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).
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Change in Fatigability of the knee extensor muscles from baseline to after 8 weeks training
Timeframe: One session before and then after 8 weeks of training
Change in single muscle fiber function form baseline to after 8 weeks training
Timeframe: Before and after completion of resistance training intervention of 8 weeks.
Change in muscle volume of the quadricep muscles form baseline to after 8 weeks training
Timeframe: Before and after completion of resistance training intervention of 8 weeks.
Change in muscle metabolism during a fatiguing knee extensor exercise from baseline to after 8 weeks resistance training
Timeframe: Before and 2-days after completion of resistance training intervention of 8 weeks.
Change in vascular function via flow-mediated dilation of the femoral artery from baseline to after 8 weeks of training
Timeframe: One session before and one after 8 weeks of training
Change in myofibrillar-ATPase efficiency from baseline to after 8 weeks of training
Timeframe: One session before and after 8 weeks of training
Change in Oxygenation of the muscle between baseline to after 8 weeks of training
Timeframe: One session before and after 8 weeks of training
Change in arteriole Vasodilation from baseline to after 8 weeks of training
Timeframe: One session before and after 8 weeks of training