The effects of heat stress on neuromuscular activity during endurance exercise

Hunter, Angus M.; Gibson, Alan St Clair; Mbambo, Ziphelele; Lambert, Mike; Noakes, Timothy D.

doi:10.1007/s00424-002-0841-x

Cited by 46 publications

(4 citation statements)

References 22 publications

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“…Both muscle and skin temperatures increased significantly as exercise progressed under all conditions, but these values were significantly higher in H+H than in both HYP and NOR. Heat stress was rather modest in the present study (32 • C) compared with previous studies (>35 Hunter et al, 2002;Lorenzo et al, 2010;Guy et al, 2016). However, in H+H, muscle and skin temperatures reached 38.1 ± 0.1 • C and 36.2 ± 0.2 • C, respectively, by the end of exercise.…”

Section: Discussioncontrasting

confidence: 74%

Endocrine and Metabolic Responses to Endurance Exercise Under Hot and Hypoxic Conditions

et al. 2020

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Purpose: We explored the effect of heat stress during an acute endurance exercise session in hypoxia on endocrine and metabolic responses. Methods: A total of 12 healthy males cycled at a constant workload (60% of the power output associated with their maximal oxygen uptake under each respective condition) for 60 min in three different environments: exercise under hot and hypoxia (H+H; fraction of inspiratory oxygen or FiO 2 : 14.5%, 32 • C), exercise under hypoxia (HYP; FiO 2 : 14.5%, 23 • C), and exercise under normoxia (NOR; FiO 2 : 20.9%, 23 • C). After completing the exercise, participants remained in the chamber for 3 h to evaluate metabolic and endocrine responses under each environment. Changes in muscle oxygenation (only during exercise), blood variables, arterial oxygen saturation, and muscle temperature were determined up to 3 h after exercise. Results: Serum erythropoietin (EPO) level was increased to similar levels in both H+H and HYP at 3 h after exercise compared with before exercise (P < 0.05), whereas no significant increase was found under NOR. No significant difference between H+H and HYP was observed in the serum EPO level, blood lactate level, or muscle oxygenation at any time (P > 0.05). Exercise-induced serum growth hormone (GH) elevation was significantly greater in H+H compared with HYP (P < 0.05) and HYP showed significantly lower value than NOR (P < 0.05). Arterial oxygen saturation during exercise was significantly lower in H+H and HYP compared with NOR (P < 0.05). Furthermore, H+H showed higher value compared with HYP (P < 0.05). Conclusion: The serum EPO level increased significantly with endurance exercise in hypoxia. However, the addition of heat stress during endurance exercise in hypoxia did not augment the EPO response up to 3 h after completion of exercise. Exercise-induced GH elevation was significantly augmented when the hot exposure was combined during endurance exercise in hypoxia. Muscle oxygenation levels during endurance

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Section: Discussioncontrasting

confidence: 74%

Endocrine and Metabolic Responses to Endurance Exercise Under Hot and Hypoxic Conditions

et al. 2020

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“…The third important Wnding was that in all conditions, HR did not change signiWcantly between the second and the last repetition, conWrming that cardiovascular drift did not occur as a result of Xuid loss and associated mechanisms to maintain cardiac output and to dissipate heat (Hunter et al 2002;Baron et al 2008). Moreover, HR and did not reach maximal values during the Wnal interval indicating that muscular parameters and not the cardiovascular response regulated the sprinting performance (Young et al 1995;Chelly and Denis 2001).…”

Section: Discussionmentioning

confidence: 88%

The eccentric muscle loading influences the pacing strategies during repeated downhill sprint intervals

Baron¹,

Deruelle²,

Moullan³

et al. 2008

Eur J Appl Physiol

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The purpose was to compare self-chosen pace during ten repetitions of 60 m running sprints performed on a level surface (SPL), or when running uphill (SPU) or downhill (SPD) on a 4.7% slope. When expressed as percent of maximal running speed for corresponding condition, SPD was lower than SPL (95.28 +/- 1.93 vs. 97.31 +/- 1.29%; P = 0.044), which was lower than SPU (97.31 +/- 1.29 vs. 98.09 +/- 0.74%; P = 0.026). Heart rates, blood lactate concentrations and general perceived exertion were lower during SPD (163.8 +/- 8.3 bpm, 11.66 +/- 1.24 mmol L( -1), and 4.1 +/- 1.0) than SPL (169.8 +/- 7.8 bpm, 13.69 +/- 0.33 mmol L(-1), and 5.8 +/- 0.6), which were lower than SPU (174.9 +/- 8.7 bpm, 15.27 +/- 0.02, mmol L(-1), and 6.3 +/- 0.5) (P < 0.05 for all analyzes). Results show that the level of eccentric muscle loading influences the pacing strategy.

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“…Whilst some studies have observed a decrease in electromyographic (EMG) activity while cycling in hot ambient conditions (Kay et al 2001; Tucker et al 2004; Tucker et al 2006), others have reported that EMG activity was not affected during running (Ftaiti et al 2001) and cycling (Hunter et al 2002). However, it is difficult to interpret such EMG data during whole-body dynamic exercise as modifications in EMG activity may be linked to alterations in exercise modality, pattern and intensity.…”

Section: Introductionmentioning

confidence: 99%

Hot ambient conditions shift the Force / EMG relationship

Racinais

2013

SpringerPlus

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PurposeThis manuscript reports the data from two interventions on human subjects aiming to determine the effect of elevated core (HOT-core, study 1, 14 participants) and skin (HOT-skin, study 2, 11 participants) temperature on the force / EMG relationship.MethodsIn both studies, participant underwent an experimental trial and a control (CON) trial, in which maximal voluntary contractions (MVC) of the plantar flexors, surface EMG recordings of both the soleus and gastrocnemius medialis (GM), and electrical stimulation of the tibial nerve were performed to determine the percentage of voluntary activation (VA). During the HOT-core trial, rectal temperature was passively increased and then clamped at 39°C by adjusting the room temperature in the range of 46-50°C. During the HOT-skin trial, tests were performed in a temperate environment (~20°C) and skin temperature was locally affected by applying a cool or a hot pack during 1 min.ResultsHOT-core resulted in a decrease in MVC torque (−19%) and VA (−5%) (p < 0.05). HOT-skin did not induce any changes in MVC torque (−1%) or VA (+0%). However, the EMG activity (RMS) was decreased both in HOT-core (soleus −40%, GM −33%) and HOT-skin (soleus −10%, GM −13%), compared with CON (p < 0.05).ConclusionThe effect of skin temperature on EMG recordings may be attributed to both methodological and physiological factors. Hot ambient conditions shift the Torque / EMG relationship to the left, with the decrement in torque induced with passive hyperthermia lower than the decrement in EMG.

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The effects of heat stress on neuromuscular activity during endurance exercise

Cited by 46 publications

References 22 publications

Endocrine and Metabolic Responses to Endurance Exercise Under Hot and Hypoxic Conditions

Endocrine and Metabolic Responses to Endurance Exercise Under Hot and Hypoxic Conditions

The eccentric muscle loading influences the pacing strategies during repeated downhill sprint intervals

Hot ambient conditions shift the Force / EMG relationship

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