Effects of dehydration and rehydration on EMG changes during fatiguing contractions

Bigard, A. X.; Sánchez, Hugo Machado; Claveyrolas, G; Martin, Steven E.; Thimonier, B; Arnaud, Maurice J.

doi:10.1097/00005768-200110000-00013

Cited by 62 publications

(69 citation statements)

References 27 publications

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“…10 Monitoring hydration status may reduce the risk of developing heat illnesses, 10 decrease performance decrements associated with hypohydration, [1][2][3][4][5][6][7][8] and prevent disqualification for weight-categorized sports. 14 have repeatedly demonstrated that refractometry is the gold standard for measuring U sg compared with other instruments, such as urinometers or reagent strips.…”

Section: Discussionmentioning

confidence: 99%

Agreement of Urine Specific Gravity Measurements Between Manual and Digital Refractometers

Minton

OʼNeal

Torres-McGehee

2015

Journal of Athletic Training

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Context: Urine specific gravity (U sg ), measured by a handheld manual refractometer (MAN), has been recognized as a valid and practical means of assessing hydration status. Newer, digital refractometers are faster and more user friendly but have not been validated against the traditional MAN.Objective: To compare the reliability and validity of 2 digital refractometer models and a MAN.Design: Descriptive laboratory study. Setting: Research laboratory.Patients or Other Participants: Sample of convenience was recruited from the local university and surrounding community (n = 82).Intervention(s): Participants provided multiple urine samples (n = 124) over a 5-month period under various hydration conditions.Main Outcome Measure(s): Urine specific gravity was compared among a MAN, a digital refractometer requiring the prism to be dipped (DIP) into a urine sample, and a digital refractometer that requires urine to be pipetted (PIP) onto its prism for analysis.Results: The MAN measurements were strongly correlated with the DIP (r = 0.99, P < .001) and PIP (r = 0.97, P < .001) measurements. Bland-Altman analyses revealed slight mean underestimation (95% upper and lower levels of agreement) between MAN and DIP (À0.0012 [0.0028] and PIP À0.0011 [0.0035], respectively) and trends toward increased underestimation at higher U sg . Measurement error ! .005 was greater for PIP (4/124, 3.2%) than for DIP (2/124, 1.6%).Conclusions: Negligible differences were exhibited between PIP and DIP, with both displaying acceptable reliability and validity compared with the MAN. However, the BlandAltman analysis suggests underestimation bias for the DIP and PIP as U sg increases, with the potential for rare but substantial underestimation when using PIP that should be recognized by clinicians, particularly when used as a screening measure in weight-class sports.

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Section: Discussionmentioning

confidence: 99%

Agreement of Urine Specific Gravity Measurements Between Manual and Digital Refractometers

Minton

OʼNeal

Torres-McGehee

2015

Journal of Athletic Training

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“…Although a hypohydrated state leads to reduced strength, 17,18 power, 19,20 and high-intensity endurance, 21,22 the protocols often used when evaluating muscular performance cannot accurately duplicate the ''real match'' situation in competitive combat sports. This holds true for both physical and mental factors.…”

mentioning

confidence: 99%

Practices of Weight Regulation Among Elite Athletes in Combat Sports: A Matter of Mental Advantage?

Pettersson

Ekström

Berg

2013

Journal of Athletic Training

103

107

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Context The combination of extensive weight loss and inadequate nutritional strategies used to lose weight rapidly for competition in weight-category sports may negatively affect athletic performance and health. Objective To explore the reasoning of elite combat-sport athletes about rapid weight loss and regaining of weight before competitions. Design Qualitative study. Setting With grounded theory as a theoretical framework, we employed a cross-examinational approach including interviews, observations, and Internet sources. Sports observations were obtained at competitions and statements by combat-sport athletes were collected on the Internet. Patients or Other Participants Participants in the interviews were 14 Swedish national team athletes (9 men, 5 women; age range, 18 to 36 years) in 3 Olympic combat sports (wrestling, judo, and taekwondo). Data Collection and Analysis Semistructured interviews with 14 athletes from the Swedish national teams in wrestling, judo, and taekwondo were conducted at a location of each participant's choice. The field observations were conducted at European competitions in these 3 sports. In addition, interviews and statements made by athletes in combat sports were collected on the Internet. Results Positive aspects of weight regulation other than gaining physical advantage emerged from the data during the analysis: sport identity, mental diversion, and mental advantage. Together and individually, these categories point toward the positive aspects of weight regulation experienced by the athletes. Practicing weight regulation mediates a self-image of being “a real athlete.” Weight regulation is also considered mentally important as a part of the precompetition preparation, serving as a coping strategy by creating a feeling of increased focus and commitment. Moreover, a mental advantage relative to one's opponents can be gained through the practice of weight regulation. Conclusions Weight regulation has mentally important functions extending beyond the common notion that combat-sport athletes reduce their weight merely to gain a physical edge over their opponents.

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“…[2][3][4] On the other hand, few experiments have analysed neuromuscular changes induced by dehydration. One study 5 indicated that sauna induced dehydration (,3% of body weight) resulted in an earlier increase in root mean square (RMS) and decrease in mean power frequency (MPF) during submaximal contraction. In contrast, Evetovich et al 6 did not find any difference in muscle fatigability between the two conditions, hydrated versus dehydrated.…”

mentioning

confidence: 99%

Effect of fluid ingestion on neuromuscular function during prolonged cycling exercise

Vallier

Grego²,

Basset³

et al. 2005

Br J Sports Med

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Objectives: To investigate the effects of fluid ingestion on neuromuscular function during prolonged cycling exercise. Methods: Eight well trained subjects exercised for 180 minutes in a moderate environment at a workload requiring ,60% maximal oxygen uptake. Two conditions, fluid (F) and no fluid (NF) ingestion, were investigated. Results: During maximal voluntary isometric contraction (MVC), prolonged cycling exercise reduced (p,0.05) the maximal force generating capacity of quadriceps muscles (after three hours of cycling) and root mean square (RMS) values (after two hours of cycling) with no difference between the two conditions despite greater body weight loss (p,0.05) in NF. The mean power frequency (MPF) for vastus lateralis muscle was reduced (p,0.05) and the rate of force development (RFD) was increased (p,0.05) only during NF. During cycling exercise, integrated electromyographic activity and perceived exertion were increased in both conditions (p,0.05) with no significant effect of fluid ingestion. Conclusions:The results suggest that fluid ingestion did not prevent the previously reported decrease in maximal force with exercise duration, but seems to have a positive effect on some indicators of neuromuscular fatigue such as mean power frequency and rate of force development during maximal voluntary contraction. Further investigations are needed to assess the effect of change in hydration on neural mechanisms linked to the development of muscular fatigue during prolonged exercise. S everal factors are well known to play a role in the reduction of performance during prolonged muscle exercise. Within this framework, prevention of dehydration by adequate fluid replacement of body water losses during endurance exercise may maintain performance.1 For example, McConell et al 2 indicated that, when cyclists replaced their fluid losses fully during a two hour ride performed at 69% of peak oxygen consumption and 21˚C, they were able to cycle 53% longer in a subsequent exercise bout at 90% of peak oxygen consumption. On the one hand, the consequences of dehydration on the physiological factors of endurance performance, including rise in core temperature and cardiac output, are well documented.2-4 On the other hand, few experiments have analysed neuromuscular changes induced by dehydration. One study 5 indicated that sauna induced dehydration (,3% of body weight) resulted in an earlier increase in root mean square (RMS) and decrease in mean power frequency (MPF) during submaximal contraction. In contrast, Evetovich et al 6 did not find any difference in muscle fatigability between the two conditions, hydrated versus dehydrated. To the best of our knowledge, the effect of dehydration induced by dynamic endurance exercise on electromyographic (EMG) signals has been investigated only by Ftaiti et al. 7 They observed that the neuromuscular pattern of the knee extensor muscles assessed by mean EMG activity during a 40 minute submaximal running exercise in the heat was slightly altered despite a 2% loss of body weig...

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Effects of dehydration and rehydration on EMG changes during fatiguing contractions

Abstract: Dhy induced an increase in muscle fatigue, associated with early changes in EMG spectral parameters. It is not clear whether these alterations could be attributed to biochemical modifications, and the role of increased perception of effort when subjects were dehydrated should be clarified.

Cited by 62 publications

References 27 publications

Agreement of Urine Specific Gravity Measurements Between Manual and Digital Refractometers

Agreement of Urine Specific Gravity Measurements Between Manual and Digital Refractometers

Practices of Weight Regulation Among Elite Athletes in Combat Sports: A Matter of Mental Advantage?

Effect of fluid ingestion on neuromuscular function during prolonged cycling exercise

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