Abstract
PurposeTo investigate potential differences in patellar tendon properties between elite and non-elite soccer players, and to establish whether tendon properties were related to power assessed during unilateral jumps performed in different directions.MethodsElite (n = 16; age 18.1 ± 1.0 years) and non-elite (n = 13; age 22.3 ± 2.7 years) soccer players performed vertical, horizontal-forward and medial unilateral countermovement jumps (CMJs) on a force plate. Patellar tendon (PT) cross-sectional area, elongation, strain, stiffness, and Young’s modulus (measured at the highest common force interval) were assessed with ultrasonography and isokinetic dynamometry.ResultsElite demonstrated greater PT elongation (6.83 ± 1.87 vs. 4.92 ± 1.88 mm, P = 0.011) and strain (11.73 ± 3.25 vs. 8.38 ± 3.06%, P = 0.009) than non-elite soccer players. Projectile range and peak horizontal power during horizontal-forward CMJ correlated positively with tendon elongation (r = 0.657 and 0.693, P < 0.001) but inversely with Young’s modulus (r = − 0.376 and − 0.402; P = 0.044 and 0.031). Peak medial power during medial CMJ correlated positively with tendon elongation (r = 0.658, P < 0.001) but inversely with tendon stiffness (r = − 0.368, P = 0.050).ConclusionsNot only does a more compliant patellar tendon appear to be an indicator of elite soccer playing status but it may also facilitate unilateral horizontal-forward and medial, but not vertical CMJ performance. These findings should be considered when prescribing talent selection and development protocols related to direction-specific power in elite soccer players.
Highlights
During the course of a match, an elite soccer player may perform up to ~ 119 maximal accelerations, ~ 35 sprints (Bradley et al 2010), ~ 50 forceful changes of direction (Withers et al 1982), and ~ 16 vertical jumps (Reilly and Thomas 1976)
The methods utilised in the previous research investigating the association between tendon properties and sport-specific performance were limited, as they measured the properties of the vastus lateralis (VL) aponeurosis rather than the patellar tendon and, had to apply a series of corrections to estimate tendon elongation (Kubo et al 2011; Bojsen-Møller et al 2005; Stafilidis and Arampatzis 2007)
There was a main effect of tendon location (F4,108 = 105.36, P < 0.001) with pairwise post hoc analyses, revealing that tendon cross-sectional area (CSA) varied along the length of the tendon (0 vs. 25%, P = 0.001; 0 vs. 50%, P < 0.001; 0 vs. 75%, P < 0.001; 0 vs. 100%, P < 0.001; 25 vs. 75%, P < 0.001; 25 vs. 100%, P < 0.001; 50 vs. 75%, P < 0.001; 50 vs. 100%, P < 0.001; 75 vs. 100%, P = 0.007; Fig. 1); except at 25 vs. 50% tendon length where there was a non-significant difference (P = 0.063; Fig. 1)
Summary
During the course of a match, an elite soccer player may perform up to ~ 119 maximal accelerations, ~ 35 sprints (Bradley et al 2010), ~ 50 forceful changes of direction (Withers et al 1982), and ~ 16 vertical jumps (Reilly and Thomas 1976). Significant correlations have been reported between 100 m race performance and VL aponeurosis compliance (Kubo et al 2000b) and maximal elongation (Stafilidis and Arampatzis 2007) This suggests that greater elongation of the VL tendon–aponeurosis complex allows the utilisation of greater energy storage and increases the shortening velocity of the knee-extensor muscle–tendon unit during sprint running. Results from some vertical jump studies are in accordance with these findings, and report that VL aponeurosis stiffness correlated inversely with the calculated difference in jump height between bilateral vertical countermovement jumps and squat jumps These data suggest that the greater compliance of the VL tendon–aponeurosis complex facilitates the augmentation in jump performance with a countermovement (i.e., when comparing bilateral vertical countermovement jumps vs squat jumps) (Kubo et al 1999). Assessing in vivo human tendon properties directly via ultrasound and isokinetic dynamometry (Seynnes et al 2009; Hansen et al 2006; Wiesinger et al 2016), on the other hand, would enable a more precise investigation of a potential relationship between tendon properties and sport-specific measures of physical performance
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