Hypoalgesia after bicycling at lactate threshold is reliable between sessions
Exercise decreases pain sensitivity known as exercise-induced hypoalgesia (EIH). However, the consistency of EIH after an acute exercise protocol based on subjective ratings of perceived exertion has been questioned. Objectives were to compare the effect on pressure pain thresholds (PPTs) after bicycling with work-rate at the lactate threshold compared with quiet rest, and investigate between-session reliability of EIH.
Thirty-four healthy subjects completed three sessions with 7 days in-between. In session 1, the lactate threshold was determined via blood samples (finger-tip pinprick, > 2 mmol/l increase from warm-up) during a graded bicycling task. In session 2 and 3, all subjects performed (1) 15 min quiet-rest, and (2) 15 min bicycling (work-rate corresponding to the lactate threshold) in the two identical sessions. PPTs at the quadriceps and trapezius muscles were assessed before and after both conditions. Reliability was assessed by intraclass correlations (ICCs).
Bicycling increased quadriceps PPT compared with quiet-rest in both sessions [mean difference: 45 kPa (95% CI 19–72 kPa), P = 0.002]; however, the increase in trapezius PPT was not significant after exercise. The EIH responses demonstrated fair between-session test–retest reliability (quadriceps: ICC = 0.45; trapezius: ICC = 0.57, P < 0.05), and agreement in EIH responders and non-responders between sessions was significant (quadriceps: κ = 0.46 and trapezius: κ = 0.43, P < 0.05).
In conclusion, bicycling at the lactate threshold increased PPT at the exercising muscle with fair reliability of the local EIH response. The results have implications for future EIH studies in subjects with and without pain and for clinicians who design exercise programs for pain relief.
KeywordsExercise Exercise-induced hypoalgesia Reliability Pressure pain thresholds Pain sensitivity
Body mass index
Conditioned pain modulation
Intraclass correlation coefficient
Numerical rating scale
Pressure pain threshold
Repeated-measures analysis of variance
Rating of perceived exertion
Rounds per minute
Standard error of measurement
Maximum rate of oxygen consumption
HBV, LKB, M-MR, SHR, and TG-N: All authors contributed to the design of the study, the analysis and interpretation of the data, as well as making intellectual contributions to its content. HBV, LKB, M-MR, and SHR collected all data in the laboratory. All authors approved the final manuscript.
No funding was received for this study. TGN is a part of Center for Neuroplasticity and Pain (CNAP) supported by the Danish National Research Foundation (DNRF121).
Compliance with ethical standards
Conflict of interest
There are no actual or potential conflicts of interest for any of the authors.
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