An investigation of relationships between hip flexor characteristics and hockey fitness tests using principal component analysis

Introduction. The energy demands of ice hockey require that performance testing of athletes be able to accurately assess fitness using the developed testing protocols. As hockey is a high-speed sport with frequent application of large impact forces, injuries occur. Groin injuries in particular have received attention recently and are thought to be a common over-use injury. This thesis investigated the relationships between some commonly used fitness tests with a specific focus on the hip flexors and extensors and, with the inclusion of biomechanical analyses, it also addressed the roles of hip strength, power, and endurance on the skating stride to provide a basis for future groin injury research. Methods. Within a two-week window, 17 subjects (M, 25 ± 5.8 yrs, 1.80 ± 0.07 m, 85.7 ± 9.0 kg) participated in Repeated Sprint Skate (RSS), Wingate Anaerobic Test (WAT), Vertical Jump (VJ), and isokinetic hip flexion/extension protocols. The video-taped first 7.0 m of the RSS was analyzed using Hu-M-An 3.0 software for kinematic characteristics about the hip. A 30 s (90g•kg-1 ) WAT protocol was used. Three isokinetic protocols testing strength (3 reps, 300/s), power (3 reps, 1800/s) and endurance (2 sets of 25 reps separated by 90 seconds rest, 1800/s) were administered. Statistical analyses including Principal Components Analysis (PCA) were conducted to investigate the relationships between the results from the testing protocols. Results. VJ power (136.37 ± 13.23 kg•m•s-1), anaerobic capacities (10.8 ± 0.9 W/kg (WAT) and 6.0 ± 0.4 W/kg (RSS)) and anaerobic powers (13.8 ± 1.3 W/kg (WAT) and 7.4 ±0.6 W/kg (RSS)) were comparable to previous literature. Hip flexion results were 1.9 ± 0.3 Nm/kg (strength) and 1.1 ± 0.2 Nm/kg (power) with a 30.9 ±13.1 % decline over 50 reps. PCA of the RSS indicated a reliance on the fatigue measurements from the six repeats and was found to correlate with hip flexion fatigue. Conclusion. Hip flexors were found to be highly susceptible to fatigue during isokinetic testing. This hip flexion endurance measurement was found to correlate with the PCA results most influenced by on-ice endurance characteristics. This finding may benefit researchers investigating groin injuries as an over-use phenomenon and suggests hip flexor specific training could be beneficial.