The effect of hypertonic saline evoked muscle pain on neurophysiological changes and exercise performance in the contralateral limb

Abstract

Non-local muscle pain may impair endurance performance through neurophysiological mechanisms, but these are relatively unknown. This study examined the effects of muscle pain on neuromuscular and neurophysiological responses in the contralateral limb. On separate visits, nine participants completed an isometric time to task failure (TTF) using the right knee extensors after intramuscular injection of isotonic saline (CTRL) or hypertonic saline (HYP) into the left vastus lateralis. Measures of neuromuscular fatigue were taken before, during and after the TTF using transcranial magnetic stimulation (TMS) and peripheral nerve stimulation. Mean pain intensity was greater in the left leg in HYP (3.3 ± 1.9) compared to CTRL (0.4 ± 0.7; P < 0.001) which was combined with a reduced TTF by 9.8% in HYP (4.54 ± 0.56 min) compared to CTRL (5.07 ± 0.77 min; P = 0.005). Maximum voluntary force was not different between conditions (all P > 0.05). Voluntary activation was lower in HYP compared to CTRL (P = 0.022). No difference was identified between conditions for doublet amplitude (P > 0.05). Furthermore, no difference in MEP·Mmax−1 or the TMS silent period between conditions was observed (all P > 0.05). Non-local pain impairs endurance performance of the contralateral limb. This impairment in performance is likely due to the faster attainment of the sensory tolerance limit from a greater amount of sensory feedback originating from the non-exercising, but painful, left leg.

The corticomuscular response to experimental pain via blood flow occlusion when applied to the ipsilateral and contralateral leg during an isometric force task

“…Contrary to our hypotheses, CON-OCC elevated perceived pain (relative to the control condition) but did not elevate RPE and had no effect on CMC, EMG activity or isometric force control in the ipsilateral-exercising leg. As per previous work, we had expected to observe a crossover effect whereby the activation of nonexercising musculature group III-IV afferents (via occlusion) would have elicited inhibitory feedback to the corticomotor circuitries and thus curtail the central motor output in the exercising limb musculature (Azevedo et al, 2022;Norbury et al, 2022). However, the evidence supporting these crossover effects remains mixed, with several studies showing concurrent rising pain in the contralateral limb, in the absence of perceptual exertion, does not affect muscle activity, voluntary drive, and thus motor unit recruitment (Aboodarda et al, 2020;Kennedy et al, 2015).…”

Topical application of isolated menthol and combined menthol‐capsaicin creams: Exercise tolerance, thermal perception, pain, attentional focus and thermoregulation in the heat

“…Examples of thoughts in each dimension were provided to the participants based on previous suggestions (Brick et al, 2014). In addition, participants were asked for their general pain response, which was accompanied by a working definition prior to the trial an unpleasant sensory and emotional experience associated with the exertion of the exercise task (Norbury et al, 2022). Participants were given time with the questionnaire, full verbal instructions and the opportunity to practice with the questions prior to the trial days.…”

Intra‐ and interindividual reliability of muscle pain induced by an intramuscular injection of hypertonic saline injection into the quadriceps

“…When injected, hypertonic saline activates Group III/IV nociceptive afferents and is suggested to induce an acute experience of pain that is comparable to clinical muscle pain (Graven‐Nielsen et al, 1997a). It is considered safe, does not impair peripheral function and can be placebo‐controlled in the form of isotonic saline (Graven‐Nielsen et al, 1997b; Graven‐Nielsen & Arendt‐Nielsen, 2003; Norbury et al, 2022a).…”

“…locomotion, stair climbing, running, cycling) (Raasch et al, 1997; Sasaki & Neptune, 2006). Based on this, a number of recent investigations have applied the hypertonic saline model of muscle pain in the VL (Canestri et al, 2021: Norbury et al, 2022a; Norbury et al, 2022b; Smith et al, 2020; Smith et al, 2021), providing evidence for the impact of acute muscle pain in a context that is translatable and functionally relevant. Therefore, the aim of this study was to quantify the intra‐ and interindividual reliability of pain intensity and pain quality measures after the singular bolus of 1 mL (a volume that is commonly used and induces a robust pain response (Norbury et al, 2022b; Smith et al, 2020; Smith et al, 2021)) 5.85% hypertonic saline injected into the VL.…”