Τετάρτη, 28 Αυγούστου 2019

Methodological Considerations Which Could Improve Spinal Cord Injury Research

Abstract

Advances in spinal cord injury-based research in the last 50 years have resulted in significant improvements to therapy options. However, the efficacy of such research could be further enhanced if threats to internal and external validity were addressed. To provide perspective, a sample topic was identified: the effects of acute and chronic exercise on clinical and sub-clinical markers of cardiovascular health. The intention was not a systematic review, nor a critique of exercise-based research, but rather a means to generate further discussion. Thirty-one articles were identified, and four common issues were found relating to: (1) sampling; (2) study design; (3) control group; and (4) clinical inference. These concerns were largely attributed to insufficient resources, and challenges associated with recruiting individuals with spinal cord injury. Overcoming these challenges will be difficult, but some opportunities include: (1) implementing multi-center trials; (2) sampling from subject groups appropriate to the research question; (3) including an appropriate control group; and (4) clearly defining clinical inference. These opportunities are not always feasible, and some easier to implement than others. However, addressing these concerns may assist in progressing spinal cord injury-based research, thereby helping to ensure steady advancement of therapy options for persons with spinal cord injury.

Effects of Aerobic Exercise on Atherosclerotic Risk in Postmenopausal Women

Abstract

Introduction

To study the effects of aerobic exercise on lipid metabolism, endothelial function, and oxidative stress reaction in postmenopausal women, in order to prevent and control atherosclerosis.

Methods

Thirty-two women with natural menopause were randomly divided into an exercise group and a control group. Participants in the exercise group (n = 16) took part in a 3-month aerobic training program according to their exercise prescription, while participants in the control group (n = 16) maintained their usual lifestyles. Lipids, endothelial function, and oxidative stress-related indicators were measured before and after the intervention.

Results

After 3 months of aerobic training at an intensity of 50–60% of cardiorespiratory fitness, serum total cholesterol and low-density lipoprotein cholesterol decreased significantly (P < 0.05), and high-density lipoprotein cholesterol increased significantly (P < 0.01). A significant reduction in endothelin (P < 0.01) and a significant increase in nitric oxide (P < 0.05) were also observed. The training intervention also delayed the increase in homocysteine and cysteine aspartate-specific protease-3 in postmenopausal women.

Conclusions

Aerobic exercise had a positive effect on blood lipids, endothelial function, and oxidative stress of postmenopausal women, and these changes may mitigate the risk of atherosclerosis occurrence. Similar exercise programs could be used as a primary atherosclerosis prevention strategy for postmenopausal women.

Effect of the Resistance Exercise on Elementary School Students’ Physical Fitness

Abstract

Background

Physical activity programs using components of resistance have the potential to improve health in school children. The purpose of this study was to examine the effect of a school-based resistance exercise program on physical fitness in elementary school students.

Methods

The sample was 256 children (mean age = 8.3 ± 2.5 years; 119 girls) from kindergarten to 5th grade. Participants performed a 10-min resistance exercise 2–3 times in each school day. Physical fitness outcomes were assessed using President’s Physical Fitness Challenge test. Measures were collected at baseline and at a 6-month post-test time point. A 2 × 2 doubly MANOVA was employed to examine the effect of sex and time.

Results

The multivariate model was statistically significant with a main time effect (Wilks’ λ = 0.19, F = 290.9, P < 0.001). Follow-univariate tests found significant differences between time-points on flex arm hang (P = 0.033), shuttle run (P < 0.001), and 1-mile run/walk times (P < 0.001).

Conclusions

A 6-month resistance exercise program improved upper body strength and cardiorespiratory endurance in elementary school aged children. The use of resistance exercise intervention during school day can be effectively used to promote physical fitness and ultimately improve the health of children.

The Sensitivity of the Critical Resistance Model to Detect Sex-Related Differences in Fatigue During Submaximal Muscular Contractions

Abstract

Purpose

Critical resistance (CR) is a fatigue threshold that, theoretically, estimates the highest sustainable resistance for repeated skeletal muscle contractions. Men are typically more susceptible to fatigue than women during sustained muscular contractions. Therefore, the purpose of this study was to compare the CR between men and women to determine the sensitivity of the CR model to detect sex-related differences in fatigue at submaximal intensities.

Methods

Ten men and 10 women completed one-repetition maximum (1RM) testing for the deadlift and repetitions to failure at 50%, 60%, 70%, and 80% of 1RM for the determination of CR. Repetitions to failure were then performed at the estimated CR.

Results

The men had a greater absolute 1RM (168 ± 27 kg vs. 115 ± 11 kg) and CR (62 ± 14 kg vs. 48 ± 6 kg), but a lower relative CR (percent of 1RM; 37 ± 6% vs. 41 ± 2%) and completed fewer repetitions at CR (45 ± 14 repetitions vs. 58 ± 12 repetitions) compared to the women.

Conclusions

The CR model was sensitive to detect sex-related differences in fatiguing muscular contractions of the deadlift. In addition, the men were more susceptible to fatigue than the women during performance of submaximal muscular contractions at CR, which may be related to sex-dependent physiological responses during fatiguing muscular contractions.

Correlations Between Myoelectric and Hemodynamic Parameters Changes in Biceps Brachii During Sustained Isometric Contraction in Healthy Elderly

Abstract

Purpose

The purpose of the present study was to evaluate the Pearson correlations between hemodynamic parameters obtained with near infrared spectroscopy (NIRS), namely total hemoglobin (tHb) and tissue oxygen index (TOI %), as indicators of blood flow and oxygen extraction, and myoelectric parameters obtained with surface multichannel electromyography (sEMG), namely fractal dimension (FD) and conduction velocity (CV) slopes, as descriptors of central and peripheral fatigue, during sustained high level isometric contractions at 60% maximal voluntary contraction (MVC), in elderly subjects.

Methods

Ten recreationally healthy elderly subjects (age 67.7 ± 4.6 years), 5 males and 5 females, performed one isometric contraction of the elbow flexors at 120° joint angle at 60% of MVC until exhaustion in two subsequent trials 1 week apart, one for the sEMG and the other one for NIRS recordings from the biceps brachii.

Results

A negative strong Pearson’s correlation between TOI % slope in the functional hyperemic phase (HP) of contraction and a positive correlation between the slope of TOI % recorded during the ischemic phase (IP) and the CV slope were found (r = − 0.76, P < 0.05; r = 0.91, P < 0.01, respectively). A negative strong correlation between tHb IP slope and tHb HP slope and TOI % IP slope and TOI % HP slope (r = − 0.78, P < 0.01; r = − 0.78, P < 0.01, respectively) were also found. No correlation was found between FD slope and hemodynamic parameters (FD slope vs. HP tHb slope, r = − 0.19; FD slope vs. IP tHb slope, r = 0.16; FD slope vs. HP TOI % slope, r = 0.19; FD slope vs. IP TOI % slope, r = 0.27).

Conclusion

In aged individuals, CV slope correlated with muscle O2 desaturation (TOI %) rather than reduced muscle blood flow (tHb) in the ischemic phase of isometric contraction to exhaustion. No correlations were found between myoelectric manifestations of central fatigue (FD slope) and data obtained by NIRS.

Differences in Kinetics, Kinematics and Muscle Activation Strategies in Male and Female Team Sport Athletes During Unanticipated Sidestepping

Abstract

Purpose

The purpose of this study was to compare kinetics, kinematics and muscle activation strategies between male and female collegiate level athletes during unanticipated sidestepping tasks to further the understanding of sex-specific differences in injury incidence and their potential influence on ACL injury risk.

Methods

Three-dimensional kinematics, ground reaction forces and surface electromyography of eight lower limb muscles were recorded during unanticipated sidestepping in 20 male soccer and 17 female field hockey National Collegiate Athletics Association Division 1 athletes. Trunk, hip and knee kinematics, knee joint moments, total muscle activation (TMA: knee, gluteal, quadriceps, hamstrings and gastrocnemii) and directed co-contraction ratios (DCCR) were compared between groups with two-sample t tests.

Results

No sex differences were observed for peak frontal and transverse plane knee moments (P > 0.05), however males had 10% greater knee flexion moments (P = 0.047). Females had lower hip flexion and abduction and greater hip internal rotation angles than males likely concomitant with the 30% reduction in gluteal TMA (P < 0.05). Females had lower quadriceps TMA during pre-contact and weight acceptance and higher hamstrings TMA during weight acceptance (P < 0.05). Group averages for DCCR were not representative of individual patterns, where the majority of males were quadriceps dominant compared with females.

Conclusions

Female and male team sport athletes display similar frontal and transverse plane knee moments, however their ability to support/counter the load applied (i.e., muscle activations strategies) to the knee joint differed.

The Health Benefits of a Pedometer-Based 100,000 Steps/Week Physical Activity Program

Abstract

Purpose

Pedometers can be an effective tool to increase step counts in a physically inactive population. In a more active population, pedometers may also be useful for further increasing physical activity and improving cardiovascular disease risk factors. Our purpose was to assess the adherence and determine the health impact of a 100,000 steps/week (14,286 steps/day) goal in a somewhat-active (7500–9999 steps/day) to active (10,000–12,500 steps/day) population.

Methods

Thirty-two apparently healthy subjects, 13 males (age 44 ± 14 years) and 19 females (age 39 ± 13 years) who had a baseline activity level between 7500 and 12,500 steps/day, were studied. Participants were assessed prior to and 16 weeks after completing a 100,000 steps/week intervention. Pre- and post-assessments of health included body composition, resting blood pressure, blood lipid profile, fasting blood glucose, and a 3-min walk test to estimate cardiorespiratory fitness.

Results

Fifty-three percent of participants adhered (≥ 90,000 steps/week) to the 100,000 steps/week physical activity program yet all participants increased their stepping by 23,303 ± 11,480 steps/week. With increased stepping, significant improvements in body composition were observed. Improvements included reduced body mass index (pre: 27.2 ± 3.6 kg/m2; post: 26.9 ± 3.6 kg/m2P = 0.026), reduced total percent body fat (pre: 35.7 ± 9.9%; post: 34.3 ± 10.4%; P < 0.001), and reduced waist circumference (pre: 83.8 ± 10.2 cm; post: 81.5 ± 10.0 cm; P = 0.001). An unexpected increase was observed for low density lipoprotein cholesterol (pre: 109.7 ± 22.7 mg/dL; post: 117.6 ± 20.4 mg/dL; P < 0.05).

Conclusions

Individuals who were previously somewhat-active or active can gain additional health benefits, particularly improvements in body composition, by increasing to 100,000 steps/week with the use of a pedometer.

Comparison of Neuromotor and Progressive Resistance Exercise Training to Improve Mobility and Fitness in Community-Dwelling Older Women

Abstract

Purpose

Neuromotor exercise, which stimulates motor fitness components (balance, agility, coordination), has been less investigated than other forms of exercise such as resistance or aerobic training to counteract the age-related impairment in mobility. The aim of the study was to verify whether neuromotor exercise was as effective as resistance training in improving mobility and related fitness components in healthy older women.

Methods

Thirty-five women (mean age 69.6 ± 3.2 years) were assigned to a neuromotor (NMT) or a progressive resistance training (PRT) group, both exercising 1 h, twice weekly for 12 weeks. The NMT group exercised static and dynamic balance, agility, speed, reaction time and coordination, while the PRT performed prevalently machine based, strengthening exercises. All participants were tested before and after the intervention for walking speed under different conditions, chair rise time, cardiorespiratory fitness, muscular strength and power. A 2 × 2 MANOVA and subsequent ANOVAs were performed to ascertain the effects of the two trainings.

Results

Similar improvements were observed for mobility (P = 0.000, \(\eta_{p}^{2}=0.73\) ) and for fitness (P = 0.000, \(\eta_{p}^{2}=0.96\) ) in both groups.

Conclusions

The present results suggest that in healthy older women improvements in mobility may be obtained through both strength and neuromotor exercise. The present results contribute to further our knowledge on the effects of neuromotor exercise for older people and add relevant information on exercise interventions targeting mobility in the elderly.

Metabolic Adaptations to Exercise Training

Abstract

The health benefits of exercise have attracted substantial attention, because regular exercise can strengthen muscles and improve endurance. Physical activity is an integral part of an overall healthy lifestyle, which helps protect against chronic diseases, such as obesity, insulin resistance and type 2 diabetes. In consideration of the differences in duration, intensity, and type of activity of exercise, it is likely to involve different signaling pathways and bring different benefits in different tissues. Here we review our growing knowledge of exercise training adaptations and regulation in cellular processes related to energy metabolism, aging and autophagy, and many important findings remain to be discovered.

Effects of Recreational Soccer on Health Outcomes: A Narrative Review

Abstract

Soccer is a very popular team sport that involves a variety of physical actions, such as sprints, accelerations, sudden decelerations, and jumps, among others. Research has placed recreational soccer in a good position as a strategy to increase physical activity levels and promote health across the lifespan. In this regard, recreational (non-competitive) soccer promotes social interaction and has the potential to increase long-term adherence to physical activity, even in those without prior experience in this sport. In this narrative review, we address the effects of recreational soccer on various health outcomes across the lifespan (i.e., from childhood to the elderly years) in both sexes. In addition, the beneficial effects of recreational soccer for people with prevalent pathologies, such as hypertension, type II diabetes mellitus, and cancer, are discussed.

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