Fatigability of Lower Limb Muscle in Older Adults: Protective Effects of Strength Training Exercise in Old Men and Women

Fatigability of Limb Muscle in Older Adults: Protective Effects of Exercise

The proposed studies will assess 1) the mechanisms for the age-related increase in fatigability during dynamic exercise (Aims 1 and 2) and 2) the effectiveness of high-velocity resistance training coupled with blood flow restriction (BFR) in improving muscle power output and fatigability in older adults (Aim 3). The first two aims are cross-sectional studies comparing young (18-35 years old) and older adults (≥60 yrs old) to test our central hypothesis that the greater accumulation of metabolites and increase in fatigability in older adults is due to either age-related impairments in skeletal muscle bioenergetics (Aim 1) and/or vascular dysfunction (Aim 2). These two aims will integrate techniques to assess whole-muscle bioenergetics (31P-MRS) and in vivo vascular function (near infrared spectroscopy; NIRS and doppler ultrasonography) with in vitro assessment of single fiber bioenergetics (epifluorescence microscopy) and vasoreactivity of isolated skeletal muscle arterioles (video microscopy). We will then determine whether bioenergetics, vascular function and fatigability are altered in older men and women in response to 8 weeks of resistance exercise training of the lower limb both with and without blood flow restriction (Aim 3).

Inclusion Criteria:

• men and women aged 18-40 years and >60 years

Exclusion Criteria:

• body mass index ≥40 kg/m2;
• type 1 or type 2 diabetes;
• uncontrolled hypertension;
• active cancer, cancer in remission, or having received treatment for any form of cancer in the previous five years;
• coronary artery disease;
• cardiovascular disease (e.g., PAD, PVD);
• abnormal and untreated thyroid function;
• chronic and/or regular nonsteroidal anti-inflammatory drugs (NSAID) consumption,
• tobacco use (includes smoking);
• any condition that presents a limitation to exercise (e.g., severe arthritis, COPD, neuromuscular disorder, moderate or severe cognitive impairment, Alzheimer's Disease, severe untreated sleep apnea).
• women who are pregnant or likely to be pregnant.
• Subjects will be excluded if they have joint pain in the exercising leg or arm. Medication use. Medications currently taken or in the previous year and known to influence muscle mass (e.g., glucocorticoids, testosterone) and cortical and neuromuscular excitability will be exclusionary, while medications that may be prevalent among older adults (e.g., statins) will be accounted for with a covariate statistical model.