Validity and reliability of the CycleOps Hammer direct drive trainer during sprint tests when compared with an SRM powermeter - a preliminary study

Background: Coaches and cyclists often use direct drive home-trainers for measuring power output (PO) during testing and training. Several devices like the Tacx Fortius (Peiffer et al., 2011: International Journal of Sports Medicine, 32, 353-356) and the Velotron trainer (Abbiss et al., 2009: International Journal of Sports Medicine, 30, 107-112) have been scientifically validated when compared to an SRM powermeter which is considered as the gold standard (Gardner et al., 2004: Medicine Science in Sports and Exercise, 36, 1252-1258). Contrarywise, others such as the Axiom Elite (Bertucci et al., 2005: International Journal of Sports Medicine, 26, 59-65) or the Kickr Power trainer (Zadow et al., 2016: International Journal of Sport Physiology and Performance, 11, 1115-1117) are less accurate and reliable. A recent study reported that the CycleOps Hammer provides valid and reliable PO measurements during graded exercise tests (100-500W). This validation procedure is nevertheless uncompleted as no comparison in maximal PO during all-out sprints have been done. Purpose: The purpose of this study was to assess the validity and reliability of PO measurement of three Cycleops Hammer trainer devices during maximal sprint tests when compared to an SRM powermeter. Methods: Three cyclists voluntarily participated in this study (Mean ± SD: 28 ± 9 years old; 1.81 ± 0.02 m; 72 ± 5 kg). Each subject performed three one-day laboratory test sessions separated by at least 48 h, that comprised successively: 1) one maximal graded exercise test (100-425 W) performed at a constant pedalling cadence (~90 rpm) ; 2) three 10-s all-out sprint tests against three different slope resistance (0.5%, 3%, 7%) ; 3) one 30-s all-out Wingate test (slope resistance of 3 %) ; and 4) a 20 min constant power test to study the potential power drift. All the tests were performed on the same road bike (Roubaix Tarmac, Specialized, USA) that was mounted on to a Hammer direct drive trainer (CycleOps, Madison, USA) and fitted with a SRM professional powermeter (SRM FSA K-Force Light, SRM GmbH, Jülich, Germany; accuracy ± 1 %). Prior to the study, the slope of the SRM powermeter was calibrated with set of weights. The zero offset of each device was performed according to the manufacturer’s recommendations before each test session. Power output (PO) and pedalling cadence (PC) were measured continuously by the two devices every second and stored in a GPS bike computer (Edge 520, Garmin, USA). The PO dif