Skeletal Muscle Strength and Endurance are Maintained during Moderate Dehydration

Abstract

This study investigated the effects of moderate dehydration (~2.5% body weight) on muscle strength and endurance using percutaneous electrical stimulation to quantify central and peripheral fatigue, and isolate the combined effects of exercise-heat stress and dehydration, vs. the effect of dehydration alone. Force production and voluntary activation were calculated in 10 males during 1 brief and 15 repeated maximal voluntary isometric contractions performed prior to (control) walking in the heat (35°C), immediately following exercise, and the next morning (dehydration). The protocol was also performed in a euhydrated state. During the brief contractions, force production and voluntary activation were maintained in all trials. In contrast, force production decreased throughout the repeated contractions, regardless of hydration status (P<0.001). The decline in force was greater immediately following exercise-heat stress dehydration compared with control and euhydration (P<0.001). When dehydration was isolated from acute post-exercise dehydration, force production was maintained similarly to control and euhydration. Despite the progressive decline in force production and the increased fatigability observed during the repeated contractions, voluntary activation remained elevated throughout each muscle function test. Therefore, moderate dehydration, isolated from acute exercise-heat stress, does not appear to influence strength during a single contraction or enhance fatigability.

Effect of Hypohydration on Muscle Endurance, Strength, Anaerobic Power and Capacity and Vertical Jumping Ability: A Meta-Analysis

“…Of these, 28 [7, 8, 11-14, 17-20, 24, 25, 30-45] met all of the inclusion criteria, thereby producing a total of 85 individual studies and weighted mean treatment effects to investigate the impact of hypohydration on upper (6/85) and lower (10/85) body muscle endurance, upper (14/85) and lower (25/85) body muscle strength, muscle anaerobic power (9/85) and capacity (9/85), and vertical jumping ability (12/85). A total of 20 research manuscripts produced more than one weighted mean treatment effect, with Hayes and Morse [25] producing ten, Ftaiti et al [34] producing two, Wilson et al [45] two, Cheuvront et al [17] two, Bigard et al [8] two, Bijlani and Sharma [30] two, Bosco et al [31] two, Bosco et al [32] six, Caterisano et al [33] three, Greiwe et al [35] four, Gutierrez et al [36] six, Jacobs [37] six, Jones et al [13] two, Judelson et al [11] six, Kraft et al [38] two, Montain et al [39] two, Naharudin and Yusof [40] six, Periard et al [41] four, Viitasalo et al [44] four, and Webster et al [12] four effect estimates. The work of Naharudin and Yusof [40] and Caterisano et al [33] contained three different groups of participants, while that of Gutierrez et al [36] contained two different groups of participants.…”

“…In this regard, Bigard et al [8] found that hypohydration accelerated the electromyographic (EMG) alterations associated with muscle fatigue during prolonged static contractions at 25 % of peak torque. However, one must note that studies have typically found hypohydration to have no statistically significant effect on voluntary muscle activation [11,18,24,41] or EMG responses during maximal voluntary static or isokinetic contractions [7,18,20,25] or during repeated and prolonged muscle contractions [34,41].…”

“…Of the 28 articles retained for analysis, hypohydration was induced via heat exposure in ten [8, 17, 33, 35-38, 40, 42, 44], via exercise plus heat exposure in ten [13,14,18,19,24,25,30,39,41,43], via exercise in a sweat suit in two [34,45], and via fluid restriction in six [7,11,12,20,31,32]. Although Webster et al [12] used exercise in a sweat suit and Judelson et al [11] used exercise plus heat exposure to dehydrate participants, the dehydration mode was All studies except that by Bosco et al [31] provided the percent change in BW (i.e., hypohydration level).…”

“…Moreover, Viitasalo et al[44] and Periard et al[41] tested participants immediately after and C16 h (including an overnight sleep) following dehydration. Hence, although the dehydration procedures used in these manuscripts were technically heat exposure and exercise plus heat exposure, respectively,…”

Sodium-induced hyperhydration decreases urine output and improves fluid balance compared with glycerol- and water-induced hyperhydration

“…Although hypohydration affects several aspects of peripheral physiology, current evidence suggests that body water losses do not impact efferent nerve signals destined to muscles. In fact, studies have typically found hypohydration to have no effect on voluntary muscle activation (Bowtell, Avenell, Hunter, & Mileva, 2013;Del Coso, Estevez, & Mora-Rodriguez, 2008;Judelson et al, 2007;Periard, Tammam, & Thompson, 2012), or electromyographic responses during maximal voluntary isometric or isokinetic contractions (Bowtell et al, 2013;Evetovich et al, 2002;Hayes & Morse, 2010;Minshull & James, 2013). To date, only one study has shown hypohydration to reduce electromyographic signal amplitudes during maximal isometric and isokinetic contractions of the knee flexors and extensors (Ftaiti, Grelot, Coudreuse, & Nicol, 2001).…”