Author(s): RASP, D., ZAUSER, M., KERN, J., SCHWIRTZ, A., PATERNOSTER, F., Institution: TECHNICAL UNIVERSITY OF MUNICH, Country: GERMANY, Abstract-ID: 2235

INTRODUCTION:
Hamstring strength (HSS) and fatigue (HF) are associated with Hamstring Injuries (HSI) in multiple sports (1). Testing of HSS plays an essential role in return to sport or the prevention of HSI. Tests have to be fast, valid, reliable, mobile and should not put athletes health at risk. Our newly developed procedure of the 90:20 Isometric Posterior Chain Test (IPCT) (2,3) is compared with gold standard dynamometry to assess whether IPCT can be used to detect HF.
METHODS:
We tested HSS of 12 soccer players via optimized IPCT, and isokinetic measurements at 180°/s during the Loughborough Intermittent Shuttle Test (LIST). HSS was assessed pre- and post-match (PreM, PostM) and during half-time (HT) with the mentioned tests. We extracted maximum resultant force (Fres) for the IPCT and concentric and eccentric peak torque (CPT, EPT) and work (CW, EW) for the isokinetic measurements. We compared isokinetic HSS with HSS of IPCT. We also extracted the angle of peak torque (APT) for CPT and EPT.
RESULTS:
At PreM, Fres showed good agreement with EPT and EW (r=0.71* and r=0.67*) for the dominant leg (DL). In the non-dominant leg (NDL), Fres significantly correlated with CPT (r=0.64*), EPT (r=0.70*), CW (r=0.78**) and EW (r=0.61*), respectively. No significant correlations were found between Fres and isokinetic parameters for neither leg at HT. A tendency between Fres and EPT (r=0.53), and EW (r=0.57) for the DL could be observed. PostM only showed a significant correlation between Fres and CW (r=0.57*) for the DL. However, there were tendencies between Fres and CPT, EPT and EW (r=0.57 each) in the DL and Fres and EPT (r=0.53) in the NDL. APT of CPT at PreM, HT and PostM were 24.7°±8.3°, 28.3°±11.1° and 25.8°±5.1° for the DL and 26,0°±9.1°, 33,6°±22.3° and 23,1°±10,2° for the NDL. APT of EPT of 37,6°±19,9°, 47,1°±16,6° and 55,7°±21,1° for the DL and 47,5°±14,9°, 44,1°±20,6° and 41,8°±17,2° forNDL were measured for the respective points in time. Despite the differences between APT and the moment of measurement, ANOVA revealed no significance for neither of the comparisons.
CONCLUSION:
For the DL, Fres and EPT/EW show good agreement for PreM. Due to fatigue, APT of EPT shifts towards a more flexed knee, why agreement between Fres and isokinetic parameters worsens. APT of CPT remain comparable throughout the LIST; so do correlations of Fres with CPT and CW. NDL shows contradicting results. Although APT of EPT shows the highest value – knee more flexed – the agreement of Fres and isokinetic parameters is best at PreM. APT of EPT shifts towards a more extended knee during LIST, whereas APT of CPT increases at HT but becomes smaller at PostM than at PreM. To conclude, the optimized IPCT is suitable to measure HSS but is not acute HF due to change of APT. The high angular velocity of 180°/s may further contribute to a restricted agreement of isokinetic and isometric parameters.
[1] Ekstrand et al., 2022, Br. J. Sports Med. [2] Matinlauri et al., 2019, PLoS One. [3] Rasp et al., 2024, under review.