RPE, blood glucose, and carbohydrate oxidation during exercise

Burgess, Maria Lonnett; Robertson, Robert J.; Davis, John L.; Norris, J.

doi:10.1249/00005768-199103000-00014

Cited by 40 publications

(39 citation statements)

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“…It is well known that the onset of fatigue can be delayed by ingesting carbohydrates after ~60 min of exercise (5)(6)(7)(8)(9)(10)21). The unique evidence obtained by this study was that RPE-C was attenuated only in the HF trial compared with the DH trial.…”

Section: Perceived Exertionmentioning

confidence: 51%

“…Fluid ingestion, especially in a hot environment, attenuates hyperthermia and cardiovascular drift (1)(2)(3)(4), and carbohydrate ingestion reduces the rating of perceived exertion (RPE) during prolonged exercise in endurance-trained subjects (5)(6)(7)(8)(9)(10). However, there is no available data about the physiological and subjective benefits of maintaining body water by ingesting fluid with or without carbohydrate supplementation during prolonged submaximal exercise in untrained healthy subjects.…”

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confidence: 99%

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The Different Effects of Fluid with and without Carbohydrate Ingestion on Subjective Responses of Untrained Men during Prolonged Exercise in a Hot Environment

Ishijima

Hashimoto

Satou³

et al. 2009

J Nutr Sci Vitaminol

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SummaryThis study examined the effects of maintaining euhydration by ingesting fluids with or without carbohydrate on subjective responses of untrained men during prolonged exercise in a hot environment. Six healthy untrained subjects completed 90 min of cycling exercises at 55% maximal oxygen consumption (V O 2 max ) in a hot environment (temperature: 28˚C, humidity: 50%) under three different experimental conditions. During the first trial, subjects did not ingest fluids during exercise (dehydration (DH) trial). In the second and third trials, subjects received mineral water (MW) and hypotonic fluid containing carbohydrate (HF), respectively, in amounts equaling their weight loss in the DH trial. At the end of exercise, the overall rating of perceived exertion (RPE-O) was lower in the MW and HF trials than in the DH trial (14.3 Ϯ 1.0 and 13.7 Ϯ 0.6 vs 17.7 Ϯ 1.0, p Ͻ 0.05, respectively). RPEcardiovascular and RPE-legs were lower at the end of exercise in the HF trial compared with the DH trial. V O 2 , heart rate (HR), and rectal temperature increased during exercise in the three trials. At the end of exercise, the drift in V O 2 was lower in the MW and HF trials than in the DH trial (304 Ϯ 41 and 339 Ϯ 40 vs 458 Ϯ 33 mL, p Ͻ 0.05, respectively). HR at the end of exercise in the HF trial was lower than in the DH trial (158 Ϯ 5 vs 173 Ϯ 7 bpm, p Ͻ 0.05). These results suggest that maintaining euhydration during prolonged exercise in untrained men could attenuate RPE-O and that hypotonic electrolyte-carbohydrate solution could attenuate RPE-legs during exercise. Key Words maintaining euhydration, perceived exertion, prolonged exercise, heat exposure Dehydration, hyperthermia and muscle glycogen depletion are the major determinant factors that induce the reduction of performance during prolonged exercise. Fluid ingestion, especially in a hot environment, attenuates hyperthermia and cardiovascular drift ( 1-4 ), and carbohydrate ingestion reduces the rating of perceived exertion (RPE) during prolonged exercise in endurance-trained subjects ( 5-10 ). However, there is no available data about the physiological and subjective benefits of maintaining body water by ingesting fluid with or without carbohydrate supplementation during prolonged submaximal exercise in untrained healthy subjects.Maintaining euhydration by fluid ingestion attenuates cardiovascular strain induced by both hyperthermia and dehydration during prolonged submaximal exercise in the heat ( 2-4 ). Gonzalez-Alonso et al. suggested that despite a marked cardiovascular drift at the 120 min of exercise, corresponding to ~60% maximal oxygen consumption (V O 2 max ) in a dehydration trial, the increase in V O 2 for exercising and nonexercising muscle of the whole body was similar to a euhydration trial ( 2 ). Additionally, it has been demonstrated that during prolonged exercise an increase in carbohydrate availability by carbohydrate supplementation attenuated RPE ( 8 , 9 , 11 ) while fluid ingestion did not attenuate the RPE ( 4 , 12 ). However, these stu...

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Section: Perceived Exertionmentioning

confidence: 51%

mentioning

confidence: 99%

The Different Effects of Fluid with and without Carbohydrate Ingestion on Subjective Responses of Untrained Men during Prolonged Exercise in a Hot Environment

Ishijima

Hashimoto

Satou³

et al. 2009

J Nutr Sci Vitaminol

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“…Indeed, a low muscle glycogen level is associated with impaired muscle function via disrupted excitation-contraction coupling (Chin and Allen 1997), but it may also be linked to detrimental effects via the central nervous system (CNS) (Green 1991;Nybo and Secher 2004). Other findings implicate hypoglycaemia as a cause of exhaustion, as glucose moves from plasma into muscle to compensate for the reduced glycogen (Burgess et al 1991;Coyle et al 1986;Kang et al 1996). Again it is unclear whether such effects would be mediated by reduced motor drive from CNS (Be´quet et al 2002;Nybo and Secher 2004) or direct impairment of muscle function (Coyle et al 1986).…”

Section: Introductionmentioning

confidence: 99%

Changes of motor drive, cortical arousal and perceived exertion following prolonged cycling to exhaustion

2005

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The aims of this study were to (1) quantify any central fatigue that occurs following prolonged dynamic exercise, i.e. reduced muscle force caused by impaired motor drive from the central nervous system and (2) determine whether decreased cortical arousal, assessed using critical flicker fusion threshold (CFF), occurs and is related to impaired exercise performance. Fifteen healthy men cycled at 70% VO2peak until exhaustion. The peak force of maximum voluntary isometric contractions (MVC) of the quadriceps muscle group was reduced by 30% at exhaustion. The voluntary activation ratio determined using superimposed tetanic stimulation fell from 0.99 to 0.86 at exhaustion. The central fatigue (%) at exhaustion was 33+/-12% (+/- SD) (assessed via the tetanus interpolation technique) and 54+/-32% (assessed via the relative decline of MVC and peak tetanic force) of the total fatigue. The MVC only partially recovered and central fatigue persisted at 30 min post-exercise. CFF increased from 39.2+/-2.3 to 41.8+/-3.5 Hz at exhaustion, but did not correlate with central fatigue. Every subject reached the highest rating of perceived exertion (RPE) at exhaustion of 20 on the Borg scale. The time to exhaustion was related to how quickly the RPE increased and to the ability to sustain exercise at very high RPE. These data suggest that with prolonged cycling: (1) there is considerable and a persistent form of central fatigue, (2) there is an increased level of cortical arousal, and (3) exhaustion is linked to very high subjective RPE.

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“…Physiological variables such as blood lactate accumulation, carbohydrate depletion, respiration rate, hydration state and aerobic capacity as well as heart rate can also influence perceived exertion (Barr et al 1991;Burgess et al 1991;Hetzler et al 1991;. Blood lactate, in particular, is closely related to perceived exertion at specific workloads, regardless of training state or training modality (Hetzler et al 1991;Seip et al 1991).…”

Section: Intensity Prescriptionmentioning

confidence: 99%