Introduction Patellar tendinopathy (PT) affects the ability to jump and land due to pain and associated corticospinal changes to motor patterning.
Whilst eccentric exercise is commonly used in rehabilitation, it can be painful to complete.1 Tendinopathy is especially problematic in competitive season, during which there are constant time and performance pressures.2 Where eccentric exercise has been completed in the competitive season, there has been poor adherence due to pain and either no benefit [Visnes, 2005] or worse outcomes [Fredberg, 2008]. There is a need for interventions that reduce pain immediately, enabling participation in sport yet do not negatively impact on muscle fatigue, which may affect performance. The purpose of this study was to compare an acute bout of either isometric or isotonic muscle contractions on patellar tendon pain and function and maximal voluntary isometric leg extension torque.
Methods This was a single blinded, randomised cross over study compared the effect of a bout of isometric and isotonic muscle contractions on patellar tendon pain, quadriceps strength and measures of corticospinal excitability and inhibition. Outcome measures were single leg decline squat pain (SLDS) for tendon pain, transcranial magnetic stimulation for corticospinal excitability and inhibition and maximal voluntary isometric contraction (MVIC) torque for quadriceps strength. Data were analysed using a split-plot in time repeated measures ANOVA.
Results Six volleyball players with PT participated (mean SLDS pain was 7.5/10 (range 7–8), mean cortical inhibition ratio was 27.53% ± 13.0). Isometric muscle contractions significantly reduced SLDS pain immediately (mean 0.16/10 range 0–1; p < 0.0001; 95% CI: -5.887– -1.280) (Figure 1) and reduced cortical inhibition to 54.95% ± 8.25 compared to isotonic contractions, (95% CI: 12.13–33.92; p = 0.0020) regardless of the order of intervention and resulted in sustained pain relief for at least 45 min post intervention. MVIC was increased following the isometric muscle contraction intervention by 18.7% but decreased following the isotonic protocol.
Discussion Compared to isotonic contractions, a single strength training bout of isometric contractions reduced patellar tendon pain immediately and for at least 45 min post intervention and increased MVIC. The reduction in pain was paralleled by a reduction cortical inhibition, providing insight into potential mechanisms. The clinical implications are that isometric muscle contractions may be used to reduce pain without associated muscle fatigue in PT.
References 1 Alfredson H, Pietila T, Jonsson P, Lorentzon R. Am J Sports Med. 1998;26(3):360–6
2 Cook J, Purdam C. Br J Sports Med. 2014;48(7):506–9
3 Visnes H, Hoksrud A, Cook J, Bahr R. Clin J Sports Med. 2005;15(4):227–34
4 Fredberg U, Bolvig L, Andersen NT. Am. J Sports Med. 2008;36(3):451–60
5 Weier AT, Pearce AJ, Kidgell DJ. Acta Physiol. 2012;206(2):109–19
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