Biomechanical Adaptations and Performance Indicators in Short Trail Running.

Glenn Björklund,Dennis-Peter Born,Thomas Stöggl,Mikael Swarén

doi:10.3389/fphys.2019.00506

Abstract

Our aims were to measure anthropometric and oxygen uptake (O2) variables in the laboratory, to measure kinetic and stride characteristics during a trail running time trial, and then analyse the data for correlations with trail running performance. Runners (13 men, 4 women: mean age: 29 ± 5 years; stature: 179.5 ± 0.8 cm; body mass: 69.1 ± 7.4 kg) performed laboratory tests to determine O2 max, running economy (RE), and anthropometric characteristics. On a separate day they performed an outdoor trail running time trial (two 3.5 km laps, total climb: 486 m) while we collected kinetic and time data. Comparing lap 2 with lap 1 (19:40 ± 1:57 min vs. 21:08 ± 2:09 min, P < 0.001), runners lost most time on the uphill sections and least on technical downhills (-2.5 ± 9.1 s). Inter-individual performance varied most for the downhills (CV > 25%) and least on flat terrain (CV < 10%). Overall stride cycle and ground contact time (GCT) were shorter in downhill than uphill sections (0.64 ± 0.03 vs. 0.84 ± 0.09 s; 0.26 ± 0.03 vs. 0.46 ± 0.90 s, both P < 0.001). Force impulse was greatest on uphill (248 ± 46 vs. 175 ± 24 Ns, P < 0.001) and related to GCT (r = 0.904, P < 0.001). Peak force was greater during downhill than during uphill running (1106 ± 135 vs. 959 ± 104 N, P < 0.01). Performance was related to absolute and relative O2 max (P < 0.01), vertical uphill treadmill speed (P < 0.001) and fat percent (P < 0.01). Running uphill involved the greatest impulse per step due to longer GCT while downhill running generated the highest peak forces. O2 max, vertical running speed and fat percent are important predictors for trail running performance. Performance between runners varied the most on downhills throughout the course, while pacing resembled a reversed J pattern. Future studies should focus on longer competition distances to verify these findings and with application of measures of 3D kinematics.

Highlights

IntroductionDue to varying surfaces and inclines compared to track and road running
Trail running is challenging, due to varying surfaces and inclines compared to track and road running
Laboratory data associated with performance were V O2 max (r = −0.71, P = 0.005 and −0.82, P < 0.001 for L · min−1 and mL · kg−1 · min−1) and vertical uphill speed (r = −0.85, P < 0.001), while running economy (RE) expressed as mL · kg−1 · km−1 (r = −0.16, P = 0.60) or J · kg−1 · m−1 (r = −0.07, P = 0.83) were not (Figure 2)

Summary

Introduction

Due to varying surfaces and inclines compared to track and road running. Relative V O2 max is shown to be an important parameter for uphill treadmill and outdoor running (Staab et al, 1992; Townshend et al, 2010), as it expresses the upper limit for aerobic power in relation to body mass. It is noteworthy that V O2 max is of lesser importance for downhill running performance, as shown in outdoor running performance (Townshend et al, 2010) and laboratory-based time trials (Liefeldt et al, 1992; Staab et al, 1992; Minetti et al, 2002; Toyomura et al, 2018). In a recent study of trail running on a more technical track with steeper downhill gradients none of the runners reached their V O2 max despite running at maximum effort (Born et al, 2017). For running over undulating rough terrain with great variations in gradient, the time spent descending is the strongest predictor for running performance (Kay, 2014)

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Conclusion