Role of the nervous system in sarcopenia and muscle atrophy with aging: strength training as a countermeasure

Associations between inflammatory markers, body composition, and physical function: the Copenhagen Sarcopenia Study

BACKGROUND

Chronic low-grade inflammation has been suggested as one of the key elements in the development of sarcopenia, but in contrast to disease-related loss of muscle mass, the role of chronic low-grade inflammation in age-related (primary) sarcopenia is still not clear. The aim of this study was to investigate low-grade inflammation in relation to age and the potential association between inflammatory biomarkers and body composition, muscle strength and physical performance in a healthy Danish cohort.

METHODS

There were 1160 generally healthy men and women (range: 22-93 years) included. Appendicular lean mass (ALM) and visceral fat normalized to height (kg/m² ) was assessed by dual-energy X-ray absorptiometry (iDXA, GE Lunar). Muscle strength and physical performance were evaluated by handgrip strength (HGS), 30 s sit-to-stand performance, and maximal gait speed (GS). Systemic levels of TNF-α, IL-6, IL-1β, IL-4, IL-13, and IFN-γ were measured using multiplex bead-based immunoassays (Bio-Rad). hsCRP was assessed using latex particle-enhanced immunoturbidimetric assays (Roche Diagnostics).

RESULTS

With age, ALM/h² , HGS, sit-to-stand performance and GS decreased, whereas visceral fat/h² increased in both men and women (P < 0.05). Systemic levels of hsCRP, TNF-α, IL-4, and IFN-γ increased with age in men and women (P < 0.05), while IL-1β increased in women only (P < 0.01). Higher levels of hsCRP were associated with lower ALM/h² in elderly (≥65 years) men and women (P < 0.001). Higher levels of hsCRP were associated with lower handgrip strength in elderly women (P < 0.05) whereas higher levels of hsCRP was not associated with lower HGS in elderly men (P = 0.056). Higher levels of hsCRP were associated with lower GS (P < 0.05), whereas IFN-γ was positively associated with GS in elderly women (P < 0.05), but not elderly men. Visceral fat index was positively associated with hsCRP in elderly men and women (P < 0.001). Compared with elderly with normal HGS, elderly men and women with low HGS displayed higher levels of TNF-α and hsCRP (P < 0.05).

CONCLUSIONS

With age, systemic levels of hsCRP, TNF-α, IL-4, and IFN-γ increased, with hsCRP and TNF-α being especially elevated in more physically frail elderly supporting the association between low-grade systemic inflammation and poor physical function. In contrast, only high levels of hsCRP were weakly associated with low muscle mass and positively associated with visceral fat and low physical function, suggesting that chronic low-grade inflammation is not the main driver of age-related loss of muscle mass as previously suggested.

Intrinsic motoneuron excitability is reduced in soleus and tibialis anterior of older adults

Age-related deterioration within both motoneuron and monoaminergic systems should theoretically reduce neuromodulation by weakening motoneuronal persistent inward current (PIC) amplitude. However, this assumption remains untested. Surface electromyographic signals were collected using two 32-channel electrode matrices placed on soleus and tibialis anterior of 25 older adults (70 ± 4 years) and 17 young adults (29 ± 5 years) to investigate motor unit discharge behaviors. Participants performed triangular-shaped plantar and dorsiflexion contractions to 20% of maximum torque at a rise-decline rate of 2%/s of each participant's maximal torque. Pairwise and composite paired-motor unit analyses were adopted to calculate delta frequency (ΔF), which has been used to differentiate between the effects of synaptic excitation and intrinsic motoneuronal properties and is assumed to be proportional to PIC amplitude. Soleus and tibialis anterior motor units in older adults had lower ΔFs calculated with either the pairwise [-0.99 and -1.46 pps; -35.4 and -33.5%, respectively] or composite (-1.18 and -2.28 pps; -32.1 and -45.2%, respectively) methods. Their motor units also had lower peak discharge rates (-2.14 and -2.03 pps; -19.7 and -13.9%, respectively) and recruitment thresholds (-1.50 and -2.06% of maximum, respectively) than young adults. These results demonstrate reduced intrinsic motoneuron excitability during low-force contractions in older adults, likely mediated by decreases in the amplitude of persistent inward currents. Our findings might be explained by deterioration in the motoneuron or monoaminergic systems and could contribute to the decline in motor function during aging; these assumptions should be explicitly tested in future investigations.

The Influence of Motor Unit Number and Muscle Activation on Early Phase Rate of Torque Development in Younger and Older Men

This study examined the influence of muscle activation and motor unit number estimation (MUNE) on early phase voluntary rate of torque development (RTD) in younger (YM) and older (OM) men. Thirty-two YM (n = 17; Age = 22 yrs) and OM (n = 15; Age = 74 yrs) volunteered to participate in this study. Early phase RTD (first 50 ms of a rapid isometric contraction; RTD₅₀) and normalized surface electromyography (first 50 ms of muscle excitation; nEMG₅₀) were recorded from the right quadricep muscle group. MUNE was examined from the right vastus lateralis. Multiple linear regression analyses revealed that nEMG₅₀ had a significant effect on RTD₅₀ independent of age group (p ≤ 0.001). nEMG₅₀ had a significant effect on RTD₅₀ in the OM group (p = 0.037). MUNE had no effect on RTD₅₀ independent of age. Older adults may depend more on muscle activation at contraction onset of early phase RTD compared to younger adults.

Comparison of available equations to estimate sit-to-stand muscle power and their association with gait speed and frailty in older people: Practical applications for the 5-rep sit-to-stand test

OBJECTIVES

This study aimed i) to compare relative sit-to-stand power (STS_rel) values yielded by the different equations reported in the literature; ii) to examine the associations between STS_rel, derived from the equations, and age, sex, frailty and habitual gait speed (HGS); and iii) to compare the ability of the different STS_rel equations to detect frailty and low HGS in older adults.

METHODS

1568 participants (>65 years) were included. STS_rel was calculated according to four validated equations. Frailty was assessed using the Frailty Trait Scale and HGS as the time to complete 3 m. ANOVA tests, regression analyses and receiver operator characteristic curves were used.

RESULTS

There were significant differences among the STS_rel values yielded by all the equations, which were higher in men compared to women and negatively associated with age (r = -0.21 to -0.37). STS_rel was positively and negative associated to HGS and frailty, respectively, in both men (r = 0.29 to 0.36 and r = -0.18 to -0.45) and women (r = 0.23 to 0.45 and r = -0.09 to -0.57) regardless of the equation used. Area under the curve values varied between 0.68 and 0.80 for Alcazar's, 0.67-0.80 for Ruiz-Cárdenas's, 0.51-0.65 for Smith's, and 0.68-0.80 for Takai's equations. Low STS_rel indicated an increased probability of having both low HGS and frailty (OR [95%CI] = 1.6 to 4.5 [1.21 to 5.79]) for all equations with the exception of Smith's equations for frailty in women.

CONCLUSIONS

All the equations presented adequate criterion validity, however, the Alcazar's equation showed the highest level of clinical relevance according to its ability to identify older people with frailty and low HGS.

Skeletal Muscle Adaptations to Exercise Training in Young and Aged Horses

In aged humans, low-intensity exercise increases mitochondrial density, function and oxidative capacity, decreases the prevalence of hybrid fibers, and increases lean muscle mass, but these adaptations have not been studied in aged horses. Effects of age and exercise training on muscle fiber type and size, satellite cell abundance, and mitochondrial volume density (citrate synthase activity; CS), function (cytochrome c oxidase activity; CCO), and integrative (per mg tissue) and intrinsic (per unit CS) oxidative capacities were evaluated in skeletal muscle from aged (n = 9; 22 ± 5 yr) and yearling (n = 8; 9.7 ± 0.7 mo) horses. Muscle was collected from the gluteus medius (GM) and triceps brachii at wk 0, 8, and 12 of exercise training. Data were analyzed using linear models with age, training, muscle, and all interactions as fixed effects. At wk 0, aged horses exhibited a lower percentage of type IIx (p = 0.0006) and greater percentage of hybrid IIa/x fibers (p = 0.002) in the GM, less satellite cells per type II fiber (p = 0.03), lesser integrative and intrinsic (p ≤ 0.04) CCO activities, lesser integrative oxidative phosphorylation capacity with complex I (PCI; p = 0.02) and maximal electron transfer system capacity (ECI+II; p = 0.06), and greater intrinsic PCI, ECI+II, and electron transfer system capacity with complex II (ECII; p ≤ 0.05) than young horses. The percentage of type IIx fibers increased (p < 0.0001) and of type IIa/x fibers decreased (p = 0.001) in the GM, and the number of satellite cells per type II fiber increased (p = 0.0006) in aged horses following exercise training. Conversely, the percentage of type IIa/x fibers increased (p ≤ 0.01) and of type IIx fibers decreased (p ≤ 0.002) in young horses. Integrative maximal oxidative capacity (p ≤ 0.02), ECI+II (p ≤ 0.07), and ECII (p = 0.0003) increased for both age groups from wk 0 to 12. Following exercise training, aged horses had a greater percentage of IIx (p ≤ 0.002) and lesser percentage of IIa/x fibers (p ≤ 0.07), and more satellite cells per type II fiber (p = 0.08) than young horses, but sustained lesser integrative and intrinsic CCO activities (p ≤ 0.04) and greater intrinsic PCI, ECI+II, and ECII (p ≤ 0.05). Exercise improved mitochondrial measures in young and aged horses; however, aged horses showed impaired mitochondrial function and differences in adaptation to exercise training.

Fatigability of the knee extensor muscles during high-load fast and low-load slow resistance exercise in young and older adults

Resistance exercise training is a cornerstone in preventing age-related declines in muscle mass and strength, and fatigability of limb muscle is important to this adaptive response. It is unknown, however, whether fatigability and the underlying mechanisms differ between different resistance exercise protocols in young and older adults. The purpose of this study was to quantify the fatigability of the knee extensors and identify the mechanisms in 20 young (22.2 ± 1.3 yr, 10 women) and 20 older adults (73.8 ± 5.4 yr, 10 women) elicited by a single session of high- and low-load resistance exercise. One leg completed a high-load protocol with contractions performed as fast as possible (HL-fast, ~80% 1 Repetition Max, 1RM), and the contralateral leg a low-load protocol performed with slow contractions (LL-slow, ~30% 1RM, 6 s concentric, 6 s eccentric). Each exercise involved four sets of eight repetitions. Before and immediately following each set, maximal voluntary isometric contractions (MVC) were performed, and voluntary activation and contractile properties quantified using electrical stimulation. The reduction in MVC was greater following the LL-slow (20%) than the HL-fast (12%, P = 0.004), with no age or sex differences. Similarly, the reduction in the amplitude of the involuntary electrically-evoked twitch was greater in the LL-slow (14%) than the HL-fast (7%, P = 0.014) and correlated with the reduction in MVC (r = 0.546, P < 0.001), whereas voluntary activation decreased only for the LL-slow protocol (5%, P < 0.001). Thus, low-load resistance exercise with slow contractions induced greater fatigability within the muscle than a more traditional high-load resistance protocol for both young and older men and women.

Relative sit-to-stand power cut-off points and their association with negatives outcomes in older adults

The purposes of this study were: (i) to evaluate the association of sit-to-stand (STS) power and body composition parameters [body mass index (BMI) and legs skeletal muscle index (SMI)] with age; (ii) to provide cut-off points for low relative STS power (STS_rel), (iii) to provide normative data for well-functioning older adults and (iv) to assess the association of low STS_rel with negative outcomes. Cross-sectional design (1369 older adults). STS power parameters assessed by validated equations, BMI and Legs SMI assessed by dual-energy X-ray absorptiometry were recorded. Sex- and age-adjusted segmented and logistic regression analyses and receiver operator characteristic curves were used. Among men, STS_rel showed a negative association with age up to the age of 85 years (− 1.2 to − 1.4%^year−1; p < 0.05). In women, a negative association with age was observed throughout the old adult life (− 1.2 to − 2.0%^year−1; p < 0.001). Cut-off values for low STS_rel were 2.5 W kg⁻¹ in men and 1.9 W kg⁻¹ in women. Low STS_rel was associated with frailty (OR [95% CI] = 5.6 [3.1, 10.1]) and low habitual gait speed (HGS) (OR [95% CI] = 2.7 [1.8, 3.9]) in men while low STS_rel was associated with frailty (OR [95% CI] = 6.9 [4.5, 10.5]) low HGS (OR [95% CI] = 2.9 [2.0, 4.1]), disability in activities of daily living (OR [95% CI] = 2.1 [1.4, 3.2]), and low quality of life (OR [95%CI] = 1.7 [1.2, 2.4]) in women. STS_rel declined with increasing age in both men and women. Due to the adverse outcomes related to STS_rel, the reported cut-off points can be used as a clinical tool to identify low STS_rel among older adults.

Effects of gravitational and iso-inertial resistance trainings using rating of perceived exertion on lower limbs muscle force and power abilities and metabolic cost of walking in healthy older adults

BACKGROUND

The purpose was to compare the effects of 8-weeks resistance training programs (Flywheel Iso-inertial, FW vs Traditional Gravity-Dependent Resistance Training, GD) performed twice a week at the same rate of perceived exertion (RPE), on muscle force and power capacities and physical performance in healthy older participants.

METHODS

Twenty-four participants were randomly assigned to either FW (male/female: 7/5, age: 67.1±3.8 yr) or GD (male/female: 6/6, age 68.3±3.0 yr) group. Knee extension maximal isometric voluntary contractions (MVC), lower limb maximal explosive power (MEP), six-minute walking distance (6MWT), timed "Up & Go" scores (TUG), metabolic cost of walking (CW) and agonist-antagonist co-contraction time (CCT) during walking were evaluated before and after training.

RESULTS

absolute MEP and MEP normalized for body mass increased only in FW than GD group (+10.8% vs +0.31%, p: 0.056, respectively; +14.8% vs +13.9%, p<0.001, respectively). Both training modalities improved MVC to a similar extent (+11.1% in FW vs +13.4% in GD, p<0.001). Analogously, 6MWT distance increased in FW and GD (+5.2 and +5.5%, p<0.041, respectively). No effects of time and training modality were observed on the other parameters.

CONCLUSIONS

The study suggests that when FW and GD are administered at the same RPE with FW performed at higher movement speed in the concentric phase, both the trainings generate similar improvements in muscle strength but only the former can promote greater muscle power enhancements than GD in healthy older adults.

Comfortable and Maximum Gait Speed in Individuals with Chronic Stroke and Community-Dwelling Controls

BACKGROUND

The relationship between maximum and comfortable gait speed in individuals with mild to moderate disability in the chronic phase of stroke is unknown.

OBJECTIVE

This study examines the relationship between comfortable and maximum gait speed in individuals with chronic stroke and whether the relationship differ from that seen in a community-dwelling elderly population. Further, we investigate the influence of age, gender, time post-stroke and degree of disability on gait speed.

MATERIALS AND METHODS

Gait speed was measured using the 10-meter walk test (10MWT) and the 30-meter walk test (30MWT) in 104 older individuals with chronic stroke and 154 community-dwelling controls, respectively.

RESULTS

We found that the maximum gait speed in individuals with stroke could be estimated by multiplying the comfortable speed by 1.41. This relationship differed significantly from that of the control group, for which the corresponding factor was 1.20. In the stroke group, age, gender and time post-stroke did not affect the relationship, whereas the degree of disability was negatively correlated with maximum speed - but not when included in the multiple analysis. In the community-dwelling population, higher age and female gender had a negative relationship with maximum gait speed. When correcting for those parameters, the coefficient was 1.07.

CONCLUSIONS

The maximum gait speed in the chronic phase of stroke can be estimated by multiplying the individual's comfortable gait speed by 1.41. This estimation is not impacted by age, gender, degree of disability and time since stroke. A similar but weaker relationship can be seen in the community-dwelling controls.

Two-Year Follow-up of a Multimodal Intervention on Functional Capacity and Muscle Power in Frail Patients With Type 2 Diabetes

OBJECTIVES

To analyze the effects of a program composed of resistance training and nutritional interventions on functional capacity, maximal strength, and power output after 2 years of follow-up, including 2 periods of 16 weeks of intervention followed by several weeks of intervention cessation in frail patients with type 2 diabetes.

DESIGN

MIDPOW is a substudy of a multicenter, multimodal intervention composed of resistance training combined with a structured diabetes and nutritional education program in frail and prefrail older people with type 2 diabetes (MID-Frail).

SETTING AND PARTICIPANTS

This study recruited 52 participants (mean age: 79 ± 5.6, 63% women), with type 2 diabetes mellitus, frail or prefrail using Fried's frailty phenotype.

METHODS

Primary outcomes of this substudy were Short Physical Performance Battery (SPPB) and maximal power output at 30% and 80% of 1RM.

RESULTS

Each set of 16 weeks of intervention resulted in significant improvements in SPPB performance by a mean of 36.1% at week 18 (P < .001) and 10.2% at week 68 (P < .05). Maximal power output improvements at 30% and 80% of the 1RM ranged from 45.2% to 57.2% at week 18 (P < .01-.001); and no significant changes were observed after the second period of intervention. After 2 years of follow-up, the SPPB and maximal power values observed remained significantly higher than the baseline.

CONCLUSIONS AND IMPLICATIONS

Resistance training combined with nutritional program improved SPPB, maximal strength, and power output in older frail patients with diabetes. These improvements were maintained above the basal levels after several weeks of intervention cessation during a 2-year follow-up.

Active older dancers have lower C-terminal Agrin fragment concentration, better balance and gait performance than sedentary peers

Motor neuron degeneration, denervation, neuromuscular junction (NMJ) fragmentation and loss of motor units (MUs), play a key-role in the development of sarcopenia. The aim of the present study was to investigate the beneficial effects of regular practice of dancing in physically active elders on concentration of C-terminal Agrin fragment (CAF), a marker of NMJ instability, muscle mass, strength, and physical performance in a group of 16 recreationally active older dancers (AOD; 70.1 ± 3.4 yr) compared to 15 age-matched sedentary peers (OS; 70.9 ± 6.2 yr). Circulating concentration of CAF was measured in serum, while morphology of the vastus lateralis and multifidus muscles was assessed by ultrasound imaging. In addition, the participants underwent two functional performance tests, the Timed Up and Go (TUG) and the 10-meter walk test (10-MWT), a lower and upper limb isometric strength test, a static and a dynamic balance test. Although no statistically significant differences were detected for both muscle morphology and isometric strength, higher CAF concentration (20%, p < 0.01) was found in OS. AOD showed a better performance in TUG (22%, p < 0.001), 10-MWT (17%, p < 0.001) and dynamic balance (25%, p < 0.01) than OS. Notably, CAF concentration correlated with dynamic balance performance (r = 0.3711, p < 0.05). Our results provide evidence that the regular practice of dancing in older age, together with non-structured light aerobic physical activities, is associated to lower CAF concentration and improved walking and balance performance. Our findings also suggest that NMJ instability, as indicated by elevated CAF serum concentration, seems to precede the loss of muscle size and alterations in muscle architecture normally associated with sarcopenia.

Chronic obstructive pulmonary disease does not impair responses to resistance training

BACKGROUND

Subjects with chronic obstructive pulmonary disease (COPD) are prone to accelerated decay of muscle strength and mass with advancing age. This is believed to be driven by disease-inherent systemic pathophysiologies, which are also assumed to drive muscle cells into a state of anabolic resistance, leading to impaired abilities to adapt to resistance exercise training. Currently, this phenomenon remains largely unstudied. In this study, we aimed to investigate the assumed negative effects of COPD for health- and muscle-related responsiveness to resistance training using a healthy control-based translational approach.

METHODS

Subjects with COPD (n = 20, GOLD II-III, FEV1predicted 57 ± 11%, age 69 ± 5) and healthy controls (Healthy, n = 58, FEV1predicted 112 ± 16%, age 67 ± 4) conducted identical whole-body resistance training interventions for 13 weeks, consisting of two weekly supervised training sessions. Leg exercises were performed unilaterally, with one leg conducting high-load training (10RM) and the contralateral leg conducting low-load training (30RM). Measurements included muscle strength (nvariables = 7), endurance performance (nvariables = 6), muscle mass (nvariables = 3), muscle quality, muscle biology (m. vastus lateralis; muscle fiber characteristics, RNA content including transcriptome) and health variables (body composition, blood). For core outcome domains, weighted combined factors were calculated from the range of singular assessments.

RESULTS

COPD displayed well-known pathophysiologies at baseline, including elevated levels of systemic low-grade inflammation ([c-reactive protein]serum), reduced muscle mass and functionality, and muscle biological aberrancies. Despite this, resistance training led to improved lower-limb muscle strength (15 ± 8%), muscle mass (7 ± 5%), muscle quality (8 ± 8%) and lower-limb/whole-body endurance performance (26 ± 12%/8 ± 9%) in COPD, resembling or exceeding responses in Healthy, measured in both relative and numeric change terms. Within the COPD cluster, lower FEV1predicted was associated with larger numeric and relative increases in muscle mass and superior relative improvements in maximal muscle strength. This was accompanied by similar changes in hallmarks of muscle biology such as rRNA-content↑, muscle fiber cross-sectional area↑, type IIX proportions↓, and changes in mRNA transcriptomics. Neither of the core outcome domains were differentially affected by resistance training load.

CONCLUSIONS

COPD showed hitherto largely unrecognized responsiveness to resistance training, rejecting the notion of disease-related impairments and rather advocating such training as a potent measure to relieve pathophysiologies.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT02598830. Registered November 6th 2015, https://clinicaltrials.gov/ct2/show/NCT02598830.

Relationship Between Sarcopenia, Obesity, Osteoporosis, and Cardiometabolic Health Conditions and Physical Activity Levels in Korean Older Adults

This study aimed to analyze the status of sarcopenia, obesity, osteoporosis, and cardiometabolic disease according to the level of physical activity (PA) among elderly people in Korea. Among the data obtained from the National Health and Nutrition Survey (2008–2011), we analyzed the data of a total of 3,573 Korean elderly people over 65 years of age who were surveyed for dual X-ray absorptiometry (DXA) and PA. Higher levels of PA were associated with a lower prevalence of cardiometabolic disease (χ² = 33.865, p < 0.001), osteoporosis (χ² = 94.198, p < 0.001), sarcopenia, obesity, and sarcopenic obesity (χ² = 71.828, p < 0.001). Above moderate-active PA was associated with lower body weight (p < 0.001), body fat mass (p < 0.001), and percent body fat (p < 0.001), and higher free-fat mass (p < 0.001) and appendicular skeletal muscle mass (ASM) (p < 0.001) than in low-active PA. In addition, when high-active is the risk factors of cardiometabolic were lower in waist circumference (p = 0.001), total cholesterol (TC) (p = 0.015), and triglyceride (TG) (p < 0.001) than low- and moderate-active PA, and higher in high-density lipoprotein cholesterol (HDL-C) (p < 0.001). The prevalence of cardiometabolic diseases was significantly decreased in high-active PA (odds ratio (OR) 0.60, 95% confidence interval (CI) 0.50–0.71); waist circumference (OR 0.85, 95% CI, 0.73–0.99; OR 0.59, 95% CI, 0.50–0.70) and HDL-C (OR 0.76, 95% CI, 0.65–0.88; OR 0.56, 95% CI, 0.47–0.67) significantly improved in moderate- and high-active PA, respectively, and TG (0.67 95% CI, 0.55–0.80) significantly improved in high-active PA. Osteoporosis (OR 0.62, 95% CI, 0.53–0.74; OR 0.46, 95% CI, 0.38–0.55) and sarcopenia (OR 0.77, 95% CI, 0.60–0.98; OR 0.73, 95% CI, 0.57–0.93) were significantly improved in moderate- and high-active PA, respectively. The incidence of obesity (OR 0.47, 95% CI, 0.39–0.57) and sarcopenic obesity (OR 0.47, 95% CI, 0.30–0.75) were significantly decreased in high-active PA. Therefore, we verified a lower prevalence of sarcopenia, osteoporosis, obesity, and cardiac metabolic disease in Korean elderly with more active PA. This suggests that more active PA maybe reduce the prevalence of sarcopenia, osteoporosis, obesity, and cardiometabolic diseases in older adults.

Cut-off Values for Lower Limb Muscle Thickness to Detect Low Muscle Mass for Sarcopenia in Older Adults

Purpose

Ultrasound-based prediction methods for the detection of low muscle mass for sarcopenia in older adults have been explored previously; however, the muscle that most accurately predicts it is unclear. This study aimed to clarify prediction accuracy and cut-off values for ultrasound-derived thigh and lower leg muscle thickness (MT) to detect low skeletal muscle mass index (SMI) in older adults and to estimate cut-off values based on two standard deviations (SD) below younger adult means for the corresponding muscles as an early detection tool for site-specific low muscle mass.

Methods

This study included 204 community-dwelling older (64 males, 140 females, mean age: 75.4 years) and 59 younger (31 males, 28 females, mean age: 22.3 years) adults. The MT of the rectus femoris, vastus intermedius, gastrocnemius, and soleus muscles was measured using ultrasound; SMI was measured using bioelectrical impedance analysis.

Results

The prevalence of a low SMI among older adults was 20.3% (n=13) for males and 21.4% (n=30) for females. The receiver operating characteristic analysis revealed that the total MT for the four muscles measured presented the highest area under the curve (AUC) value to predict low SMI for males (0.849) and females (0.776). The AUC value was the highest for the total MT of the gastrocnemius and soleus muscles for males and the gastrocnemius for females (0.836, 0.748; cut-off value: 5.67 cm, 1.42 cm, respectively). Muscle-specific differences between the low SMI-predicting and SD-based cut-off values were observed. The SD-based value for the rectus femoris (1.85 cm) was substantially higher than the low SMI-predicting value (1.51 cm) in males.

Conclusion

Ultrasound measurement of lower leg muscles may be a simple, robust measure to detect low muscle mass for sarcopenia. Additionally, cut-off values for site-specific muscle mass loss may not always agree with those for whole-limb muscle mass loss.

Muscle-nerve communication and the molecular assessment of human skeletal muscle denervation with aging

Muscle fiber denervation is a major contributor to the decline in physical function observed with aging. Denervation can occur through breakdown of the neuromuscular junctions (NMJ) itself, affecting only that particular fiber, or through the death of a motor neuron, which can lead to a loss of all the muscle fibers in that motor unit. In this review, we discuss the muscle-nerve relationship, where signaling from both the motor neuron and the muscle fiber is required for maximal preservation of neuromuscular function in old age. Physical activity is likely to be the most important single factor that can contribute to this preservation. Furthermore, we propose that inactivity is not an innocent bystander, but plays an active role in denervation through the production of signals hostile to neuron survival. Investigating denervation in human muscle tissue samples is challenging due to the shared protein profile of regenerating and denervated muscle fibers. In this review, we provide a detailed overview of the key traits observed in immunohistochemical preparations of muscle biopsies from healthy, young, and elderly individuals. Overall, a combination of assessing tissue samples, circulating biomarkers, and electrophysiological assessments in humans will prove fruitful in the quest to gain more understanding of denervation of skeletal muscle. In addition, cell culture models represent a valuable tool in the search for key signaling factors exchanged between muscle and nerve, and which exercise has the capacity to alter.

Resistance Training With Partial Blood Flow Restriction in a 99-Year-Old Individual: A Case Report

In aging populations for which the use of high loads is contraindicated, low load resistance training associated with blood flow restriction (RT-BFR) is an alternative strategy to induce muscle mass gains. This study investigates the effects of RT-BFR on muscle mass, muscle function, and quality of life of a 99-year-old patient with knee osteoarthritis and advanced muscle mass deterioration. Training protocol consisted of 24 sessions of a unilateral free-weight knee extension exercise associated with partial blood flow restriction through a manometer cuff set at 50% of complete vascular occlusion pressure. We evaluated: cross-sectional area (CSA) and thickness (MT) of the vastus lateralis muscle by ultrasound; function through the Timed Up and Go (TUG) test; and quality of life (QoL) by the WHOQOL-bref, WHOQOL-OLD and WOMAC questionnaires. All tests were performed prior to the training period (Pre) and after the 12th (Mid) and 24th (Post) sessions. Changes were considered significant if higher than 2 times the measurement's coefficient of variation (CV). After 24 sessions, there was an increase of 12% in CSA and 8% in MT. Questionnaires scores and TUG values worsened from Pre to Mid and returned in Post. We consider RT-BFR a viable and effective strategy to promote muscle mass gains in nonagenarians and delay the decline in functionality and QoL associated with aging.

Effects of 12 weeks of resistance training on rat gut microbiota composition

In addition to its health benefits, exercise training has been noted as a modulator of the gut microbiota. However, the effects of resistance training (RT) on gut microbiota composition remain unknown. Wistar rats underwent 12 weeks of RT. Body mass, glucose tolerance, visceral body fat, triglyceride concentration and food consumption were evaluated. The gut microbiota was analyzed by 16S rRNA gene sequencing. Rats that underwent RT showed lower body mass (P=0.0005), lower fat content (P=0.02) and better glucose kinetics (P=0.047) when compared with the control. Improvements in the diversity and composition of the gut microbiota were identified in the RT group. The relative abundance of Pseudomonas, Serratia and Comamonas decreased significantly after 12 weeks of RT (P<0.001). These results suggest that RT has the potential to enhance the diversity of the gut microbiota and improve its biological functions.

Improper Remodeling of Organelles Deputed to Ca2+ Handling and Aerobic ATP Production Underlies Muscle Dysfunction in Ageing

Proper skeletal muscle function is controlled by intracellular Ca2+ concentration and by efficient production of energy (ATP), which, in turn, depend on: (a) the release and re-uptake of Ca2+ from sarcoplasmic-reticulum (SR) during excitation-contraction (EC) coupling, which controls the contraction and relaxation of sarcomeres; (b) the uptake of Ca2+ into the mitochondrial matrix, which stimulates aerobic ATP production; and finally (c) the entry of Ca2+ from the extracellular space via store-operated Ca2+ entry (SOCE), a mechanism that is important to limit/delay muscle fatigue. Abnormalities in Ca2+ handling underlie many physio-pathological conditions, including dysfunction in ageing. The specific focus of this review is to discuss the importance of the proper architecture of organelles and membrane systems involved in the mechanisms introduced above for the correct skeletal muscle function. We reviewed the existing literature about EC coupling, mitochondrial Ca2+ uptake, SOCE and about the structural membranes and organelles deputed to those functions and finally, we summarized the data collected in different, but complementary, projects studying changes caused by denervation and ageing to the structure and positioning of those organelles: a. denervation of muscle fibers-an event that contributes, to some degree, to muscle loss in ageing (known as sarcopenia)-causes misplacement and damage: (i) of membrane structures involved in EC coupling (calcium release units, CRUs) and (ii) of the mitochondrial network; b. sedentary ageing causes partial disarray/damage of CRUs and of calcium entry units (CEUs, structures involved in SOCE) and loss/misplacement of mitochondria; c. functional electrical stimulation (FES) and regular exercise promote the rescue/maintenance of the proper architecture of CRUs, CEUs, and of mitochondria in both denervation and ageing. All these structural changes were accompanied by related functional changes, i.e., loss/decay in function caused by denervation and ageing, and improved function following FES or exercise. These data suggest that the integrity and proper disposition of intracellular organelles deputed to Ca2+ handling and aerobic generation of ATP is challenged by inactivity (or reduced activity); modifications in the architecture of these intracellular membrane systems may contribute to muscle dysfunction in ageing and sarcopenia.

Neuromuscular junction instability and altered intracellular calcium handling as early determinants of force loss during unloading in humans

Key points

Few days of unloading are sufficient to induce a decline of skeletal muscle mass and function; notably, contractile force is lost at a faster rate than muscle mass.

The reasons behind this disproportionate loss of muscle force are still poorly understood.

We provide strong evidence of two mechanisms only hypothesized until now for the rapid muscle force loss in only 10 days of bed rest.

Our results show that an initial neuromuscular junction instability, accompanied by alterations in the innervation status and impairment of single fibre sarcoplasmic reticulum function contribute to the loss of contractile force in front of a preserved myofibrillar function and central activation capacity.

Early onset of neuromuscular junction instability and impairment in calcium dynamics involved in excitation–contraction coupling are proposed as eligible determinants to the greater decline in muscle force than in muscle size during unloading.

Abstract

Unloading induces rapid skeletal muscle atrophy and functional decline. Importantly, force is lost at a much higher rate than muscle mass. We aimed to investigate the early determinants of the disproportionate loss of force compared to that of muscle mass in response to unloading. Ten young participants underwent 10 days of bed rest (BR). At baseline (BR0) and at 10 days (BR10), quadriceps femoris (QF) volume (VOL) and isometric maximum voluntary contraction (MVC) were assessed. At BR0 and BR10 blood samples and biopsies of vastus lateralis (VL) muscle were collected. Neuromuscular junction (NMJ) stability and myofibre innervation status were assessed, together with single fibre mechanical properties and sarcoplasmic reticulum (SR) calcium handling. From BR0 to BR10, QFVOL and MVC decreased by 5.2% (P = 0.003) and 14.3% (P < 0.001), respectively. Initial and partial denervation was detected from increased neural cell adhesion molecule (NCAM)‐positive myofibres at BR10 compared with BR0 (+3.4%, P = 0.016). NMJ instability was further inferred from increased C‐terminal agrin fragment concentration in serum (+19.2% at BR10, P = 0.031). Fast fibre cross‐sectional area (CSA) showed a trend to decrease by 15% (P = 0.055) at BR10, while single fibre maximal tension (force/CSA) was unchanged. However, at BR10 SR Ca²⁺ release in response to caffeine decreased by 35.1% (P < 0.002) and 30.2% (P < 0.001) in fast and slow fibres, respectively, pointing to an impaired excitation–contraction coupling. These findings support the view that the early onset of NMJ instability and impairment in SR function are eligible mechanisms contributing to the greater decline in muscle force than in muscle size during unloading.

Few days of unloading are sufficient to induce a decline of skeletal muscle mass and function; notably, contractile force is lost at a faster rate than muscle mass.

The reasons behind this disproportionate loss of muscle force are still poorly understood.

We provide strong evidence of two mechanisms only hypothesized until now for the rapid muscle force loss in only 10 days of bed rest.

Our results show that an initial neuromuscular junction instability, accompanied by alterations in the innervation status and impairment of single fibre sarcoplasmic reticulum function contribute to the loss of contractile force in front of a preserved myofibrillar function and central activation capacity.

Early onset of neuromuscular junction instability and impairment in calcium dynamics involved in excitation–contraction coupling are proposed as eligible determinants to the greater decline in muscle force than in muscle size during unloading.

Load-velocity relationship in the horizontal leg-press exercise in older women and men

This study analyzed the predictive ability of movement velocity to estimate the relative load (i.e., % of one-repetition maximum [1RM]) during the horizontal leg-press exercise in older women and men. Twenty-four women and fourteen men living in community-dwelling centers volunteered to participate in this study. All participants performed a progressive loading test up to 1RM in the horizontal leg-press. The fastest peak velocity (PV) and mean velocity (MV) attained with each weight were collected for analysis. Linear regression equations were modeled for women and men. We observed very strong linear relationships between both velocity variables and the relative load in the horizontal leg-press in women (PV: r² = 0.93 and standard error of the estimate (SEE) = 5.96% 1RM; MV: r² = 0.94 and SEE = 5.59% 1RM) and men (PV: r² = 0.93 and SEE = 5.96% 1RM; MV: r² = 0.94 and SEE = 5.97% 1RM). The actual 1RM and the estimated 1RM using both the PV and MV presented trivial differences and very strong relationships (r = 0.98-0.99) in both sexes. Men presented significantly higher (p < 0.001-0.05) estimated PV and MV against all relative loads compared to women (average PV = 0.81 vs. 0.69 m·s^-1 and average MV = 0.44 vs. 0.38 m·s^-1). Our data suggest that movement velocity accurately estimates the relative load during the horizontal leg-press in older women and men. Coaches and researchers can use the proposed sex-specific regression equations in the horizontal leg-press to implement velocity-monitored resistance training with older adults.

The Influence of Specific Bioactive Collagen Peptides on Body Composition and Muscle Strength in Middle-Aged, Untrained Men: A Randomized Controlled Trial

It has been shown that specific collagen peptides combined with resistance training (RT) improves body composition and muscle strength in elderly sarcopenic men. The main purpose of this RCT study was to investigate the efficacy of the identical specific collagen peptides combined with RT on body composition and muscle strength in middle-aged, untrained men. Furthermore, in the exploratory part of the study, these results were compared with another group that had received whey protein in addition to the RT. Ninety-seven men completed this study and participated in a 12-week RT program. They ingested 15 g of specific collagen peptides (n = 30; CP-G), placebo (n = 31; P-G), or whey protein (n = 36; WP-G) daily. Changes in fat free mass and fat mass were determined by dual-energy X-ray absorptiometry (DXA), and isometric leg strength was measured. All participants had significantly (p < 0.01) improved levels in fat free mass (ΔCP-G = 3.42 ± 2.54 kg; ΔP-G = 1.83 ± 2.09 kg; ΔWP-G = 2.27 ± 2.56 kg), fat mass (ΔCP-G = -5.28 ± 3.19 kg; ΔP-G = -3.39 ± 3.13 kg; ΔWP-G = -4.08 ± 2.80 kg) and leg strength (ΔCP-G = 163 ± 189 N; ΔP-G = 100 ± 154 N; ΔWP-G = 120 ± 233 N). The main analysis revealed a statistically significantly higher increase in fat free mass (p = 0.010) and decrease in fat mass (p = 0.023) in the CP-G compared with the P-G. The exploratory analysis showed no statistically significant differences between WP-G and CP-G or P-G, regarding changes of fat free mass and fat mass. In conclusion, specific collagen peptide supplementation combined with RT was associated with a significantly greater increase in fat free mass and a decrease in fat mass compared with placebo. RT combined with whey protein also had a positive impact on body composition, but the respective effects were more pronounced following the specific collagen peptide administration.

Heavy resistance training in the management of hip pain in older adults: A case series

Background and Purpose: Resistance training has been shown to improve strength, endurance, and function in healthy older adults. The purpose of this case series was to describe the outcomes of a rehabilitation program consisting of heavy resistance training in older adults for management of hip pain. Case Description: Two male patients, aged 69 and 71, with chronic hip pain, participated in a six-week progressive resistance training rehabilitation program at loads equivalent to 76-81% of their one repetition maximum. Outcomes were assessed at evaluation, three, and six weeks. Outcomes included the Lower Extremity Functional Scale, hip and lumbar mobility, and the Five Times Sit to Stand test. Outcomes: By six weeks, each patient reported 0/10 pain and demonstrated clinically important improvements on the LEFS. Both patients' final scores on the Five Times Sit to Stand test fell below the 15 second value for being at risk for falls. Patient One increased his lifting capacity for the deadlift by 92%, and Patient Two by 56%. Both patients were able to deadlift >70% of their one repetition maximum by the conclusion of this report. Discussion: To our knowledge, this is the first report of the outcomes of utilizing heavy resistance training in elderly adults with hip pain in a rehabilitative setting. Both patients demonstrated clinically important improvements in pain, disability, global lower extremity strength, and function by the conclusion of six weeks duration. Further research is needed regarding the effectiveness of heavy resistance training for the treatment of elderly adults with musculoskeletal pain.

Down stair walking: A simple method to increase muscle mass and performance in 65+ year healthy people

Exercise is important for prevention of sarcopenia in the elderly population. We tested two training modalities, ascending or descending stair walking, representing concentric (CON) and eccentric (ECC) exercise, respectively. We also tested the effects of additional weight during eccentric exercise (ECC+). Thirty-two healthy men and women (70 ± 3 [mean ± SE] yrs.) were randomly assigned to CON, ECC, or ECC+ (carrying +15% of body weight in a vest) in a 3 (n = 32) or 6 (n = 21) week intervention (3 sessions/week). Data was analysed by mixed models approach. Rate of perceived exertion (RPE; Borg scale 6-20; mean values from 3 and 6 weeks) during training did not differ between CON (12.3 ± 0.4), ECC (11.5 ± 0.3), and ECC+ (11.7 ± 0.4). After 6 weeks, leg muscle mass increased more in ECC+ (+0.29 ± 0.09 kg) vs CON (+0.08 ± 0.05 kg) (P<0.05) but not different from ECC (+0.16 ± 0.06 kg). 6-minute walk test (6MWT) increased after 6 weeks more (P<0.05) in ECC+ (+85 ± 23 m) compared with ECC (+37 ± 13 m) and CON (+27 ± 12 m). Intramyocellular glycogen content increased from 359 ± 19 nmol/mg d.w. in CON (to 511 ± 65 and 471 ± 44 after 3 and 6 wks, respectfully (P<0.05)), but not in ECC (to 344 ± 28 after 6 weeks) or in ECC+ (to 389 ± 20 after 6 weeks). Conclusion: carrying extra weight while descending stair walking do not increase RPE, but the ECC+ training resulted in greater muscle responses compared with CON, but glycogen synthesis was stimulated only in CON. Descending stairs is a simple model for prevention and treatment of sarcopenia and the stimulus is enhanced by carrying extra weights.

Effects of Power Training on Physical Activity, Sitting Time, Disability, and Quality of Life in Older Patients With Type 2 Diabetes During the COVID-19 Confinement

BACKGROUND

To evaluate the effectiveness of a multicomponent supervised and unsupervised training program focused on muscle power to counteract the potential changes in sedentary behavior, disability, physical activity (PA), and health-related quality of life (HRQoL) caused by the COVID-19 pandemic domiciliary confinement in prefrail older adults with type 2 diabetes mellitus.

METHODS

Thirty-five older adults with type 2 diabetes mellitus were assigned to 2 groups according to their frailty status: exercise training group (prefrail or frail; n = 21; 74.7 [4.5] y; 33.3% male) and control group (robust; n = 14; 73.1 [3.9] y; 42.9% male). The exercise training group followed a multicomponent training program focusing on muscle power: supervised (5 wk) and unsupervised (6 wk). The primary outcomes, including PA and sitting time, perceived disability, and HRQoL, were assessed at the baseline and after 11 weeks.

RESULTS

At the end of confinement, there were significant decreases in PA in both groups (P < .05). Thus, sitting time increased more in the control group than in the exercise training group (P < .05). The HRQoL measures remained unchanged.

CONCLUSIONS

Muscle power training before and during mandatory COVID-19 self-isolation in type 2 diabetes mellitus older adults (1) attenuates the COVID-19 domiciliary confinement-related increase in sitting time and (2) slightly decreases the self-reported levels of disability and maintains HRQoL.

Effects of Resistance Training With Machines and Elastic Tubes on Functional Capacity and Muscle Strength in Community-Living Older Women: A Randomized Clinical Trial

The aim of the present study is to compare the effects of 12 weeks of resistance training with machines and elastic tubes on functional capacity and muscular strength in older women aged 60 years or over. The participants were randomized into two groups: a machine group (n = 23) and an elastic group (n = 20). They performed 12 weeks of progressive resistance training, twice a week, with similar exercises. Outcomes were assessed at three time points: baseline, postintervention, and 8 weeks after the end of the training. A significant intragroup effect was demonstrated for both groups at postintervention on functional tests and muscle strength. For the functional reach test and elbow flexion strength (180°/s), only the machine group demonstrated significant intragroup differences. No differences were observed between groups for any outcome. At the 8-week follow-up, functional capacity outcome values were maintained. The muscle strength outcome values decreased to baseline scores, without differences between groups.

The Effect of Resistance Training in Women on Dynamic Strength and Muscular Hypertrophy: A Systematic Review with Meta-analysis

BACKGROUND

The effect of resistance training (RT) on adaptations in muscular strength and hypertrophy has never been examined in an exclusively female synthesis of the literature.

OBJECTIVE

The objectives of this study were threefold: (1) to systematically review the literature on female adaptations to RT, characterising the effect in terms of muscular strength and hypertrophy; (2) to distinguish the individual effects of intervention duration, frequency, and intensity on these adaptations via sub-analysis; (3) to draw evidence-based conclusions regarding training expectations in female populations.

METHODS

Three electronic databases were searched using terms related to RT combined with females or women. Random-effects meta-analyses were undertaken to estimate the effect of RT on muscular strength and hypertrophy in females. Possible predictors that may have influenced training-related effects (e.g., training intensity and volume) were explored using univariate analyses.

RESULTS

The systematic search identified 14,067 articles of which a total of 24 studies met the inclusion criteria and were eligible. Upper body strength was assessed in 15 studies, lower body strength in 19 studies, and muscular hypertrophy in 15 studies. Study duration lasted between 4 weeks and 12 months. Large-effect sizes were found for upper body strength (Hedges' g = 1.70; p < 0.001) and lower body strength (Hedges' g = 1.40; p < 0.001). Following use of the Trim and Fill method (due to presence of publication bias), a large effect still remained for upper body strength (Hedges' g = 1.07), although a medium effect was found for lower body strength (Hedges' g = 0.52). A medium effect was found for muscular hypertrophy (g = 0.52, p = 0.002). Sub-analyses revealed that the moderating variables "training frequency" and "training volume" significantly influenced lower body muscular strength (p < 0.001). "Training frequency" and "sets per exercise" moderated the RT effects on upper body strength (p < 0.01). No moderating variables were found to significantly influence muscular hypertrophy. A trend for a moderating effect on upper body strength was found for "age of participants" (p = 0.08), whereby younger participants experienced a greater effect. A moderating effect was also observed where supervised training had a larger influence on the adaptation of lower body strength (p = 0.05) compared with unsupervised training. Methodological quality for the studies included in the review was found to be moderate.

CONCLUSIONS

RT elicits large improvements in muscular strength and hypertrophy in healthy adult females. Training volume and frequency appear to be important variables that influence muscular strength.

Middle-age people with multiple sclerosis demonstrate similar mobility characteristics to neurotypical older adults

BACKGROUND

Clinical trials often report significant mobility differences between neurotypical and atypical groups, however, these analyses often do not determine which measures are capable of discriminating between groups. Additionally, indirect evidence supports the notion that some mobility impaired populations demonstrate similar mobility deficits. Thus, the current study aimed to provide a comprehensive analysis of three distinct aspects of mobility (walking, turning, and balance) to determine which variables were significantly different and were also able to discriminate between neurotypical older adults (OA) and middle-aged people with multiple sclerosis (PwMS), and between middle-aged neurotypical adults and PwMS.

METHODS

This study recruited 21 neurotypical OA, 19 middle-aged neurotypical adults, and 30 people with relapsing remitting MS. Participants came into the laboratory on two separate occasions to complete mobility testing while wearing wireless inertial sensors. Testing included a self-selected pace two-minute walk, a series of 180˚ and 360˚ turns, and a clinical balance test capturing a total of 99 distinct mobility characteristics. We determined significant differences for gait and turning measures through univariate analyses and a series of repeated measures analysis of variance in determining significance for balance conditions and measures. In determining discrimination between groups, the Area Under the Curve (AUC) was calculated for all individual mobility measures with a threshold of 0.80, denoting excellent discrimination. Additionally, a stepwise regression of the top five AUC producing variables was performed to determine whether a combination of variables could enhance discrimination while accounting for multicollinearity.

RESULTS

The results between neurotypical OA and middle-aged PwMS demonstrated significant differences for three gait and one turning variable, with no variable or combination of variables able to provide excellent discrimination between groups. Between middle-age neurotypical adults and PwMS a variety of mean and variability gait measures demonstrated significant differences between groups; however, no variable or combination of variables met discriminatory threshold. For turning, five 360˚ turn variables demonstrated significant differences and furthermore, the combination of 360˚ mean turn duration and variability of peak turn velocity were able to discriminate between groups. Finally, the majority of postural sway measures demonstrated significant group differences and the ability to discriminate between groups, particularly during more challenging balance conditions where participants stood on a compliant surface.

CONCLUSION

These results offer a comprehensive analysis of mobility differences and measures capable of discriminating between middle-age neurotypical adults and PwMS. Additionally, these results provide evidence that OA and middle-age PwMS display similar movement characteristics and thus a potential indicator of advanced aging from a mobility perspective.

The effects of ageing on functional capacity and stretch-shortening cycle muscle power

[Purpose] To examine the effects of age and gender in an ageing population with respect to functional decline and the relationship between muscle power and functional capacity. [Participants and Methods] The cohort (N=154) was subdivided into youngest-old (65–70 years.; n=62), middle-old (71–75 years.; n=46), and oldest-old (76–81 years.; n=46). Measures of mechanical muscle function included countermovement jump height, muscle power, leg strength and grip strength. Functional performance-based measures included heel-rise, postural balance, Timed Up and Go, and gait speed. [Results] The oldest-old performed significantly worse than the middle-old, whereas the youngest-old did not outperform the middle-old to the same extent. Increased contribution of muscle power was observed with increasing age. Males had consistently higher scores in measures of mechanical muscle function, whereas no gender differences were observed for functional capacity. [Conclusion] The age-related decline in functional capacity appears to accelerate when approaching 80 years of age and lower limb muscle power seems to contribute to a greater extent to the preservation of functional balance and gait capacity at that stage. Males outperform females in measures of mechanical muscle function independent of age, while the findings give no support for the existence of gender differences in functional capacity.

The Benefits of Strength Training on Musculoskeletal System Health: Practical Applications for Interdisciplinary Care

Global health organizations have provided recommendations regarding exercise for the general population. Strength training has been included in several position statements due to its multi-systemic benefits. In this narrative review, we examine the available literature, first explaining how specific mechanical loading is converted into positive cellular responses. Secondly, benefits related to specific musculoskeletal tissues are discussed, with practical applications and training programmes clearly outlined for both common musculoskeletal disorders and primary prevention strategies.

Orthostatic hypotension and age-related sarcopenia

Objectives

This study aims to determine the association of sarcopenia with orthostatic hypotension (OH) which is a significant precursor to falls and related injuries in elderly patients.

Patients and methods

A total of 91 outpatients (18 males, 73 females; mean age 79.3±4.0 years; range, 75 to 91 years) were prospectively enrolled and those who were eligible underwent comprehensive sarcopenia assessment including measurement of muscle mass, strength, physical performance, anthropometric measurements along with frailty tests. Patients classified as sarcopenic or non-sarcopenic based on these measurements underwent supine and standing blood pressure (BP) measurements. The frequency of OH was compared between the two groups.

Results

Of the 91 patients, 29 (31.9%) had sarcopenia. There was no statistical difference in measurements of functional tests which consisted of gait speed, timed up-and-go test and handgrip strength. However, timed sit-to-stand test values were higher in sarcopenic patients (18.2±7.9 vs. 15.0±5.1, p=0.04). Patients with sarcopenia developed OA and intolerance more often compared to the non-sarcopenic patients (n=15 [50.0%] vs. n=14 [23.0%], p<0.01 and n=13 [44.8%] vs. n=9 [15.3%], p<0.01, respectively). The adjusted odds ratio for sarcopenia was 7.80 (95% confidence interval 1.77-34.45), p=0.007.

Conclusion

Age-related sarcopenia increases the risk of OA in the elderly. This may in part explain the increased incidence of falls and also help identification of risky elderly patients for orthostatic BP drops.

Effects of Chair-Based, Low-Load Elastic Band Resistance Training on Functional Fitness and Metabolic Biomarkers in Older Women

Strength training can improve myriad health parameters in elderly cohorts. Although potentially more appropriate for the elderly, low-load resistance training protocols have been less investigated. We aimed to examine the effects of 12 weeks of chair-based, low-load resistance training with elastic band (EBT) on functional fitness and metabolic biomarkers in older women. One hundred sixty-eight women were allocated randomly to an elastic band resistance training (EBT, n = 86, 75.7 ± 8.9 years, 71.3 ± 12.2 kg) or a control group (CON, n = 82, 74.5 ± 8.2years, 70.6 ± 12.0 kg). RT protocol consisted of periodized chair-based, low-load whole-body resistance exercises (2 sets, 12-15 repetitions, 40-60% of one repetition maximum-1RM) using an elastic band, twice weekly for 12 weeks. The resistance training program was generally designed to maintain internal load over time, provided with increasing intensity using various elastic bands (Thera-Band). Functional fitness (30-s Chair Stand,30-s Arm Curl, 2-min Step Test, Chair Sit-and-Reach, Back Scratch, 8-Foot Up-and-Go, Handgrip Strength) and metabolic markers (Fasting blood glucose, triglycerides, total cholesterol, high (HDL) and low (LDL) density lipoprotein) were measured before and after the training period. To detect pre/post intervention changes and between group- differences 2x2 repeated measures ANOVA was applied. Significant improvements over time for all fitness variables for EBT comparing to CON were obtained (F = 12.78, p < 0.05 for 30-s Chair Stand; F = 14.04, p < 0.05 for 30-s Arm Curl; F = 5.18, p < 0.05 for 2-min Step Test; F = 10.90, p < 0.05 for Chair Sit-and-Reach; F = 16.57, p < 0.05 for Back Scratch; F = 11.79, p < 0.05 for 8-foot Up-and-Go; and F = 29.25, p < 0.05 for Handgrip Strength). In addition, significant improvements over time for all but one (triglycerides) biomarkers for EBT comparing to CON were obtained (F = 7.30, p < 0.05 for blood sugar levels; F = 13.36, p < 0.05 for total cholesterol; F = 8.61, p < 0.05 for HDL; and F = 11.53, p < 0.05 for LDL). Furthermore, the participants' adherence to training sessions of over 90% was reported. In conclusion, 12 weeks of EBT is safe and beneficial for improving health-related fitness and metabolic biomarkers in older women and seems to be viable model to ensure a high training adherence rate.

Skeletal Muscle Adaptations Following 80 Weeks of Resistance Exercise in Older Adults

BACKGROUND AND PURPOSE

We followed and documented skeletal muscle adaptations from 4 resistance exercise (RE) prescriptions in older adults over the course of a 2-year, 80-week training study.

METHODS

Forty-three older men and women-65.2 (3.5) years, 167.2 (7.5) cm, and 72.5 (14.7) kg-completed one of the following RE prescriptions: high-load 2 days per week (HL2D; n = 12), low-load 2 days per week (LL2D; n = 9), high-load 3 days per week (HL3D, n = 12), or low-load 3 days per week (LL3D, n = 10). High-load prescriptions consisted of 3 sets of 8 repetitions with 80% 1-repetition maximum (1-RM) and low-load prescriptions completed 3 sets of 16 repetitions with 40% 1-RM. Each session consisted of 12 exercises targeting major muscle groups and training loads were adjusted every fifth week to maintain progressive overload. Participants completed 40 weeks of supervised training, had a 2-month break, and then resumed another 40 weeks of supervised training. Bone-free lean body mass (BFLBM) and appendicular lean mass (ALM) were assessed via dual-energy x-ray absorptiometry and muscle cross-sectional area (mCSA) of the rectus femoris with diagnostic ultrasound across the intervention.

RESULTS AND DISCUSSION

Groups responded similarly with significant increases in total strength (54.9%), upper body strength (42.7%), lower body strength (61.5%), and specific strength (50.3%, strength/BFLBM) over 80 weeks (all P < .001). Significant increases for BFLBM (3.0%), ALM (3.5%), and mCSA (48.7%) were also observed (all P ≤ .019). The only difference among groups indicated HL3D displaying significantly greater percent increase than LL2D for ALM (P = .043).

CONCLUSIONS

Resistance exercise performed 2 or 3 days per week with moderate to heavy loads can improve muscle strength and induce small but perhaps clinically significant increases in BFLBM and mCSA in older adults over a 2-year period of supervised training.

Age- and Sex-Specific Changes in Lower-Limb Muscle Power Throughout the Lifespan

BACKGROUND

Our main goal was to evaluate the pattern and time course of changes in relative muscle power and its constituting components throughout the life span.

METHODS

A total of 1,305 subjects (729 women and 576 men; aged 20-93 years) participating in the Copenhagen Sarcopenia Study took part. Body mass index (BMI), leg lean mass assessed by dual-energy X-ray absorptiometry (DXA), and leg extension muscle power (LEP) assessed by the Nottingham power rig were recorded. Relative muscle power (normalized to body mass) and specific muscle power (normalized to leg lean mass) were calculated. Segmented regression analyses were used to identify the onset and pattern of age-related changes in the recorded variables.

RESULTS

Relative muscle power began to decline above the age of 40 in both women and men, with women showing an attenuation of the decline above 75 years. Relative muscle power decreased with age due to (i) the loss of absolute LEP after the fourth decade of life and (ii) the increase in BMI up to the age of 75 years in women and 65 years in men. The decline in absolute LEP was caused by a decline in specific LEP up to the age of 75 in women and 65 in men, above which the loss in relative leg lean mass also contributed.

CONCLUSIONS

Relative power decreased (i) above 40 years by the loss in absolute power (specific power only) and the increase in body mass, and (ii) above ~70 years by the loss in absolute power (both specific power and leg lean mass).

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

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

The eccentric mechanotransduction, neuro-muscular transmission, and structural reversibility of muscle fatty infiltration. An experimental advanced disuse muscle-wasting model of rabbit supraspinatus

INTRODUCTION

Full-thickness rotator cuff tear is present in almost 50% of patients over age 65 years, and its degree is known to be a good predictor of the severity of muscle-wasting (MW) sarcopaenia, also known as fatty degeneration (FD). A FD CT grade > 2° is recognized as a borderline of its reversibility. A disuse model of supraspinatus FD (grade 2) in rabbits provides clinically relevant data. Therefore, the present study evaluates the correlation between eccentric mechanotransduction, neuromuscular transmission (NT), and reversibility of muscle fatty infiltration (MFI) in rabbit supraspinatus FD > 2°.

MATERIAL AND METHODS

The supraspinatus tendon was detached from the greater tubercle, infraspinatus, and subscapularis in 16 rabbits. The tendon was reinserted after 12 weeks, and the animals were euthanized 24 weeks after reconstruction. MFI was measured in the middle part of the supraspinatus. Single-fibre EMG (SFEMG) examination of the supraspinatus NT was performed on 4 animals.

RESULTS

The power of analysis was 99%. Significant differences in MFI volume were found between the operated (4.6 ±1.1%) and the opposite control sides (2.91 ±0.61%) (p < 0.001). SFEMG revealed no significant differences between the disuse and the control supraspinatus muscles (p > 0.05); however, 6.5% of the examined muscle fibres exhibited NT disorders combined with blockade of conduction in 2.5% of muscle fibres.

CONCLUSIONS

Critical MFI in a disuse model of rabbit supraspinatus FD, CT grade > 2°, is substantially reversible by eccentric training despite subclinical impairment of neuromuscular transmission. In addition, 0.63% reversal of MFI is correlated with 1% hypertrophy of type I and II muscle fibre diameter.

Strength Training: In Search of Optimal Strategies to Maximize Neuromuscular Performance

Training with low-load exercise performed under blood flow restriction can augment muscle hypertrophy and maximal strength to a similar extent as the classical high-load strength training method. However, the blood flow restriction method elicits only minor neural adaptations. In an attempt to maximize training-related gains, we propose using other protocols that combine high voluntary activation, mechanical tension, and metabolic stress.

Effects of a dynamic combined training on impulse response for middle-aged and elderly patients with osteoporosis and knee osteoarthritis: a randomized control trial

Dynamic combined training is a crucial component in treating musculoskeletal conditions to increase muscle strength and improve functional ability. This randomized control trial aimed to examine the effect of dynamic combined training on muscle strength and contractile rate of force development (RFD) in patients with osteoporosis (OP) and knee osteoarthritis (KOA). 58 participants with OP or KOA were randomly assigned to a control group (CG) (CGOP, n = 12; CGKOA, n = 15) or training group (TG) (TGOP, n = 14; TGKOA, n = 17). The training group participated in a 12-week, three-days-per-week supervised program consisting of stretching and warm-up exercises (10 min), hydraulic resistance training (40 min), and cool-down and relaxation exercises (10 min). All participants were evaluated at baseline and post-training. The maximal voluntary contraction (MVC) and contractile RFD at 0-200 ms increased significantly in middle-aged and older patients with OP. As for KOA, the dynamic combined training program was effective in improving the muscle strength. The maximal voluntary contraction (MVC) and contractile RFD at 0-200 ms increased significantly (by 29.22%, P = .000 and 27.25%, P = .019, respectively) in middle-aged and older patients with OP. In the KOA group, MVC and contractile RFD improved but did not reach statistical significance. The dynamic combined training program is effective for health promotion in older adults with OP or KOA.

Power Versus Sarcopenia: Associations with Functionality and Physical Performance Measures

BACKGROUND/OBJECTIVE

While assessment of sarcopenia has drawn much attention, assessment of low muscle power has not been studied widely. This is, to a large extend, due to a more difficult assessment of power in practice. We aimed to compare the associations of low power and sarcopenia with functional and performance measures.

MATERIAL AND METHODS

We designed a retrospective and cross-sectional study. Community-dwelling outpatient older adults applied to a university hospital between 2012 and 2020 composed the population. We estimated body composition by bioimpedance analysis. Other measures were handgrip strength, timed-up-and-go-test (TUG), usual gait speed (UGS), activities of daily living (ADL) and instrumental activities of daily living (IADL) tests. We assessed muscle power by a practical equation using a 5-repetition sit-to-stand power test. We adjusted the power by body weight and defined low muscle power threshold as the lowest sex-specific tertile. We noted demographic characteristics, number of medications, and diseases. We defined sarcopenia by EWGSOP2 definition.

RESULTS

Cut points for low relative muscle power were <2.684 and <1.962 W/kg in males and females, respectively. Low muscle power was related with both measures of disability (impaired ADL and IADL) (OR=2.4, 95% CI= 1.4-4.0, p=0.001; OR=2.4, 95% CI= 1.4-4.1, p=0.001; respectively). Low muscle strength (i.e. probable sarcopenia) was only related with disability in IADL (OR=3.6, 95% CI= 1.6-8.; p=0.002); confirmed sarcopenia was related with neither measures. Low muscle power was not related with impaired TUG (p=1) but with impaired UGS (OR=6.6, 95% CI= 3.6-11.0; p<0.001). Probable sarcopenia was not related with impaired TUG (p=0.08) but with impaired UGS (OR=2.4, 95% CI= 1.1-5.3; p=0.03) and confirmed sarcopenia was related with neither measures (p=1, p=0.3; respectively).

CONCLUSION

Low muscle power detected by simple and practically applicable CSST (Chair Sit To-Stand Test) power test was a convenient measure associated with functional and performance measures. It was related to functionality and performance measures more than sarcopenia. Future longitudinal studies are needed to examine whether it predicts future impairment in ADL, IADL, and performance measures.

Biomarkers for length of hospital stay, changes in muscle mass, strength and physical function in older medical patients: protocol for the Copenhagen PROTECT study-a prospective cohort study

INTRODUCTION

Sarcopenia is generally used to describe the age-related loss of muscle mass and strength believed to play a major role in the pathogenesis of physical frailty and functional impairment that may occur with old age. The knowledge surrounding the prevalence and determinants of sarcopenia in older medical patients is scarce, and it is unknown whether specific biomarkers can predict physical deconditioning during hospitalisation. We hypothesise that a combination of clinical, functional and circulating biomarkers can serve as a risk stratification tool and can (i) identify older acutely ill medical patients at risk of prolonged hospital stays and (ii) predict changes in muscle mass, muscle strength and function during hospitalisation.

METHOD AND ANALYSIS

The Copenhagen PROTECT study is a prospective cohort study consisting of acutely ill older medical patients admitted to the acute medical ward at Copenhagen University Hospital, Bispebjerg and Frederiksberg, Denmark. Assessments are performed within 24 hours of admission and include blood samples, body composition, muscle strength, physical function and questionnaires. A subgroup of patients transferred to the Geriatric Department are included in a smaller geriatric cohort and have additional assessments at discharge to evaluate the relative change in circulating biomarker concentrations, body composition, muscle strength and physical function during hospitalisation. Enrolment commenced 4 November 2019, and proceeds until August 2021.

ETHICS AND DISSEMINATION

The study protocol has been approved by the local ethics committee of Copenhagen and Frederiksberg (H-19039214) and the Danish Data Protection Agency (P-2019-239) and all experimental procedures were performed in accordance with the Declaration of Helsinki. Findings from the project, regardless of the outcome, will be published in relevant peer-reviewed scientific journals in online (www.clinicaltrials.gov).

TRIAL REGISTRATION NUMBER

NCT04151108.

Functional relevance of resistance training-induced neuroplasticity in health and disease

Repetitive, monotonic, and effortful voluntary muscle contractions performed for just a few weeks, i.e., resistance training, can substantially increase maximal voluntary force in the practiced task and can also increase gross motor performance. The increase in motor performance is often accompanied by neuroplastic adaptations in the central nervous system. While historical data assigned functional relevance to such adaptations induced by resistance training, this claim has not yet been systematically and critically examined in the context of motor performance across the lifespan in health and disease. A review of muscle activation, brain and peripheral nerve stimulation, and imaging data revealed that increases in motor performance and neuroplasticity tend to be uncoupled, making a mechanistic link between neuroplasticity and motor performance inconclusive. We recommend new approaches, including causal mediation analytical and hypothesis-driven models to substantiate the functional relevance of resistance training-induced neuroplasticity in the improvements of gross motor function across the lifespan in health and disease.

Analysis of Vertical Micro Acceleration While Standing Reveals Age-Related Changes

In this study, we investigated the fluctuation characteristics of micro vertical acceleration of center of mass (vCOMacc) in standing and examined the usefulness of vCOMacc as an aging marker for standing control abilities. Sixteen young and 18 older adults participated in this experiment. Data for vCOMacc were calculated as the vertical ground reaction force value divided by each participant’s body mass using a force plate. The COMacc frequency structure was determined using the continuous wavelet transform to analyze the relative frequency characteristics. For time domain analysis, we determined the root mean square (RMS) and maximum amplitude (MA) of the integrated power spectral density. We also analyzed the correlation between vCOMacc and lower limb muscle activity. The relative frequency band of vCOMacc was higher in older than young adults, and the time domain indicators were sufficient to distinguish the effects of aging. Regarding the relationship between vCOMacc during standing and muscle activity, a correlation was found with the soleus muscle in young adults, while it was moderately correlated with the gastrocnemius muscle in older adults. The cause of vCOM may be related to differences in muscle activity, and vCOMacc may be utilized to more easily assess the effects of aging in standing control.

Feasibility and estimated efficacy of blood flow restricted training in female patients with rheumatoid arthritis: a randomized controlled pilot study

Objectives: The study aimed to evaluate the feasibility of a blood flow restriction (BFR) training regimen in patients with rheumatoid arthritis (RA); and to compare the effects of 4 weeks of BFR training with low-intensity strength training on muscle strength, muscle endurance, and joint pain in patients with RA.Method: In this non-blinded pilot randomized controlled trial, 18 women with RA aged 18-65 years performed low-intensity strength training for the lower limbs three times a week for 4 weeks, and were randomized to train with or without occlusion bands. The primary outcomes were registration of the recruitment process, compliance with training sessions, side effects, perceived pain, and a satisfaction survey. The secondary outcomes were changes in muscle strength, muscle endurance, and joint pain.Results: The findings of this pilot study included a challenging recruitment process, well tolerated training and test protocols, overall good patient satisfaction, no serious side effects, and high compliance. Both groups achieved significant improvements in knee extensor strength from baseline to follow-up, with a change of 11.5 kg [interquartile range (IQR) 9.8;13.0] in the intervention group and 8.4 kg (IQR 5.5;12.4) in the control group, and a significant between-group difference in favour of the intervention group (p = 0.0342).Conclusions: The feasibility results of this study indicated a challenging recruitment process, general satisfaction with the BFR and exercises, good compliance, and only expected non-serious side effects. BFR training may improve knee extensor strength in women with RA, compared low-intensity strength training without BFR.

Is hard physical work in the early working life associated with back pain later in life? A cross-sectional study among 5700 older workers

OBJECTIVES

Physically demanding work increases the risk of developing musculoskeletal disorders during working life, with low back pain (LBP) as the most prevalent and debilitating musculoskeletal disorder worldwide. However, a lack of knowledge exists about the role of early working years on musculoskeletal health later in life. This study investigated whether an exposure-response association exists between physical demands in early working life and risk of LBP in later working life.

DESIGN

Cross-sectional study.

SETTING, PARTICIPANTS AND OUTCOME MEASURE

In the SeniorWorkingLife study, 5909 wage earners aged ≥50 years with currently sedentary work replied to a questionnaire survey in 2018 about physical work demands during their first working years (exposure) and current LBP (outcome). Associations between physical work demands in the early working years and current LBP were modelled using general linear models controlling for various confounders, combined with model-assisted weights based on national registers.

RESULTS

Hard physical work during early working life was associated with more intense LBP later in life among senior workers with currently sedentary jobs. In the fully adjusted model, workers with 'standing/walking work with lifting/carrying' and 'heavy or fast work that is physically strenuous' during the first years of working life reported higher LBP intensity than those with sedentary work during their first working years (0.2 (95% CI, 0.0 to 0.4) and 0.6 (95% CI, 0.4 to 0.9), respectively).

CONCLUSION

Work involving lifting/carrying or work that is physically strenuous in early life is associated with higher intensity of LBP among older workers with currently sedentary employment. These findings suggest that early working life may have an impact on later working years and underscore the necessity for careful introduction and instruction to the working environment for retaining musculoskeletal health and prolonging working life.

TRIAL REGISTRATION NUMBER

NCT03634410.

Variable innervation of the first dorsal interosseous muscle: an electrophysiological study

Background

The first dorsal interosseous muscle (FDI) is usually innervated by the deep branch of the ulnar nerve. However, as was first noted by Sunderland in 1946, some individuals have variable innervation of the FDI. This study investigated the incidence of variable innervation of the FDI by using electrophysiological examination and further evaluated the relevance of this variation in patients with cubital tunnel syndrome (CuTS).

Methods

This study included 211 patients who underwent peripheral nerve surgery in Huashan hospital, Fudan University, between October, 2012 and February, 2014. The patients were divided into three groups: the carpal tunnel syndrome (CTS) group, the CuTS group and the control group. During surgery, electromyography was used to determine FDI variation, and a hand function instrument was employed to estimate the pinch strength between the thumb and index finger in both hands of the CuTS patients.

Results

The electromyogram test showed that 22 of the patients enrolled had variable innervation of the FDI. Compared with the CTS group and the control group, the incidence of variable innervation of the FDI was much higher in the CuTS group (P<0.05). Patients under the age of 60 years old in the CuTS group were more likely to have the variation (P=0.043). A higher pinch strength ratio was significantly associated with variable innervation of the FDI in the CuTS patients (P=0.030).

Conclusions

Using electromyography, our study demonstrated that the variable innervation of the FDI could be innervated by the median nerve. In the CuTS patients, the higher incidence of FDI variation was possibly related to age. This variation might lead to a better prognosis for CuTS patients.

Innovations in Geroscience to enhance mobility in older adults

Aging is the primary risk factor for functional decline; thus, understanding and preventing disability among older adults has emerged as an important public health challenge of the 21st century. The science of gerontology - or geroscience - has the practical purpose of "adding life to the years." The overall goal of geroscience is to increase healthspan, which refers to extending the portion of the lifespan in which the individual experiences enjoyment, satisfaction, and wellness. An important facet of this goal is preserving mobility, defined as the ability to move independently. Despite this clear purpose, this has proven to be a challenging endeavor as mobility and function in later life are influenced by a complex interaction of factors across multiple domains. Moreover, findings over the past decade have highlighted the complexity of walking and how targeting multiple systems, including the brain and sensory organs, as well as the environment in which a person lives, can have a dramatic effect on an older person's mobility and function. For these reasons, behavioral interventions that incorporate complex walking tasks and other activities of daily living appear to be especially helpful for improving mobility function. Other pharmaceutical interventions, such as oxytocin, and complementary and alternative interventions, such as massage therapy, may enhance physical function both through direct effects on biological mechanisms related to mobility, as well as indirectly through modulation of cognitive and socioemotional processes. Thus, the purpose of the present review is to describe evolving interventional approaches to enhance mobility and maintain healthspan in the growing population of older adults in the United States and countries throughout the world. Such interventions are likely to be greatly assisted by technological advances and the widespread adoption of virtual communications during and after the COVID-19 era.

The influence of sex, training intensity, and frequency on muscular adaptations to 40 weeks of resistance exercise in older adults

The purpose of this investigation was to identify the influence that sex, training intensity, and frequency have on long-term resistance exercise (RE) outcomes in older adults.

METHODS

One-hundred eleven older adults (men: 41, women: 70) completed either: high-intensity RE 2d/week (HI-2D; n = 29), low-intensity RE 2d/week (LI-2D; n = 32), high-intensity RE 3d/week (HI-3D, n = 20), or low-intensity RE 3d/week (LI-3D, n = 30). HI protocols completed 3 sets of 8 repetitions with 80% one-repetition maximum (1-RM) while LI completed 3 sets of 16 repetitions with 40% 1-RM. Total and regional bone free lean body mass (BFLBM) were assessed via dual-energy x-ray absorptiometry and cross-sectional area (mCSA) of the rectus femoris.

RESULTS

mCSA was the only muscle quantity parameter to increase (p = 0.043). Significant trial effects for upper body, lower body, and specific strength were observed (all p < 0.001). Significant sex × time interactions (p < 0.001) were observed for upper and lower body strength, however, men and women displayed similar increases in lower body (45.7 ± 29.6 vs 46.4 ± 34.9%), upper body (33.1 ± 21.0 vs 33.4 ± 24.7%), and specific strength (36.5 ± 28.5 vs 40.1 ± 28.7%). A group × time interaction for lower body strength indicated that at 20-weeks HI-2D and LI-3D displayed greater lower body strength than LI-2D (both p < 0.009), and at 40-weeks HI-2D, HI-3D, and LI-3D displayed significantly greater lower body strength than LI-2D (all p < 0.038).

CONCLUSIONS

These observations indicate that older men and women display similar long-term RE outcomes. Additionally, regardless of frequency or intensity, the current prescriptions were effective for increasing strength, however these data suggest HI-2D > LI-2D and LI-3D > LI-2D but similar outcomes among HI-2D, HI-3D, and LI-3D. The variety of effective RE approaches provides flexibility among older adults for selecting a lifestyle intervention that would be most sustainable.

Sarcopenia: Molecular Pathways and Potential Targets for Intervention

Aging is associated with sarcopenia. The loss of strength results in decreased muscle mass and motor function. This process accelerates the progressive muscle deterioration observed in older adults, favoring the presence of debilitating pathologies. In addition, sarcopenia leads to a decrease in quality of life, significantly affecting self-sufficiency. Altogether, these results in an increase in economic resources from the National Health Systems devoted to mitigating this problem in the elderly, particularly in developed countries. Different etiological determinants are involved in the progression of the disease, including: neurological factors, endocrine alterations, as well as nutritional and lifestyle changes related to the adoption of more sedentary habits. Molecular and cellular mechanisms have not been clearly characterized, resulting in the absence of an effective treatment for sarcopenia. Nevertheless, physical activity seems to be the sole strategy to delay sarcopenia and its symptoms. The present review intends to bring together the data explaining how physical activity modulates at a molecular and cellular level all factors that predispose or favor the progression of this deteriorating pathology.