The lifestyle interventions and independence for elders (LIFE) pilot study: design and methods.

The LIFE study is a multicenter pilot for a proposed full scale, two-arm randomized controlled trial that will contrast the effect of a physical activity intervention with a successful aging education program on the occurrence of incident major mobility disability (the inability to complete a 400 m walk) or death in at-risk sedentary older adults. Four hundred older adults from 4 clinical sites will be recruited for this purpose. All participants will be followed for at least 1-year; however, we will continue to follow all participants until the final randomized individual has reached the 1-year mark.

Effect of leg muscle contraction velocity on functional performance in older men and women.

Objectives: To explore the relationship between impairment (skeletal muscle strength and contraction velocity) and function in community-dwelling older adults.

Design: Cross-sectional.

Setting: University-based human physiology laboratory.

Identification of a molecular signature of sarcopenia.

Investigating the molecular mechanisms underlying sarcopenia in humans with the use of microarrays has been complicated by low sample size and the variability inherent in human gene expression profiles. We have conducted a study using Affymetrix GeneChips to identify a molecular signature of aged skeletal muscle. The molecular signature was defined as the set of expressed genes that best distinguished the vastus lateralis muscle of young (n = 10) and older (n = 12) male subjects, when a k-nearest neighbor supervised classification method was used in conjunction with a signal-to-noise ratio gene selection method and a holdout cross-validation procedure.

Impact of muscle power and force on gait speed in disabled older men and women.

Background: The purpose of this study was to explore the relationship between muscle power output at different external resistances and performance of functional tasks. The authors hypothesized that power at 40% skeletal muscle 1 repetition maximum (1RM), in which contraction velocity is high, would explain more of the variability in tasks such as level walking than would peak power or 1RM strength, in which contraction velocity is lower.

Methods: Participants were men and women (n = 48; ages 65-91 years) with physical disability as evidenced by 2 or more deficits on the Medical Outcomes Study Short Form physical function subscale or a score of 9 or less on the Established Populations for the Epidemiologic Studies of the Elderly short physical performance battery.

Use of self-report to predict ability to walk 400 meters in mobility-limited older adults.

Objectives: To determine whether the ability to walk 400 m could be predicted from self-reported walking habits and abilities in older adults and to develop an accurate self-report measure appropriate for observational trials of mobility when functional measures are impractical to collect.

Design: Cross-sectional.

Setting: University-based human physiology laboratory.

Validation of the Late-Life Function and Disability Instrument.

Objectives: To assess the concurrent and predictive validity of the Late-Life Function and Disability Instrument (LLFDI).

Design: Cross-sectional.

Setting: University-based human physiology laboratory.

High-intensity resistance training improves muscle strength, self-reported function, and disability in long-term stroke survivors.

Background And Purpose: To evaluate the efficacy of supervised high-intensity progressive resistance training (PRT) on lower extremity strength, function, and disability in older, long-term stroke survivors.

Methods: Forty-two volunteers aged 50 years and above, 6 months to 6 years after a single mild to moderate stroke, were randomized into either a control group of upper extremity stretching or a PRT group that received a 12-week supervised high-intensity resistance training program consisting of bilateral leg press (LP), unilateral paretic and nonparetic knee extension (KE), ankle dorsiflexion (DF), and plantarflexion (PF) exercises. Functional performance was assessed using the 6-minute walk, stair-climb time, repeated chair-rise time, and habitual and maximal gait velocities.

Increased Velocity Exercise Specific to Task (InVEST) training: a pilot study exploring effects on leg power, balance, and mobility in community-dwelling older women.

Objectives: To evaluate a dynamic form of weighted vest exercise suitable for home use and designed to enhance muscle power, balance, and mobility.

Design: A single-blind, randomized, controlled trial.

Setting: Outpatient exercise research facility situated within an academic long-term care center.

Contraction-mediated mTOR, p70S6k, and ERK1/2 phosphorylation in aged skeletal muscle.

With age, skeletal muscle experiences substantial atrophy and weakness. Although resistance training can increase muscle size and strength, the myogenic response to exercise and the capacity for muscle hypertrophy in older humans and animals is limited. In the present study, we assessed the ability of muscle contractile activity to activate cellular pathways involved in muscle cell growth and myogenesis in adult (Y; 6 mo old) and aged (O; 30 mo old) Fischer 344 x Brown Norway rats.

Use of phosphocreatine kinetics to determine the influence of creatine on muscle mitochondrial respiration: an in vivo 31P-MRS study of oral creatine ingestion.

Recent human isolated muscle fiber studies suggest that phosphocreatine (PCr) and creatine (Cr) concentrations play a role in the regulation of mitochondrial respiration rate. To determine whether similar regulatory mechanisms are present in vivo, this study examined the relationship between skeletal muscle mitochondrial respiration rate and end-exercise PCr, Cr, PCr-to-Cr ratio (PCr/Cr), ADP, and pH by using (31)P-magnetic resonance spectroscopy in 16 men and women (36.9 +/- 4.

Differential activation of mTOR signaling by contractile activity in skeletal muscle.

The cellular mechanisms by which contractile activity stimulates skeletal muscle hypertrophy are beginning to be elucidated and appear to include activation of the phosphatidylinositol 3-kinase signaling substrate mammalian target of rapamycin (mTOR). We examined the time course and location of mTOR phosphorylation in response to an acute bout of contractile activity. Rat hindlimb muscle contractile activity was elicited by high-frequency electrical stimulation (HFES) of the sciatic nerve.

Changes in function and disability after resistance training: does velocity matter?: a pilot study.

Objective: To compare the effects of high- and low-velocity resistance training on functional performance and disability outcomes in physically limited older women.

Design: A total of 16 wk of high-velocity resistance training or traditional low-velocity resistance training consisting of knee extension and leg press exercises was performed three times per week by 30 women with self-reported disability to compare their effect on functional performance and disability. Tests of dynamic balance, stair-climb time, chair-rise time, and gait velocity were used to assess changes in functional performance.

Regulation of neuregulin/ErbB signaling by contractile activity in skeletal muscle.

Putative roles of neuregulin (NRG) and the ErbB receptors in skeletal muscle biology include myogenesis, ACh receptor expression, and glucose transport. To date, however, the physiological regulation of NRG/ErbB signaling has not been examined. We tested the hypothesis that contractile activity in vivo induces NRG/ErbB activation.

The 6-minute walk test in mobility-limited elders: what is being measured?

Background: The 6-minute walk (6mw) is a well-established measure of aerobic capacity in elders with cardiorespiratory and peripheral vascular disease and may be an accurate measure of functional performance in healthy elders. In mobility-limited elders, a population at risk for disability, impairments in strength and power are predictive of performance-based measures of function. Though commonly utilized as an outcome measure among otherwise healthy mobility-limited elders, it is not clear whether the 6mw best represents a measure of functional limitation, aerobic capacity, or both.

What are the dietary protein requirements of physically active individuals? New evidence on the effects of exercise on protein utilization during post-exercise recovery.

Exercise and physical activity increase energy expenditure up to 10-fold. This brief review will focus on the effect of exercise on protein requirements. Evidence has accumulated that amino acids are oxidized as substrates during prolonged submaximal exercise.

Weighted stair climbing in mobility-limited older people: a pilot study.

Objectives: To evaluate weighted stair climbing exercise (SCE) as a means of increasing lower extremity muscle power in mobility-limited older people.

Design: Single-blinded, randomized controlled pilot study.

Setting: Human physiology laboratory of a metropolitan university.

High-velocity resistance training increases skeletal muscle peak power in older women.

Objectives: Peak power declines more precipitously than strength with advancing age and is a reliable measure of impairment and a strong predictor of functional performance. We tested the hypothesis that a high-velocity resistance-training program (HI) would increase muscle power more than a traditional low-velocity resistance-training program (LO).

Design: Randomized controlled trial.

The relationship between leg power and physical performance in mobility-limited older people.

Objectives: The purpose of this study was to assess the influence of leg power and leg strength on the physical performance of community-dwelling mobility-limited older people.

Design: Cross-sectional analysis of baseline data from a 12-week randomized controlled exercise-intervention study.

Setting: Exercise laboratory within the Department of Health Science of an urban university.