Effect of Pre-Exercise Caffeine Intake on Endurance Performance and Core Temperature Regulation During Exercise in the Heat: A Systematic Review with Meta-Analysis

Naulleau, Catherine; Jeker, David; Pancrate, Timothée; Claveau, Pascale; Deshayes, Thomas A.; Burke, Louise M.; Goulet, Eric

doi:10.1007/s40279-022-01692-1

Cited by 7 publications

(5 citation statements)

References 70 publications

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“…DITI was performed using the Iris-XP Digital infrared imaging system (Medicore, Seoul, Republic of Korea). Volunteers scheduled for DITI were informed about general precautions such as avoiding exposure to cold or hot environments, not smoking, and not consuming caffeine for 1 h before the test [ 18 ].…”

Section: Methodsmentioning

confidence: 99%

Reference Standard for Digital Infrared Thermography of the Surface Temperature of the Lower Limbs

et al. 2023

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Digital infrared thermographic imaging (DITI) is a supplementary diagnostic technique to visualize the surface temperature of the human body. However, there is currently no reference standard for the lower limbs for accurate diagnosis. In this study, we performed DITI on the lower limbs of 905 healthy Korean volunteers (411 males and 494 females aged between 20 and 69 years) to obtain reference standard data. Thermography was conducted on the front, back, lateral sides, and sole area, and 188 regions of interest (ROIs) were analyzed. Additionally, subgroup analysis was conducted according to the proximity of ROIs, sex, and age groups. The mean temperatures of ROIs ranged from 24.60 ± 5.06 to 28.75 ± 5.76 °C and the absolute value of the temperature difference between both sides reached up to 1.06 ± 2.75 °C. According to subgroup analysis, the sole area had a significantly lower temperature than any other areas, men had higher temperatures than women, and the elderly had higher temperatures than the young adults except for the 20s age group (p < 0.001, respectively). This result could be used as a foundation for the establishment of a reference standard for DITI. Practical patient DITI can be accurately interpreted using these data, and it can serve as a basis for further scientific research.

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Section: Methodsmentioning

confidence: 99%

Reference Standard for Digital Infrared Thermography of the Surface Temperature of the Lower Limbs

et al. 2023

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“…Indeed, the previous meta-analytical findings support this observation and have been corroborated further by a recent meta-analysis, which demonstrated a 0.1°C/h greater Tcore rate of rise following caffeine supplementation (Naulleau et al, 2022). Overall, this suggests that caffeine has an undesirable (i.e.…”

Section: Caffeinesupporting

confidence: 55%

The effect of taurine supplementation on physiological and thermoregulatory responses in humans during rest and exercise in hot environmental conditions

Peel

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This thesis details the meta-analytical and experimental work conducted to investigate the effects of dietary supplements, specifically taurine, on physiological and thermoregulatory responses in humans during heat exposure. Meta-analysis determined that the ergogenic effects of many dietary supplements on endurance exercise performance appear affected by the heat. Supplements established to be efficacious in thermoneutral conditions, such as caffeine and creatine provided no performance benefit, while amino acids (e.g. taurine) demonstrated the greatest ergogenicity. Of the supplements meta-analysed for their thermoregulatory effects, several amino acids, anti-oxidants and anti-inflammatories, and those affecting fluid balance, offered the greatest benefits during heat exposure. Conversely, supplements enhancing nitric oxide bioavailability had no effect on thermal balance, and caffeine induced a thermogenic effect when ingested in the heat. Overall, taurine had the greatest performance and thermoregulatory responses, and was, therefore, selected as the focus of the subsequent empirical data chapters. Within the experimental studies of the thesis, taurine supplementation augmented thermal sweating during fixed metabolic heat production in hot conditions, including increased whole-body sweat loss, local sweat rate and sweat gland activation, alongside enhancing cutaneous vasodilation. Greater thermal sweating translated to heightened evaporative heat dissipation and reduced heat storage, as modelled by partitional calorimetry. Improved thermal tolerance was also observed, through a delayed transition to uncompensable heat stress. Drivers of the thermal sweating response and the measurement techniques used to assess these were established to be sufficiently reliable to control thermal sweating and detect likely changes, respectively. This indicates that the findings regarding taurine’s effects on thermal sweating are genuine and unaffected by these influencing factors. Taurine may exert these thermoregulatory effects through its vaso-active and osmoregulatory roles, though this requires further investigation. Nevertheless, taurine may offer a potential dietary supplementation strategy to support thermoregulation in hot environmental conditions that permit dry and evaporative heat transfer.

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“…Although these factors ensure the internal validity of these laboratory studies, they limit their ecological validity. For example, a recent meta‐analysis has shown that caffeine ingestion before exercise in the heat significantly increases the rate of change in core temperature 101 . There was a large variability in how work intensity was reported, which does not allow for an adequate synthesis.…”

Section: Discussionmentioning

confidence: 99%

“…For example, a recent meta-analysis has shown that caffeine ingestion before exercise in the heat significantly increases the rate of change in core temperature. 101 There was a large variability in how work intensity was reported, which does not allow for an adequate synthesis. We recommend harmonizing the reporting of work intensity by reporting the metabolic rate in W or kcal/h, as recommended by current guidelines.…”

Section: Limitations For Testing the Effectiveness Of Work-rest Regim...mentioning

confidence: 99%

Work–rest regimens for work in hot environments: A scoping review

Deshayes,

Hsouna,

Braham

et al. 2024

American J Industrial Med

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BackgroundTo limit exposures to occupational heat stress, leading occupational health and safety organizations recommend work–rest regimens to prevent core temperature from exceeding 38°C or increasing by ≥1°C. This scoping review aims to map existing knowledge of the effects of work–rest regimens in hot environments and to propose recommendations for future research based on identified gaps.MethodsWe performed a search of 10 databases to retrieve studies focused on work–rest regimens under hot conditions.ResultsForty‐nine articles were included, of which 35 were experimental studies. Most studies were conducted in laboratory settings, in North America (71%), on healthy young adults, with 94% of the 642 participants being males. Most studies (66%) employed a protocol duration ≤240 min (222 ± 162 min, range: 37–660) and the time‐weighted average wet‐bulb globe temperature was 27 ± 4°C (range: 18–34). The work–rest regimens implemented were those proposed by the American Conference of Governmental and Industrial Hygiene (20%), National Institute of Occupational Safety and Health (11%), or the Australian Army (3%). The remaining studies (66%) did not mention how the work–rest regimens were derived. Most studies (89%) focused on physical tasks only. Most studies (94%) reported core temperature, whereas only 22% reported physical and/or mental performance outcomes, respectively. Of the 35 experimental studies included, 77% indicated that core temperature exceeded 38°C.ConclusionsAlthough work–rest regimens are widely used, few studies have investigated their physiological effectiveness. These studies were mainly short in duration, involved mostly healthy young males, and rarely considered the effect of work–rest regimens beyond heat strain during physical exertion.

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Effect of Pre-Exercise Caffeine Intake on Endurance Performance and Core Temperature Regulation During Exercise in the Heat: A Systematic Review with Meta-Analysis

Cited by 7 publications

References 70 publications

Reference Standard for Digital Infrared Thermography of the Surface Temperature of the Lower Limbs

Reference Standard for Digital Infrared Thermography of the Surface Temperature of the Lower Limbs

The effect of taurine supplementation on physiological and thermoregulatory responses in humans during rest and exercise in hot environmental conditions

Work–rest regimens for work in hot environments: A scoping review

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