Brief Summary
With the NBA season approaching we look to shift attention to one of the more commonly encountered issues associated with jumping and landing sports, Patella Tendinopathy. This issue is widely encountered across elite level basketball as well as many other sporting codes and can be challenging to manage. With many strategies published on the management of Patella Tendinopathy (PT), this summary aims to outline the work conducted by Rio et al (2016), which involved the utilisation of isometrics to induce tendinopathy related pain relief. The aim of this research article was to assess if either isotonic or isometric exercise would induce immediate pain relief in PT. A secondary aim was to explore underlying mechanisms and associated changes to cortical motor function.
This study was a single-blinded, randomised cross-over trial with two intervention arms. 6 volleyball players were recruited, 3 with unilateral and 3 with bilateral PT symptoms. The diagnosis of PT was made by a physiotherapist. All 6 had discomfort present during jumping, landing and a decline single leg squat. Diagnosis was confirmed under ultrasound imaging. All athletes involved were playing competitively once weekly and training twice weekly. Motor neuroaxis was investigated using single pulsed transcranial magnetic stimulation (TMS). Paired-pulse TMS can measure short-interval intra-cortical inhibition (SICI), which is thought to be mediated at a cortical level rather than at the spinal cord and quantifies the effect of the inhibitory neurons that synapse in the primary motor cortex. These allow researchers to better understand the central and peripheral contributions to any exercise mediated response. All testing was completed exactly 1 week apart to ensure stability of loading prior to testing. The order of intervention was randomised by asking the athlete to draw an opaque sealed envelope with no external markings (concealed randomisation).
Baseline testing at week 1 was completed without any intervention to ensure strength and pain testing measures, and TMS measures themselves, did not affect the primary outcome measures and to familiarise participants with the equipment and protocol. The single leg decline squat was used as a tendon pain provocation test. Participants provided a numerical pain rating score for the decline squat on a rating scale with ‘0, no pain’ and ‘10, worst possible pain’. Maximal voluntary isometric contraction (MVIC) torque for the quadriceps on the tested side was recorded in Nm using seated knee extension with the knee in 60° flexion. Baseline measures of corticospinal excitability and short-interval intra-cortical inhibition (SICI) were obtained using single-pulse and paired-pulse TMS, respectively. Athletes were also asked to complete a Victorian Institute of Sport Assessment–patellar tendon questionnaire (VISA-P). At weeks 2 and 3, baseline measures were repeated (to enable comparison to week 1 baseline as well as the baseline of that intervention session).
Figure 1.
Isometric and Isotonic protocols were matched for time under tension and rest between sets (Table 1). Repetition maximum and MVIC were determined in the familiarisation session. As muscle work during isometric exercise and isotonic exercise cannot be directly measured, protocols were matched for perceived exertion on the basis of pilot studies. Follow up testing occurred immediately after the intervention consisting of pain and strength testing measures and TMS measures. This testing was repeated 45 minutes post intervention (figure 1).
Table 1.
Participants had substantial tendon pain. Mean VISA-P was 52.8 (47.5 to 66.5). There were no systematic differences detected in baseline single leg decline squat (SLDS) pain, stimulus-response slope, SICI or MVIC at the first or each subsequent testing session indicating sufficient wash-out between sessions. Baseline SLDS pain did not differ significantly prior to either intervention. Preisometric intervention pain (mean±SD) was 7/ 10±2.04 and pre-isotonic intervention pain was 6.33/10±2.80 (p>0.99). Isometric exercise reduced pain on the SLDS (mean ±SD) immediately from 7/10±2.04 to 0.17/10±0.41 (p=0.004); the reduction was sustained at 45min (p<0.001; figure 2). Isotonic exercise resulted in immediate pain relief on SLDS (mean±SD) from 6.33/10±2.80 to 3.75/10±4.67 (p=0.04), but this was not sustained at 45min. This corresponds to an immediate mean reduction in pain following isometric exercise of 6.8/10 compared with 2.6/10 post-isotonic exercise. Individual data are shown in figure 3.
Figure 2 
Figure 3 
Isometric exercise immediately reduced PT pain, this effect was sustained for at least 45 min. There was a smaller magnitude immediate effect for isotonic exercise that was not sustained. Release of intracortical inhibition was associated with pain reduction and may be implicated as an underlying mechanism for the changes in pain. There was an increase in MVIC post-isometric exercise that may be attributed to a decrease in intracortical inhibition.
Conclusion
The findings of this study justify the selection of isometric loading for the immediate pain relief in athletes with PT pain. This implies that isometric loading could be used in the management of PT pain during the competitive phase of an athletes season to reduce discomfort and motor inhibition prior to training and competition given the fact that effects can be seen for 45min post exercise. In effect, isometric loading could provide a window that allows clinicians working with athletes in patella tendon rehabilitation to load the athlete and train movement strategies more effectively.
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