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Exercise training increases skeletal muscle strength independent of hypertrophy in older adults aged 75 years and older
Abstract
Aim
We investigated whether exercise‐mediated acquisition of muscle mass and strength would occur in a concurrent manner in older adults.
Methods
A total of 152 community‐dwelling older adults (young‐old aged 65–74 years, old‐old aged >75 years) were allocated into either 8‐week comprehensive exercise training or the control group. Participants (n = 136) completed all pre‐ and post‐intervention testing visits (young‐old n = 73, old‐old n = 63). Older adults in exercise groups were subjected to a series of programmed elastic band and free exercises twice per week at three to five sets of 15–20 repetitions. Body composition, skeletal muscle mass, knee strength (extensors and flexors) and gait‐related physical function were evaluated as main variables.
Results
As expected, muscular mass and knee strength (both extensors and flexors) were inversely correlated with age in the old‐old group (all P < 0.001). However, knee extensor strength was the only lower limb component inversely correlated with age in the young‐old group (P < 0.043). Knee extensor strength was significantly increased by exercise training in both the young‐old and old‐old groups (young old P < 0.042, old‐old P < 0.011). Training‐induced muscle hypertrophy was observed only in the young‐old group (P < 0.025). the correlation of knee extensor strength against gait‐related physical function was the greatest, followed by knee flexor strength and muscle mass.
Conclusions
The present results showed that age‐associated strength decline of the knee extensor occurs earlier compared with the knee flexor during the aging process, and exercise training increases muscular strength without significant changes of muscle mass in older adults aged aged ≥75 years. Geriatr Gerontol Int 2019; ••: ••–••.
... Twelve RCTs [41][42][43][44]48,[52][53][54][55][56][57][58] examined the effect of exercise on muscle mass, as described in Table 1. Of these studies, one trial performed aerobic exercise as an intervention [44], one performed circuit exercise training [53], and all the rest performed resistance exercise training. ...
... Of these studies, one trial performed aerobic exercise as an intervention [44], one performed circuit exercise training [53], and all the rest performed resistance exercise training. The types of resistance exercises differed between studies; one of them used only bodyweight exercises [58], others used elastic bands [52,55] or weights [41,43,56], and others used a combination of the above [42,48,57,58]; only one trial used aerobic training alone [44]. Participants in five of the included studies [43,48,53,54,56] had sarcopenia, whereas only one included post-menopausal women [42], and all the rest trials had healthy older adults. ...
... Of these studies, one trial performed aerobic exercise as an intervention [44], one performed circuit exercise training [53], and all the rest performed resistance exercise training. The types of resistance exercises differed between studies; one of them used only bodyweight exercises [58], others used elastic bands [52,55] or weights [41,43,56], and others used a combination of the above [42,48,57,58]; only one trial used aerobic training alone [44]. Participants in five of the included studies [43,48,53,54,56] had sarcopenia, whereas only one included post-menopausal women [42], and all the rest trials had healthy older adults. ...
This study aimed to review the current evidence on the independent and combined effects of diet and exercise and their impact on skeletal muscle mass in the elderly population. Skeletal muscle makes up approximately 40% of total body weight and is essential for performing daily activities. The combination of exercise and diet is known to be a potent anabolic stimulus through stimulation of muscle protein synthesis from amino acids. Aging is strongly associated with a generalized deterioration of physiological function, including a progressive reduction in skeletal muscle mass and strength, which in turn leads to a gradual functional impairment and an increased rate of disability resulting in falls, frailty, or even death. The term sarcopenia, which is an age-related syndrome, is primarily used to describe the gradual and generalized loss of skeletal muscle mass (mainly in type II muscle fibers) and function. Multimodal training is emerging as a popular training method that combines a wide range of physical dimensions. On the other hand, nutrition and especially protein intake provide amino acids, which are essential for muscle protein synthesis. According to ESPEN, protein intake in older people should be at least 1 g/kgbw/day. Essential amino acids, such as leucine, arginine, cysteine, and glutamine, are of particular importance for the regulation of muscle protein synthesis. For instance, a leucine intake of 3 g administered alongside each main meal has been suggested to prevent muscle loss in the elderly. In addition, studies have shown that vitamin D and other micronutrients can have a protective role and may modulate muscle growth; nevertheless, further research is needed to validate these claims. Resistance-based exercise combined with a higher intake of dietary protein, amino acids, and/or vitamin D are currently recognized as the most effective interventions to promote skeletal muscle growth. However, the results are quite controversial and contradictory, which could be explained by the high heterogeneity among studies. It is therefore necessary to further assess the impact of each individual exercise and nutritional approach, particularly protein and amino acids, on human muscle turnover so that more efficient strategies can be implemented for the augmentation of muscle mass in the elderly.
... [21,22] Maintaining skeletal muscle function and improving nutritional status can reduce the progression of frailty due to the stress of surgery, thereby reducing postoperative complications and risk of mortality while preventing a decline in activities of daily living (ADL). Exercise therapy can increase muscle strength and mass in older adults, [23,24] as well as improve insulin resistance, [25] which aids in reducing postoperative complications and improves prognosis. Amino acids, particularly leucine, activate the mammalian target of rapamycin signaling pathway [26,27] and promote the synthesis of muscle protein, thereby contributing to the maintenance and increase in muscle mass and strength, as well as improving insulin resistance. ...
... Muscle strength and mass can increase after 8-12 weeks of exercise, even in older adults. [23,24] Maintaining physical function is crucial in older adults as it affects levels of social activity and QOL, resulting in a decline in physical function observed after short-term intervention in this study. ...
Background Preoperative frailty is a risk factor for postoperative complications and poor prognosis in older patients. We aimed to investigate the impact of preoperative exercise and nutritional interventions on the frequency of postoperative complications, physical function, and activities of daily living (ADL) one year postoperatively in frail older patients with gastrointestinal cancer. Methods This single-center, randomized controlled trial included 62 patients aged ≥ 70 years who were scheduled for elective surgery for gastrointestinal cancer with decreased grip strength or walking speed between October 2017 and December 2022. The participants were randomly assigned to the control (n = 33) and intervention (n = 29) groups. Participants in the intervention group performed resistance exercises and consumed amino acid-containing jelly daily at home for 14 days. All participants were followed up for one year. Variables were compared using the two-sided Student's t-test or Fisher's exact test. Statistical significance was set at p < 0.05. Results After exclusion, 45 patients were included in the analysis, with 27 and 18 in the control and intervention groups, respectively. The average age was 80.4 years, and 37.8% of the participants were male. Postoperative complications were observed in 48.1% and 44.4% of the control and intervention groups, respectively (95% confidence interval (CI) 0.57–2.07). Postoperative delirium was observed in 25.9% and 33.3% of the control and intervention groups, respectively (95% CI 0.31–1.94). No significant differences were observed between the two groups in grip strength, walking speed, and skeletal muscle index during follow-up. However, knee extension strength was better maintained in the intervention group at discharge (preoperatively: 100.2 ± 18.3% vs 119.1 ± 68.8%, p = 0.19; discharge: 86.7 ± 22.0% vs 119.3 ± 72.0%, p = 0.044). The proportion of patients with decreased ADL or death was lower in the intervention group than in the control group one year postoperatively (42.3% vs 23.5%; RR 0.56, 95% CI 0.08–1.92). Conclusions A 14-day preoperative exercise and nutritional intervention program did not significantly reduce the frequency of postoperative complications in frail older patients with gastrointestinal cancer. However, it aided in maintaining knee extension strength at discharge. Trial Registration: UMIN (University Hospital Medical Information Network) Clinical Trials Registry (ID: UMIN000024526), registered on 1 December 2016.
... Na etapa de revisão de título, resumo e do texto completo, estudos foram excluídos por não serem relacionadas a idosos (6 estudos) e estudos quais não eram exclusivos de intervenção com exercicio (19 estudos), que não se referiam a medida de hipertrofi a (2 estudos) e que não se tratavam de intervenção com treinamento de força (6 estudos). Isso resultou em 14 estudos de leitura completa, revisados e avaliados para seleção, os quais atenderam aos critérios de elegibilidade e foram incluídos em nossa revisão sistemática [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] . Esses são apresentados no Fluxograma. ...
... Todavia, foi observado que os estudos que não obtiveram aumento signifi cativo, são referentes a estudos com comparações entre variações de treinamento de força (grupo controle ativo), o que justifi ca não haver diferenças. Em relação aos estudos com diferenças entre os grupos, todos são estudos de comparações entre grupo intervenção com treino de força e grupos controle sem realização de exercício (apenas acompanhamento) [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] . Destacamos que além de não apresentar hipertrofi a, em alguns casos após o período de acompanhamento verifi cou-se atrofi a muscular. ...
OBJECTIVE: To systematically summarize the literature considering studies that address strength training and its effects on muscle hypertrophy in healthy older people. METHODS: The search was developed on the PubMed platform considering the PICOS strategy. The search date of the selected studies included the last 5 years (01.01.2017 to 07.21.2021). Studies in any language were considered. As eligibility criteria, the studies were required to contain: healthy older people; interventions with strength exercises; outcomes with hypertrophy measures (MRI, ultrasound, etc). RESULTS: In total, 14 studies were included, totaling 470 older individuals (296 participants in the experimental group and 174 participants in the control group), aged between 60 and 80 years. The strength training interventions took place over between 4 and 30 weeks, with sessions from 1 to 7 times a week. Tests of balance, measurement of muscle temperature, capacity and functional performance, and strength tests were also carried out, with the most common being the 1 repetition maximum test (1RM). For the hypertrophy measurements, dual energy X-ray (DXA), ultrasound, bioelectrical impedance, and computed tomography were used. The analyzed studies showed a significant increase in muscle volume in the intervention groups when compared to control groups (follow-up or comparison). However, studies with comparison groups (another strength training strategy or protocol) also showed increases in muscle volume, with no differences between groups. CONCLUSION: Strength training is effective in promoting improvements in muscle volume in older adults.
... cm over a 15-year period, with a more pronounced decrease observed in older-old adults compared to their younger counterparts [31]. Additionally, research has identified lower calf circumference cut-off values signifying low muscle mass in older adults with limited mobility, such as stroke patients (32 cm for women and 33 cm for men) [32], or those who have been hospitalized (28 cm for women and 30 cm for men) [33], in contrast to community-dwelling older adults. In our study, the cut-off value for calf circumference indicating low muscle mass in older-old adults (age ≥ 75 years) appeared similar to the overall results. ...
Background
Calf circumference is recommended as a marker for low muscle mass and as a case finding in the diagnosis of sarcopenia. However, the cut-off value differed by ethic and region. Currently there is no study among Thai population. Therefore, we aimed to identify the optimal cutoff value of calf circumference as a screening tool for low skeletal muscle mass in independent Thai older adults. Subgroup analysis was performed for obesity and adults over 75 years.
Methods
This cross-sectional cohort studied in an outpatient geriatric check-up clinic. Participants, aged 60 and above, needed to be independent in basic activities of daily living to meet the inclusion criteria. Exclusion criteria comprised active malignancy, cardiac, pulmonary, or neurovascular diseases necessitating hospitalization in the preceding three months, chronic renal diseases requiring renal replacement therapy, and unstable psychiatric disorders. We measured the maximum calf circumference and appendicular skeletal muscle mass (ASMI) using bioelectrical impedance analysis (BIA). Low muscle mass is defined according to the Asian Working Group of Sarcopenia (AWGS) 2019 consensus.
Results
We enrolled 6,404 elderly adults (mean age 67.3 ± 5.1 years), with a 47% prevalence of low muscle mass in women and 25% in men. Lower muscle mass significantly correlated with reduced BMI and waist circumference in both genders (p < 0.001). Optimal cut-off values for low muscle mass screening were < 33 cm (sensitivity 80.1%, specificity 60.5%) for women and < 34 cm (sensitivity 85.4%, specificity 70.2%) for men. Subgroup analysis for those with BMI ≥ 25 kg/m² suggested raising the cut-off for women to < 34 cm (sensitivity 80.6%, specificity 54.0%) and for men to < 35 cm (sensitivity 88.7%, specificity 55.2%) to enhance specificity without substantial sensitivity loss. In the older-old adult subgroup (≥ 75 years), optimal cut-off values were < 33 cm (sensitivity 84.6%, specificity 79.9%) for women and < 34 cm (sensitivity 75.6%, specificity 87.0%) for men.
Conclusions
There is a strong correlation between calf circumference and ASMI in independent Thai older adults. Calf circumference can serve as a screening tool for identifying low muscle mass. The recommended cut-off values for men and women are 34 cm and 33 cm, respectively in alignment with AWGS 2019 recommendation. Incorporating a 1-cm higher cut-off value for obese older adults improves the accuracy of muscle mass screening.
Trial registration
Thai clinical trial registry: TCTR20200511003.
... Finally, although aging may impair the hypertrophic responses to mechanical overload, this is a more nuanced topic in the literature. Multiple studies have indicated that resistance training can lead to skeletal muscle hypertrophy in older adults (68,722,737,740,(875)(876)(877)(878)(879)(880)(881)(882)(883)(884)(885)(886), albeit some studies have indicated that aging impairs acute anabolic signaling and longer-term hypertrophic responses (880,(887)(888)(889). A recent meta-analysis by Straight et al. (890) suggests that increase in myofiber size with resistance training is impaired in older participants, which supports the notion that aging blunts hypertrophic outcomes. ...
Mechanisms underlying mechanical overload-induced skeletal muscle hypertrophy have been extensively researched since the landmark report by Morpurgo (1897) of "work-induced hypertrophy" in dogs that were treadmill-trained. Much of the pre-clinical rodent and human resistance training research to date supports that involved mechanisms include enhanced mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling, an expansion in translational capacity through ribosome biogenesis, increased satellite cell abundance and myonuclear accretion, and post-exercise elevations in muscle protein synthesis rates. However, several lines of past and emerging evidence suggest additional mechanisms that feed into or are independent of these processes are also involved. This review will first provide a historical account as to how mechanistic research into skeletal muscle hypertrophy has progressed. A comprehensive list of mechanisms associated with skeletal muscle hypertrophy is then outlined and areas of disagreement involving these mechanisms are presented. Finally, future research directions involving many of the discussed mechanisms will be proposed.
... Previous studies have shown that reducing body fat rather than increasing muscle mass, and placing importance on muscle functions, such as muscle strength, can be effective in preventing falls. These results agree with those reported previously [67][68][69]. Accordingly, to increase stride length and gait speed stably during walking, the elderly require a strategy to improve muscle function and reduce body fat through exercise and rehabilitation programs. ...
Background and Objectives: Previous studies have revealed that independent variables (lower extremity strength, postural control ability, and body composition) influence gait performance and variability, but the difference in the relative influence between these variables is unclear. Hence, this study determines the variable that is the most influential predictor of gait performance and variability among potential independent variables in the elderly. Materials and Methods: Seventy eight subjects aged ≥60 years participated. For each subject, the gait variables and lower extremity muscle strength were measured using an accelerometer worn on both feet during a 6-minute walk and a manual force sensor, respectively. The static balance ability was measured through two force plates, and the body composition was measured by applying bioelectrical impedance analysis. Linear regression analyses were performed stepwise to determine whether these variables affect gait performance and variability. Results: After adjusting for sex and gait performance, the ankle strength, body fat mass, mean velocity in the medial-lateral direction, ankle plantar flexion strength, and girth were predictors of gait speed dorsiflexion, gait performance, swing width of the gait performance , walking speed, and gait variability, respectively. Conclusions: Overall, gait performance in the elderly is related to muscle strength, postural control, and body composition in a complex manner, but gait variability appears to be more closely related to ankle muscle strength. This study provides further evidence that muscle strength is important in motor function and stability.
... To maintain the motor skills of the elderly and prevent their dependence on others, aerobic exercise and resistance training are performed in exercise classes by community residents and in day care service centers [1][2][3][4]. However, easier ways to continuously increase or maintain muscle power are needed for individuals with problems such as dementia and decreased motivation. ...
Tsubahara A, Kamiue M, Ito T, Kishimoto T, Kurozumi C. Measurement of maximal muscle contraction force induced by high-frequency magnetic stimulation: a preliminary study on the identification of the optimal stimulation site. Jpn J Compr Rehabil Sci 2021; 12: 27-31.
Purpose: To identify the optimal stimulation site and technique for inducing strong muscle contraction using a high-frequency magnetic stimulator.
Methods: High-frequency magnetic stimulation was administered to the right vastus lateralis (VL) of eight healthy adults at maximal intensity within the range of tolerable pain. The stimulation sites were as follows: section A, the area between the lateral edge of the base of the patella (LEBP) and the distal one-third of the thigh (point D); section B, the area between point D and the proximal one-third of the thigh (point P). Isometric maximal muscle contraction forces induced by magnetic stimulation (Stim-MCF) were compared between the two sections.
Results: The Stim-MCF was significantly higher in section B than in section A. Additionally, the sites susceptible to stimulation were confined to a narrow area near point D in section A and the central part between points D and P in section B. The degree of pain was very low in both sections.
Conclusion: The optimal site for magnetic stimulation of the VL was limited to the central part of the thigh. In addition to the superficial proximal sub-branch, the deep proximal sub-branch and/or deeply clustered motor nerve endings may have been stimulated. Our results suggested that moving the probe was a useful way to identify the site that elicited the strongest muscle contraction force.
... Consistent with this concept is the evidence that functional measures of muscle (i.e., grip strength, gait speed) are strong predictors of biological age (15). Given that the hypertrophic response to resistance exercise is reduced in aging relative to youth, yet increases in strength and power are achievable (26)(27)(28), the mechano-biology of muscle mass is of primary concern. ...
The decline in the mass and function of bone and muscle is an inevitable consequence of healthy aging with early onset and accelerated decline in those with chronic disease. Termed osteo-sarcopenia, this condition predisposes the decreased activity, falls, low-energy fractures, and increased risk of co-morbid disease that leads to musculoskeletal frailty. The biology of osteo-sarcopenia is most understood in the context of systemic neuro-endocrine and immune/inflammatory alterations that drive inflammation, oxidative stress, reduced autophagy, and cellular senescence in the bone and muscle. Here we integrate these concepts to our growing understanding of how bone and muscle senses, responds and adapts to mechanical load. We propose that age-related alterations in cytoskeletal mechanics alter load-sensing and mechano-transduction in bone osteocytes and muscle fibers which underscores osteo-sarcopenia. Lastly, we examine the evidence for exercise as an effective countermeasure to osteo-sarcopenia.
... mobility-limited, it is possible that the intensity and effort level achieved was too low to elicit an optimal hypertrophy stimulus. Another possible explanation for the observed small effects on muscle growth could be age-related attenuation of muscle plasticity (Petrella et al., 2006;Slivka et al., 2008;Raue et al., 2009;Rivas et al., 2014;Lee et al., 2019;Karlsen et al., 2019;Skoglund et al., 2020). Although it is known that muscle adaptations to exercise can occur in advanced age, and even if they are smaller compared to young healthy individuals, they still seem to be specific to the exercise load, type of exercise and physical function at baseline (Frontera et al., 1988;Sipila and Suominen, 1995;Harridge et al., 1999;Ferri et al., 2003;Wernbom et al., 2007;Raue et al., 2009;Aas et al., 2020). ...
Older adults are encouraged to engage in multicomponent physical activity, which includes aerobic and muscle-strengthening activities. The current work is an extension of the Vitality, Independence, and Vigor in the Elderly 2 (VIVE2) study – a 6-month multicenter, randomized, placebo-controlled trial of physical activity and nutritional supplementation in community dwelling 70-year-old seniors. Here, we examined whether the magnitude of changes in muscle size and quality differed between major lower-extremity muscle groups and related these changes to functional outcomes. We also examined whether daily vitamin-D-enriched protein supplementation could augment the response to structured physical activity. Forty-nine men and women (77 ± 5 yrs) performed brisk walking, muscle-strengthening exercises for the lower limbs, and balance training 3 times weekly for 6 months. Participants were randomized to daily intake of a nutritional supplement (20 g whey protein + 800 IU vitamin D), or a placebo. Muscle cross-sectional area (CSA) and radiological attenuation (RA) were assessed in 8 different muscle groups using single-slice CT scans of the hip, thigh, and calf at baseline and after the intervention. Walking speed and performance in the Short Physical Performance Battery (SPPB) were also measured. For both CSA and RA, there were muscle group × time interactions (P < 0.01). Significant increases in CSA were observed in 2 of the 8 muscles studied, namely the knee extensors (1.9%) and the hip adductors (2.8%). For RA, increases were observed in 4 of 8 muscle groups, namely the hip flexors (1.1 HU), hip adductors (0.9 HU), knee extensors (1.2 HU), and ankle dorsiflexors (0.8 HU). No additive effect of nutritional supplementation was observed. While walking speed (13%) and SPPB performance (38%) improved markedly, multivariate analysis showed that these changes were not associated with the changes in muscle CSA and RA after the intervention. We conclude that this type of multicomponent physical activity program results in significant improvements in physical function despite relatively small changes in muscle size and quality of some, but not all, of the measured lower extremity muscles involved in locomotion.
... mobility-limited, it is possible that the intensity and effort level achieved was too low to elicit an optimal hypertrophy stimulus. Another possible explanation for the observed small effects on muscle growth could be age-related attenuation of muscle plasticity (Petrella et al., 2006;Slivka et al., 2008;Raue et al., 2009;Rivas et al., 2014;Lee et al., 2019;Karlsen et al., 2019;Skoglund et al., 2020). Although it is known that muscle adaptations to exercise can occur in advanced age, and even if they are smaller compared to young healthy individuals, they still seem to be specific to the exercise load, type of exercise and physical function at baseline (Frontera et al., 1988;Sipila and Suominen, 1995;Harridge et al., 1999;Ferri et al., 2003;Wernbom et al., 2007;Raue et al., 2009;Aas et al., 2020). ...
Background
Nutritional supplementation and structured physical activity have been shown to positively influence muscle mass and strength in older adults. The efficacy of long‐term nutritional supplementation in combination with structured physical activity in this population remains unclear.
Objective
To examine the effects of a combined intervention of nutritional supplementation and structured physical activity compared to a placebo, on measures of total‐body and thigh composition and knee extensor strength in a cohort of mobility‐limited older adults across two sites (Boston, MA, USA and Stockholm, Sweden).
Design
Mobility‐limited (Short Physical Performance Battery (SPPB) ≤9) and vitamin D insufficient (serum 25(OH) D 9 – 24 ng/ml) older adults were recruited for this study. All subjects participated in a physical activity program (3x/week for 24 weeks), involving walking, strength, balance, and flexibility exercises. Subjects were randomized consume a daily nutritional supplement (150kcal, 20g whey protein, 800IU vitamin D, 4 fl. oz. beverage) or placebo (30kcal, non‐nutritive). We examined total‐body composition (DXA), thigh composition (CT), and muscle strength, power, and quality before and after the 6‐month intervention.
Results
149 subjects were randomized into the study (mean age=77.5±5.4; female=46.3%; mean SPPB= 7.9±1.2; mean vitamin D=18.7±6.4 ng/ml). Adherence across supplement and placebo groups was similar for the physical activity intervention (75% and 72%, respectively) and the study product (86% and 88%, respectively). After the intervention period both groups demonstrated improvements in total‐body composition, subcutaneous fat, intermuscular fat, and strength measures. Nutritional supplementation lead to further losses of intermuscular fat (treatment effect: −0.33 cm ² , 95% CI: −0.68 ~ 0.02), increased normal density muscle (treatment effect: 3.17 cm ² , 95% CI: 0.52 ~ 5.83), and an increase in serum 25(OH)D (treatment effect: 4.55 ng/ml, 95% CI: 2.03 ~ 7.08).
Conclusions
Six‐months of structured physical activity resulted in improvements in body composition, subcutaneous fat, intermuscular fat, and strength measures. The addition of nutritional supplementation resulted in a greater decline in intermuscular fat and improved muscle density. These results suggest nutritional supplementation provides additional benefits in mobility‐limited and vitamin D deficient older adults.
Support or Funding Information
This study was supported in part by Nestle' Health Science. In addition, this work was also supported by the U.S. Department of Agriculture (USDA), under agreement No. 58‐1950‐0‐014 and the Boston Claude D. Pepper Center Older American Independence Centers (OAIC; 1P30AG031679). Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the USDA.
... Many recent studies suggest that regimented physical activity, including resistance training, can be beneficial in maintaining muscle strength and function in elderly individuals (Pahor et al., 2014;Losa-Reyna et al., 2019;Martínez-Velilla et al., 2019;Rodriguez-Mañas et al., 2019;Yu et al., 2019). However, although physical training is beneficial at any age, the anabolic response to exercise decreases substantially with aging (Welle et al., 1996;Phillips et al., 2017;Lee et al., 2019). This review explores the mechanisms of cellular and molecular adaptations of skeletal muscle to exercise, with a focus on the aging-associated changes that cause hinderance of its anabolic response to exercise. ...
Loss of muscle mass and strength with aging, also termed sarcopenia, results in a loss of mobility and independence. Exercise, particularly resistance training, has proven to be beneficial in counteracting the aging-associated loss of skeletal muscle mass and function. However, the anabolic response to exercise in old age is not as robust, with blunted improvements in muscle size, strength, and function in comparison to younger individuals. This review provides an overview of several physiological changes which may contribute to age-related loss of muscle mass and decreased anabolism in response to resistance training in the elderly. Additionally, the following supplemental therapies with potential to synergize with resistance training to increase muscle mass are discussed: nutrition, creatine, anti-inflammatory drugs, testosterone, and growth hormone (GH). Although these interventions hold some promise, further research is necessary to optimize the response to exercise in elderly patients.
Aging encompasses the natural processes of birth, growth, and aging, during which the functional ability of muscles gradually decreases, leading to the loss of muscle size and reduced exercise performance known as sarcopenia. This condition is closely associated with weakness, osteoporosis, and degenerative diseases, increasing the risk of falls, fractures, metabolic diseases, and mortality due to limitations in physical performance among the elderly. This study investigated the effects of exercise intervention on biological markers related to skeletal muscle mass and functions in conjunction with aging. At age of four or twenty, the C57BL/6 mice were assigned to Young control (Y-Con, n = 10) or exercise training (Y--Exe, n = 10), and Aged control (A-Con, n=10) or exercise training (A-Exe, n = 10). Exercise intervention was performed on a rodent motor-driven treadmill with a frequency of 5 days per week for 8 weeks. As a consequence, exercise intervention in mice resulted in positive changes in IGF-1 signaling and muscle phenotype compared to mice that did not undergo exercise intervention, specifically showing prominent effects in the A-Exe group compared to the A-Con group. The mitigating effects of exercise intervention on age-related skeletal muscle dysfunction were accompanied by enhanced exercise performance and muscle function, as assessed by grip strength and the rotarod test. The current findings support previous studies that have reported the positive effect of exercise intervention in alleviating age-related declines in exercise performance and muscle function in older adults.
Background
The optimal prescription and precise recommendations of resistance training volume for older adults is unclear in the current literature. In addition, the interactions between resistance training volume and program duration as well as physical health status remain to be determined when assessing physical function, muscle size and hypertrophy and muscle strength adaptations in older adults.
Objectives
This study aimed to determine which resistance training volume is the most effective in improving physical function, lean body mass, lower-limb muscle hypertrophy and strength in older adults. Additionally, we examined whether effects were moderated by intervention duration (i.e. short term, < 20 weeks; medium-to-long term, ≥ 20 weeks) and physical health status (i.e. physically healthy, physically impaired, mixed physically healthy and physically impaired; PROSPERO identifier: CRD42023413209).
Methods
CINAHL, Embase, LILACS, PubMed, Scielo, SPORTDiscus and Web of Science databases were searched up to April 2023. Eligible randomised trials examined the effects of supervised resistance training in older adults (i.e. ≥ 60 years). Resistance training programs were categorised as low (LVRT), moderate (MVRT) and high volume (HVRT) on the basis of terciles of prescribed weekly resistance training volume (i.e. product of frequency, number of exercises and number of sets) for full- and lower-body training. The primary outcomes for this review were physical function measured by fast walking speed, timed up and go and 6-min walking tests; lean body mass and lower-body muscle hypertrophy; and lower-body muscle strength measured by knee extension and leg press one-repetition maximum (1-RM), isometric muscle strength and isokinetic torque. A random-effects network meta-analysis was undertaken to examine the effects of different resistance training volumes on the outcomes of interest.
Results
We included a total of 161 articles describing 151 trials (n = 6306). LVRT was the most effective for improving timed up and go [− 1.20 standardised mean difference (SMD), 95% confidence interval (95% CI): − 1.57 to − 0.82], 6-min walk test (1.03 SMD, 95% CI: 0.33–1.73), lean body mass (0.25 SMD, 95% CI: 0.10–0.40) and muscle hypertrophy (0.40 SMD, 95% CI: 0.25–0.54). Both MVRT and HVRT were the most effective for improving lower-limb strength, while only HVRT was effective in increasing fast walking speed (0.40 SMD, 95% CI: − 0.57 to 0.14). Regarding the moderators, our results were independent of program duration and mainly observed for healthy older adults, while evidence was limited for those who were physically impaired.
Conclusions
A low resistance training volume can substantially improve healthy older adults’ physical function and benefits lean mass and muscle size independently of program duration, while a higher volume seems to be necessary for achieving greater improvements in muscle strength. A low volume of resistance training should be recommended in future exercise guidelines, particularly for physically healthy older adults targeting healthy ageing.
Aging refers to the natural processes of birth, growth, and aging. As aging progresses, the functional ability of muscles gradually decreases, leading to loss of muscle mass and reduced exercise performance, referred to as sarcopenia. Sarcopenia is closely associated with weakness, osteoporosis, and degenerative diseases. It is related to the risk of falls, fractures, weakness, metabolic diseases, and death owing to limitations of physical performance in the elderly. Sarcopenia is influenced by complex factors, such as lifestyle, smoking, nutritional imbalance, and changes associated with aging. In this study, we aimed to investigate the biological mechanisms affecting protein expression and exercise performance in aging mice to identify the biological factors related to sarcopenia. The results showed that the Aged-Con group showed decreased muscle strength and muscle fiber size, as well as decreased exercise performance. Further, IGF-1 signaling was reduced in the Aged-Con group. In contrast, reduced IGF-1 signaling was alleviated in the Aged-Exe group; the decreased muscle size and exercise performance were also alleviated in the Aged-Exe group. Overall, these findings suggest that regular moderate exercise can prevent aging-induced sarcopenia and improve exercise performance.
Aging is associated with profound alterations in skeletal muscle, including loss of muscle mass and function, local inflammation, altered mitochondrial physiology, and attenuated anabolic responses to exercise termed anabolic resistance. "Inflammaging," the chronic, low-grade inflammation associated with aging, may contribute to many of the age-related derangements in skeletal muscle, including its ability to respond to exercise and nutritional stimuli. Inflammation and exercise are closely intertwined in numerous ways. A single bout of muscle-damaging exercise stimulates an acute inflammatory response in the skeletal muscle that is essential for muscle repair and regeneration; however, the chronic systemic and local inflammation associated with aging may impair acute inflammatory and anabolic responses to exercise. In contrast, exercise training is anti-inflammatory, targeting many of the potential root causes of inflammaging. In this review, we discuss the interplay between inflammation and exercise in aging and highlight potential therapeutic targets for improving adaptive responses to exercise in older adults.
Reductions in skeletal muscle mass and function are often reported in patients with cancer-associated weight loss and are associated with reduced quality of life, impaired treatment tolerance, and increased mortality. Although cellular changes, including altered mitochondrial function, have been reported in animals, such changes have been incompletely characterized in humans with cancer. Whole body and skeletal muscle physical function, skeletal muscle mitochondrial function and whole-body protein turnover were assessed in 8 patients with cancer-associated weight loss (10.1±4.2% body weight over 6-12 months) and 19 age-, sex-, and BMI-matched healthy controls to characterize skeletal muscle changes at the whole body, muscle, and cellular level. Potential pathways involved in cancer-induced alterations in metabolism and mitochondrial function were explored by interrogating skeletal muscle and plasma metabolomes. Despite similar lean mass compared to control participants, patients with cancer exhibited reduced habitual physical activity (57% fewer daily steps), cardiorespiratory fitness (22% lower VO 2 peak [mL/kg/min]) and leg strength (35% lower isokinetic knee extensor strength) and greater leg neuromuscular fatigue (36% greater decline in knee extensor torque). Concomitant with these functional declines, patients with cancer had lower mitochondrial oxidative capacity (25% lower State 3 O 2 flux [pmol/s/mg tissue]) and ATP production (23% lower State 3 ATP production [pmol/s/mg tissue]) and alterations in phospholipid metabolite profiles indicative of mitochondrial abnormalities. Whole body protein turnover was unchanged. These findings demonstrate mitochondrial abnormalities concomitant with whole-body and skeletal muscle functional derangements associated with human cancer, supporting future work studying the role of mitochondria in the muscle deficits associated with cancer.
Interventions based on resistance training have been shown to counteract muscle disuse and therefore combat muscle strength and muscle mass loss, with positive effects on physical functioning, mobility, independence, psychological well-being, and quality of life. Unfortunately, a low percentage of older adults meet international recommendations on resistance training probably due to fear, health concerns, pain, fatigue, or lack of social support. There is a need for evidence-based guidelines and recommendations for resistance exercise for older adults to safely and gradually introduce this type of training into their routines. However, there is no “average” older adult, and so it is impossible to provide a single recommendation that is fully representative, especially across age groups. All individuals respond differently to resistance training, and progression should be closely monitored to be able to individually adjust the training program; consequently, different methods available for assessing muscle strength and physical function that serve to analyze the effectiveness of interventions are discussed in this chapter. New strategies used in combination with resistance training in older adults are also addressed, in order to provide novel insights regarding the resistance strength training in this population group.
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.
This study aimed to evaluate the effects of resistive exercise (RE) with head rotation exercise (RE+HRE) on postural balance, lower limb muscle strength, and gait in older women. This study was conducted from December 7, 2015 to January 29, 2016 in Seoul, South Korea. Forty older women were recruited at welfare center and randomly allocated to RE+HRE (n = 20) or RE (n = 20) groups. The RE+HRE group performed RE+HRE for 60 min twice per week for 6 weeks, using an elastic band with variable resistance along the length. The HRE included horizontal or vertical head movement during the exercise. The RE group performed RE in a similar manner, but without head movements. The outcome measures were static postural balance (one-leg stance test, functional reach test, and postural sway), dynamic postural balance (timed up and go test, four square step test, and Mini-balance evaluation systems test), lower limb muscle strength (sit-to-stand test), and temporal gait parameters. In the RE+HRE group, all variables were significantly improved compared to baseline (p < .05), and postural balance and gait were significantly improved compared to those in the RE group (p < .05). These findings suggest that RE+HRE can improve dynamic postural balance, gait speed, and cadence in older women.
Aim:
Exercise is one of the most important components in frailty prevention and treatment. Therefore, we systematically reviewed the effect of resistance training (RT) alone or combined with multimodal exercise intervention on muscle hypertrophy, maximal strength, power output, functional performance, and falls incidence in physically frail elderly.
Methods:
MEDLINE, Cochrane CENTRAL, PEDro, and SPORTDiscus databases were searched from 2005 to 2017. Studies must have mentioned the effects of RT (i.e., included or not in multimodal training) on at least one of the following parameters: muscle mass, muscle strength, muscle power, functional capacity, and risk of falls in frail elderly.
Results:
The initial search identified 371 studies and 16 were used for qualitative analysis for describing the effect of strength training performed alone or in a multimodal exercise intervention. We observed that RT alone or in a multimodal training may induce increases of 6.6-37% in maximal strength; 3.4-7.5% in muscle mass, 8.2% in muscle power, 4.7-58.1% in functional capacity and risk of falls, although some studies did not show enhancements.
Conclusion:
Frequency of 1-6 sessions per week, training volume of 1-3 sets of 6-15 repetitions and intensity of 30-70%1-RM promoted significant enhancements on muscle strength, muscle power, and functional outcomes. Therefore, in agreement with previous studies, we suggest that supervised and controlled RT represents an effective intervention in frailty treatment.
[Purpose] To compare measurements of knee extensor and flexor muscle strength performed using a hand-held dynamometer and an isokinetic dynamometer in apparently healthy subjects. [Subjects and Methods] Thirty adult volunteers underwent knee muscle strength evaluation using an isokinetic or a hand-held dynamometer. [Results] Strong positive correlations were found between the 2 methods, with correlation coefficients r ranging from 0.72 (95% confidence interval [CI], 0.48−0.8to 0.87 (95% CI, 0.75−0.94), depending on the muscle group and the isokinetic evaluation mode. The reproducibility of the hand-held dynamometer findings was good, judged by a coefficient of variation of 3.2–4.2%. However, the correlation between the 2 methods for the assessment of flexor/extensor ratios ranged from −0.04 to 0.46. [Conclusion] Knee extensor and flexor muscle strength recorded with a hand-held dynamometer is reproducible and significantly correlated with the isokinetic values, indicating that this method may in some cases be a useful replacement for isokinetic strength measurement. However, for strength ratio assessment, and when judged against the isokinetic standard, a hand-held dynamometer is not a valid option. © 2016 The Society of Physical Therapy Science. Published by IPEC Inc.
Background:
Resistance training (RT) is an intervention frequently used to improve muscle strength and morphology in old age. However, evidence-based, dose-response relationships regarding specific RT variables (e.g., training period, frequency, intensity, volume) are unclear in healthy old adults.
Objectives:
The aims of this systematic review and meta-analysis were to determine the general effects of RT on measures of muscle strength and morphology and to provide dose-response relationships of RT variables through an analysis of randomized controlled trials (RCTs) that could improve muscle strength and morphology in healthy old adults.
Data sources:
A computerized, systematic literature search was performed in the electronic databases PubMed, Web of Science, and The Cochrane Library from January 1984 up to June 2015 to identify all RCTs related to RT in healthy old adults.
Study eligibility criteria:
The initial search identified 506 studies, with a final yield of 25 studies. Only RCTs that examined the effects of RT in adults with a mean age of 65 and older were included. The 25 studies quantified at least one measure of muscle strength or morphology and sufficiently described training variables (e.g., training period, frequency, volume, intensity).
Study appraisal and synthesis methods:
We quantified the overall effects of RT on measures of muscle strength and morphology by computing weighted between-subject standardized mean differences (SMDbs) between intervention and control groups. We analyzed the data for the main outcomes of one-repetition maximum (1RM), maximum voluntary contraction under isometric conditions (MVC), and muscle morphology (i.e., cross-sectional area or volume or thickness of muscles) and assessed the methodological study quality by Physiotherapy Evidence Database (PEDro) scale. Heterogeneity between studies was assessed using I (2) and χ (2) statistics. A random effects meta-regression was calculated to explain the influence of key training variables on the effectiveness of RT in terms of muscle strength and morphology. For meta-regression, training variables were divided into the following subcategories: volume, intensity, and rest. In addition to meta-regression, dose-response relationships were calculated independently for single training variables (e.g., training frequency).
Results:
RT improved muscle strength substantially (mean SMDbs = 1.57; 25 studies), but had small effects on measures of muscle morphology (mean SMDbs = 0.42; nine studies). Specifically, RT produced large effects in both 1RM of upper (mean SMDbs = 1.61; 11 studies) and lower (mean SMDbs = 1.76; 19 studies) extremities and a medium effect in MVC of lower (mean SMDbs = 0.76; four studies) extremities. Results of the meta-regression revealed that the variables "training period" (p = 0.04) and "intensity" (p < 0.01) as well as "total time under tension" (p < 0.01) had significant effects on muscle strength, with the largest effect sizes for the longest training periods (mean SMDbs = 2.34; 50-53 weeks), intensities of 70-79 % of the 1RM (mean SMDbs = 1.89), and total time under tension of 6.0 s (mean SMDbs = 3.61). A tendency towards significance was found for rest in between sets (p = 0.06), with 60 s showing the largest effect on muscle strength (mean SMDbs = 4.68; two studies). We also determined the independent effects of the remaining training variables on muscle strength. The following independently computed training variables are most effective in improving measures of muscle strength: a training frequency of two sessions per week (mean SMDbs = 2.13), a training volume of two to three sets per exercise (mean SMDbs = 2.99), seven to nine repetitions per set (mean SMDbs = 1.98), and a rest of 4.0 s between repetitions (SMDbs = 3.72). With regard to measures of muscle morphology, the small number of identified studies allowed us to calculate meta-regression for the subcategory training volume only. No single training volume variable significantly predicted RT effects on measures of muscle morphology. Additional training variables were independently computed to detect the largest effect for the single training variable. A training period of 50-53 weeks, a training frequency of three sessions per week, a training volume of two to three sets per exercise, seven to nine repetitions per set, a training intensity from 51 to 69 % of the 1RM, a total time under tension of 6.0 s, a rest of 120 s between sets, and a rest of 2.5 s between repetitions turned out to be most effective.
Limitations:
The current results must be interpreted with caution because of the poor overall methodological study quality (mean PEDro score 4.6 points) and the considerable large heterogeneity (I (2) = 80 %, χ (2) = 163.1, df = 32, p < 0.01) for muscle strength. In terms of muscle morphology, our search identified nine studies only, which is why we consider our findings preliminary. While we were able to determine a dose-response relationship based on specific individual training variables with respect to muscle strength and morphology, it was not possible to ascertain any potential interactions between these variables. We recognize the limitation that the results may not represent one general dose-response relationship.
Conclusions:
This systematic literature review and meta-analysis confirmed the effectiveness of RT on specific measures of upper and lower extremity muscle strength and muscle morphology in healthy old adults. In addition, we were able to extract dose-response relationships for key training variables (i.e., volume, intensity, rest), informing clinicians and practitioners to design effective RTs for muscle strength and morphology. Training period, intensity, time under tension, and rest in between sets play an important role in improving muscle strength and morphology and should be implemented in exercise training programs targeting healthy old adults. Still, further research is needed to reveal optimal dose-response relationships following RT in healthy as well as mobility limited and/or frail old adults.
In 2008, we published an article arguing that the age-related loss of muscle strength is only partially explained by the reduction in muscle mass and that other physiologic factors explain muscle weakness in older adults (Clark BC, Manini TM. Sarcopenia =/= dynapenia. J Gerontol A Biol Sci Med Sci. 2008;63:829-834). Accordingly, we proposed that these events (strength and mass loss) be defined independently, leaving the term "sarcopenia" to be used in its original context to describe the age-related loss of muscle mass. We subsequently coined the term "dynapenia" to describe the age-related loss of muscle strength and power. This article will give an update on both the biological and clinical literature on dynapenia-serving to best synthesize this translational topic. Additionally, we propose a working decision algorithm for defining dynapenia. This algorithm is specific to screening for and defining dynapenia using age, presence or absence of risk factors, a grip strength screening, and if warranted a test for knee extension strength. A definition for a single risk factor such as dynapenia will provide information in building a risk profile for the complex etiology of physical disability. As such, this approach mimics the development of risk profiles for cardiovascular disease that include such factors as hypercholesterolemia, hypertension, hyperglycemia, etc. Because of a lack of data, the working decision algorithm remains to be fully developed and evaluated. However, these efforts are expected to provide a specific understanding of the role that dynapenia plays in the loss of physical function and increased risk for disability among older adults.
A frailty paradigm would be useful in primary care to identify older people at risk, but appropriate metrics at that level are lacking. We created and validated a simple instrument for frailty screening in Europeans aged ≥50. Our study is based on the first wave of the Survey of Health, Ageing and Retirement in Europe (SHARE, http://www.share-project.org), a large population-based survey conducted in 2004-2005 in twelve European countries.
Subjects: SHARE Wave 1 respondents (17,304 females and 13,811 males). Measures: five SHARE variables approximating Fried's frailty definition. Analyses (for each gender): 1) estimation of a discreet factor (DFactor) model based on the frailty variables using LatentGOLD. A single DFactor with three ordered levels or latent classes (i.e. non-frail, pre-frail and frail) was modelled; 2) the latent classes were characterised against a biopsychosocial range of Wave 1 variables; 3) the prospective mortality risk (unadjusted and age-adjusted) for each frailty class was established on those subjects with known mortality status at Wave 2 (2007-2008) (11,384 females and 9,163 males); 4) two web-based calculators were created for easy retrieval of a subject's frailty class given any five measurements.
Females: the DFactor model included 15,578 cases (standard R2 = 0.61). All five frailty indicators discriminated well (p < 0.001) between the three classes: non-frail (N = 10,420; 66.9%), pre-frail (N = 4,025; 25.8%), and frail (N = 1,133; 7.3%). Relative to the non-frail class, the age-adjusted Odds Ratio (with 95% Confidence Interval) for mortality at Wave 2 was 2.1 (1.4 - 3.0) in the pre-frail and 4.8 (3.1 - 7.4) in the frail. Males: 12,783 cases (standard R2 = 0.61, all frailty indicators had p < 0.001): non-frail (N = 10,517; 82.3%), pre-frail (N = 1,871; 14.6%), and frail (N = 395; 3.1%); age-adjusted OR (95% CI) for mortality: 3.0 (2.3 - 4.0) in the pre-frail, 6.9 (4.7 - 10.2) in the frail.
The SHARE Frailty Instrument has sufficient construct and predictive validity, and is readily and freely accessible via web calculators. To our knowledge, SHARE-FI represents the first European research effort towards a common frailty language at the community level.
Gait disturbances are among the more common symptoms in the elderly. Reduced mobility markedly impairs quality of life, and the associated falls increase morbidity and mortality.
Review of the literature based on a selective search (PubMed) on the terms "gait," "gait disorder," "locomotion," "elderly," "geriatric" and "ageing" (2000-11/2009) and the findings of the authors' own studies on gait changes in old age and on the functional brain imaging of gait control.
Gait disturbances in the elderly are often of multifactorial origin. The relevant pathogenetic factors include sensory deficits (visual, vestibular, somatosensory), neurodegenerative processes (cortical, extrapyramidal motor, cerebellar), toxic factors (medications, alcohol), and anxiety (primary or concerning falls). A clinically oriented classification of gait disorders is proposed, which, on the basis of the characterization of gait and the accompanying clinical findings, enables identification of the etiological factors and points the way to rational therapy. Current research topics in the study of gait disturbances are also discussed, including quantitative gait analysis, interactions between locomotion and cognition (dual tasking), and functional imaging approaches.
The evaluation of elderly patients whose chief complaint is a gait disturbance should be directed toward the identification of specific deficits. This is the prerequisite for rational therapy, even when the problem is of multifactorial origin. The preservation of mobility is important in itself, and also because the ability to walk is closely correlated with cognitive performance.
Sarcopenia reflects a progressive withdrawal of anabolism and an increased catabolism, along with a reduced muscle regeneration capacity. Muscle force and power decline more than muscle dimensions: older muscle is intrinsically weak. Sarcopenic obesity (SO) among the elderly corroborates to the loss of muscle mass increasing the risk of metabolic syndrome development. Recent studies on the musculoskeletal adaptations with ageing and key papers on the mechanisms of muscle wasting, its functional repercussions and on SO are included. Neuropathic, hormonal, immunological, nutritional and physical activity factors contribute to sarcopenia. Selective fast fibre atrophy, loss of motor units and an increase in hybrid fibres are typical findings of ageing. Satellite cell number decreases reducing muscle regeneration capacity. SO promotes further muscle wasting and increases risk of metabolic syndrome development. The proportion of fast to slow fibres seems maintained in old age. In elderly humans, nuclear domain is maintained constant. Basal protein synthesis and breakdown show little changes in old age. Instead, blunting of the anabolic response to feeding and exercise and of the antiproteolytic effect of insulin is observed. Further understanding of the mechanisms of sarcopenia requires disentangling of the effects of ageing alone from those of disuse and disease. The causes of the greater anabolic resistance to feeding and exercise of elderly women need elucidating. The enhancement of muscle regeneration via satellite cell activation via the MAPK/notch molecular pathways seems particularly promising.
Aging skeletal muscle is characterized not only by a reduction in size (sarcopenia) and strength but also by an increase in fatty infiltration (myosteatosis). An effective countermeasure to sarcopenia is resistance exercise; however, its effect on fatty infiltration is less clear.
To examine in resistance-trained older persons whether muscle attenuation, a noninvasive measure of muscle density reflecting intramuscular lipid content, is altered with training status.
Thirteen healthy community-dwelling men and women aged 65-83 years (body mass index 27.0+/-1.2, mean+/-SE) had computed-tomography scans of the mid-thigh performed following 24 weeks of training, 24 weeks of detraining, and 12 weeks of retraining. Training and retraining were undertaken twice weekly for several upper- and lower-body muscle groups. Skeletal muscle attenuation in Hounsfield units (HU) as well as mid-thigh muscle volume was obtained for the quadriceps and hamstrings. Muscle strength was assessed by 1-repetition maximum and physical function by a battery of tests.
The average change in muscle strength following training, detraining and retraining was 48.8+/-2.9%, -17.6+/-1.3%, and 19.8+/-2.0%, respectively. Strength changes were accompanied by significant alterations in muscle density (p<0.001), with the quadriceps HU decreasing by 7.7+/-1.0% following detraining and increasing by 5.4+/-0.5% with retraining. For the hamstrings HU measure, detraining and retraining resulted in an 11.9+/-1.4% loss and a 5.5+/-1.8% gain, respectively. There was no significant change in muscle volume.
Cessation of resistance exercise in trained older persons increases the fatty infiltration of muscle, while resumption of exercise decreases it. Monitoring changes in both muscle size and fat infiltration may enable a more comprehensive assessment of exercise in combating age-related muscular changes.
Muscle dysfunction and associated mobility impairment, common among the frail elderly, increase the risk of falls, fractures, and functional dependency. We sought to characterize the muscle weakness of the very old and its reversibility through strength training. Ten frail, institutionalized volunteers aged 90 ± 1 years undertook 8 weeks of high-intensity resistance training. Initially, quadriceps strength was correlated negatively with walking time (r= -.745). Fat-free mass (r=.732) and regional muscle mass (r=.752) were correlated positively with muscle strength. Strength gains averaged 174% ±31% (mean ± SEM) in the 9 subjects who completed training. Midthigh muscle area increased 9.0%± 4.5%. Mean tandem gait speed improved 48% after training. We conclude that high-resistance weight training leads to significant gains in muscle strength, size, and functional mobility among frail residents of nursing homes up to 96 years of age.
(JAMA. 1990;263:3029-3034)
To evaluate the validity of a leg-to-leg bioimpedance analysis (BIA) system in predicting body composition as measured by dual-energy X-ray absorptiometry (DXA) in postmenopausal women.
Body fat mass (FM), %Fat and fat free mass (FFM) were measured in 124 postmenopausal women (age: 51-63 y, body mass index (BMI): 17-38 kg/m2) first by the leg-to-leg BIA system, and then by DXA as reference method. Bland-Altman analysis was used to determine the bias and 95% limits of agreement between the two methods for the assessment of the individual. Precision error (CV%) of the BIA system was obtained by repeated measurements with intermediate repositioning.
The leg-to-leg BIA system had a high reproducibility with within-day CVs being 0.6% for FFM and 1.1% for FM, and between-day CVs about twice that. The impedance index (Ht2/Z) obtained by the leg-to-leg BIA was moderately correlated to FFM measured by DXA (r=0.66). A significant, systematic bias was observed between the two methods. The BIA system overestimated FM by a mean of 3.1 kg, and underestimated FFM by 2.7 kg. The analysis of 95% limits of agreement showed that for most individuals, %Fat estimated by the BIA might differ from that measured by DXA by 12% below to 45% above, indicating the lack of agreement between the two methods for the assessment of the individual.
The leg-to-leg BIA system can provide simple, rapid and highly reproducible measurements of body composition for groups, but it has limited accuracy for the assessment of the individual. Population-specific equations will be needed to improve its accuracy in estimating body composition in postmenopausal women.
Effects of a 24-week strength training performed twice weekly (24 ST) (combined with explosive exercises) followed by either a 3-week detraining (3 DT) and a 21-week re-strength-training (21 RST) (experiment A) or by a 24-week detraining (24 DT) (experiment B) on neural activation of the agonist and antagonist leg extensors, muscle cross-sectional area (CSA) of the quadriceps femoris, maximal isometric and one repetition maximum (1-RM) strength and jumping (J) and walking (W) performances were examined. A group of middle-aged (M, 37-44 years, n = 12) and elderly (E, 62-77, n = 10) and another group of M (35-45, n = 7) and E (63-78, n = 7) served as subjects. In experiment A, the 1-RM increased substantially during 24 ST in M (27%, P<0.001) and E (29%, P<0.001) and in experiment B in M (29%, P<0.001) and E (23%, P<0.01). During 21 RST the 1-RM was increased by 5% at week 48 (P<0.01) in M and 3% at week 41 in E (n.s., but P<0.05 at week 34). In experiment A the integrated electromyogram (IEMG) of the vastus muscles in the 1-RM increased during 24 ST in both M (P<0.05) and E (P<0.001) and during 21 RST in M for the right (P<0.05) and in E for both legs (P<0.05). The biceps femoris co-activation during the 1-RM leg extension decreased during the first 8-week training in M (from 29+/-5% to 25+/-3%, n.s.) and especially in E (from 41+/-11% to 32+/-9%, P<0.05). The CSA increased by 7% in M (P<0.05) and by 7% in E (P<0.001), and by 7% (n.s.) in M and by 3% in E (n.s.) during 24 ST periods. Increases of 18% (P<0.001) and 12% (P<0.05) in M and 22% (P<0.001) and 26% (P<0.05) in E occurred in J. W speed increased (P<0.05) in both age groups. The only decrease during 3 DT was in maximal isometric force in M by 6% (P<0.05) and by 4% (n.s.) in E. During 24 DT the CSA decreased in both age groups (P<0.01), the 1-RM decreased by 6% (P<0.05) in M and by 4% (P<0.05) in E and isometric force by 12% (P<0.001) in M and by 9% (P<0.05) in E, respectively, while J and W remained unaltered. The strength gains were accompanied by increased maximal voluntary neural activation of the agonists in both age groups with reduced antagonist co-activation in the elderly during the initial training phases. Neural adaptation seemed to play a greater role than muscle hypertrophy. Short-term detraining led to only minor changes, while prolonged detraining resulted in muscle atrophy and decreased voluntary strength, but explosive jumping and walking actions in both age groups appeared to remain elevated for quite a long time by compensatory types of physical activities when performed on a regular basis.
Estimates of body-composition change in older adults are mostly derived from cross-sectional data.
We examined the natural longitudinal patterns of change in fat-free mass (FFM) and fat mass (FM) in older adults and explored the effect of physical activity, weight change, and age on these changes.
The body composition measured by hydrodensitometry and the level of sports and recreational activity (SRA) of 53 men and 78 women with a mean (+/-SD) initial age of 60.7 +/- 7.8 y were examined on 2 occasions separated by a mean (+/-SD) time of 9.4 +/- 1.4 y.
FFM decreased in men (2.0% per decade) but not in women, whereas FM increased similarly in both sexes (7.5% per decade). Levels of SRA decreased more in men than in women over the follow-up period. Baseline age and level of SRA were inversely and independently associated with changes in FM in women only. Neither age nor level of SRA was associated with changes in FFM in men or women. Weight-stable subjects lost FFM. FFM accounted for 19% of body weight in those who gained weight, even in the presence of decreased levels of SRA. Loss of FFM (33% of body weight) was pronounced in those who lost weight, despite median SRA levels >4184 kJ/wk.
On average, FM increased; however, the increase in women was attenuated with advancing age. The decrease in FFM over the follow-up period was small and masked the wide interindividual variation that was dependent on the magnitude of weight change. The contribution of weight stability, modest weight gains, or lifestyle changes that include regular resistance exercise in attenuating lean-tissue loss with age should be explored.
Low muscle strength is associated with mortality, presumably as a result of low muscle mass (sarcopenia) and physical inactivity. Grip strength was longitudinally collected in 1071 men over a 25-year period. Muscle mass was estimated by using 24-hour creatinine excretion and physical activity values, obtained by questionnaire. Survival analysis examined the impact of grip strength and rate of change in strength on all-cause mortality over 40 years. Lower and declining strength are associated with increased mortality, independent of physical activity and muscle mass. In men <60 years, rate of loss of strength was more important than the actual levels. In men >/=60 years, strength was more protective than the rate of loss, which persisted when muscle mass was considered. Strength and rate of change in strength contribute to the impact of sarcopenia on mortality. Although muscle mass and physical activity are important, they do not completely account for the impact of strength and changes in strength.
Sarcopenia, the reduction of muscle mass and strength that occurs with aging, is widely considered one of the major causes of disability in older persons. Surprisingly, criteria that may help a clinician to identify persons with impaired muscle function are still lacking. Using data from a large representative sample of the general population, we examined how muscle function and calf muscle area change with aging and affect mobility in men and women free of neurological conditions. We tested several putative indicators of sarcopenia, including knee extension isometric torque, handgrip, lower extremity muscle power, and calf muscle area. For each indicator, sarcopenia was considered to be present when the measure was >2 SDs below the mean. For all four measures, the prevalence of sarcopenia increased with age, both in men and women. The age-associated gradient in prevalence was maximum for muscle power and minimum for calf-muscle area. However, lower extremity muscle power was no better than knee-extension torque or handgrip in the early identification of poor mobility, defined either as walking speed <0.8 m/s or inability to walk at least 1 km without difficulty and without developing symptoms. Optimal cutoff values that can be used in the clinical practice to identify older persons with poor mobility were developed. The findings of the study lay the basis for a cost-effective, clinical marker of sarcopenia based on a measure of isometric handgrip strength. Our findings should be verified in a longitudinal study.
Skeletal muscle mass declines with age, as does the potential for overload-induced fast-twitch skeletal muscle hypertrophy. Because 5'-AMP-activated protein kinase (AMPK) activity is thought to inhibit skeletal muscle protein synthesis and may therefore modulate muscle mass and hypertrophy, the purpose of this investigation was to examine AMPK phosphorylation status (a marker of AMPK activity) and its potential association with the attenuated overload-induced hypertrophy observed in aged skeletal muscle. One-week overload of fast-twitch plantaris and slow-twitch soleus muscles was achieved in young adult (8 mo; n = 7) and old (30 mo; n = 7) Fischer344 x Brown Norway male rats via unilateral gastrocnemius ablation. Significant (P < or = 0.05) age-related atrophy (as measured by total protein content) was noted in plantaris and soleus control (sham-operated) muscles. In fast-twitch plantaris muscles, percent hypertrophy with overload was significantly attenuated with age, whereas AMPK phosphorylation status as determined by Western blotting [phospho-AMPK (Thr172)/total AMPK] was significantly elevated with age (regardless of loading status). There was also a main effect of loading on AMPK phosphorylation status in plantaris muscles (overload > control). Moreover, a strong and significant negative correlation (r = -0.82) was observed between AMPK phosphorylation status and percent hypertrophy in the overloaded plantaris muscles of all animals. In contrast to the plantaris, overload-induced hypertrophy of the slow-twitch soleus muscle was similar between ages, and AMPK phosphorylation in this muscle was also unaffected by age or overload. These data support the possibility that an age-related elevation in AMPK phosphorylation may partly contribute to the attenuated hypertrophic response observed with age in overloaded fast-twitch plantaris muscle.
The loss of muscle mass is considered to be a major determinant of strength loss in aging. However, large-scale longitudinal studies examining the association between the loss of mass and strength in older adults are lacking.
Three-year changes in muscle mass and strength were determined in 1880 older adults in the Health, Aging and Body Composition Study. Knee extensor strength was measured by isokinetic dynamometry. Whole body and appendicular lean and fat mass were assessed by dual-energy x-ray absorptiometry and computed tomography.
Both men and women lost strength, with men losing almost twice as much strength as women. Blacks lost about 28% more strength than did whites. Annualized rates of leg strength decline (3.4% in white men, 4.1% in black men, 2.6% in white women, and 3.0% in black women) were about three times greater than the rates of loss of leg lean mass ( approximately 1% per year). The loss of lean mass, as well as higher baseline strength, lower baseline leg lean mass, and older age, was independently associated with strength decline in both men and women. However, gain of lean mass was not accompanied by strength maintenance or gain (ss coefficients; men, -0.48 +/- 4.61, p =.92, women, -1.68 +/- 3.57, p =.64).
Although the loss of muscle mass is associated with the decline in strength in older adults, this strength decline is much more rapid than the concomitant loss of muscle mass, suggesting a decline in muscle quality. Moreover, maintaining or gaining muscle mass does not prevent aging-associated declines in muscle strength.
Human aging is characterized by skeletal muscle wasting, a debilitating condition which sets the susceptibility for diseases that directly affect the quality of life and often limit life span. Sarcopenia, i.e. the reduction of muscle mass and/or function, is the consequence of a reduction of protein synthesis and an increase in muscle protein degradation. In addition, the capacity for muscle regeneration is severely impaired in aging and this can lead to disability, particularly in patients with other concomitant diseases or organ impairment. Immobility and lack of exercise, increased levels of proinflammatory cytokines, increased production of oxygen free radicals or impaired detoxification, low anabolic hormone output, malnutrition and reduced neurological drive have been advocated as being responsible for sarcopenia. It is intriguing to notice that multiple pathways converge on skeletal muscle dysfunction, but the factors involved sometimes diverge to different pathways, thus intersecting at critical points. It is reasonable to argue that the activity of these nodes results from the net balance of regulating mechanisms, as in the case of the GH/IGF-1 axis, the testosterone and cortisol functions, the pro- and anti-inflammatory cytokines and receptors. Both genetic and epigenetic mechanisms operate in regulating the final phenotype, the extent of muscle atrophy and reduction in strength and force generation. It is widely accepted that intervention on lifestyle habits represents an affordable and practical way to modify on a large scale some detrimental outcomes of aging, and particularly sarcopenia. The identification of the molecular chain able to reverse sarcopenia is a major goal of studies on human aging.
The purpose of this study was to investigate whole muscle and single muscle fiber adaptations in very old men in response to progressive resistance training (PRT). Six healthy independently living old men (82 +/- 1 yr; range 80-86 yr, 74 +/- 4 kg) resistance-trained the knee extensors (3 sets, 10 repetitions) at approximately 70% one repetition maximum 3 days/wk for 12 wk. Whole thigh muscle cross-sectional area (CSA) was assessed before and after PRT using computed tomography (CT). Muscle biopsies were obtained from the vastus lateralis before and after the PRT program. Isolated myosin heavy chain (MHC) I and IIa single muscle fibers (n = 267; 142 pre; 125 post) were studied for diameter, peak tension, shortening velocity, and power. An additional set of isolated single muscle fibers (n = 2,215; 1,202 pre; 1,013 post) was used to identify MHC distribution. One repetition maximum knee extensor strength increased (P < 0.05) 23 +/- 4 kg (56 +/- 4 to 79 +/- 7 kg; 41%). Muscle CSA increased (P < 0.05) 3 +/- 1 cm2 (120 +/- 7 to 123 +/- 7 cm2; 2.5%). Single muscle fiber contractile function and MHC distribution were unaltered with PRT. These data indicate limited muscle plasticity at the single-muscle fiber level with a resistance-training program among the very old. The minor increases in whole muscle CSA coupled with the static nature of the myocellular profile indicate that the strength gains were primarily neurological. These data contrast typical muscle responses to resistance training in young ( approximately 20 yr) and old ( approximately 70 yr) humans and indicate that the physiological regulation of muscle remodeling is adversely modified in the oldest old.
Explosive resistance training (ERT) improves muscle strength and power in older adults. Previous work has determined that the Borg rating of perceived exertion (RPE) scale can be used to regulate ERT loads for older adults on the leg press exercise. The purpose of this study was to assess the relationship between the Borg RPE scale and ERT loads relative to the one repetition maximum (%1RM) in older adults during the chest press exercise. Healthy seniors (n = 10 men, mean [SD] age 75.8 [7.9]; n = 10 women, age 73.0 [6.3]) took part in two sessions on non-consecutive days. During the first session, subjects reported their RPE during multiple ERT repetitions on the chest press for seven loads across the spectrum of 'light' to 'heavy', ranging from 20-105% body weight. The loads, concealed from the participants, were presented in randomized order. During the second session, a 1RM strength test was conducted. Each load experienced on the first visit was calculated as %1RM. RPE was averaged across subjects for each 5% range of 1RM from 35% 1RM to 110% 1RM. Regression analysis was used to determine if RPE predicts %1RM during chest press ERT. RPE predicted the %1RM corresponding with chest press ERT loads (R = 97.6%, SEE 3.6, P < 0.001). Loads that would elicit both strength and power gains (70-90 %1RM) corresponded with an RPE of 14-17. As previously demonstrated with the leg press, ERT loads can be regulated for older adults during the chest press using RPE, allowing ERT to be conducted without maximal strength testing. This approach may increase the adoption of this training method for a broader spectrum of seniors.
Primary aging is the progressive and inevitable process of bodily deterioration during adulthood. In skeletal muscle, primary aging causes defective mitochondrial energetics and reduced muscle mass. Secondary aging refers to additional deleterious structural and functional age-related changes caused by diseases and lifestyle factors. Secondary aging can exacerbate deficits in mitochondrial function and muscle mass, concomitant with the development of skeletal muscle insulin resistance. Exercise opposes deleterious effects of secondary aging by preventing the decline in mitochondrial respiration, mitigating aging-related loss of muscle mass and enhancing insulin sensitivity. This review focuses on mechanisms by which exercise promotes "healthy aging" by inducing modifications in skeletal muscle.
Dynapenia (pronounced dahy-nuh-pē-nē-a, Greek translation for poverty of strength, power, or force) is the age-associated loss of muscle strength that is not caused by neurologic or muscular diseases. Dynapenia predisposes older adults to an increased risk for functional limitations and mortality. For the past several decades, the literature has largely focused on muscle size as the primary cause of dynapenia; however, recent findings have clearly demonstrated that muscle size plays a relatively minor role. Conversely, subclinical deficits in the structure and function of the nervous system and/or impairments in the intrinsic force-generating properties of skeletal muscle are potential antecedents to dynapenia. This review highlights in the contributors to dynapenia and the etiology and risk factors that predispose individuals to dynapenia. In addition, we address the role of nutrition in the muscular and neurologic systems for the preservation of muscle strength throughout the life span.
Although loss of muscle mass is considered a cause of diminished muscle strength with aging, little is known regarding whether composition of aging muscle affects strength. The skeletal muscle attenuation coefficient, as determined by computed tomography, is a noninvasive measure of muscle density, and lower values reflect increased muscle lipid content. This investigation examined the hypothesis that lower values for muscle attenuation are associated with lower voluntary isokinetic knee extensor strength at 60 degrees/s in 2,627 men and women aged 70-79 yr participating in baseline studies of the Health ABC Study, a longitudinal study of health, aging, and body composition. Strength was higher in men than in women (132.3 +/- 34.5 vs. 81.4 +/- 22.0 N x m, P < 0.01). Men had greater muscle attenuation values (37.3 +/- 6.5 vs. 34.7 +/- 7.0 Hounsfield units) and muscle cross-sectional area (CSA) at the midthigh than women (132.7 +/- 22.4 vs. 93.3 +/- 17.5 cm(2), P < 0.01 for both). The strength per muscle CSA (specific force) was also higher in men (1.00 +/- 0.21 vs. 0.88 +/- 0.21 N x m x cm(-2)). The attenuation coefficient was significantly lower for hamstrings than for quadriceps (28.7 +/- 8.7 vs. 41.1 +/- 6.9 Hounsfield units, P < 0.01). Midthigh muscle attenuation values were lowest (P < 0.01) in the eldest men and women and were negatively associated with total body fat (r = -0.53, P < 0.01). Higher muscle attenuation values were also associated with greater specific force production (r = 0.26, P < 0.01). Multivariate regression analysis revealed that the attenuation coefficient of muscle was independently associated with muscle strength after adjustment for muscle CSA and midthigh adipose tissue in men and women. These results demonstrate that the attenuation values of muscle on computed tomography in older persons can account for differences in muscle strength not attributed to muscle quantity.
Resistance training (RT) is a proven sarcopenia countermeasure with a high degree of potency. However, sustainability remains a major issue that could limit the appeal of RT as a therapeutic approach without well-defined dosing requirements to maintain gains.
To test the efficacy of two maintenance prescriptions on muscle mass, myofiber size and type distribution, and strength. We hypothesized the minimum dose required to maintain RT-induced adaptations would be greater in the old (60-75 yr) versus young (20-35 yr).
Seventy adults participated in a two-phase exercise trial that consisted of RT 3 d·wk for 16 wk (phase 1) followed by a 32-wk period (phase 2) with random assignment to detraining or one of two maintenance prescriptions (reducing the dose to one-third or one-ninth of that during phase 1).
Phase 1 resulted in expected gains in strength, myofiber size, and muscle mass along with the typical IIx-to-IIa shift in myofiber-type distribution. Both maintenance prescriptions preserved phase 1 muscle hypertrophy in the young but not the old. In fact, the one-third maintenance dose led to additional myofiber hypertrophy in the young. In both age groups, detraining reversed the phase 1 IIx-to-IIa myofiber-type shift, whereas a dose response was evident during maintenance training with the one-third dose better maintaining the shift. Strength gained during phase 1 was largely retained throughout detraining with only a slight reduction at the final time point.
We conclude that older adults require a higher dose of weekly loading than the young to maintain myofiber hypertrophy attained during a progressive RT program, yet gains in specific strength among older adults were well preserved and remained at or above levels of the untrained young.
Sarcopenia is thought to be accompanied by increased muscle fat infiltration. However, no longitudinal studies have examined concomitant changes in muscle mass, strength, or fat infiltration in older adults.
We present longitudinal data on age-related changes in leg composition, strength, and muscle quality (MQ) in ambulatory, well-functioning men and women. We hypothesized that muscle cross-sectional area (CSA) and strength would decrease and muscular fat infiltration would increase over 5 y.
Midthigh muscle, subcutaneous fat (SF), and intermuscular fat (IMF) CSAs and isokinetic leg muscle torque (MT) and MQ (MT/quadriceps CSA) were examined over 5 y in the Health, Aging, and Body Composition study cohort (n = 1678).
Men experienced a 16.1% loss of MT, whereas women experienced a 13.4% loss. Adjusted annualized decreases in MT were 2-5 times greater than the loss of muscle CSA in those who lost weight and in those who remained weight-stable. Weight gain did not prevent the loss of MT, despite a small increase in muscle CSA. Only those who gained weight had an increase in SF (P < 0.001), whereas those who lost weight also lost SF (P < 0.001). There was an age-related increase in IMF in men and women (P < 0.001), and IMF increased in those who lost weight, gained weight, or remained weight-stable (all P < 0.001).
Loss of leg MT in older adults is greater than muscle CSA loss, which suggests a decrease in MQ. Additionally, aging is associated with an increase in IMF regardless of changes in weight or SF.
The purpose of this study was to objectively compare the difficulty and determine the contribution of strength and muscle mass to the performance of physical tasks of daily living in a group of younger and older women. A cross-sectional design was used. Volunteer participants were from the community of Birmingham, AL; there were 21 older (aged 60-75 years) and 20 younger (23-34 years) healthy women in the study. Subjects were matched for height and weight. Their testing included total and regional body composition evaluation by use of dual-energy x-ray absorptiometry, isometric strength tests of elbow flexors and knee extensors, and integrated electromyography (IEMG) evaluation while the subjects were standing from and sitting into a chair, and while they were carrying a small load (weight relative to strength). A two-way analysis of variance and a two-way analysis of covariance with repeated measures, Pearson product correlation, and first-order partial correlations were used to analyze the data. A significant inverse correlation was observed between age and isometric strength of both the knee extensors and elbow flexors. Adjusting for upper leg lean tissue did not change the significant inverse correlation between age and knee extensor strength. However, after an adjustment for arm lean tissue, there was no significant correlation between elbow flexor strength and age. Older women experienced significantly greater difficulty in standing than younger women as measured by quadriceps normalized IEMG (i.e., IEMG during task/IEMG during maximum isometric strength test). This difference persisted even after the covariate upper leg lean tissue was added to the model. No significant difference was observed between younger and older women for difficulty (biceps normalized IEMG) during the carry task after the covariate arm lean tissue was added to the model. The older women in this study had less strength in the knee extensors and experienced greater difficulty standing from a chair than the younger women, even after the covariate upper leg lean tissue was added to the model. This suggests that other factors, in addition to loss of lean tissue, contribute to the age-related decline of muscular strength and the ability to perform tasks with the legs. In contrast, although elbow flexor strength declined, this appeared to be largely due to decreased arm lean tissue mass.
To compare hamstring to quadriceps muscle coactivity during level walking, stair ascent, and stair decent between individuals with and without knee osteoarthritis.
In a cross-sectional study, subjects with grade II knee osteoarthritis (n = 26), healthy age- and gender-matched (n = 20) and healthy, young adults (n = 20) performed three activities of daily living. During the stance phase of these activities surface electromyography was measured. Two coactivity ratios were computed, the biceps femoris to vastus lateralis ratio and the ratio of the biceps femoris EMG activity relative to the EMG activity measured during contraction- and velocity-specific maximal voluntary biceps femoris contraction, i.e., biceps femoris to maximal biceps femoris activity.
Subjects with knee osteoarthritis had significantly higher coactivity than age-matched healthy adults and young adults and healthy adults had more coactivity than young adults regardless the type of coactivity ratio. The biceps femoris to vastus lateralis ratio yielded 25% higher coactivity value than the biceps femoris to maximal biceps femoris ratio (P < 0.0001). The EMG activity of the vastus lateralis relative to maximal vastus lateralis EMG activity was 92% in subjects with knee osteoarthritis, 57% in age-matched controls, and 47% in young adults (P < 0.0001).
Patients with knee osteoarthritis revealed increased hamstring muscle activation while executing activities of daily living. Altered muscle activation at the knee may interfere with normal load distribution in the knee and facilitate disease progression. Therapeutic interventions should focus not only on quadriceps strengthening but also on improving muscle balance at the knee.
The authors used the meta-analytic approach to examine the effects of aerobic exercise on lipids and lipoproteins in adults 50 years of age and older. Twenty-eight outcomes representing 1427 subjects (806 exercise, 621 control) were available for pooling. Random-effects modeling yielded statistically significant improvements of 1.1%, 5.6%, 2.5%, and 7.1%, respectively, for total cholesterol (mean +/- SEM in mg/dL, -3.3+/-1.7; 95% confidence interval [CI], -6.5 to -0.02; p=0.05), high-density lipoprotein cholesterol (2.5+/-1.0; 95% CI, 0.7-4.4; p=0.01), low-density lipoprotein cholesterol (-3.9+/-1.9; 95% CI, -7.7 to -0.08; p=0.05), ratio of total cholesterol to high-density lipoprotein cholesterol (-0.8+/-0.2; 95% CI, -1.2 to -0.4; p<0.001), but not triglycerides (-7.0+/-3.6; 95% CI, -14.0 to 0.1; p=0.06). After conducting sensitivity analyses, only the improvements in high-density lipoprotein cholesterol and the ratio of total cholesterol to high-density lipoprotein cholesterol remained statistically significant (p<0.05 for both). It was concluded that aerobic exercise increases high-density lipoprotein cholesterol and decreases the ratio of total cholesterol to high-density lipoprotein cholesterol in older adults.
We compared the effect of a 10-week resistance training program on peak isometric torque, muscle hypertrophy, voluntary activation and electromyogram signal amplitude (EMG) of the knee extensors between young and elderly women. Nine young women (YW; range 20-30 years) and eight elderly women (EW; 64-78 years) performed three sets of ten repetitions at 75% 1 repetition maximum for the bilateral leg extension and bilateral leg curl 3 days per week for 10 weeks. Peak isometric torque, EMG and voluntary activation were assessed before, during, and after the training period, while knee extensor lean muscle cross-sectional area (LCSA) and lean muscle volume (LMV) were assessed before and after the training period only. Similar increases in peak isometric torque (16% and 18%), LCSA (13% and 12%), LMV (10% and 9%) and EMG (19% and 21%) were observed between YW and EW, respectively, at the completion of training (P<0.05), while the increase in voluntary activation in YW (1.9%) and EW (2.1%) was not significant (P>0.05). These findings provide evidence to indicate that participation in regular resistance exercise can have significant neuromuscular benefits in women independent of age. The lack of change in voluntary activation following resistance training in both age groups despite the increase in EMG may be related to differences between measurements in their ability to detect resistance training-induced changes in motor unit activity. However, it is possible that neural adaptation did not occur and that the increase in EMG was due to peripheral adaptations.
An imbalance in the agonist/antagonist ratio has been identified as a pathologic factor. Using an isokinetic dynamometer, several studies have investigated the loss of quadriceps strength due to fatigue, but few have explored this phenomenon in the hamstrings. This study assessed the decline in strength of the hamstring and quadriceps muscles with fatigue. The goal was to determine whether a divergence in the decline in strength occurs that would affect the hamstring to quadriceps ratio of endurance. Twenty-seven professional soccer players were selected for endurance testing to evaluate fatigue on an isokinetic dynamometer. The decline in hamstring strength was significantly greater than that of the quadriceps after 15 repetitions for the dominant leg and after 40 repetitions for the nondominant leg. This study also revealed a decline in the endurance ratio compared with the maximal strength ratio in the dominant leg after 30 repetitions. In fatigue states, the decline in hamstring strength diverges from that of the quadriceps in both legs. This difference in resistance to fatigue provokes an imbalance that may affect the stabilizing function of the thigh muscles. These results can be considered as indicators of an increased risk of injury during exhausting effort.
Longitudinal changes in body composition in older men and women: role of body weight change and physical activity
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