The use of global positioning systems (GPS), or more appropriately named ‘wearable technology’, in high-performance sport is becoming increasingly popular despite having a considerable price tag. As this technology is not only very expensive, but is also heavily contributing towards the inclusion and exclusion of athletes from training and competition, the validity and reliability of these devices is significantly important. Whilst GPS units have been shown to possess reasonable reliability when measuring long distances at slow-moderate speeds, they tend to struggle during short-distance, high-speed movements – particularly during rapid randomised directional changes. The tri-axial accelerometer appears to be a valid and reliable measure for quantifying acceleration forces in three perpendicular planes (x, y, and z). However, the use of the “Player/Body Load” value seems questionable due to the potential non-inclusion of rotational force data from the gyroscope, which may therefore underestimate sport-specific movements such as: tackling, jumping, and blocking. In support of this issue, movement classification has been shown to improve by 2-14% when the gyroscope data is combined with the accelerometer data. Despite this, at least to our knowledge, no evidence supports the validity and/or reliability of the gyroscope, magnetometer, or the heart rate monitor. All in all, these devices may be no better at monitoring performance than the equipment included within a typical smart phone (e.g. iPhone). This should not necessarily discredit their quality, as the equipment within both the wearables and the iPhone ‘may’ be highly-sophisticated and accurate, though there is limited evidence to support their efficacy.
Keywords: GPS unit, micro-sensor, wearables, wearable technology, micro-technology, tri-axial accelerometer, gyroscope, magnetometer, vectors, sports science