Effects of dehydration on isometric muscular strength and endurance

Abstract

To examine the effects of rapid dehydration on isometric muscular strength and endurance, seven men were tested at baseline (control) and after a dehydration (dHST) and a euhydration (eHST) heat stress trial. The dHST consisted of intermittent sauna exposure until 4% of body mass was lost, whereas the eHST consisted of intermittent sauna exposure (same duration as dHST) with water replacement. Peak torque was determined for the knee extensors and elbow flexors during three isometric maximal voluntary contractions. Time to fatigue was determined by holding a maximal voluntary contraction until torque dropped below 50% peak torque for 5 s. Strength and endurance were assessed 3.5 h after the HSTs (no food or water intake). Body mass was decreased 3.8+/-0.4% post dHST and 0.4+/-0.3% post eHST. Plasma volume was decreased 7.5+/-4.6% and 5.7+/-4.4%, 60 and 120 min post dHST, respectively. A small (1.6 mEq x L[-1]) but significant increase was found for serum Na+ concentration 60 min post dHST but had returned to predehydration level 120 min post dHST. Serum K+ and myoglobin concentrations were not affected by HSTs. Peak torque was not different (P > 0.05) among control, dHST, and eHST for the knee extensors (Mean (Nm)+/-SD, 285+/-79, 311+/-113, and 297+/-79) and elbow flexors (79+/-12, 83+/-15, and 80+/-12). Time to fatigue was not different (P > 0.05) among control, dHST and eHST for the knee extensors (Mean (s)+/-SD. 42.4+/-11.5, 45.3+/-7.6, and 41.8+/-6.0) and elbow flexors (48.2+/-8.9, 44.0+/-9.4, and 46.0+/-6.4). These results provide evidence that isometric strength and endurance are unaffected 3.5 h after dehydration of approximately 4% body mass.

Impact of dehydration on a full body resistance exercise protocol

“…The strenuous nature of the resistance protocol prompted one dropout and necessitated highly Wt participants. Therefore, this study more precisely replicated the demands of ecologically common resistance exercise protocols (i.e., session duration, multiple muscle groups, and repeated lifts) than much of the previous literature which has focused on maximal force production during single bouts of resistance exercise (Bosco et al 1968(Bosco et al , 1974Evetovich et al 2002;Ftaiti et al 2001;Greiwe et al 1998;Houston et al 1981;Montain et al 1998;Saltin 1964;Serfass et al 1984;Viitasalo et al 1987). Total repetitions for all exercises and total repetitions within each of the six exercises were signiWcantly lower for DEHY versus HE, indicating dehydration (»3%) impaired resistance exercise performance.…”

“…Studies measuring dehydration eVects on muscular strength or anaerobic performance are sparse and have yielded mixed results, showing signiWcant impairment (Bigard et al 2001;Bosco et al 1968Bosco et al , 1974Ftaiti et al 2001;Greenleaf et al 1967;Houston et al 1981;Judelson et al 2007b;SchoVstall et al 2001;Viitasalo et al 1987;Yoshida et al 2002), no eVects (Cheuvront et al 2006;Evetovich et al 2002;Greiwe et al 1998;Judelson et al 2007b; Montain et al 1998;Saltin 1964;Serfass et al 1984;Singer and Weiss 1968;Yoshida et al 2002) or even signiWcant improvements (Ahlman and Karvonen 1961;Widerman and Hagan 1982). Studies examining muscular endurance have shown signiWcant impairment (Bosco et al 1974;Caterisano et al 1988;Montain et al 1998;Torranin et al 1979) and no diVerence (Caterisano et al 1988;Ftaiti et al 2001;Greiwe et al 1998).…”

“…Studies examining muscular endurance have shown signiWcant impairment (Bosco et al 1974;Caterisano et al 1988;Montain et al 1998;Torranin et al 1979) and no diVerence (Caterisano et al 1988;Ftaiti et al 2001;Greiwe et al 1998). Inconsistent Wndings may relate to methodological diVerences in mode of mass reduction (passive/active, diuretic, and caloric restriction), level of dehydration, and testing protocols.…”

Promotion of Healthy Weight-Control Practices in Young Athletes

“…However, skinfold measurement requires trained personnel and may not be as accurate for individuals with obesity. 28, 29,52 In addition, there are racial and ethnic differences in the location of body mass storage and fat deposition that affect skin fold measurements. 53,54 Hydrostatic (underwater) weight and air displacement plethysmography are simple to perform but require expensive equipment; both methods may underestimate body fat percentage in extremely lean athletes.…”

Human Water and Electrolyte Balance

“…However, for a given person and event, the greater the dehydration level (after achieving the threshold for performance degradation) the greater the performance decrement. Dehydration probably does not alter muscle strength, 56 but sometimes has been reported to reduce dynamic small muscle endurance. 57,58 In addition, dehydration of over 2% often adversely influences cognitive function in the heat; however, this area requires more research.…”