Figure 1. Protocol overview for testing, digoxin, forearm exercise and leg cycle exercise.

A, after giving informed consent, participants underwent screening, baseline testing and were randomised into treatment groups initially taking either digoxin or placebo, and in a crossover design, followed then by the alternative treatment; participants then underwent familiarisation and variability testing, with all test procedures and timing detailed in the methods. B, protocol for forearm exercise trials (FA) indicating timing of forearm blood flow measures and of arterial and antecubital venous blood sampling, in relation to exercise and recovery times. C, protocol for leg cycling exercise trials indicating timing of muscle biopsies and of arterial and antecubital venous blood sampling, in relation to exercise and recovery times. F, fatigue.