A Pilot Study on Skeletal Muscle Proteome Dynamics in Younger and Older Men Undertaking Normal Activity or Resistance Exercise Training.

The goal of this basic research study is to investigate effect of resistance exercise on the quality of muscle proteins in younger and older men. The main question\[s\] it aims to answer \[is/are\]: whether there is a difference in muscle protein quality between younger and older adults and if resistance exercise training has a beneficial impact on the quality of muscle proteins? Participants will perform five bouts of unilateral leg press exercise during a 14 day period of deuterium oxide consumption and biopsy samples will be taken from both their exercised leg and non-exercised leg before and after the intervention period to enable the measurement of muscle protein abundances and turnover rates.

Experimental Intervention Baseline muscle biopsy On day -1 of the experimental intervention (around 7 days after the initial assessment), you will need to arrive at the laboratory at \~8 am after an overnight fast. A blood sample (7 ml) will be collected via venipuncture and muscle samples will be collected by percutaneous biopsy of the vastus lateralis (quadriceps) of each leg (see below for more detail). Deuterium Oxide consumption On the next day (Experiment Day 0) you will consume the stable isotope, deuterium oxide (D2O - see below for more details), which is a tracer that can be used to measure the turnover rate of proteins inside you muscle. You will consume a dose of 13.3 ml D2O per kg body weight on Day 0. This equates to \~1 L of liquid for a person of 75 kg body weight. The liquid must be consumed in 4 doses of \~250 ml each at 2 h intervals, during which time you will be monitored for potential side effect (see below) by the research team, this means you will need to be available for 6 h on this day. (N.B. during this period you will have access to office and catering facilities on the LJMU Byrom Street site). On subsequent days of the experiment you will need to consume one maintenance dose of 0.67 ml D2O per Kg body weight (e.g. 50 ml for a person of 75 kg body weight) - self-administered each day, at a standardised time of day until day 14. Unilateral leg-press exercise On days 1, 4, 7, 10 and 13 of the experimental intervention, you will perform supervised single-legged resistance exercise (unilateral leg-press) at a standardised time of day. Each session will begin with a warm-up consisting of 5 repetitions at 70 % of 10RM. You will then perform three sets of 10 repetitions at a lifting intensity of 90 % of 10 RM with 2- to 3-min rest between sets. On days 1 and 7 we will collect a venous blood sample (7 ml) and a finger-prick blood sample (\~0.2 ml). Post-intervention muscle biopsy On day 15 of the experimental intervention, you will arrive at the laboratory at 8 am after an overnight fast. A blood sample (7 ml) will be collected via venipuncture and muscle samples will be collected by percutaneous biopsy of the vastus lateralis (quadriceps) of each leg. Post-intervention muscle function test On day 18 of the experimental intervention, isokinetic torque of the knee extensor muscles will be assessed via isokinetic dynamometry (IKD). Consistent with the initial assessment (Experiment day -7), you will first perform a warm-up (5 min at 50 W on a cycle ergometer) and then complete a test protocol consisting of four consecutive maximal knee extension movements of each leg at two different fixed movement velocities, 1.05 rad.sec-1 (60 deg.sec-1) and 3.14 rad·sec-1 (180 deg.sec-1) from which peak torque (Nm) data will be recorded. This assessment will be scheduled at a time of day roughly equivalent to that of your initial visit.