Load Monitoring With Consumer Wearables in Amateur Endurance Athletes: Signal, Noise and Behaviour Change

Consumer wearable devices are now used routinely by amateur endurance athletes to estimate training
load through step counts, heart rate, energy expenditure, and GPS-derived pace and distance, yet
validation studies consistently find measurement error that varies substantially by metric, device, and
exercise intensity, with wrist-worn optical heart-rate accuracy in particular degrading markedly during
high-intensity effort. A separate and distinct evidence base addresses whether wearable feedback actually
changes training behaviour, generally finding a modest short-term increase in physical activity that
attenuates over months of continued use. This review synthesises the device-validation and
behaviour-change literature relevant to consumer wearable load monitoring in amateur endurance
athletes, distinguishing genuine physiological signal from measurement noise and situating both within
the separate question of whether wearable data sustainably changes training behaviour.