Effects of Three Different Exercise Strategies for Optimizing Aerobic Capacity and Skeletal Muscle Performance in Older Adults: A Pilot Study.

This Brief Report describes a pilot study of the effect of 12 weeks of stationary bicycle high-intensity interval training, stationary bicycle moderate-intensity continuous training, and resistance training on cardiorespiratory, muscular, and physical function measures in insufficiently-active older adults (N=14; 66.4±3.9 years; 3 male, 11 female). After baseline testing, participants were randomly assigned to one of the exercise groups. High-intensity interval training and moderate-intensity continuous training had small-to-large effect sizes on cardiorespiratory/endurance and physical function measures, but very small effect sizes on muscular measures. Resistance training had small-to-large effect sizes on cardiorespiratory, muscular, and physical function measures. This pilot study should be interpreted cautiously, but findings suggest that resistance exercise may be the most effective of the three studied exercise strategies for older adults as it can induce beneficial adaptations across multiple domains. These effect sizes can be used to determine optimal sample sizes for future investigations.

Comparison of a Multi-Component Physical Function Battery to Usual Walking Speed for Assessing Lower Extremity Function and Mobility Limitation in Older Adults.

OBJECTIVES: To compare a composite measure of physical function that comprises locomotor and non-locomotor tests (i.e., the Mobility Battery Assessment (MBA)) with traditional measures of mobility (4-m usual gait speed (UGS), six-minute walk (6MW) gait speed, and short physical performance battery (SPPB) score) for assessing lower extremity function and discriminating community dwelling older adults with and without mobility limitations. DESIGN: Cross-sectional, observational study. SETTING: Laboratory-based. PARTICIPANTS: 89 community-dwelling older adults (74.9±6.7). MEASUREMENTS: Using principal component analysis we derived an MBA score for 89 community-dwelling older adults, and quantified 4-m UGS, 6MW gait speed, and SPPB score. The MBA score was based on five lab-based tests. We also quantified self-reported lower extremity function/mobility using the Neuro-QOL Lower Extremity Function-Mobility instrument. Based on this data a continuous score was derived and subjects were classified as "mobility limited" or "non-mobility limited". Correlations between the mobility measures and the Neuro-QOL score were calculated, and ROC curves were constructed to determine the AUC for the mobility measures ability to predict mobility limitations. RESULTS: The MBA had the largest AUC (0.92) for discriminating mobility limitations and exhibited the strongest correlation (0.73) with the Neuro-QOL Lower Extremity Function-Mobility Scale. The worst performing predictors were the 4-meter UGS and stair climb power both with an AUC of 0.8 for discriminating mobility limitations, and a low correlation with Neuro-QOL Lower Extremity Function Scale of 0.39 and 0.46, respectively. CONCLUSION: The MBA score moderately improves the magnitude of correlation and discrimination of mobility limitation in older adults than singular, standard tests of mobility.

Relationship of Physical Frailty to Phosphocreatine Recovery in Muscle after Mild Exercise Stress in the Oldest-Old Women.

BACKGROUND: Physical frailty is a clinical syndrome associated with aging and manifesting as slowness, weakness, reduced physical activity, weight loss, and/or exhaustion. Frail older adults often report that their major problem is "low energy", and there is indirect evidence to support the hypothesis that frailty is a syndrome of dysregulated energetics. We hypothesized that altered cellular energy production underlies compromised response to stressors in the frail. METHODS: We conducted a pilot study to assess muscle energetics in response to a mild isometric exercise challenge in women (n=30) ages 84-93 years. The frailty status was assessed by a validated physical frailty instrument. Localized phosphorus (P31) magnetic resonance spectroscopy with a 1.5T magnet was used to assess the kinetics of Phosphocreatine recovery in the tibialis anterior muscle following maximal isometric contraction for 30 seconds. RESULTS: Phosphocreatine recovery following exertion, age-adjusted, was slowest in the frail group (mean=189 sec; 95%CI: 150,228) compared to pre-frail (mean=152 sec; 95%CI: 107,197) and nonfrail subjects (mean=132 sec; 95%CI: 40,224). The pre-frail and frail groups had 20 sec (95%CI: -49,89) and 57 sec (95%CI: -31,147) slower phosphocreatine recovery, respectively, than the non-frail. This response was paralleled by dysregulation in glucose recovery in response to oral glucose tolerance test in women from the same study population. CONCLUSIONS: Impaired muscle energetics and energy metabolism might be implicated in the physical frailty syndrome.

Effects of Running Wheel Activity and Dietary HMB and ß-alanine Co-Supplementation on Muscle Quality in Aged Male Rats.

OBJECTIVE: Loss of skeletal muscle function is linked to increased risk for loss of health and independence in older adults. Dietary interventions that can enhance aging muscle function, alone or in combination with exercise, may offer an effective way to reduce these risks. The goal of this study was to evaluate the muscular effects of beta-hydroxy-beta-methylbutyrate (HMB) and beta-alanine (ß-Ala) co-supplementation in aged Sprague-Dawley rats with voluntary access to running wheels (RW). METHODS: Aged (20 months) rats were housed with ad libitum access to RW while on a purified diet for 4 weeks, then balanced for RW activity and assigned to either a control or an experimental diet (control + HMB and ß-Ala) for the next 4 weeks (n = 10/group). At the end of the study, we assessed muscle size, in situ force and fatigability in the medial gastrocnemius muscles, as well as an array of protein markers related to various age- and activity-responsive signaling pathways. RESULTS: Dietary HMB+ß-Ala did not improve muscle force or fatigue resistance, but a trend for increased muscle cross-sectional area (CSA) was observed (P = 0.077). As a result, rats on the experimental diet exhibited reduced muscle quality (force/CSA; P = 0.032). Dietary HMB+ß-Ala reduced both the abundance of PGC1-α (P = 0.050) and the ratio of the lipidated to non-lipidated forms of microtubule-associated protein 1 light chain 3 beta (P = 0.004), markers of mitochondrial biogenesis and autophagy, respectively. Some alterations in myostatin signaling also occurred in the dietary HMB+ß-Ala group. There was an unexpected difference (P = 0.046) in RW activity, which increased throughout the study in the animals on the control diet, but not in animals on the experimental diet. CONCLUSIONS: These data suggest that the short-term addition of dietary HMB+ß-Ala to modest physical activity provided little enhancement of muscle function in this model of uncomplicated aging.

A Pilot Study of Age-Related Changes in the Sphingolipid Composition of the Rat Sarcoplasmic Reticulum.

BACKGROUND: Muscle strength declines more rapidly than muscle size, manifesting as a loss of muscle quality. One putative contributor to this impairment of muscle quality is impaired sarcoplasmic reticulum (SR) function. OBJECTIVES: The principal objective of this study was to characterize the sphingolipid composition of the SR in adult and aging rat muscles. A secondary, exploratory objective was to test for associations between SR sphingolipids and SR function (i.e., Ca2+ release). DESIGN: Using an animal model, the objectives were evaluated in a pre-clinical, cross-sectional study. SETTING: Data were collected in an academic research laboratory. PARTICIPANTS: Medial gastrocnemius muscles of adult (n=8; 7-8 months) and aged (n=8; 24-25 months), male F344/BN hybrid rats were processed to extract SR. MEASUREMENTS: Sphingolipids in the SR were measured using tandem mass spectrometry. Fatty acid concentrations within the major sphingolipid classes were evaluated via Principal Component Analysis (PCA). In a subset of samples, SR Ca2+ release rates were determined using fluorometric methods, and associations with specific (based on results of PCA) fatty acid concentrations were evaluated. RESULTS: Aging SR showed an overall decline in the ratio of unsaturated to saturated fatty acids. Age-specific differences were observed for hexosylceramide and ceramide-1-phosphate. Within subset of samples with SR Ca2+ release data, a significant negative association between Ca2+ release and C1P18:0 and trends for positive associations with hexCER24:0 and 24:1 were observed. CONCLUSIONS: These preliminary, pre-clinical data suggest that changes in SR sphingolipids may play a role in age-related impairment of muscle function. Further work is needed to explore this hypothesis, as SR sphingolipids may prove a fruitful target for interventions, be they physical (i.e., exercise), nutritional or pharmacological.

Ageing, but not yet senescent, rats exhibit reduced muscle quality and sarcoplasmic reticulum function.

AIM: Reduced muscle force greater than expected from loss of muscle mass has been reported in ageing muscles. Impaired sarcoplasmic reticulum (SR) Ca(2+) release has been implicated as a possible mechanism, and attributed to several factors, including loss of ryanodine receptor (RYR) expression and protein binding. The aim of this study was to evaluate muscle quality and SR Ca(2+) release in ageing rats that were not so old that major atrophy had occurred. METHODS: We collected in situ force data from the plantarflexor muscle group and muscle mass from the constituent muscles to determine muscle quality (force/mass) in adult (6-8 months) and ageing (24 months) rats (n=8/group). We evaluated SR Ca(2+) uptake and release, and determined expression of key proteins associated with Ca(2+) release [RYR and FK506 binding protein (FKBP)] and uptake (SERCA, parvalbumin, calsequestrin). RESULTS: Plantarflexor force and muscle quality were reduced with ageing (approx. 28 and 34%, respectively), but atrophy was limited, and significant only in the medial gastrocnemius (approx. 15%). The fast phase of SR Ca(2+) release was reduced with ageing in both gastrocnemii, as was FKBP expression and FKBP-RYR binding, but RYR expression was not affected. Similar, but non-significant changes were present in the plantaris, but the soleus muscle generally showed no ageing-related changes. CONCLUSION: These data suggest a possible role for impaired SR Ca(2+) release in ageing-related loss of muscle quality, although not through loss of RYR expression.

Variable-frequency trains offset low-frequency fatigue in human skeletal muscle.

Variable-frequency trains that exploit the catchlike property of skeletal muscle can augment force production in fatigued skeletal muscle. The present study is the first to examine the effect of such trains during recovery. The quadriceps femoris muscles of 12 healthy individuals were fatigued using six-pulse, 14.3-Hz trains delivered at a rate of 1/s for 3 min. The force-generating ability of the muscle was tested with several constant-frequency trains (8.3-100 Hz) and a variable-frequency train before and after fatigue and at 2, approximately 13, and approximately 38 min of recovery. The variable-frequency train produced significant augmentation of force versus the best constant-frequency train (12.5 Hz) in acute fatigue and during recovery. The fatiguing protocol also induced low-frequency fatigue (LFF); the time courses of the degree of LFF and the amount of variable-frequency train force augmentation were inversely related (r = 0.629; F = 38.024; P

Effects of activation frequency and force on low-frequency fatigue in human skeletal muscle.

No comparison of the amount of low-frequency fatigue (LFF) produced by different activation frequencies exists, although frequencies ranging from 10 to 100 Hz have been used to induce LFF. The quadriceps femoris of 11 healthy subjects were tested in 5 separate sessions. In each session, the force-generating ability of the muscle was tested before and after fatigue and at 2, approximately 13, and approximately 38 min of recovery. Brief (6-pulse), constant-frequency trains of 9.1, 14.3, 33.3, and 100 Hz and a 6-pulse, variable-frequency train with a mean frequency of 14.3 Hz were delivered at 1 train/s to induce fatigue. Immediately postfatigue, there was a significant effect of fatiguing protocol frequency. Muscles exhibited greater LFF after stimulation with the 9.1-, 14.3-, and variable-frequency trains. These three trains also produced the greatest mean force-time integrals during the fatigue test. At 2, approximately 13, and approximately 38 min of recovery, however, the LFF produced was independent of the fatiguing protocol frequency. The findings are consistent with theories suggesting two independent mechanisms behind LFF and may help identify the optimal activation pattern when functional electrical stimulation is used.

Effects of activation pattern on human skeletal muscle fatigue.

Variable-frequency stimulation trains (VFTs) that take advantage of the catchlike property of skeletal muscle have been shown to augment the force production of fatigued muscles compared with constant-frequency trains (CFTs). The present study is the first to report the force augmentation produced by VFTs after fatiguing the muscle with VFTs versus fatiguing the muscle with CFTs. Data were obtained from the human quadriceps femoris muscles of 12 healthy subjects. Each subject participated in three experimental sessions. Each session fatigued the muscle with one of three protocols: CFTs with 70-ms interpulse intervals (CFT70); CFTs with 55.5-ms interpulse intervals (CFT55.5); or VFTs. Following each fatiguing protocol the muscles were tested with all three stimulation patterns (i.e., CFT55.5, CFT70, and VFT). At the end of the fatiguing protocol the VFT produced force-time integrals and peak forces approximately 18% and 32% greater than the CFT70, respectively. The testing trains showed that the VFT produced approximately 25-35% greater force-time integrals than either CFT and approximately 35-47% greater peak forces than the CFT70. For each testing train, approximately 10-15% greater force-time integrals were seen when the muscles were fatigued with the CFTs than when fatigued with the VFTs. These results support suggestions that VFTs may be useful during clinical applications of electrical stimulation.

In-season management of shoulder pain in a collegiate swimmer: a team approach.

Shoulder pain is a common problem among competitive swimmers, often limiting their ability to train and compete. Although a number of rehabilitation programs for shoulder injuries have been reported in the literature, there is a lack of objective data regarding the effectiveness of these protocols in the competitive swimming population. This case report describes the evaluation and treatment of shoulder pain in an NCAA Division I swimmer during the competitive season. Once a physical therapy diagnosis was made, a plan of care was developed to address each component impairment. This required the input of the team trainers, the team physician, and an orthopaedic surgeon. A chief component of the athlete's rehabilitation involved allowing the athlete to compete, but not practice. Excellent results were achieved, as evidenced by symptom reduction and swimming performance. This case report highlights the interactive, team approach necessary for optimal management of the injured athlete.