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Isometric exercise induces analgesia and reduces inhibition in patellar tendinopathy
  1. Ebonie Rio1,
  2. Dawson Kidgell2,
  3. Craig Purdam3,
  4. Jamie Gaida1,4,
  5. G Lorimer Moseley5,
  6. Alan J Pearce6,
  7. Jill Cook1
  1. 1Department of Physiotherapy, School of Primary Health Care, Monash University, Melbourne, Victoria, Australia
  2. 2Department of Rehabilitation, Nutrition and Sport, School of Allied Health, La Trobe University, Melbourne, Victoria, Australia
  3. 3Department of Physical Therapies, Australian Institute of Sport, Bruce, Australian Capital Territory, Australia
  4. 4University of Canberra, Canberra, Australian Capital Territory, Australia
  5. 5Sansom Institute for Health Research, University of South Australia & Pain Adelaide, Adelaide, South Australia, Australia
  6. 6Cognitive Neuroscience Unit, Deakin University, Burwood, Victoria, Australia
  1. Correspondence to Ebonie Rio, Department of Physiotherapy, School of Primary Health Care, Monash University, Peninsula Campus, P.O. Box 527, Frankston, Melbourne, VIC 3199, Australia; ebonie.rio{at}monash.edu

Abstract

Background Few interventions reduce patellar tendinopathy (PT) pain in the short term. Eccentric exercises are painful and have limited effectiveness during the competitive season. Isometric and isotonic muscle contractions may have an immediate effect on PT pain.

Methods This single-blinded, randomised cross-over study compared immediate and 45 min effects following a bout of isometric and isotonic muscle contractions. Outcome measures were PT pain during the single-leg decline squat (SLDS, 0–10), quadriceps strength on maximal voluntary isometric contraction (MVIC), and measures of corticospinal excitability and inhibition. Data were analysed using a split-plot in time-repeated measures analysis of variance (ANOVA).

Results 6 volleyball players with PT participated. Condition effects were detected with greater pain relief immediately from isometric contractions: isometric contractions reduced SLDS (mean±SD) from 7.0±2.04 to 0.17±0.41, and isotonic contractions reduced SLDS (mean±SD) from 6.33±2.80 to 3.75±3.28 (p<0.001). Isometric contractions released cortical inhibition (ratio mean±SD) from 27.53%±8.30 to 54.95%±5.47, but isotonic contractions had no significant effect on inhibition (pre 30.26±3.89, post 31.92±4.67; p=0.004). Condition by time analysis showed pain reduction was sustained at 45 min postisometric but not isotonic condition (p<0.001). The mean reduction in pain scores postisometric was 6.8/10 compared with 2.6/10 postisotonic. MVIC increased significantly following the isometric condition by 18.7±7.8%, and was significantly higher than baseline (p<0.001) and isotonic condition (p<0.001), and at 45 min (p<0.001).

Conclusions A single resistance training bout of isometric contractions reduced tendon pain immediately for at least 45 min postintervention and increased MVIC. The reduction in pain was paralleled by a reduction in cortical inhibition, providing insight into potential mechanisms. Isometric contractions can be completed without pain for people with PT. The clinical implications are that isometric muscle contractions may be used to reduce pain in people with PT without a reduction in muscle strength.

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