Electrically Induced Knee Pain Does Not Alter Time-to-Task Failure During Submaximal Knee Extension Exercise

The application of pain to skeletal muscle during exercise has been shown to induce central fatigue and reduce exercise performance. Joint pain, like that experienced in those with osteoarthritis, could also lead to central fatigue and reduce exercise performance remains unclear. PURPOSE: The purpose of this study was to determine if electrically induced knee joint pain applied to either the exercising knee (ipsilateral pain; IP) or the contralateral knee (contralateral pain; CP) altered time-to-task failure (TTF) during knee extension exercise. METHODS: Twenty-two participants (Females = 9, Males = 12, N/A = 1) completed five visits (2 familiarization and 3 experimental) separated by 48 hours. At the beginning of each of the visits, the electrical stimulus eliciting a knee pain rating of 4/10 was determined. The location of the pain (IP, CP, or control of no pain) was randomized among the visits. An intermittent, submaximal time-to-task failure protocol was performed with a target force of 15% over critical torque at a 6 sec:4 sec work to rest cycle until force output does not meet target force consecutively for 3 contractions. MVC after 60 seconds of exercise, the last assessed MVC, and the MVC performed immediately after task failure was reached was reported during TTF protocol. RESULTS: Mixed model ANOVA found no significant interactions in TTF between pain location (CP, IP, or control) and sex (p = 0.43), nor were there main effects for sex (357 ± 261 sec vs. 430 ± 262 sec for women and men, respectively; p = 0.54) or for pain condition (351 ± 278 sec vs. 352 ± 203 sec vs. 477 ± 428 sec for IP, CP, and Control, respectively; p = 0.14). There was no effect of knee pain location or sex on the change in MVC during for immediately following exercise (p ≥ 0.18 for each interaction). The decline in MVC at the end of exercise was similar among the pain conditions (-25.1 ± 17.5 vs. -22.8 ± 19.8 vs. -22.8 ± 18.4% for Control, IP, and CP, respectively, p = 0.81). CONCLUSIONS: Location of knee pain stimulus did not impact time-to-task failure. There was no difference between the location of knee pain stimulus and reduced exercise performance on TTF protocol.