database scale was used to assess the methodological quality of the included studies. Eighteen moderate-to-high quality (median of 5 PEDro points) studies were eligible, comprising a total of 746 athletes. None of the included studies reported injuries related to the PJT intervention. The main findings showed small-to-moderate effects (p < 0.05) of PJT on linear sprint speed (ES = 0.70), squat jump (ES = 0.56), countermovement jump (CMJ) (ES = 0.80), CMJ with arm swing (ES = 0.63), drop jump (ES = 0.81), and spike jump height (ES = 0.84). Sub-analyses of moderator factors included 48 data sets. Only age had a significant effect on CMJ performance. Participants aged ≥16 years achieved greater improvements in CMJ performance compared to <16 years old (ES = 1.28 and 0.38, respectively; p = 0.022). No significant differences (p = 0.422) were identified between amateur (ES = 0.62) and professional volleyball players (ES = 1.01). In conclusion, PJT seems safe and is effective in improving measures of physical fitness in amateur and professional volleyball players, considering studies performed in both male and female.

Engagement in Muscle-Strengthening Activities Lowers Sarcopenia Risk in Older Adults Already Adhering to the Aerobic Physical Activity Guidelines

Sarcopenia in older adults is associated with a higher risk of falls, disability, loss of independence, and mortality. Current physical activity (PA) guidelines recommend engagement in muscle-strengthening activities (MSA) in addition to aerobic moderate-to-vigorous physical activity (MVPA). However, little is known about the impact of MSA in addition to adherence to the MVPA recommendation in the guidelines. The aim of the present cross-sectional study was to determine whether or not engagement in MSA is linked to sarcopenia risk in older adults who meet the PA guidelines of 150 min of MVPA per week. A total of 193 community-dwelling older men and women (65–70 years) were included in the study. A continuous sex-specific clustered sarcopenia risk score (SRS) was created based on muscle mass assessed using bioelectrical impedance analysis, handgrip strength, and five times sit-to-stand (5STS) time, assessed using standardized procedures. Adherence to PA guidelines was assessed using the Actigraph GT3x accelerometer and the EPAQ2 questionnaire. Guideline adherence to MSA twice a week was related to a significantly (p < 0.05) lower SRS compared to those who did not. This finding was evident after adjustment for adherence to the protein intake guideline and abdominal obesity. Similar impacts were observed for muscle mass and 5-STS but not for handgrip strength. In conclusion, guideline adherence to MSA is related to lower sarcopenia risk in older adults who already accumulate 150 weekly minutes of MVPA, which reinforces the promotion of the MSA guideline, alongside the MVPA guideline, to fight against sarcopenia progression in ageing populations.

Comparison between velocity-specific exercise and isometric exercise on neck muscle functions and performance: a randomised clinical trial

Background

Evidence has shown that velocity-specific exercise results in additional benefits for peripheral joint muscles by promoting their functions, however, its effects on spinal muscles are yet to be investigated. This study aimed to examine the feasibility and effects of velocity-specific exercise compared to isometric exercise on cervical muscle functions and performance in healthy individuals.

Methods

Thirty healthy adults were randomised to practise either the velocity-specific exercise (VSE, n = 15) or isometric exercise (IE, n = 15) for 6 weeks. Functions and performance of the cervical extensors and flexors were assessed pre- and post-program, by analyzing the peak torque and electromyography during the isokinetic testing, and cross-sectional area of the deep cervical muscles at rest. The self-reported level of difficulty and post-exercise soreness during the exercise were recorded to evaluate the feasibility and safety of the two exercise programs.

Results

Both VSE and IE exercises resulted in significant improvement of the muscle functions and performance while there were no between-group differences at reassessment of the (a) cross-sectional area of longus colli and semispinalis capitis; (b) EMG amplitude in sternocleidomastoid and cervical erector spinae, and (c) peak torque values. Further analysis revealed that degree of correlation between extension torque and EMG amplitude of cervical erector spinae increased in both groups. However, significant correlation was found only in VSE group post-program. There were no significant differences for the level of difficulty and post-exercise soreness found between two groups.

Conclusions

Both velocity-specific and isometric exercises significantly promoted cervical muscle functions and performance. The present study confirms that velocity-specific exercise can be practised safely and it also contributes to a greater enhancement in neuromuscular efficiency of the cervical extensors. These findings indicate that the velocity-specific exercise can be considered as a safe alternative for training of the cervical muscles. Further study is recommended to examine its benefit and application for promoting the muscle functions and recovery in symptomatic individuals.

Ciliary Neurotrophic Factor Receptor rs41274853 Polymorphism Is Associated With Weightlifting Performance in Japanese Weightlifters

Homma, H, Kobatake, N, Sekimoto, Y, Saito, M, Mochizuki, Y, Okamoto, T, Nakazato, K, Nishiyama, T, and Kikuchi, N. Ciliary neurotrophic factor receptor rs41274853 polymorphism is associated with weightlifting performance in Japanese weightlifters. J Strength Cond Res 34(11): 3037-3041, 2020-At least 69 genetic markers are associated with power athlete status. In the present study, we investigated the genotype frequency of the ciliary neurotrophic factor receptor (CNTFR) rs41274853 polymorphism and the association between specific CNTFR genotype and weightlifting performance in Japanese weightlifters. One hundred sixty-five Japanese weightlifters (103 men and 62 women) and 338 controls (122 men and 216 women) participated in the present case-control study. Saliva samples were collected using the Oragene DNA self-collection kit and genotyping for the CNTFR (rs41274853) polymorphism was performed using the TaqMan assay. A questionnaire, noting each subject's best record in an official weightlifting competition, was used to obtain the weightlifting performance. The frequencies of the CNTFR genotypes CC, CT, and TT were 56, 32, 12% in the weightlifters, and 53, 40, and 7% in the controls, respectively. There was no significant difference in CNTFR genotype frequencies between the weightlifters and controls. However, the frequency of the CT + TT genotype was significantly higher in international-level weightlifters than in the national-level weightlifters. The relative value per body weight of snatch, clean, and jerk, and total record were significantly higher in the athletes with CT + TT genotype than in the athletes with CC genotype (p < 0.05). Our results suggest that the CNTFR rs41274853 CT + TT genotype is associated with weightlifting performance in Japanese weightlifters. The CNTFR rs41274853 polymorphism may enable coaches to develop tailor-made training programs for individual athletes. In addition, strength and conditioning coaches could benefit from genetic information when assessing potential athletic talents and creating strength training programs for their athletes.

Effect of a 6-week strength-training program on neuromuscular efficiency in type 2 diabetes mellitus patients

Background

The neuromuscular system generates human movement. The functional capacity of the neuromuscular system in patients with type 2 diabetes mellitus (T2DM) is decreased and this affects the generation of muscle force. Exercise is recommended as an effective treatment in such cases. Short-duration strength training causes neural adaptations in healthy participants, but the effects of strength training on T2DM are unclear. The present study aimed to evaluate the effect of strength training on neuromuscular efficiency of lower limb muscles in T2DM.

Methods

Surface electromyograms (SEMG) of the knee flexors and extensors were recorded during isometric contractions. The ratio of peak torque to SEMG amplitude was calculated as neuromuscular efficiency. Measurements were taken before the intervention after 6 weeks of non-training, and after 6 weeks of strength training.

Results

SEMG amplitudes did not differ among the subsequent measurement sessions. Flexor and extensor peak torque increased after the strength-training program. The neuromuscular efficiency of all muscles increased after the 6 weeks of strength training.

Conclusion

A 6-week strength-training program increased the neuromuscular efficiency and peak torque in patients with T2DM; however, the electrical properties of the muscles did not change. These results may be related to increased neural adaptations and motor learning in the early stages of strength training.

Adaptations of the Upper Body to Plyometric Training in Cricket Players of Different Age Groups

CONTEXT

Neuromuscular adaptations following exercise training are believed to enhance sports performance. While abundant research is available on adaptations of the lower body to plyometric training, little is known about adaptations of the upper body to plyometric training.

OBJECTIVE

To examine the effect of plyometric training on neuromuscular adaptations in cricket players of different age groups.

DESIGN

Randomized parallel group active-controlled trial.

SETTING

Research laboratory, school cricket ground, and sports complex field.

PARTICIPANTS

Fifty-nine cricket players were randomly assigned to either the experimental group or the control group.

INTERVENTIONS

The experimental group was subjected to 8 weeks of medicine ball plyometric training held thrice per week. Neuromuscular adaptations were analyzed pretraining and posttraining in 3 age groups: <18, 18-25, and >25 years. Analysis of variance was used to ascertain the training effects between and within the 6 subgroups, that is, age group <18 years (control and experimental), age group 18-25 years (control and experimental), and age group >25 years (control and experimental).

MAIN OUTCOME MEASURES

Muscle activation, upper body balance, upper body power, and muscle strength.

RESULTS

Out of 59, 55 participants completed the study. Subjects aged <18 years (adolescents) showed significantly greater improvements than those from the groups 18-25 years and >25 years (adults) on upper body balance and upper body power. Significant improvements were observed in the experimental subjects of all age groups on their muscle activity of biceps brachii, upper body balance, and upper body power following medicine ball plyometric training.

CONCLUSIONS

Though adolescent subjects were found to be more adaptive than adult subjects, experimental subjects showed significantly greater neuromuscular adaptations to medicine ball plyometric training than controls. These findings emphasize the need for coaches and athletic trainers to inculcate medicine ball plyometric exercises in training regimes of cricket players so as to improve their upper body performance.

Immediate Effects of a Single Spinal Manipulation on Lower-Limb Strength in Healthy Individuals: A Critically Appraised Topic

Clinical Scenario: Many people with lower quarter musculoskeletal dysfunction present with muscle weakness. Strength training hypertrophies muscle and increases strength, but often requires periods over 6 weeks, which can exceed the episode of care. Weakness can persist despite muscle hypertrophy, particularly in the early stages of joint pathology or in the presence of limb or spinal joint hypomobility, which may inhibit muscle activation. Emerging evidence suggests spinal manipulation can increase short-term strength. Screening for specific muscle weakness that could benefit from manipulation to particular spinal segments could facilitate efficient clinical intervention. Although the neuromuscular mechanisms through which manipulation can increase strength remains a topic of investigation, immediate gains can benefit patients by jump-starting an exercise program to train new muscle function gained and enhancing the motivation to continue strengthening. Evidence from randomized controlled trials would provide support for using manipulation to increase muscle strength, while studying healthy people would eliminate confounding factors, such as pain and pathology. Clinical Question: Does randomized controlled trial-level evidence support the concept that a single lumbar spine manipulation session can increase lower-limb strength in healthy individuals? Summary of Key Findings: Level 1b evidence of moderate quality from 3 randomized controlled trials showed immediate small to large effect size muscle strength increases immediately after lumbar spine manipulation. Clinical Bottom Line: Lumbar spine manipulation can result in immediate lower-limb isometric strength increases. While healthy people with normal muscle strength may improve minimally, joint manipulation for people with knee and hip weakness who are otherwise healthy can result in large effect size strength gains. Strength of Recommendation: Moderate quality level 1b evidence from randomized controlled trials with small samples support the use of spinal manipulation to immediately increase lower-limb strength. Additional studies investigating impact on strength and function immediately in people with musculoskeletal pathology are warranted.

Muscle fiber composition, jumping performance, and rate of force development adaptations induced by different power training volumes in females

This study aimed to investigate the effect of 3 different eccentric-only power training volumes on muscle fiber type composition and power performance. Twenty-nine females were assigned into 3 groups and performed 10 weeks of either 3 (low volume), 6 (moderate volume), or 9 (high volume) sets/session of 4 fast-velocity eccentric-only half-squats against 70% of concentric 1-repetition maximum (1RM), followed by 3 maximum countermovement jumps (CMJs) after each set. Half-squat 1RM, CMJ height/power, maximum isometric force, rate of force development (RFD) and muscle fiber cross-sectional area (CSA) were increased in all groups (p = 0.001). Low-volume training induced higher increases in CMJ height/power and early RFD, compared with the moderate- and high-volume training programs (p < 0.001). Significant reductions in type IIx muscle fiber percentages and %CSAs were found after moderate- and high-volume training, with concomitant increases in type IIa fibers (p = 0.001). Significant correlations were found between the changes in type IIa and type IIx percentages, fiber CSA, %CSA, and the changes in performance (r: -0.787 to 0.792; p < 0.05). These results suggest that relatively large eccentric power training volumes may result in detrimental neuromuscular adaptations, minimal changes in early RFD, and a reduction of type IIx muscle fiber percentage. Novelty Low but not high volume of power training maintains type IIx muscle fibers. Early rate of force development increases after a low- or moderate-power training volume, but not after a high-power training volume. Training-induced changes in type IIx muscle fiber percentage is related with changes in early rate of force development.

Medial Gastrocnemius Muscle Activity during Single-Leg Hopping to Exhaustion

This study described changes in leg muscle activation characteristics during exhaustive single-leg hopping. Twenty-seven healthy men performed trials (132 hops/min) to exhaustion, without a target height, to a target height with visual feedback and target height with tactile feedback. Mean muscle activation amplitude of the medial gastrocnemius (MG) decreased during the anticipatory period while duration of MG activity was maintained when hopping to a target height and contrasted the changes during hopping without a target height. Changes to MG activity were specific to whether the hopping height had been maintained or not. Changes during the anticipatory period of MG activity, indicative of adaptation in descending motor pathways, implicate utility of a motor learning strategy to allow completion of an exhaustive task.

Maslinic acid derived from olive fruit in combination with resistance training improves muscle mass and mobility functions in the elderly

Maslinic acid, derived from olive fruit, reduces pro-inflammation cytokines, which are involved in muscle fiber atrophy. Therefore, the maslinic acid ingestion may enhance the muscular response to resistance training through anti-inflammatory action. We therefore conducted a parallel, double-blind, randomized, placebo-controlled trial that examined whether a combination of maslinic acid supplementation and resistance training improve mobility functions in community-dwelling elderly persons. Over a 12-week period, 36 participants underwent moderate resistance training and are assigned to the maslinic acid supplementation (n = 17, 60 mg/day) or the placebo (n = 19) group. At baseline and at 12-weeks, we assessed body composition, grip strength, walking speed, leg strength, mobility functions, and knee pain scores. Following the 12-weeks, skeletal muscle mass, segmental muscle mass (right arm, left arm, and trunk) and knee pain score of the right leg were significantly improved in the maslinic acid group, while there was no change or parameters had worsened in the placebo group. Grip strength of the better side significantly increased only in the maslinic acid group. These results suggest that maslinic acid supplementation combined with moderate resistance training may increase upper muscle mass and grip strength, and reduce knee pain, could be effective for preventing mobility-related disability in elderly persons. Clinical trial registration number: UMIN000017207.

The General Adaptation Syndrome: A Foundation for the Concept of Periodization

Recent reviews have attempted to refute the efficacy of applying Selye's general adaptation syndrome (GAS) as a conceptual framework for the training process. Furthermore, the criticisms involved are regularly used as the basis for arguments against the periodization of training. However, these perspectives fail to consider the entirety of Selye's work, the evolution of his model, and the broad applications he proposed. While it is reasonable to critically evaluate any paradigm, critics of the GAS have yet to dismantle the link between stress and adaptation. Disturbance to the state of an organism is the driving force for biological adaptation, which is the central thesis of the GAS model and the primary basis for its application to the athlete's training process. Despite its imprecisions, the GAS has proven to be an instructive framework for understanding the mechanistic process of providing a training stimulus to induce specific adaptations that result in functional enhancements. Pioneers of modern periodization have used the GAS as a framework for the management of stress and fatigue to direct adaptation during sports training. Updates to the periodization concept have retained its founding constructs while explicitly calling for scientifically based, evidence-driven practice suited to the individual. Thus, the purpose of this review is to provide greater clarity on how the GAS serves as an appropriate mechanistic model to conceptualize the periodization of training.

Resistance training does not induce uniform adaptations to quadriceps

Resistance training may differentially affect morphological adaptations along the length of uni-articular and bi-articular muscles. The purpose of this study was to compare changes in muscle morphology along the length of the rectus femoris (RF) and vastus lateralis (VL) in response to resistance training. Following a 2-wk preparatory phase, 15 resistance-trained men (24.0 ± 3.0 y, 90.0 ± 13.8 kg, 174.9 ± 20.7 cm) completed pre-training (PRE) assessments of muscle thickness (MT), pennation angle (PA), cross-sectional area (CSA), and echo-intensity in the RF and VL at 30, 50, and 70% of each muscle’s length; fascicle length (FL) was estimated from respective measurements of MT and PA within each muscle and region. Participants then began a high intensity, low volume (4 x 3–5 repetitions, 3min rest) lower-body resistance training program, and repeated all PRE-assessments after 8 weeks (2 d ∙ wk^-1) of training (POST). Although three-way (muscle [RF, VL] x region [30, 50, 70%] x time [PRE, POST]) repeated measures analysis of variance did not reveal significant interactions for any assessment of morphology, significant simple (muscle x time) effects were observed for CSA (p = 0.002) and FL (p = 0.016). Specifically, average CSA changes favored the VL (2.96 ± 0.69 cm², p < 0.001) over the RF (0.59 ± 0.20 cm², p = 0.011), while significant decreases in average FL were noted for the RF (–1.03 ± 0.30 cm, p = 0.004) but not the VL (–0.05 ± 0.36 cm, p = 0.901). No other significant differences were observed. The findings of this study demonstrate the occurrence of non-homogenous adaptations in RF and VL muscle size and architecture following 8 weeks of high-intensity resistance training in resistance-trained men. However, training does not appear to influence region-specific adaptations in either muscle.

Impact of Aging on Endurance and Neuromuscular Physical Performance: The Role of Vascular Senescence

The portion of society aged ≥60 years is the fastest growing population in the Western hemisphere. Aging is associated with numerous changes to systemic physiology that affect physical function and performance. We present a narrative review of the literature aimed at discussing the age-related changes in various metrics of physical performance (exercise economy, anaerobic threshold, peak oxygen uptake, muscle strength, and power). It also explores aging exercise physiology as it relates to global physical performance. Finally, this review examines the vascular contributions to aging exercise physiology. Numerous studies have shown that older adults exhibit substantial reductions in physical performance. The process of decline in endurance capacity is particularly insidious over the age of 60 years and varies considerably as a function of sex, task specificity, and individual training status. Starting at the age of 50 years, aging also implicates an impressive deterioration of neuromuscular function, affecting muscle strength and power. Muscle atrophy, together with minor deficits in the structure and function of the nervous system and/or impairments in intrinsic muscle quality, plays an important role in the development of neuromotor senescence. Large artery stiffness increases as a function of age, thus triggering subsequent changes in pulsatile hemodynamics and systemic endothelial dysfunction. For this reason, we propose that vascular senescence has a negative impact on cerebral, cardiac, and neuromuscular structure and function, detrimentally affecting physical performance.

Inspiratory muscle training reduces diaphragm activation and dyspnea during exercise in COPD

Among patients with chronic obstructive pulmonary disease (COPD), those with the lowest maximal inspiratory pressures experience greater breathing discomfort (dyspnea) during exercise. In such individuals, inspiratory muscle training (IMT) may be associated with improvement of dyspnea, but the mechanisms for this are poorly understood. Therefore, we aimed to identify physiological mechanisms of improvement in dyspnea and exercise endurance following inspiratory muscle training (IMT) in patients with COPD and low maximal inspiratory pressure (Pi_max). The effects of 8 wk of controlled IMT on respiratory muscle function, dyspnea, respiratory mechanics, and diaphragm electromyography (EMGdi) during constant work rate cycle exercise were evaluated in patients with activity-related dyspnea (baseline dyspnea index <9). Subjects were randomized to either IMT or a sham training control group ( n = 10 each). Twenty subjects (FEV₁ = 47 ± 19% predicted; Pi_max  = -59 ± 14 cmH₂O; cycle ergometer peak work rate = 47 ± 21% predicted) completed the study; groups had comparable baseline lung function, respiratory muscle strength, activity-related dyspnea, and exercise capacity. IMT, compared with control, was associated with greater increases in inspiratory muscle strength and endurance, with attendant improvements in exertional dyspnea and exercise endurance time (all P < 0.05). After IMT, EMGdi expressed relative to its maximum (EMGdi/EMGdi_max) decreased ( P < 0.05) with no significant change in ventilation, tidal inspiratory pressures, breathing pattern, or operating lung volumes during exercise. In conclusion, IMT improved inspiratory muscle strength and endurance in mechanically compromised patients with COPD and low Pi_max. The attendant reduction in EMGdi/EMGdi_max helped explain the decrease in perceived respiratory discomfort despite sustained high ventilation and intrinsic mechanical loading over a longer exercise duration. NEW & NOTEWORTHY In patients with COPD and low maximal inspiratory pressures, inspiratory muscle training (IMT) may be associated with improvement of dyspnea, but the mechanisms for this are poorly understood. This study showed that 8 wk of home-based, partially supervised IMT improved respiratory muscle strength and endurance, dyspnea, and exercise endurance. Dyspnea relief occurred in conjunction with a reduced activation of the diaphragm relative to maximum in the absence of significant changes in ventilation, breathing pattern, and operating lung volumes.

Effects of an In-season Plyometric Training Program on Repeated Change of Direction and Sprint Performance in the Junior Soccer Player

Hammami, M, Negra, Y, Aouadi, R, Shephard, RJ, and Chelly, MS. Effects of an in-season plyometric training program on repeated change of direction and sprint performance in the junior soccer player. J Strength Cond Res 30(12): 3312-3320, 2016-We aimed to determine the gains in explosive movements of male junior soccer players induced by incorporating an 8-week plyometric training program (PTP) into a standard soccer conditioning regimen 5 months after the beginning of the competitive season. Our hypothesis was that PTP would enhance explosive movements, and thus sprint running, repeated shuttle sprint ability (RSSA), agility and the ability to make repeated changes of direction (RCOD). A group of junior soccer players were randomly divided into 2 groups: an experimental group (E, n = 15, age 15.7 ± 0.2 years) and a control group (C, n = 13, age 15.8 ± 0.2 years). The participants in E and C performed training exercises and matches together, but for an 8-week period in the latter part of the season, the experimental group replaced a part of the normal regimen (the tactical session) by a biweekly course of PTP (hurdle and drop jumps). Two familiarization sessions were held 2 weeks before definitive testing. The ability of the players was assessed by 3 agility tests (a sprint test with 180° turns, a 9-3-6-3-9 m sprint with backward and forward running, and a four 5-m sprint test with turns); 2 repeated sprint tests (RSSA and RCOD); and running times over 5-, 10-, 20-, 30-, and 40-m distances. Participants in E showed gains relative to C in sprint times (p ≤ 0.05 for 5, 10, and 20 m), and 2 of 3 the RCOD parameters (RCOD best, p ≤ 0.001; RCOD total, p ≤ 0.05). However, with the pattern of plyometric training that we adopted, and perhaps because participants were in good initial physical condition, the agility and RSSA test scores remained unchanged. Nevertheless, we conclude that our PTP can be commended to junior soccer players as a means of improving important components of their physical performance.

Training at non-damaging intensities facilitates recovery from muscle atrophy

INTRODUCTION

Resistance training promotes recovery from muscle atrophy, but optimum training programs have not been established. We aimed to determine the optimum training intensity for muscle atrophy.

METHODS

Mice recovering from atrophied muscles after 2 weeks of tail suspension underwent repeated isometric training with varying joint torques 50 times per day.

RESULTS

Muscle recovery assessed by maximal isometric contraction and myofiber cross-sectional areas (CSAs) were facilitated at 40% and 60% maximum contraction strength (MC), but at not at 10% and 90% MC. At 60% and 90% MC, damaged and contained smaller diameter fibers were observed. Activation of myogenic satellite cells and a marked increase in myonuclei were observed at 40%, 60%, and 90% MC.

CONCLUSIONS

The increases in myofiber CSAs were likely caused by increased myonuclei formed through fusion of resistance-induced myofibers with myogenic satellite cells. These data indicate that resistance training without muscle damage facilitates efficient recovery from atrophy. Muscle Nerve 55: 243-253, 2017.

Resistance training intensity and volume affect changes in rate of force development in resistance-trained men

PURPOSE

To compare the effects of two different resistance training programs, high intensity (INT) and high volume (VOL), on changes in isometric force (FRC), rate of force development (RFD), and barbell velocity during dynamic strength testing.

METHODS

Twenty-nine resistance-trained men were randomly assigned to either the INT (n = 15, 3-5 RM, 3-min rest interval) or VOL (n = 14, 10-12 RM, 1-min rest interval) training group for 8 weeks. All participants completed a 2-week preparatory phase prior to randomization. Measures of barbell velocity, FRC, and RFD were performed before (PRE) and following (POST) the 8-week training program. Barbell velocity was determined during one-repetition maximum (1RM) testing of the squat (SQ) and bench press (BP) exercises. The isometric mid-thigh pull was used to assess FRC and RFD at specific time bands ranging from 0 to 30, 50, 90, 100, 150, 200, and 250 ms.

RESULTS

Analysis of covariance revealed significant (p < 0.05) group differences in peak FRC, FRC at 30-200 ms, and RFD at 50-90 ms. Significant (p < 0.05) changes in INT but not VOL in peak FRC (INT: 9.2 ± 13.8 %; VOL: -4.3 ± 10.2 %), FRC at 30-200 ms (INT: 12.5-15.8 %; VOL: -1.0 to -4.3 %), and RFD at 50 ms (INT: 78.0 ± 163 %; VOL: -4.1 ± 49.6 %) were observed. A trend (p = 0.052) was observed for RFD at 90 ms (INT: 58.5 ± 115 %; VOL: -3.5 ± 40.1 %). No group differences were observed for the observed changes in barbell velocity.

CONCLUSIONS

Results indicate that INT is more advantageous than VOL for improving FRC and RFD, while changes in barbell velocity during dynamic strength testing are similarly improved by both protocols in resistance-trained men.

Index of fatigue quadriceps in soccer athletes after anterior cruciate ligament reconstruction

OBJECTIVE

The present study aimed to evaluate the muscle fatigue of the quadriceps muscle in high-performance soccer players undergoing (anterior cruciate ligament) ACL reconstruction.

METHODS

We evaluated 17 high-performance soccer players from three professional soccer teams of a state in Brazil from August 2011 to July 2012. All subjects were evaluated between 5.5 and 7 months after ACL reconstruction with a Biodex® isokinetic dynamometer (System 4 Pro) with test protocol CON/CON at 60°/s and 300°/s with 5 and 15 repetitions, respectively. In the calculation of local muscle fatigue, the fatigue index was used, which is calculated by dividing the labor done in the first one-third of the repetitions by that done at the final one-third of the repetitions, and multiplying by 100 to express a unit in percentage (i.e., as a discrete quantitative variable).

RESULTS

All subjects were male, with a mean age of 21.3 ± 4.4 years and mean BMI 23.4 ± 1.53 cm; left dominance was observed in 47% (n = 8) of athletes, and right dominance, in 53% (n = 9) of athletes; and the limb involved in the lesion was the dominant in 29% (n = 5) and the non-dominant in 71% (n = 12). Fatigue rates were 19.6% in the involved limb and 29.0% in the non-involved limb.

CONCLUSION

The results allow us to conclude that there was no significant difference between the limbs involved and not in ACL injuries regarding local muscle fatigue. No association was observed between the dominant side and the limb involved in the ACL injury.

Evaluation of a Task-Based Intervention After Tendon Transfer to Restore Lateral Pinch

OBJECTIVE

To quantify changes in pinch force and brachioradialis (BR) activation after a task-based training program designed to improve pinch force after BR to flexor pollicis longus (FPL) transfer.

DESIGN

One-group repeated-measures design compared pinch force and BR activation pre- and posttraining. Significant differences were tested with Wilcoxon signed-rank tests for pairwise comparisons at the P≤.05 level.

SETTING

Testing occurred in a Veterans Affairs Medical Center research laboratory and training was in a home setting.

PARTICIPANTS

Participants with cervical spinal cord injury (SCI) and previous BR to FPL transfer were enrolled in the study (N=8). Six patients completed the training program and posttraining measures.

INTERVENTIONS

The 10-week training was a home program that included novel activities to increase BR activation and practice producing pinch force in a variety of upper limb postures. Participants were provided with the task-based training equipment and instructed to practice 3 times per week.

MAIN OUTCOME MEASURES

Fine-wire electromyography of the transferred BR was recorded in maximum effort pinch force (N). Secondary measures included the strength and activation of the antagonist elbow extensor.

RESULTS

Pinch force increased 3.7N (.38kg) and BR muscle activation increased 10% (P≤.05) after the training. There was no increase in elbow extension strength, but participants with previous posterior deltoid to triceps transfer achieved greater activation of the antagonist elbow extensor.

CONCLUSIONS

The findings from this pilot study suggest that outcomes of tendon transfer and conventional therapy can be improved for patients with chronic cervical SCI.

The effect of training volume and intensity on improvements in muscular strength and size in resistance-trained men

This investigation compared the effect of high-volume (VOL) versus high-intensity (INT) resistance training on stimulating changes in muscle size and strength in resistance-trained men. Following a 2-week preparatory phase, participants were randomly assigned to either a high-volume (VOL; n = 14, 4 × 10-12 repetitions with ~70% of one repetition maximum [1RM], 1-min rest intervals) or a high-intensity (INT; n = 15, 4 × 3-5 repetitions with ~90% of 1RM, 3-min rest intervals) training group for 8 weeks. Pre- and posttraining assessments included lean tissue mass via dual energy x-ray absorptiometry, muscle cross-sectional area and thickness of the vastus lateralis (VL), rectus femoris (RF), pectoralis major, and triceps brachii muscles via ultrasound images, and 1RM strength in the back squat and bench press (BP) exercises. Blood samples were collected at baseline, immediately post, 30 min post, and 60 min postexercise at week 3 (WK3) and week 10 (WK10) to assess the serum testosterone, growth hormone (GH), insulin-like growth factor-1 (IGF1), cortisol, and insulin concentrations. Compared to VOL, greater improvements (P < 0.05) in lean arm mass (5.2 ± 2.9% vs. 2.2 ± 5.6%) and 1RM BP (14.8 ± 9.7% vs. 6.9 ± 9.0%) were observed for INT. Compared to INT, area under the curve analysis revealed greater (P < 0.05) GH and cortisol responses for VOL at WK3 and cortisol only at WK10. Compared to WK3, the GH and cortisol responses were attenuated (P < 0.05) for VOL at WK10, while the IGF1 response was reduced (P < 0.05) for INT. It appears that high-intensity resistance training stimulates greater improvements in some measures of strength and hypertrophy in resistance-trained men during a short-term training period.

Influence of strength training variables on strength gains in adults over 55 years-old: a meta-analysis of dose-response relationships

OBJECTIVES

The importance of strength training to elderly individuals is well established. However, the dose-response relationship of the benefits of strength training in this population is unclear. The purpose of the study was to use meta-analysis to investigate the dose-response of the effects of strength training in elderly individuals.

DESIGN

Fifteen studies with a total of 84 effect-sizes were included. The analyses examined the dose-response relationships of the following training variables 'intensity', 'number of sets', 'weekly frequency', and 'training duration' on strength improvement.

METHODS

The studies selected met the following inclusion criteria: (a) randomized controlled trials; (b) trained healthy subjects of both genders; (c) trained subjects aged 55 years or older; (d) strength increases were determined pre- and post-training; (e) use of similar strength evaluation techniques (strength determined by a repetition maximum test) and training routine (dynamic concentric-eccentric knee extension exercise to train the quadriceps muscle group). The effect-sizes were calculated using fixed and random effect models with the main effects determined by meta-regression.

RESULTS

Many combinations of training variables resulted in strength increases. However meta-regression indicated only "training duration" had a significant dose-response relationship to strength gains (p=0.001). Over durations of 8-52 weeks, longer training durations had a greater effect on strength gains compared to shorter duration protocols.

CONCLUSIONS

Resistive training causes strength gains in elderly individuals, provided the training duration is sufficiently long, regardless of the combination of other training variables.

Differential effects of targeted tongue exercise and treadmill running on aging tongue muscle structure and contractile properties

Age-associated changes in tongue muscle structure and strength may contribute to dysphagia in elderly people. Tongue exercise is a current treatment option. We hypothesized that targeted tongue exercise and nontargeted exercise that activates tongue muscles as a consequence of increased respiratory drive, such as treadmill running, are associated with different patterns of tongue muscle contraction and genioglossus (GG) muscle biochemistry. Thirty-one young adult, 34 middle-aged, and 37 old Fischer 344/Brown Norway rats received either targeted tongue exercise, treadmill running, or no exercise (5 days/wk for 8 wk). Protrusive tongue muscle contractile properties and myosin heavy chain (MHC) composition in the GG were examined at the end of 8 wk across groups. Significant age effects were found for maximal twitch and tetanic tension (greatest in young adult rats), MHCIIb (highest proportion in young adult rats), MHCIIx (highest proportion in middle-aged and old rats), and MHCI (highest proportion in old rats). The targeted tongue exercise group had the greatest maximal twitch tension and the highest proportion of MHCI. The treadmill running group had the shortest half-decay time, the lowest proportion of MHCIIa, and the highest proportion of MHCIIb. Fatigue was significantly less in the young adult treadmill running group and the old targeted tongue exercise group than in other groups. Thus, tongue muscle structure and contractile properties were affected by both targeted tongue exercise and treadmill running, but in different ways. Studies geared toward optimizing dose and manner of providing targeted and generalized tongue exercise may lead to alternative tongue exercise delivery strategies.

Sign Chi Do and physical function: a pilot study

Participating in strength, balance, and flexibility training reduces the risk for decreased physical function for older adults. This pilot study tested the effect of an exercise intervention on physical function. A pretest/posttest single-group design was used to test the effect of a 12-week Sign Chi Do (SCD) exercise intervention on upper body strength (arm curls) and lower body strength (chair stands); balance (Timed Up & Go and one-leg stance), and flexibility (back scratch). Five community-dwelling older adults not participating in strength, flexibility, or balance training completed the study. Strength scores improved by at least 2 arm curls or chair stands for those at risk for loss of physical function. Timed Up & Go scores improved by an average of 3.83 (range 1.98-4.98) seconds for those at risk for falls. All flexibility scores remained in the upper 75th percentile. Continued practice of SCD has the potential to improve physical function for older adults.

Spike shape analysis of surface electromyographic activity in wrist flexor and extensor muscles of the world's fastest drummer

Spike shape analysis (SSA) is a method to infer motor unit (MU) activity by examining interference pattern of surface electromyography (sEMG). SSA has succeeded to assess neuromuscular adaptations after dynamic training; however, it has not been used to assess muscle activities during the dynamic movements as seen in music performance. The present study used SSA to investigate sEMG activities of wrist flexor and extensor muscles in the winner of a contest to find the world's fastest drummer (WFD) during performing rhythmic wrist flexion/extension movements with one hand using a handheld drumstick. SSA measures of the WFD were compared with those in the two control groups: non-drummers (NDs) and ordinary drummers (ODs). We found that the WFD showed significantly high mean spike frequency (MSF), short mean spike duration (MSD), and small mean number of peaks per spike (MNPPS) compared with the control groups. These results suggest that the WFD had exceptional MU activity such as higher MU discharge rate, more MU recruitment, and/or higher MU synchronization to achieve extraordinary fast 10-Hz drumming performance. SSA will be useful to investigate the muscle activity seen in music performance.