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

TITLE=Biomechanical Adaptations and Performance Indicators in Short Trail Running

JOURNAL=Frontiers in Physiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2019.00506

DOI=10.3389/fphys.2019.00506

ISSN=1664-042X

ABSTRACT=<p>Our aims were to measure anthropometric and oxygen uptake (<inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover><mml:mrow><mml:mi mathvariant="normal">V</mml:mi></mml:mrow><mml:mrow><mml:mo mathvariant="normal">˙</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math></inline-formula>O<sub>2</sub>) 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 <inline-formula><mml:math id="M2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover><mml:mrow><mml:mi mathvariant="normal">V</mml:mi></mml:mrow><mml:mrow><mml:mo mathvariant="normal">˙</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math></inline-formula>O<sub>2 max</sub>, 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, <italic>P</italic> &lt; 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 &gt; 25%) and least on flat terrain (CV &lt; 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 <italic>P</italic> &lt; 0.001). Force impulse was greatest on uphill (248 ± 46 vs. 175 ± 24 Ns, <italic>P</italic> &lt; 0.001) and related to GCT (<italic>r</italic> = 0.904, <italic>P</italic> &lt; 0.001). Peak force was greater during downhill than during uphill running (1106 ± 135 vs. 959 ± 104 N, <italic>P</italic> &lt; 0.01). Performance was related to absolute and relative <inline-formula><mml:math id="M3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover><mml:mrow><mml:mi mathvariant="normal">V</mml:mi></mml:mrow><mml:mrow><mml:mo mathvariant="normal">˙</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math></inline-formula>O<sub>2 max</sub> (<italic>P</italic> &lt; 0.01), vertical uphill treadmill speed (<italic>P</italic> &lt; 0.001) and fat percent (<italic>P</italic> &lt; 0.01). Running uphill involved the greatest impulse per step due to longer GCT while downhill running generated the highest peak forces. <inline-formula><mml:math id="M4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover><mml:mrow><mml:mi mathvariant="normal">V</mml:mi></mml:mrow><mml:mrow><mml:mo mathvariant="normal">˙</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math></inline-formula>O<sub>2 max</sub>, 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.</p>