Mixed-methods resistance training increases power and strength of young and older men

The use of individual and collective selection, optimisation and compensation (SOC) strategies and their association with work ability among senior workers

Background Selection, optimisation, and compensation (SOC) can be important strategies for maintaining work ability as we age. This study aimed to explore differences in self-reported individual and collective use of SOC strategies across job functions, as well as their association with self-rated work ability.

METHODS

In the third wave of the SeniorWorkingLife study, 10,798 workers aged 50 + , across the job function categories "Office work", "work with people", and "work in the field of production", replied to questions about collective and individual SOC strategies and work ability. Using multiple regression, we modelled associations between SOC and work ability.

RESULTS

Associations between SOC and work ability were generally weaker among participants working in the field of production. Both individual and collective use of selection had much weaker associations with work ability in the job functions "office work" and "working with people". In the job function "working in the field of production", only collective compensation was positively associated with work ability while individual selection was significantly but negatively associated with work ability.

CONCLUSIONS

The use of SOC may be particularly beneficial for older employees working with people. Optimisation and compensation may be the most important SOC strategies for maintaining the work ability of older employees working with people and doing office work. For older employees working in the field of production, collective optimisation may support the maintenance of work ability while reduced work ability may be associated with the use of individual selection as a "coping strategy".

National Strength and Conditioning Association Position Statement on Weightlifting for Sports Performance

ABSTRACT

Comfort, P, Haff, GG, Suchomel, TJ, Soriano, MA, Pierce, KC, Hornsby, WG, Haff, EE, Sommerfield, LM, Chavda, S, Morris, SJ, Fry, AC, and Stone, MH. National Strength and Conditioning Association position statement on weightlifting for sports performance. J Strength Cond Res XX(X): 000-000, 2022-The origins of weightlifting and feats of strength span back to ancient Egypt, China, and Greece, with the introduction of weightlifting into the Olympic Games in 1896. However, it was not until the 1950s that training based on weightlifting was adopted by strength coaches working with team sports and athletics, with weightlifting research in peer-reviewed journals becoming prominent since the 1970s. Over the past few decades, researchers have focused on the use of weightlifting-based training to enhance performance in nonweightlifters because of the biomechanical similarities (e.g., rapid forceful extension of the hips, knees, and ankles) associated with the second pull phase of the clean and snatch, the drive/thrust phase of the jerk and athletic tasks such as jumping and sprinting. The highest force, rate of force development, and power outputs have been reported during such movements, highlighting the potential for such tasks to enhance these key physical qualities in athletes. In addition, the ability to manipulate barbell load across the extensive range of weightlifting exercises and their derivatives permits the strength and conditioning coach the opportunity to emphasize the development of strength-speed and speed-strength, as required for the individual athlete. As such, the results of numerous longitudinal studies and subsequent meta-analyses demonstrate the inclusion of weightlifting exercises into strength and conditioning programs results in greater improvements in force-production characteristics and performance in athletic tasks than general resistance training or plyometric training alone. However, it is essential that such exercises are appropriately programmed adopting a sequential approach across training blocks (including exercise variation, loads, and volumes) to ensure the desired adaptations, whereas strength and conditioning coaches emphasize appropriate technique and skill development of athletes performing such exercises.

Determining the cortical, spinal and muscular adaptations to strength-training in older adults: A systematic review and meta-analysis

There are observable decreases in muscle strength as a result of ageing that occur from the age of 40, which are thought to occur as a result of changes within the neuromuscular system. Strength-training in older adults is a suitable intervention that may counteract the age-related loss in force production. The neuromuscular adaptations (i.e., cortical, spinal and muscular) to strength-training in older adults are largely equivocal and a systematic review with meta-analysis will serve to clarify the present circumstances regarding the benefits of strength-training in older adults. 20 studies entered the meta-analysis and were analysed using a random-effects model. A best evidence synthesis that included 36 studies was performed for variables that had insufficient data for meta-analysis. One study entered both. There was strong evidence that strength-training increases maximal force production, rate of force development and muscle activation in older adults. There was limited evidence for strength-training to improve voluntary-activation, the volitional-wave and spinal excitability, but strong evidence for increased muscle mass. The findings suggest that strength-training performed between 2 and 12 weeks increases strength, rate of force development and muscle activation, which likely improves motoneurone excitability by increased motor unit recruitment and improved discharge rates.

Randomised Controlled Trial of Fish Oil Supplementation on Responsiveness to Resistance Exercise Training in Sarcopenic Older Women

This study aims to investigate the effects of fish oil supplementation on the muscle adaptive response to resistance exercise training, physical performance and serum levels of inflammatory cytokines in sarcopenic older women. A randomised, double-blind, placebo-controlled trial is performed with thirty-four sarcopenic women (2010 European Consensus of Sarcopenia), aged ≥ 65 years. The participants are allocated into the following two groups: Exercise and Fish Oil (EFO) and Exercise and Placebo (EP). Both groups undertook a resistance exercise programme over 14 weeks. All participants are instructed to ingest 4 g/day of food supplements; the EP group received sunflower oil capsules, and the EFO group, fish oil capsules. The cross-sectional area (CSA) of the quadriceps muscle is calculated using magnetic resonance imaging (MRI). The strength of the lower limbs is measured using isokinetic dynamometry. Both groups show improvements in CSA and strength after the intervention. Changes in EFO are significantly greater compared with EP for muscle strength (peak torque, 19.46 Nm and 5.74 Nm, respectively, p < 0.001). CSA increased after the intervention in both groups (EFO; 6.11% and EP; 2.91%), although there is no significant difference between the groups (p = 0.23). There are no significant intra-group, inter-group or time differences in any of the cytokines measured. The use of fish oil supplementation potentiates the neuromuscular response to the anabolic stimulus from training, increasing muscle strength and physical performance in sarcopenic older women.

Within Session Exercise Sequencing During Programming for Complex Training: Historical Perspectives, Terminology, and Training Considerations

The primary aim of this narrative review was to outline the historical genesis of resistance training strategies that incorporate high-load, low-velocity exercises and low-load, high-velocity exercises in the same training session allowing for different "exercise sequences" to be simultaneously implemented. Discrepancies between scientific works and the terminology used within contemporary sport science publications are identified. Upon review of the literature, we propose "complex training" to be considered an umbrella term with 4 different implementations, generally used to indicate a method in which movement velocity or load is altered between sets and/or exercises within the same session with the aim of improving slow and fast force expression. We propose the following terminology for said implementations: contrast training-exercise sequence with alternating high-load and low-load (higher-velocity) exercises in a set-by-set fashion within the same session (corresponding with 'contrast pairs' and 'intra-contrast rest'); descending training-several sets of high-load (e.g., back squat) exercises completed before the execution of several sets of low-load, higher-velocity (e.g., vertical jump) exercises within the same session; ascending training-several sets of low-load, higher-velocity exercises completed before several sets of high-load exercises within the same session; and French contrast training-subset of contrast training in which a series of exercises are performed in sequence within a single session: heavy compound exercise, plyometric exercise, light-to-moderate load compound exercise that maximises movement speed (i.e., external power), and a plyometric exercise (often assisted). Finally, practical applications and training considerations are presented.

High-velocity resistance training mitigates physiological and functional impairments in middle-aged and older adults with and without mobility-limitation

The aim of the present study was to compare the neuromuscular, morphological, and functional responses to a high-velocity resistance training (HVRT) program between three cohorts: middle-aged adults (40–55 years, n = 18), healthy older adults (> 60 years, n = 18), and mobility-limited older adults (n = 8). Participants were tested before and after a 4-week control period and then assigned to a 12-week HVRT intervention. Investigated outcomes included ultrasound-derived muscle thickness and quality, maximal dynamic strength (1RM), maximal voluntary isometric contraction (MVIC), and muscle activation (sEMG), as well as muscle power and functional performance. After the intervention, quadriceps muscle thickness, 1RM, and sEMG improved in all three groups (all p < 0.05), whereas muscle quality improved only in middle-aged and older participants (p ≤ 0.001), and MVIC only in middle-aged and mobility-limited older adults (p < 0.05). With a few exceptions, peak power improved in all groups from 30–90% 1RM (p < 0.05) both when tested relative to pre-training or post-training 1RM workloads (all p < 0.05). Both mobility-limited older adults and older adults improved their short physical performance battery score (p < 0.05). Chair stand, stair climb, maximal gait speed, and timed up-and-go performance, on the other hand, improved in all three groups (p < 0.05), but no change was observed for habitual gait speed and 6-min walk test performance. Overall, our results demonstrate that a HVRT intervention can build a stronger foundation in middle-aged individuals so that they can better deal with age-related impairments at the same time that it can mitigate already present physiological and functional impairments in older adults with and without mobility-limitation.

High-velocity resistance training as a tool to improve functional performance and muscle power in older adults

The aging process results in several physiological impairments that, in turn, may predispose older individuals to a series of restrictions on their functional capacity. These impairments are important to understand so that suitable conditions for healthier aging can be pursued. In this review, we first summarize the effects of aging on the neuromuscular system, as well as on the relation between the main age-associated physiological impairments and functional performance with an emphasis on muscle power output. We then proceed to discuss the effects of resistance training, specifically high-velocity resistance training (HVRT), on the aforementioned neuromuscular impairments, and on functional performance in healthy and mobility-limited older adults. Collectively, available evidence suggests that HVRT seems to be a safe and effective intervention for improving muscle power, functional performance, and mobility of older individuals. It also seems that mobility-limited older adults may improve power and functional performance to a greater extent than their healthy counterparts after HVRT, which is in line with the principle of diminishing returns. Considering that only a very limited number of investigations directly compared the effects of HVRT in more than one of the aforementioned groups, studies comparing the adaptations to HVRT of middle-aged adults and older adults with distinct functional capacities would be valuable to determine whether there are differences in neuromuscular adaptations, functional performance, and functional reserve among these groups.

Rate of Force Development Is Related to Maximal Force and Sit-to-Stand Performance in Men With Stages 3b and 4 Chronic Kidney Disease

Introduction: The primary aims of the present study were to assess the relationships of early (0–50 ms) and late (100–200 ms) knee extensor rate of force development (RFD) with maximal voluntary force (MVF) and sit-to-stand (STS) performance in participants with chronic kidney disease (CKD) not requiring dialysis.

Methods: Thirteen men with CKD (eGFR = 35.17 ±.5 ml/min per 1.73 m², age = 70.56 ±.4 years) and 12 non-CKD men (REF) (eGFR = 80.31 ± 4.8 ml/min per 1.73 m², age = 70.22 ±.9 years) performed maximal voluntary isometric contractions to determine MVF and RFD of the knee extensors. RFD was measured at time intervals 0–50 ms (RFD₀₋₅₀) and 100–200 ms (RFD_100−200). STS was measured as the time to complete five repetitions. Measures of rectus femoris grayscale (RF GSL) and muscle thickness (RF MT) were obtained via ultrasonography in the CKD group only. Standardized mean differences (SMD) were used to examine differences between groups. Bivariate relationships were assessed by Pearson's product moment correlation.

Results: Knee extensor MVF adjusted for body weight (CKD=17.14 ±.1 N·kg^0.67, REF=21.55 ±.3 N·kg^0.67, SMD = 0.79) and STS time (CKD = 15.93 ±.4 s, REF = 12.23 ±.7 s, SMD = 1.03) were lower in the CKD group than the REF group. Absolute RFD_100−200 was significantly directly related to adjusted MVF in CKD (r = 0.56, p = 0.049) and REF (r = 0.70, p = 0.012), respectively. STS time was significantly inversely related to absolute (r = −0.75, p = 0.008) and relative RFD₀₋₅₀ (r = −0.65, p = 0.030) in CKD but not REF (r = 0.08, p = 0.797; r = 0.004, p = 0.991). Significant inverse relationships between RF GSL adjusted for adipose tissue thickness and absolute RFD_100−200 (r =−0.59, p = 0.042) in CKD were observed.

Conclusion: The results of the current study highlight the declines in strength and physical function that occur in older men with CKD stages 3b and 4 not requiring dialysis. Moreover, early RFD was associated with STS time in CKD while late RFD was associated MVF in both CKD and REF.

Clinical Trial Registration: ClinicalTrials.gov, identifier: NCT03160326 and NCT02277236.

Evidence-based recommendations for resistance and power training to prevent frailty in community-dwellers

Frailty is a reversible state of reduced resilience to stressful events resulting from a multisystem impairment of the human body. As frailty progresses, people become more vulnerable to numerous adverse events, including falls and fractures, cognitive decline, disability, hospitalization, nursing home placement, and death. As such, substantial health care costs are associated with frailty. These features have led to the recognition of frailty as a public health problem. The identification of strategies for the management of frailty has, therefore, become a topic of extensive instigation. In this context, resistance (RT) and power training (PT) have received considerable attention, and experts in the field have recently suggested that both training modalities may improve frailty-related parameters. However, most studies have only included robust people and investigated frailty as a secondary outcome, so that current literature only allows RT and PT preventive programs against frailty to be designed. Here, we provide evidence-based critical recommendations for the prescription of RT and PT programs against incident frailty in community-dwellers.

High physical work demands have worse consequences for older workers: prospective study of long-term sickness absence among 69 117 employees

Objective

This study investigates the role of age for the prospective association between physical work demands and long-term sickness absence (LTSA).

Methods

We followed 69 117 employees of the general working population (Work Environment and Health in Denmark study 2012–2018), without LTSA during the past 52 weeks preceding initial interview, for up to 2 years in the Danish Register for Evaluation of Marginalisation. Self-reported physical work demands were based on a combined ergonomic index including seven different types of exposure during the working day. Using weighted Cox regression analyses controlling for years of age, gender, survey year, education, lifestyle, depressive symptoms and psychosocial work factors, we determined the interaction of age with physical work demands for the risk of LTSA.

Results

During follow-up, 8.4% of the participants developed LTSA. Age and physical work demands interacted (p<0.01). In the fully adjusted model, very high physical work demands were associated with LTSA with HRs of 1.18 (95% CI 0.93 to 1.50), 1.57 (95% CI 1.41 to 1.75) and 2.09 (95% CI 1.81 to 2.41) for 20, 40 and 60 years old (point estimates), respectively. Results remained robust in subgroup analyses including only skilled and unskilled workers and stratified for gender.

Conclusion

The health consequences of high physical work demands increase with age. Workplaces should consider adapting physical work demands to the capacity of workers in different age groups.

Prediction of One Repetition Maximum Using Reference Minimum Velocity Threshold Values in Young and Middle-Aged Resistance-Trained Males

Background: This study determined the accuracy of different velocity-based methods when predicting one-repetition maximum (1RM) in young and middle-aged resistance-trained males. Methods: Two days after maximal strength testing, 20 young (age 21.0 ± 1.6 years) and 20 middle-aged (age 42.6 ± 6.7 years) resistance-trained males completed three repetitions of bench press, back squat, and bent-over-row at loads corresponding to 20–80% 1RM. Using reference minimum velocity threshold (MVT) values, the 1RM was estimated from the load-velocity relationships through multiple (20, 30, 40, 50, 60, 70, and 80% 1RM), two-point (20 and 80% 1RM), high-load (60 and 80% 1RM) and low-load (20 and 40% 1RM) methods for each group. Results: Despite most prediction methods demonstrating acceptable correlations (r = 0.55 to 0.96), the absolute errors for young and middle-aged groups were generally moderate to high for bench press (absolute errors = 8.2 to 14.2% and 8.6 to 20.4%, respectively) and bent-over-row (absolute error = 14.9 to 19.9% and 8.6 to 18.2%, respectively). For squats, the absolute errors were lower in the young group (5.7 to 13.4%) than the middle-aged group (13.2 to 17.0%) but still unacceptable. Conclusion: These findings suggest that reference MVTs cannot accurately predict the 1RM in these populations. Therefore, practitioners need to directly assess 1RM.

Hormonal and Metabolic Changes of Aging and the Influence of Lifestyle Modifications

Increased life expectancy combined with the aging baby boomer generation has resulted in an unprecedented global expansion of the elderly population. The growing population of older adults and increased rate of age-related chronic illness has caused a substantial socioeconomic burden. The gradual and progressive age-related decline in hormone production and action has a detrimental impact on human health by increasing risk for chronic disease and reducing life span. This article reviews the age-related decline in hormone production, as well as age-related biochemical and body composition changes that reduce the bioavailability and actions of some hormones. The impact of hormonal changes on various chronic conditions including frailty, diabetes, cardiovascular disease, and dementia are also discussed. Hormone replacement therapy has been attempted in many clinical trials to reverse and/or prevent the hormonal decline in aging to combat the progression of age-related diseases. Unfortunately, hormone replacement therapy is not a panacea, as it often results in various adverse events that outweigh its potential health benefits. Therefore, except in some specific individual cases, hormone replacement is not recommended. Rather, positive lifestyle modifications such as regular aerobic and resistance exercise programs and/or healthy calorically restricted diet can favorably affect endocrine and metabolic functions and act as countermeasures to various age-related diseases. We provide a critical review of the available data and offer recommendations that hopefully will form the groundwork for physicians/scientists to develop and optimize new endocrine-targeted therapies and lifestyle modifications that can better address age-related decline in heath.

Why Are Masters Sprinters Slower Than Their Younger Counterparts? Physiological, Biomechanical, and Motor Control Related Implications for Training Program Design

Elite sprint performances typically peak during an athlete's 20s and decline thereafter with age. The mechanisms underpinning this sprint performance decline are often reported to be strength-based in nature with reductions in strength capacities driving increases in ground contact time and decreases in stride lengths and frequency. However, an as-of-yet underexplored aspect of Masters sprint performance is that of age-related degradation in neuromuscular infrastructure, which manifests as a decline in both strength and movement coordination. Here, the authors explore reductions in sprint performance in Masters athletes in a holistic fashion, blending discussion of strength and power changes with neuromuscular alterations along with mechanical and technical age-related alterations. In doing so, the authors provide recommendations to Masters sprinters-and the aging population, in general-as to how best to support sprint ability and general function with age, identifying nutritional interventions that support performance and function and suggesting useful programming strategies and injury-reduction techniques.

Aging and Recovery After Resistance-Exercise-Induced Muscle Damage: Current Evidence and Implications for Future Research

Aging is anecdotally associated with a prolonged recovery from resistance training, though current literature remains equivocal. This brief review considers the effects of resistance training on indirect markers of muscle damage and recovery (i.e., muscle soreness, blood markers, and muscle strength) in older males. With no date restrictions, four databases were searched for articles relating to aging, muscle damage, and recovery. Data from 11 studies were extracted for review. Of these, four reported worse symptoms in older compared with younger populations, while two have observed the opposite, and the remaining studies (n = 6) proposed no differences between age groups. It appears that resistance training can be practiced in older populations without concern for impaired recovery. To improve current knowledge, researchers are urged to utilize more ecologically valid muscle-damaging bouts and investigate the mechanisms which underpin the recovery of muscle soreness and strength after exercise in older populations.

Cognitive Ability in Midlife and Labor Market Participation Among Older Workers: Prospective Cohort Study With Register Follow-up

Background

The study aimed to determine the association of individual cognitive ability in late midlife with labor market participation among older workers.

Methods

This prospective cohort study estimates the risk of long-term sickness absence, disability pension, early retirement, and unemployment from scores on the Intelligenz-Struktur-Test 2000R by combining data from 5076 workers from the Copenhagen Aging and Midlife Biobank with a register on social transfer payments. Analyses were stepwise adjusted for age, gender, physical and psychosocial work environment, health behaviors, occupational social class, education, and chronic diseases.

Results

In the fully adjusted model, low cognitive ability (≥1 standard deviation below the mean for each gender) and high cognitive ability (≥1 standard deviation above the mean for each gender) were not associated with risk of any of the four labor market outcomes.

Conclusion

Individual cognitive ability in late midlife was not associated with risk of long-term sickness absence, disability pension, early retirement, and unemployment in the fully adjusted model. Thus, no direct effect of individual cognitive ability in late midlife was observed on the risk of permanently or temporarily leaving the labor market.

Effects of age on vertical jump performance and muscle morphology characteristics in females

BACKGROUND

Declines in muscle morphology and function are commonly reported as a consequence of aging. However, few studies have investigated the influence of age on a comprehensive set of muscle function-related measures (i.e., reactive strength, power, etc.) that focuses on a dynamic performance task such as the vertical jump across the adult life span. This study aimed to examine the effects of age on muscle morphology characteristics (muscle cross-sectional area [CSA] and echo intensity [EI]) and vertical jump height, power, and reactive strength index (RSI) in females.

METHODS

Twenty-six young (22±2 years), 30 middle-aged (36±5 years), and 23 older (71±5 years) females participated in this study. Muscle CSA and EI were determined from ultrasound scans of the vastus lateralis. Countermovement jumps were used to assess jump height, RSI, movement time, and peak power (Pmax).

RESULTS

Muscle CSA, jump height, and Pmax were higher for the young compared to the old and middle-aged (P≤0.027) and for the middle-aged compared to the old (P<0.001). Movement time and EI values were lower (P≤0.004) and RSI values were higher (P<0.001) for the young and middle-aged compared to the old; however, no differences were observed between the young and middle-aged (P=0.367-0.620).

CONCLUSIONS

Of all the variables assessed in this study, RSI exhibited the greatest decline (76%) between the young and old females. Such findings highlight the importance of reactive strength when assessing age-related changes in neuromuscular performance.

Preserved Capacity for Adaptations in Strength and Muscle Regulatory Factors in Elderly in Response to Resistance Exercise Training and Deconditioning

Aging is related to an inevitable loss of muscle mass and strength. The mechanisms behind age-related loss of muscle tissue are not fully understood but may, among other things, be induced by age-related differences in myogenic regulatory factors. Resistance exercise training and deconditioning offers a model to investigate differences in myogenic regulatory factors that may be important for age-related loss of muscle mass and strength. Nine elderly (82 ± 7 years old) and nine young, healthy persons (22 ± 2 years old) participated in the study. Exercise consisted of six weeks of resistance training of the quadriceps muscle followed by eight weeks of deconditioning. Muscle biopsy samples before and after training and during the deconditioning period were analyzed for MyoD, myogenin, insulin-like growth-factor I receptor, activin receptor IIB, smad2, porin, and citrate synthase. Muscle strength improved with resistance training by 78% (95.0 ± 22.0 kg) in the elderly to a similar extent as in the young participants (83.5%; 178.2 ± 44.2 kg) and returned to baseline in both groups after eight weeks of deconditioning. No difference was seen in expression of muscle regulatory factors between elderly and young in response to exercise training and deconditioning. In conclusion, the capacity to gain muscle strength with resistance exercise training in elderly was not impaired, highlighting this as a potent tool to combat age-related loss of muscle function, possibly due to preserved regulation of myogenic factors in elderly compared with young muscle.

Perspective: Pragmatic Exercise Recommendations for Older Adults: The Case for Emphasizing Resistance Training

Optimal health benefits from exercise are achieved by meeting both aerobic and muscle strengthening guidelines, however, most older adults (OAs) do not exercise and the majority of those who do only perform one type of exercise. A pragmatic solution to this problem may be emphasizing a single exercise strategy that maximizes health benefits. The loss of muscle mass and strength at an accelerated rate are hallmarks of aging that, without intervention, eventually lead to physical disability and loss of independence. Additionally, OAs are at risk of developing several chronic diseases. As such, participating in activities that can maintain or increase muscle mass and strength, as well as decrease chronic disease risk, is essential for healthy aging. Unfortunately, there is a widely held belief that adaptations to aerobic and resistance exercise are independent of each other, requiring the participation of both types of exercise to achieve optimal health. However, we argue that this assertion is incorrect, and we discuss crossover adaptations of both aerobic and resistance exercise. Aerobic exercise can increase muscle mass and strength, though not consistently and may be limited to exercise that overloads a particular muscle group, such as stationary bicycling. In contrast, resistance exercise is effective at maintaining muscle health with increasing age, and also has significant effects on cardiovascular disease (CVD) risk factors, type 2 diabetes (T2D), cancer, and mortality. We posit that resistance exercise is the most effective standalone exercise strategy for improving overall health in OAs and should be emphasized in future guidelines.

Nicotinamide riboside-A missing piece in the puzzle of exercise therapy for older adults?

Maintaining physical mobility is important for preventing age-related comorbidities in older adults. Endurance and resistance training prevent mobility loss in aging, but exercise alone does not always achieve the expected improvements in physical and cardiopulmonary function. Recent preclinical evidence suggests that a reason for the variability in exercise training responses may be the age-related dysregulation of the nicotinamide adenine dinucleotide (NAD+) metabolome. NAD+ is an essential enzymatic cofactor in energetic and signaling pathways. Endogenous NAD+ pool is lower in several chronic and degenerative diseases (e.g., cardiovascular diseases, Alzheimer's and Parkinson's diseases, muscular dystrophies), and also in aging. Exercise requires a higher energy expenditure than a resting state, thus a state of NAD+ insufficiency with reduced energy metabolism, could result in an inadequate exercise response. Recently, the NAD+ precursor nicotinamide riboside (NR), a vitamin B3 derivate, showed an ability to improve NAD+ metabolome homeostasis, restoring energy metabolism and cellular function in various organs in animals. NR has also been tested in older humans and is considered safe, but the effects of NR supplementation alone on physical performance are unclear. The purpose of this review is to examine the preclinical and clinical evidence on the effect of NR supplementation strategies alone and in combination with physical activity on mobility and skeletal muscle and cardiovascular function.

High physical work demands and working life expectancy in Denmark

Objective

In most European countries, political reforms gradually increase the statutory retirement age to counter the economic costs of a growing elderly population. However, working to a high age may be difficult for people with hard physical labour. We aim to study the impact of high physical work demands on working life expectancy (WLE).

Methods

We combined physical work demands assessed by job exposure matrix (JEM) and longitudinal high-quality national registers (outcome) in 1.6 million Danish workers to estimate WLE and years of sickness absence, unemployment and disability pension. The JEM value for physical work demand is a summarised score of eight ergonomic exposures for 317 occupations groups, sex and age. The WLE was estimated using a multistate proportional hazards model in a 4-year follow-up period.

Results

Individuals with high physical work demands had a significantly lower WLE, than those with low physical work demands, with largest differences seen among women. At age 30 years, women with high physical work demands can expect 3.1 years less working, 11 months more of sickness absence and 16 months more of unemployment than low-exposed women. For 30-year-old men, the corresponding results were 2.0 years, 12 months and 8 months, respectively.

Conclusion

Our findings show that high physical work demands are a marked risk factor for a shortened working life and increased years of sickness absence and unemployment. The results are important when selecting high-risk occupations, and expand the knowledge base for informed political decision making concerning statutory retirement age.

Resistance Training for Older Adults: Position Statement From the National Strength and Conditioning Association

Fragala, MS, Cadore, EL, Dorgo, S, Izquierdo, M, Kraemer, WJ, Peterson, MD, and Ryan, ED. Resistance training for older adults: position statement from the national strength and conditioning association. J Strength Cond Res 33(8): 2019-2052, 2019-Aging, even in the absence of chronic disease, is associated with a variety of biological changes that can contribute to decreases in skeletal muscle mass, strength, and function. Such losses decrease physiologic resilience and increase vulnerability to catastrophic events. As such, strategies for both prevention and treatment are necessary for the health and well-being of older adults. The purpose of this Position Statement is to provide an overview of the current and relevant literature and provide evidence-based recommendations for resistance training for older adults. As presented in this Position Statement, current research has demonstrated that countering muscle disuse through resistance training is a powerful intervention to combat the loss of muscle strength and muscle mass, physiological vulnerability, and their debilitating consequences on physical functioning, mobility, independence, chronic disease management, psychological well-being, quality of life, and healthy life expectancy. This Position Statement provides evidence to support recommendations for successful resistance training in older adults related to 4 parts: (a) program design variables, (b) physiological adaptations, (c) functional benefits, and (d) considerations for frailty, sarcopenia, and other chronic conditions. The goal of this Position Statement is to a) help foster a more unified and holistic approach to resistance training for older adults, b) promote the health and functional benefits of resistance training for older adults, and c) prevent or minimize fears and other barriers to implementation of resistance training programs for older adults.

Muscle Strength Training Alters Muscle Activation of the Lower Extremity during Side-Step Cutting in Females

The objective of this study was to examine the effects of muscle strength training on knee kinematics/kinetics and muscle activation patterns during anticipated side-step cutting. Three-dimensional knee kinematics/kinetics data and muscle activation of selected lower extremity muscles were measured while performing cutting before and after completing 10-week circuit strength training mixed typical resistance training and power training (intervention) or no training (control) from 25 female subjects. The muscle strength of quadriceps and hamstrings were measured before and after training using isokinetic dynamometer. No statistically significant differences were observed in quadriceps and hamstrings muscle strength, all kinematic/kinetic variables, and muscle activation for the control group. Both quadriceps (p = 0.005) and hamstrings (p = 0.030) muscle strength were increased after training. An increased biceps femoris (p = 0.003) and H:Q ratio of activation (p = 0.016), as well as decreased gastrocnemius muscle activation (p = 0.012) during pre-activation phase in intervention group were found. No significant differences were found in knee kinematics and kinetics both at the time frame of the initial contact and the peak tibial anterior shear force after training. In conclusion, muscle strength training altered some muscle activations of lower extremity muscles, which might affect the risk of ACL injury, but it did not change the kinematic/kinetic parameters.

Strong Labour Market Inequality of Opportunities at the Workplace for Supporting a Long and Healthy Work-Life: The SeniorWorkingLife Study

Most European countries are gradually increasing the state pension age, but this may run counter to the capabilities and wishes of older workers. The objective of this study is to identify opportunities in the workplace for supporting a prolonged working life in different groups in the labour market. A representative sample of 11,200 employed workers ≥ 50 years responded to 15 questions in random order about opportunities at their workplace for supporting a prolonged working life. Respondents were stratified based on the Danish version of the International Standard Classification of Occupations (ISCO). Using frequency and logistic regression procedures combined with model-assisted weights based on national registers, results showed that the most common opportunities at the workplace were possibilities for more vacation, reduction of working hours, flexible working hours, access to treatment, further education and physical exercise. However, ISCO groups 5–9 (mainly physical work and shorter education) had in general poorer access to these opportunities than ISCO groups 1–4 (mainly seated work and longer education). Women had poorer access than men, and workers with reduced work ability had poorer access than those with full work ability. Thus, in contrast with actual needs, opportunities at the workplace were lower in occupations characterized by physical work and shorter education, among women and among workers with reduced work ability. This inequality poses a threat to prolonging working life in vulnerable groups in the labour market.

STRONG-D: Strength training regimen for normal weight diabetics: Rationale and design

BACKGROUND

Currently, there is a lack of data on effective lifestyle recommendations for normal-weight diabetics (NWD), who can represent up to 1 in 5 individuals with Type II Diabetes Mellitus (T2DM). NWD is especially prevalent in Asian populations and the elderly. Specific exercise treatment recommendations are needed for patients with normal-weight diabetes (NWD), as those in this category face higher mortality rates than overweight and obese diabetics. Standard T2DM treatment recommends aerobic training; however, performing aerobic training alone may not be appropriate for NWD and strength training may be a more effective treatment recommendation.

OBJECTIVE

While it is known that strength and aerobic training are beneficial in obese diabetics, there is currently insufficient evidence to recommend this regimen in NWD. The Strength Training Regimen for Normal Weight Diabetics (STRONG-D) study aims to determine the best exercise regimen for NWD and address the current lack of appropriate physical activity recommendations for this population. The primary goal of this study is to determine whether strength training aids glycemic control better than aerobic training in NWD.

STUDY DESIGN

STRONG-D is a three-arm randomized controlled trial designed to compare the clinical effectiveness of structured strength training only, aerobic training only, and combination (strength + aerobic) training sessions, modeled after the intervention in the Health Benefits of Aerobic and Resistance Training in T2DM patients (HART-D) study. Potential participants meeting eligibility criteria of HbA1c values of 6.5% to 13.0% and BMI of 18.5 kg/m2 to 25 kg/m2 will be enrolled. After randomization, participants will begin a 9-month exercise intervention. The primary outcomes will be HbA1c levels. The secondary endpoints will include physical fitness, body composition measured by Dual X-Ray Absorptiometry (DXA) scans, and leg strength and endurance measured by Biodex testing. Initial follow-up visits will occur at 3 months, 6 months, and 9 months. To determine the long-term effects of the exercise intervention, passive follow-up will continue via electronic health records (EHR) until a 24-month follow-up visit. A total of 282 participants will be randomized into the three study arms determine the clinically significant differences between strength-only, aerobic-only and combination regimens.

Influence of physical and psychosocial working conditions for the risk of disability pension among healthy female eldercare workers: Prospective cohort

Aim: To investigate the influence of physical and psychosocial working conditions on the risk of disability pension among eldercare workers. Methods: After responding to a questionnaire in 2005, 4699 healthy female eldercare workers – free from chronic musculoskeletal pain, depressive symptoms and long-term sickness absence – were followed for 11 years in the Danish Register for Evaluation of Marginalization. Time-to-event analyses estimated the hazard ratio (HR) for disability pension from physical exertion during work, emotional demands, influence at work, role conflicts, and quality of leadership. Analyses were mutually adjusted for these work environmental factors as well as for age, education, smoking, leisure physical activity and body mass index. Results: During follow-up, 7.6% received disability pension. Physical exertion and emotional demands were associated with risk of disability pension, and both interacted with age. In age-stratified analyses, older eldercare workers (mean age 53 years at baseline) with moderate and high physical exertion (reference: low) were at increased risk with HRs of 1.51, 95% CI [1.06–2.15] and 2.54, 95% CI [1.34–4.83], respectively. Younger eldercare workers (mean age 36 years at baseline) with moderate emotional demands (reference: low) were at decreased risk with an HR of 0.57, 95% CI [0.37–0.85]. Conclusions: While a higher level of physical exertion is a risk factor for disability pension among older female eldercare workers, a moderate level of emotional demands is associated with lower risk among the younger workers. The age of the worker may be an important factor when providing recommendations for promoting a long and healthy working life.

Variability in Individual Response to Aerobic Exercise Interventions Among Older Adults

Although a plethora of evidence supports the benefits of exercise among older adults, a majority of studies have emphasized group differences, while giving little, if any, attention to individual differences. Given the lack of data on variability in response, the present review examined how nonresponse to aerobic exercise has been defined in older adult populations and characteristics associated with nonresponse among older adults. The results of this review suggest that interindividual variability in response of maximal oxygen consumption to aerobic exercise interventions is prevalent among older adults (1.4-63.4%); age, sex, race, and body mass index may not be critical determinants of nonresponse; whereas health status, baseline fitness, and exercise dose appear important. Future intervention studies should evaluate and report the variability in individual response of older adults to exercise; investigators should develop programs that allow for modification of components to assist older adults in achieving optimal benefit from exercise programs.

Internal Loads, but Not External Loads and Fatigue, Are Similar in Young and Middle-Aged Resistance-Trained Males during High Volume Squatting Exercise †

Little is known about the internal and external loads experienced during resistance exercise, or the subsequent fatigue-related response, across different age groups. This study compared the internal (heart rate, OMNI ratings of perceived exertion (RPE), session RPE) and external loads (peak velocity and power and volume load) during high volume squatting exercise (10 × 10 at 60% one-repetition maximum (1RM)) and the fatigue-related response (maximal voluntary contraction (MVC), voluntary activation (VA), resting doublet force, peak power, and blood lactate) in young (n = 9; age 22.3 ± 1.7 years) and middle-aged (n = 9; age 39.9 ± 6.2 years) resistance-trained males. All internal load variables and peak velocity illustrated unclear differences between groups during exercise. Peak power and volume load were likely higher in the young group compared to their middle-aged counterparts. The unclear differences in MVC, VA and blood lactate between groups after exercise were accompanied by very likely greater decrements in resting doublet force and peak power at 20 and 80% 1RM in the middle-aged group compared to the young group. These data indicate that internal load is not different between young and middle-aged resistance-trained males, though certain external load measures and the fatigue response are.

Muscle morphology and performance in master athletes: A systematic review and meta-analyses

INTRODUCTION

The extent to which chronic exercise training preserves age-related decrements in physical function, muscle strength, mass and morphology is unclear. Our aim was to conduct a systematic review of the literature to determine to what extent chronically trained master athletes (strength/power and endurance) preserve levels of physical function, muscle strength, muscle mass and morphology in older age, compared with older and younger controls and young trained individuals.

METHODS

The systematic data search included Medline, EMBASE, SPORTDiscus, CINAHL and Web of Science databases.

INCLUSION CRITERIA

i) master athletes mean exercise training duration ≥20 years ii) master athletes mean age of cohort >59 years) iii) at least one measurement of muscle mass/volume/fibre-type morphology and/or strength/physical function.

RESULTS

Fifty-five eligible studies were identified. Meta-analyses were carried out on maximal aerobic capacity, maximal voluntary contraction and body composition. Master endurance athletes (42.0 ± 6.6 ml kg^-1 min^-1) exhibited VO_2max values comparable with young healthy controls (43.1 ± 6.8 ml kg^-1 min^-1, P = .84), greater than older controls (27.1 ± 4.3 ml kg^-1 min^-1, P < 0.01) and master strength/power athletes (26.5 ± 2.3 mlkg^-1 min^-1, P < 0.01), and lower than young endurance trained individuals (60.0 ± 5.4 ml kg^-1 min^-1, P < 0.01). Master strength/power athletes (0.60 (0.28-0.93) P < 0.01) and young controls (0.71 (0.06-1.36) P < 0.05) were significantly stronger compared with the other groups. Body fat% was greater in master endurance athletes than young endurance trained (-4.44% (-8.44 to -0.43) P < 0.05) but lower compared with older controls (7.11% (5.70-8.52) P < 0.01).

CONCLUSION

Despite advancing age, this review suggests that chronic exercise training preserves physical function, muscular strength and body fat levels similar to that of young, healthy individuals in an exercise mode-specific manner.

A review of the reliability of biomechanical variables produced during the isometric mid-thigh pull and isometric squat and the reporting of normative data

The use of isometric strength testing, particularly the isometric mid-thigh pull (IMTP) has increased dramatically over the last decade. The IMTP and isometric squat (ISqT) provide one aspect of performance monitoring with variables such as peak force and rate of force development being derived from the force-time curve. The reliability of some of these variables is conflicting in the literature, and the reporting of the reliability is not standardised across the research. The majority of research only reports intraclass correlation coefficients with very few studies reporting coefficient of variation and 90% confidence intervals. Additionally, methods used to calculate variables from the force-time curve differ across studies. An aim of muscle strength testing is to provide normative values for specific sports, allowing coaches to distinguish between performance levels or evaluate the effects of training on performance. This narrative review aims to evaluate studies that have researched the reliability and/or reported normative data for both tests. Additionally, the testing protocols and the force-time curve analysis techniques utilised are discussed, concluding with practical applications for coaches on the uses and limitations of these tests. Results demonstrate that peak force is the most reliable measure and can be used to determine maximum strength capabilities.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Exercise Improves V˙O2max and Body Composition in Androgen Deprivation Therapy-treated Prostate Cancer Patients

INTRODUCTION

Prostate cancer is the most common cancer in men, and patients treated with androgen deprivation therapy (ADT) experience unfavorable changes in body composition and associated metabolic complications, which can increase the risk of cardiovascular disease. We examined the effect of a 6-month program of aerobic and resistance exercise aimed at improving body composition and cardiorespiratory health in this population.

METHODS

Ninety-seven men (43-90 yr) with localized prostate cancer receiving ADT were randomized to either exercise (EX, n = 50) or usual care (CON, n = 47). Supervised exercise was undertaken twice weekly at moderate to high intensity. Measures of cardiorespiratory capacity (V˙O2max), resting metabolic rate, central blood pressure, hemodynamic variables, blood markers, and body composition were assessed.

RESULTS

There was a significant group-time interaction present for V˙O2max (P = 0.033) with a treatment effect for EX of 0.11 L·min (95% confidence interval [CI] = 0.04-0.19) (relative to body mass = 1.3 mL·kg·min, 95% CI = 0.3-2.3) and fat oxidation (P = 0.037) of 12.0 mg·min (95% CI = 2.3-21.7). Similarly, there was a significant improvement in glucose (P < 0.001) for EX of -0.5 mmol·L (95% CI = -0.8 to -0.3), with no change in prostate-specific antigen or testosterone as a result of exercise. Body composition was enhanced for EX with adjusted mean differences in lean mass (P = 0.015) of 0.8 kg (95% CI = 0.3-1.3), total fat mass (P = 0.020) of -1.1 kg (95% CI = -1.8 to -0.5), and trunk fat mass (P < 0.001) of -1.0 kg (95% CI = -1.4 to -0.6).

CONCLUSION

A 6-month combined aerobic and resistance exercise program has a significant favorable effect on cardiorespiratory capacity, resting fat oxidation, glucose, and body composition despite the adverse effects of hormone suppression. Combined aerobic and resistance training should be considered a key adjuvant component in men undergoing ADT for the treatment of prostate cancer.

Dehydroepiandrosterone supplementation combined with Weight-Loading Whole-Body Vibration Training (WWBV) affects exercise performance and muscle glycogen storage in middle-aged C57BL/6 mice

Background: Adequate nutritional intake and an optimal training program are important elements of any strategy to preserve or increase muscle mass and strength during aging. Purpose: In the current study, we investigate the effects of Dehydroepiandrosterone (DHEA), one of the most abundant circulating steroids in humans and a precursor hormone, supplementation combined with a weight-loading whole-body vibration (WWBV) on exercise performance, physical fatigue-related biochemical responses and testosterone content in middle-aged 9 months old C57BL/6 mice. Methods: Male middle-aged C57BL/6 mice were divided into 3 groups (n = 8 per group) and treated for 4 weeks with the following: 1) Sedentary control (SC) with vehicle 2) DHEA supplementation (DHEA, 10.2 mg/kg) and 3) DHEA supplementation with WWBV training (DHEA: 10.2 mg/kg; WBV: 5.6 Hz, 2 mm, 0.13 g). Exercise performance was evaluated by forelimb grip strength and time to exhaustion, as well as changes in body composition and anti-fatigue levels after a 15-min swimming exercise. Fatigue-related biochemical responses of serum lactate, ammonia, glucose, creatine kinase (CK), and blood urea nitrogen (BUN) were measured following the swimming exercise. In addition, the biochemical parameters and the testosterone levels were measured at the end of the experiment. Results: DHEA supplementation combined with WWBV training for 4 weeks significantly decreased the amount of white adipose tissue and increased the food and water intake. Additionally, WWBV+DHEA supplementation improved exercise performance, testosterone levels and glycogen contents of both liver and muscle. WWBV+DHEA supplementation also decreased serum lactate, ammonia and BUN levels, while increasing glucose levels following the 15-min swim test. Conclusion: Taken together, our results suggest that combining the WWBV training program with DHEA supplementation could provide an anti-fatigue pharmacological effect for elderly populations.

Both Baseline and Change in Lower Limb Muscle Strength in Younger Women Are Independent Predictors of Balance in Middle Age: A 12-Year Population-Based Prospective Study

Poor balance is a risk factor for falls and fracture in older adults, but little is known about modifiable factors affecting balance in younger women. This study aimed to examine whether lower limb muscle strength (LMS) in young women and changes in LMS are independent predictors of balance in middle age. This was an observational 10-year follow-up of 470 women aged 25 to 44 years at baseline who had previously participated in a 2-year population-based randomized controlled trial of osteoporosis education interventions. Linear regression was used to examine the association between baseline LMS (by dynamometer) and change in LMS over 12 years with balance at 12 years (timed up and go test [TUG], step test [ST], functional reach test [FRT], and lateral reach test [LRT]). LMS declined by a mean of 17.3 kg over 12 years. After adjustment for potential confounders, baseline and change in LMS were independently beneficially associated with TUG (β = -0.008 sec/kg, 95% confidence interval [CI] -0.01 to -0.006, and β = -0.006 sec/kg, 95% CI -0.009 to -0.003 for baseline and change, respectively), FRT (β = 0.057 cm/kg, 95% CI 0.030 to 0.084, and β = 0.071 cm/kg, 95% CI 0.042 to 0.101, respectively), and LRT (β = 0.030 cm/kg, 95% CI 0.012 to 0.049, and β = 0.022 cm/kg, 95% CI 0.002 to 0.043, respectively) 12 years later. There was an association between baseline LMS and ST (β = 0.044 steps/kg, 95% CI 0.022 to 0.067) but not between change in LMS and ST. Among young women, greater LMS at baseline and slower decline over time are both associated with better balance in midlife. Analogous to the contributions of peak bone mass and bone loss to fracture risk in older adults, this suggests that both improvement of muscle strength in younger age and prevention of age-related loss of muscle strength could be potentially useful strategies to improve balance and reduce falls in later life. © 2017 American Society for Bone and Mineral Research.

Predictors of Change in Physical Function in Older Adults in Response to Long-Term, Structured Physical Activity: The LIFE Study

OBJECTIVES

To evaluate the extent of variability in functional responses in participants in the Lifestyle Interventions and Independence for Elders (LIFE) study and to identify the relative contributions of intervention adherence, physical activity, and demographic and health characteristics to this variability.

DESIGN

Secondary analysis.

SETTING

Multicenter institutions.

PARTICIPANTS

A volunteer sample (N=1635) of sedentary men and women aged 70 to 89 years who were able to walk 400m but had physical limitations, defined as a Short Physical Performance Battery (SPPB) score of ≤9.

INTERVENTIONS

Moderate-intensity physical activity (n=818) consisting of aerobic, resistance, and flexibility exercises performed both center-based (2times/wk) and home-based (3-4times/wk) sessions or health education program (n=817) consisting of weekly to monthly workshops covering relevant health information.

MAIN OUTCOME MEASURES

Physical function (gait speed over 400m) and lower extremity function (SPPB score) assessed at baseline and 6, 12, and 24 months.

RESULTS

Greater baseline physical function (gait speed, SPPB score) was negatively associated with change in gait speed (regression coefficient β=-.185; P<.001) and change in SPPB score (β=-.365; P<.001), whereas higher number of steps per day measured by accelerometry was positively associated with change in gait speed (β=.035; P<.001) and change in SPPB score (β=.525; P<.001). Other baseline factors associated with positive change in gait speed and/or SPPB score include younger age (P<.001), lower body mass index (P<.001), and higher self-reported physical activity (P=.002).

CONCLUSIONS

Several demographic and physical activity-related factors were associated with the extent of change in functional outcomes in participants in the LIFE study. These factors should be considered when designing interventions for improving physical function in older adults with limited mobility.

Loads and Movement Speeds Dictate Differences in Power Output During Circuit Training

Power training has become a common exercise intervention for improving muscle strength, power, and physical function while reducing injury risk. Few studies, however, have evaluated acute load changes on power output during traditional resistance training protocols. Therefore, the aim of this study was to quantify the effects of different loading patterns on power output during a single session of circuit resistance training (CRT). Nine male (age = 19.4 ± 0.9 years) and 11 female participants (age = 20.6 ± 1.6 years) completed 3 CRT protocols during separate testing sessions using 7 pneumatic exercises. Protocols included heavy load explosive contraction (HLEC: 80% one repetition maximum [1RM], maximum speed concentric-2 seconds eccentric), heavy load controlled contraction (HLCC: 80% 1RM, 2 seconds concentric-2 seconds eccentric), and moderate load explosive contraction (MLEC: 50% 1RM, maximum speed concentric-2 seconds eccentric). Protocols were assigned randomly using a counterbalanced design. Power for each repetition and set were determined using computerized software interfaced with each machine. Blood lactate was measured at rest and immediately postexercise. For male and female participants, average power was significantly greater during all exercises for HLEC and MLEC than HLCC. Average power was greatest during the HLEC for leg press (LP), hip adduction (ADD), and hip abduction (ABD) (p ≤ 0.05), whereas male participants alone produced their greatest power during HLEC for leg curl (LC) (p < 0.001). For male and female participants, significantly greater power was detected by set for LP, lat pull-down (LAT), ADD, LC, and ABD for the MLEC protocol (p < 0.02) and for LP, LAT, CP, and LC for the HLEC protocol (p < 0.03). A condition × sex interaction was seen for blood lactate changes ((Equation is included in full-text article.)= 0.249; p = 0.024), with female participants producing a significantly greater change for MLEC than HLEC (Mdiff = 1.61 ± 0.35 mmol·L; p = 0.011), whereas male participants showed no significant differences among conditions. Performing a CRT protocol using explosive training patterns, especially at high loads for lower-body exercises and moderate loads for upper-body exercises, produces significantly higher power than controlled speed training in most exercises. These results provide exercisers, personal trainers, and strength coaches with information that can assist in the design of training protocols to maximize power output during CRT.

Focusing on Increasing Velocity during Heavy Resistance Knee Flexion Exercise Boosts Hamstring Muscle Activity in Chronic Stroke Patients

Background. Muscle strength is markedly reduced in stroke patients, which has negative implications for functional capacity and work ability. Different types of feedback during strength training exercises may alter neuromuscular activity and functional gains. Objective. To compare levels of muscle activity during conditions of blindfolding and intended high contraction speed with a normal condition of high-intensity knee flexions. Methods. Eighteen patients performed unilateral machine knee flexions with a 10-repetition maximum load. Surface electromyography (EMG) was recorded from the quadrics and hamstring muscles and normalized to maximal EMG (nEMG) of the nonparetic limb. Results. For the paretic leg, the speed condition showed higher values of muscle activity compared with the normal and blindfolded conditions for both biceps femoris and semitendinosus. Likewise, the speed condition showed higher co-contraction values compared with the normal and blindfolded conditions for the vastus lateralis. No differences were observed between exercise conditions for the nonparetic leg. Conclusion. Chronic stroke patients are capable of performing heavy resistance training with intended high speed of contraction. Focusing on speed during the concentric phase elicited higher levels of muscle activity of the hamstrings compared to normal and blindfolded conditions, which may have implications for regaining fast muscle strength in stroke survivors.

Influence of physical and psychosocial work environment throughout life and physical and cognitive capacity in midlife on labor market attachment among older workers: study protocol for a prospective cohort study

Background

As average life span increases, elderly will account for an increasing proportion of the total population in most parts of the world. Thus, initiatives to retain older workers at the labor market are becoming increasingly important. This study will investigate the influence of physical and psychosocial work environment throughout working life and physical and cognitive capacity in midlife on labor market attachment among older workers.

Methods/Design

Approximately 5000 participants (aged 50–60 years) from the Copenhagen Aging and Midlife Biobank (CAMB) will be followed prospectively in a national register (DREAM), containing information on a week-to-week basis about social transfer payments for about 5 million Danish residents. Using Cox regression, we will model the risk of long-term sickness absence, disability pension, early retirement and unemployment within a 4 to 6 year period from the baseline measurement as a function of the following predictors: 1) physical work demands throughout working life, 2) psychosocial working conditions throughout working life, 3) physical capacity in midlife, 4) cognitive capacity in midlife. Estimates will be adjusted for age, sex, lifestyle, socioeconomic position, chronic disease and long-term sickness absence prior to baseline.

Discussion

The project will generate new knowledge on risk factors for loss of labor market attachment. The results will potentially contribute in identifying factors that could be targeted in future interventions for maintaining a longer and healthier working life among older workers.

The Current Understanding of Sarcopenia: Emerging Tools and Interventional Possibilities

The purpose of this review is to provide health practitioners and physicians the most current state of the research on sarcopenia, its consequences, and to offer a summary of consensus guidelines for identification based on the most recent and compelling investigations and analyses. To accomplish this, the causes and consequences of sarcopenia will be described, and definitions and screening methods are updated. Importantly, interventional recommendations for sarcopenia will be discussed with a special emphasis on the effects of resistance training on sarcopenia-related outcomes. Furthermore, due to the increasing usage of hormone treatment as a strategy to combat sarcopenia, special consideration on the effects of hormone changes with aging and as interventions will be briefly reviewed.

Feasible modalities and long-term effects of elastic band exercises in nursing home older adults in wheelchairs: A cluster randomized controlled trial

BACKGROUND

Physical activity holds promise for mobility-impaired older adults to prevent further disabilities and improve their health. However, staffing constraints have made it challenging to promote physical activity in long-term care facilities.

OBJECTIVES

To test the feasibility and effects of 12 months Wheelchair-bound Senior Elastic Band (WSEB) group-exercises that were led by volunteers for the first six months followed by the DVD-guided for another six months on functional fitness, activities of daily living (ADL), and sleep quality of nursing home older adults in wheelchairs.

DESIGN

Cluster randomized controlled trial with two groups, pre-test and post-tests.

SETTINGS

Ten nursing homes, Taiwan.

PARTICIPANTS

127 participants participated voluntarily; 107 of them completed the study.

INCLUSION CRITERIA

(1) aged 65 years and over, (2) using wheelchairs for mobility, (3) living in facility for at least three months, (4) cognitively intact, and (5) heavy or moderate dependency in ADL. Majority of participants were middle-old older adults (75-84 years old, 53.2%), female (51.4%), and had chronic illnesses (98.1%).

METHODS

Participants were randomly assigned by facility to either the experimental (five nursing homes, n=56) or control group (five nursing homes, n=51). The WSEB program was conducted three times per week and 40 min per session in two stages: volunteer-led for the first six months (stage I) followed by the DVD-guided modality for another six months (stage II). The primary outcomes (functional fitness: lung capacity, body flexibility, range of joint motion, and muscle strength and endurance) and the secondary outcomes (ADL measured by the Barthel Index; sleep quality measured by the Pittsburgh Sleep Quality Index) of the participants were measured at three time points: pre-test, at the six-month interval, and at the end of 12 months of the study. No blinding was applied.

RESULTS

All of the functional fitness indicators of the experimental group participants improved significantly (p<.05), and were all better than the control group at six-month and 12-month of the study (p<.05). No symptoms of discomfort occurred during interventions.

CONCLUSIONS

Nursing home older adults in wheelchairs who received WSEB exercise training had better functional fitness, ADL, and sleep quality than those who did not. It was a feasible way of carrying out this exercise program by using the volunteer-led followed by the DVD-guided modalities. The program can be applied in institutional settings routinely.

The use of the isometric squat as a measure of strength and explosiveness

The isometric squat has been used to detect changes in kinetic variables as a result of training; however, controversy exists in its application to dynamic multijoint tasks. Thus, the purpose of this study was to further examine the relationship between isometric squat kinetic variables and isoinertial strength measures. Subjects (17 men, 1-repetition maximum [1RM]: 148.2 ± 23.4 kg) performed squats 2 d · wk(-1) for 12 weeks and were tested on 1RM squat, 1RM partial squat, and isometric squat at 90° and 120° of knee flexion. Test-retest reliability was very good for all isometric measures (intraclass correlation coefficients > 0.90); however, rate of force development 250 milliseconds at 90° and 120° seemed to have a higher systematic error (relative technical error of measurement = 8.12%, 9.44%). Pearson product-moment correlations indicated strong relationships between isometric peak force at 90° (IPF 90°) and 1RM squat (r = 0.86), and IPF 120° and 1RM partial squat (r = 0.79). Impulse 250 milliseconds (IMP) at 90° and 120° exhibited moderate to strong correlations with 1RM squat (r = 0.70, 0.58) and partial squat (r = 0.73, 0.62), respectively. Rate of force development at 90° and 120° exhibited weak to moderate correlations with 1RM squat (r = 0.55, 0.43) and partial squat (r = 0.32, 0.42), respectively. These findings demonstrate a degree of joint angle specificity to dynamic tasks for rapid and peak isometric force production. In conclusion, an isometric squat performed at 90° and 120° is a reliable testing measure that can provide a strong indication of changes in strength and explosiveness during training.

Determining the Optimum Power Load in Jump Squat Using the Mean Propulsive Velocity

The jump squat is one of the exercises most frequently used to improve lower body power production, which influences sports performance. However, the traditional determination of the specific workload at which power production is maximized (i.e., optimum power load) is time-consuming and requires one-repetition maximum tests. Therefore, the aim of this study was to verify whether elite athletes from different sports would produce maximum mean propulsive power values at a narrow range of mean propulsive velocities, resulting in similar jump heights. One hundred and nine elite athletes from several individual/team sport disciplines underwent repetitions at maximal velocity with progressive loads, starting at 40% of their body mass with increments of 10% to determine the individual optimum power zone. Results indicated that regardless of sport discipline, the athletes’ optimum mean propulsive power was achieved at a mean propulsive velocity close to 1.0 m.s⁻¹ (1.01 ± 0.07 m.s⁻¹) and at a jump height close to 20 cm (20.47 ± 1.42 cm). Data were narrowly scattered around these values. Therefore, jump squat optimum power load can be determined simply by means of mean propulsive velocity or jump height determination in training/testing settings, allowing it to be implemented quickly in strength/power training.

Medium-intensity, high-volume "hypertrophic" resistance training did not induce improvements in rapid force production in healthy older men

The aim of the study was to determine whether it is possible to improve both maximum and rapid force production using resistance training that is typically used to induce muscle hypertrophy in previously untrained older men. Subjects (60-72 years) performed 20 weeks of "hypertrophic" resistance training twice weekly (n = 27) or control (n = 11). Maximum dynamic and isometric leg press, as well as isometric force over 0-100 ms, and maximum concentric power tests were performed pre- and post-intervention. Muscle activity was assessed during these tests by surface electromyogram of the vastus lateralis and medialis muscles. Muscle hypertrophy was assessed by panoramic ultrasound of the vastus lateralis. The intervention group increased their maximum isometric (from 2268 ± 544 to 2538 ± 701 N) and dynamic force production (from 137 ± 24 to 165 ± 29 kg), and these changes were significantly different to control (isometric 12 ± 16 vs. 1 ± 9 %; dynamic 21 ± 12 vs. 2 ± 4 %). No within- or between-group differences were observed in rapid isometric force or concentric power. Relative increases in vastus lateralis cross-sectional area trended to be statistically greater in the intervention group (10 ± 8 vs. 3 ± 6 %, P = 0.061). It is recommendable that resistance training programs for older individuals integrate protocols emphasizing maximum force/muscle hypertrophy and rapid force production in order to induce comprehensive health-related and functionally important improvements in this population.