Maximal strength performance,efficiency, and myoelectric responses with differing intra-set rest intervals during paired set training

IntroductionThe purpose of this study was to investigate the effect of different rest intervals within paired sets (PS) on total work and training volume, efficiency (training volume load/session duration time), and myoelectric activity.MethodFifteen trained men participated in this study. Four experimental protocols were applied: P30 (30 s rest), P60 (60 s rest), P90 (90 s rest), and P120 (120 s rest). The PS bout consisted of a bench press (BP)/lat pull down (LPD), 30° incline bench press (BP30)/wide-grip seated row (SR), and triceps extension (TE)/biceps curl (BC) exercises. Surface electromyography (sEMG) activity of the biceps and triceps brachii were recorded.ResultsVolume load (repetitions x number of exercise sets x loads) was significantly lower for the P30 (5385.8 ± 1224 kg) versus the P60 (6755.6 ± 1398.5 kg), P90 (7358.3 ± 1490.3 kg), and P120 (7463 ± 1310 kg) protocols. No significant differences in sEMG activity was noted between protocols. The efficiency (kg·min⁻¹) of P30 (633.6 ± 144) was significantly higher versus P60 (397.4 ± 82.2), P90 (288.5 ± 58.4), and P120 (219.5 ± 38.5).ConclusionShort intra-set rest intervals (60 s) within PS may be a potential alternative for increasing the volume load, since longer intra-rest (90 s and 120 s) intervals do not provide additional benefits.     

Feasibility and preliminary efficacy of a hypopressive exercise program on postmenopausal cancer survivors: A pilot study

BackgroundCancer-related fatigue (CRF) is a common symptom during and after cancer treatment that negatively affects the patient's quality of life. Exercise is one of the most effective non-pharmacological treatments for CRF. Multimodal exercise therapy programs that include hypopressive exercises, relaxation and myofascial release may be beneficial for CRF. The aim of this pilot study was to evaluate the feasibility and efficacy of a multimodal program on CRF and lower limb functional strength in postmenopausal women diagnosed with cancer.Methods7 postmenopausal women (age = 55.28 years; BMI = 26.05 kg/m2) who had a cancer diagnosis participated in a supervised and progressive 55-min class once per week for 12-weeks. CRF was measured using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Cancer Related Fatigue 12 and lower limb strength was assessed with the sit and stand test.ResultsNo adverse events were reported during the training period and all participants completed the exercise protocol. There was a significant increase (p = 0.01) in lower limb functional strength (pre: 19.60 (SD = 2.19) vs post: 24.60(SD = 2.19)) with an effect size of d = 2.28 and a decrease in CRF (p = 0.245) (pre: 29.36 ± 24.42; post: 17.85 ± 14.23) with a trivial effect size (d < 0.5).ConclusionsThese preliminary findings indicate that a supervised once per week multimodal program that includes hypopressive exercises for postmenopausal cancer survivors increased lower limb functional strength without exacerbating their CRF. These findings support further randomized trials of hypopressive training programs on patients with cancer.     

TIMELINE OF GAINS IN QUADRICEPS STRENGTH SYMMETRY AND PATIENT-REPORTED FUNCTION EARLY AFTER ACL RECONSTRUCTION

Background:Quadriceps weakness is a predictor of long-term knee function and strength recovery can vary from months to years after anterior cruciate ligament reconstruction (ACLR). However, few studies evaluate quadriceps strength and self-reported function within the first several weeks after ACLR.Hypothesis/Purpose:To examine changes over time in quadriceps strength symmetry, quadriceps peak torque, and self-reported knee function prior to and at six, 12, and 24 weeks post-ACLR. The hypotheses were 1) quadriceps strength symmetry, bilateral quadriceps peak torque, and patient-reported function would improve over time from pre-ACLR to 24 weeks post-ACLR and 2) significant improvements in patient-reported function, but not strength symmetry, would occur between time points.Study Design:Prospective, cohort studyMethods:Thirty participants completed four testing sessions: pre-surgery and six, 12, and 24 weeks post-ACLR. Isometric quadriceps strength testing was performed at six weeks and isokinetic quadriceps strength was measured at all other testing points. Quadriceps index was calculated to evaluate between limb quadriceps strength symmetry. The Knee injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee Subjective Knee Evaluation Form (IKDC) were administered at each time point. A repeated-measures analysis of variance evaluated changes over time, with post-hoc comparisons to determine at which time-point significant changes occurred.Results:Quadriceps strength symmetry, involved limb quadriceps peak torque and all patient-reported outcome scores increased over time (p<0.02). Post-hoc tests showed that neither self-reported outcomes, nor quadriceps index improved between pre-surgery and six-weeks post-ACLR. From six to 12 weeks post-ACLR, scores on IKDC and KOOS Pain, Symptoms, Quality of Life, and Sport subscales improved (p≤0.003). From 12 to 24 weeks post-ACLR, quadriceps strength symmetry, involved limb quadriceps peak torque, KOOS-Symptoms, Quality of Life, and Sport subscales and the IKDC improved (p≤0.01). Uninvolved limb quadriceps peak torque did not change across any time point (p≥0.18).Conclusion:Patient-reported knee function increased between six and 24 weeks post-ACLR, while increases in involved limb quadriceps strength and quadriceps strength symmetry were not noted until 12-24 weeks post-ACLR.Level of Evidence:2b, individual cohort study     

采用SWOT法对高职医药营销专业就业形势的分析

据高职医药营销专业就业难的现状,采用SWOT分析法对该专业存在的优势、劣势、机会和威胁进行深入客观的分析.以便权衡利弊,帮助毕业生克服就业过程中的不足,协助学校审视自身存在的劣势,为高职医药营销专业就业形势改善提供参考.     

Relationships between motor unit size and recruitment threshold in older adults: implications for size principle

As a part of the aging process, motor unit reorganization occurs in which small motoneurons reinnervate predominantly fast-twitch muscle fibers that have lost their innervation. We examined the relationship between motor unit size and the threshold force for recruitment in two muscles to determine whether older individuals might develop an alternative pattern of motor unit activation. Young and older adults performed isometric contractions ranging from 0 to 50% of maximal voluntary contraction in both the first dorsal interosseous (FDI) and tibialis anterior (TA) muscles. Muscle fiber action potentials were recorded with an intramuscular needle electrode and motor unit size was computed using spike-triggered averaging of the global EMG signal (macro EMG), which was also obtained from the intramuscular needle electrode. As expected, older individuals exhibited larger motor units than young subjects in both the FDI and the TA. However, moderately strong correlations were obtained for the macro EMG amplitude versus recruitment threshold relationship in both the young and older adults within both muscles, suggesting that the size principle of motor unit recruitment seems to be preserved in older adults.     

The effects of kettlebell training on strength,power, and endurance

Abstract

Background:

Kettlebell training is becoming increasingly popular but there is limited evidence to compare kettlebell training’s effects on strength, power, and endurance compared to traditional resistance or plyometric training. The popularity of kettlebell training appears to be based on anecdotal reports rather than on scientific evidence supporting training effects.

Objective:

To systematically review the effects of kettlebell training on strength, power, and endurance. The systematic review will also examine any adverse events associated with kettlebell training.

Methods:

A systematic review of literature indexed in the following databases: Medline, CINAHL, SportsDiscus, ProQuest, PEDro, and PubMed, was conducted. The quality of the studies was graded using the Physiotherapy Evidence Database Scale (PEDro).

Results:

Five studies satisfied the eligibility criteria and were included in this review. The populations studied age range was 18–72 years old. Methodological scores based on the PEDro scale ranged from 3 to 7 out of 10. Kettlebell training demonstrated improvements for a number of strength measures: time×group for bench press (P<0·05) and back extension (P<0·053), main effect for clean and jerk (P<0·05) and certain power measures such as improved explosive strength comparable to a jump squat control (19·8% increase). Improved postural control was demonstrated in one study (P?=?0·04). Kettlebell training did not have an effect on aerobic endurance as measured by VO₂ max. No adverse events were reported in any of these studies.

Conclusions:

Moderate evidence indicates that kettlebell training may be safe and effective for increasing certain functional strength and power measures and may show positive results with postural control in young, healthy populations. Kettlebell training has not been found to be efficacious in increasing aerobic endurance.     

Serum hormones during prolonged training of neuromuscular performance

Summary The effects of a 24-weeks' progressive training of neuromuscular performance capacity on maximal strength and on hormone balance were investigated periodically in 21 male subjects during the course of the training and during a subsequent detraining period of 12 weeks. Great increases in maximal strength were noted during the first 20 weeks, followed by a plateau phase during the last 4 weeks of training. Testosterone/cortisol ratio increased during training. During the last 4 weeks of training changes in maximal strength correlated with the changes in testosterone/cortisol (P<0.01) and testosterone/SHBG (P<0.05) ratios. During detraining, correlative decreases were found between maximal strength and testosterone/cortisol ratio (P<0.05) as well as between the maximal strength and testosterone/SHBG ratio (P<0.05). No statistically significant changes were observed in the levels of serum estradiol, lutropin (LH), follitropin (FSH), prolactin, and somatotropin. The results suggest the importance of the balance between androgenic-anabolic activity and catabolizing effects of glucocorticoids during the course of vigorous strength training.     

Muscle force and muscle torque in humans require different methods when adjusting for differences in body size

Different methods for adjusting muscle strength (S) to normalise for differences in various estimates of body size [such as body mass (m) or, infrequently, some other anthropometrical measurements] have been either proposed or applied when presenting the results of muscle function tests in various medical, ergonomic, and sport related studies. However, the fact that the relationship between S and body size may differ when muscle torque (measured using a standard isokinetic apparatus) and muscle force (measured using a dynamometer) are recorded has not been taken into account. To address this problem, we tested both muscle force and muscle torque under isometric conditions in six different muscle groups. The relationship assumed between S and m was S=k·m ^b and, according to a simple mechanical model based on geometrical similarity we developed, the exponential parameter b would be expected to equal 1.00 and 0.67 for torque and force, respectively. The experimentally obtained values for the parameter b were higher for muscle torque than for muscle force in five out of the six muscle groups tested (P=0.068; Wilcoxon matched pairs test). Despite a relatively wide scatter, the mean (SD) values were also close to those predicted, being b=0.67 (0.19) (corresponding to the allometric scaling method) and b=1.02 (0.34) (corresponding to the ratio standards method) for muscle force and for muscle torque, respectively. Therefore, we concluded that the ratio standards and allometric scaling should be employed to adjust S for body size when muscle torque and muscle force, respectively, are tested. Electronic Publication