Prior to the exercise bouts, baseline measurements were taken. On completion, two different exercise regimes were carried out to examine different facets of muscle function. In the first, PCr recovery kinetics was examined by undertaking short bouts of continuous exercise. Subsequently, Navitoclax nmr after a recovery period, a ramp exercise protocol was undertaken in which the workload was continually increased until

the point of participant failure. The participants were positioned in the scanner head first in a prone position such that the subject’s right quadriceps muscle was centred directly over a 6-cm 31P transmit/receive surface coil. They were subsequently secured to the scanner bed using Velcro straps at the thigh, buttocks, lower back, and middle back to minimise extraneous movement. In order to undertake exercise testing, a custom-designed nylon ergometer frame fitted onto the bed in alignment with the subject’s feet and a base unit was positioned behind the bed. Cuffs with Velcro straps were secured to the subject’s foot and attached to a rope which passed around pulleys housed within the frame to the base unit, where they were attached to non-magnetic weights. Prior to the beginning of exercise, images were acquired to confirm that the quadriceps Doxorubicin muscle was

positioned directly above the 31P coil. Subsequently, a pre-exercise baseline spectrum was acquired with long repetition time (TR = 20 s) in which the relative unsaturated peak amplitudes could be determined. Molar concentrations of PCr and ATP were subsequently calculated via the ratio of Pi:PCr and Pi:ATP, assuming a resting concentration of ATP of 8.2 mmol/L. The exercise protocol consisted of one-legged knee extensions, which resulted in the lifting of weights via the pulley system. The extensions took place at a frequency of 0.67 Hz with the foot moving over a distance of ∼0.22 m, with both visual and audio cues being given to ensure that the rate of contraction was maintained at the desired value. To examine PCr recovery

kinetics, two 24-s bouts of exercise were performed, separated by a recovery acetylcholine period of 4 min. In order to obtain a significant PCr depletion (∼40%), thereby maximising the accuracy of the recovery data fitting, exercise was undertaken with weights of mass 1 kg less than the maximum weight each subject achieved during the previous familiarity session. As the rate of PCr recovery has previously been shown to be pH dependent,30 and 31 exercise bouts were limited to 24 s as we have previously determined that exercise for that period does not lead to a measurable decrease in pH. The ramp protocol involved the participants continually exercising to volitional fatigue. Initially, exercise was carried out with a weight of 1 kg mass. This was then increased by 0.5 kg every 30 s until exhaustion, the time of which was recorded. During exercise and recovery, 31P data were acquired every 1.