Effects of Supplemental Carbohydrate Ingestion During Superimposed Electromyostimulation Exercise in Elite Weightlifters

Abstract

The purpose of this investigation was to test the effects of carbohydrate supplementation on blood parameters and force output during superimposed electromyostimulation (SEMS) single-leg isometric contractions. We hypothesized that carbohydrate ingestion before and during muscle contractions would lead to greater glucose availability and greater total force output for the session. Six elite resistance trained male subjects participated in a randomized, counterbalanced, double-blind study. The subjects were randomly assigned to placebo (PL) or carbohydrate (CHO). The subjects in CHO consumed 1 g of carbohydrate per kilogram of body mass loading dose and 0.17 g of carbohydrate · per kilogram of body mass every 6 minutes during the exercise protocol. The PL received an equal volume of a solution made of saccharin and aspartame. The exercise protocol consisted of repeated 20-second isometric contractions of quadriceps muscle at 50% maximal voluntary contraction followed by 40 seconds of rest until failure occurred. Importantly, quadriceps maximal voluntary contraction with SEMS was performed in the beginning and then every 5 minutes during the last 3 seconds of isometric contractions throughout the exercise protocol. Venous blood samples were taken preexercise, immediately postexercise, and at 5 minutes postexercise and analyzed for glucose, nonesterified fatty acids, and glycerol. Our results indicate that CHO ingestion increased (p < 0.05) plasma glucose, but no significant differences (p > 0.05) were detected for nonesterified fatty acids or glycerol. Importantly, total force output during exercise protocol was higher (p < 0.05) in CHO compared with that in PL. Therefore, our data suggest that CHO supplementation before and during exercise may be beneficial for individuals performing high-volume resistance training.

Glucose Ingestion Does Not Improve Maximal Isokinetic Force

“…Another study investigating the role of carbohydrate ingestion during a time to fatigue task found no significant difference (CHO vs. PL) in either the number of successful sets (3.5 6 3.2 vs. 3.5 6 2.7), repetitions (20.4 6 14.9 vs. 19.7 6 13.1), or total work (29.9 6 22.3 kJ vs. 28.6 6 19.5 kJ) performed in the squat exercise (5 repetitions per set) at an intensity of 85% 1RM (12). Possible explanations for the differences observed between the studies of Wax et al (27,28) and Kulik et al (12) may stem from the type of muscular contractions adopted. In particular, isometric contractions at 50% of MVC are expected to partially occlude blood supply (2) and therefore increase the reliance on anaerobic metabolism, specifically through glycolysis.…”

“…The studies by Wax et al (27,28), which demonstrated significant improvements in performance with carbohydrate consumption during a time to exhaustion task used a very different protocol to the one adopted in this study. Their protocol consisted of repeated 20-second isometric contractions at 50% MVC followed by 40 seconds of rest until exhaustion.…”

“…Previous research identified improved performance during isometric time to exhaustion tasks with glucose supplementation (27,28), although this benefit of glucose did not translate to improved performance during dynamic contractions (12). Moreover, exercise-induced glycogen depletion of muscle fibers has been associated with a decrement in maximal muscular strength during a single dynamic contraction (9).…”

“…However, the effect of glucose supplementation on performance of shorter duration (,60 minutes) is inconsistent, with only a limited number of studies reporting some improvements in performance (1,13,15,27,28), wherein 2 of these studies had a duration greater than 50 minutes (1,15). Additionally, although the study by Lee et al (13) demonstrated improved performance during multiple short-duration (2 3 30-second efforts interspersed with 10 3 10-second efforts) cycling bouts after ingestion of carbohydrate, this benefit was ascribed to improved performance in the first 30 seconds' effort only.…”

“…Some studies have reported a benefit in time to exhaustion tasks (;16 minutes vs. 29 (27,28)) and performance over multiple resistance training sessions (8), whereas others observed no improvements in either performance (12,14,25) or perceived exertion (24) with dietary carbohydrate manipulation or acute carbohydrate ingestion. Given the ingestion of carbohydrate has other potential benefits (e.g., promoting an anabolic environment (23)) and has not previously been associated with decrements in performance, the ingestion of carbohydrate is still generally recommended for resistance training (7,19).…”