Effects of experimentally induced muscle pain on endurance performance: A proof‐of‐concept study assessing neurophysiological and perceptual responses

• Published in: Psychophysiology 2021-06, Vol.58 (6), p.e13810-n/a
• Main Authors: Canestri, Raul, Franco‐Alvarenga, Paulo Estevão, Brietzke, Cayque, Vinícius, Ítalo, Smith, Samuel A., Mauger, Alexis R., Goethel, Márcio Fagundes, Pires, Flávio Oliveira
• Format: Article
• Language: English
• Subjects: Adult; Bicycling - physiology; Contraction; Cortex (frontal); Cortex (motor); Cortex (parietal); EEG; Electroencephalography; Electromyography; endurance performance; Fatigue; Humans; hypertonic saline; Injection; Male; Motor Cortex; Muscle contraction; Muscle Fatigue - physiology; Muscle pain; Myalgia - chemically induced; Pain perception; perceived exertion; Physical Endurance - physiology; Physical Exertion - physiology; Prefrontal Cortex; Quadriceps Muscle; Saline Solution, Hypertonic
• ISSN: 0048-5772; 1469-8986; 1540-5958
• DOI: 10.1111/psyp.13810

Pain arising from exercise potentiates fatigue and impairs the performance of endurance exercise. We assessed neurophysiological and perceptual responses to endurance exercise performed under experimentally induced muscle pain by a model that separates muscle pain from muscle fatigue. After a series of pilot studies investigating different hypertonic saline volumes, 17 healthy males performed a preliminary VO2PEAK test before performing a familiarization of the cycling time‐to‐exhaustion exercise (80% of the peak power output in the VO2PEAK test). Participants, performed a baseline exercise session before the sessions with hypertonic and isotonic saline injections in the vastus lateralis of both legs, in a crossover and counterbalanced design. Neurophysiological and perceptual responses such as electroencephalography (EEG) in frontal, prefrontal, parietal, and motor cortex, electromyography (EMG) of the vastus lateralis and biceps femoris muscles, ratings of perceived exertion (RPE), pain sensation, and affective valence were measured at rest and during exercise. The hypertonic injection reduced the resting EEG alpha‐beta ratio in the frontal and prefrontal cortex. When compared to exercise performed after the isotonic injection (430.5 ± 152.6 s), hypertonic injection shortened the time‐to‐exhaustion (357.5 ± 173.0 s), reduced the EMG of the assessed muscles, and increased the muscle co‐contraction during exercise. The hypertonic injection also reduced the EEG alpha‐beta ratio in the prefrontal and parietal cortex, increased RPE and pain sensation, and reduced affective valence during exercise. This proof‐of‐concept study showed that hypertonic injection‐induced muscle pain reduced endurance performance, promoting centrally mediated alterations in motor command and cortical activation, as well as an interplay of perceptual responses. Intense exercise induces muscle pain, which potentiates muscle fatigue and reduces performance. We investigated neurophysiological and perceptual responses to exercise after inducing muscle pain by a model that separates muscle pain from muscle fatigue. Pain induced by hypertonic saline injection shifted the activation in pain cortical areas at rest and during exercise, altered the motor command to peripheral muscles assessed with EMG, and reduced performance. Muscle pain also influenced perceived exertion and displeasure during exercise.