Superimposed electromyostimulation (SEMS) training involves artificially activating the muscle while performing voluntary contractions during a resistance exercise protocol. This style of exercise training has been used in the rehabilitation setting as a compliment to voluntary resistance training (24,35). Also, SEMS is used to increase muscle strength and to accelerate hypertrophy after immobilization-induced atrophy (e.g., casting during an injury) (35,41). The SEMS training programs are also being used by healthy individuals (13,14) and competitive athletes (38) to enhance muscle strength and physical performance during sport-specific skills (7,10,18). This modality of training has been shown to enhance muscle strength more so than just normal strength training alone (26,27).
In particular, it has been reported that electromyostimulation of the quadriceps muscle results in greater increases in muscle strength (4), thereby potentially augmenting anaerobic sport performance (10,39,40,42). The SEMS enhanced the physical performance of elite and subelite healthy athletes in sporting activities such as tennis (39), basketball (40), volleyball (42), swimming (46), rugby (1), track and field (54), and ice hockey (10). The increased physical performance may be attributed to an augmented muscle activation of pattern (16), thus causing increased force production and anaerobic performance (52).
Conversely, acute application of SEMS has been shown to result in increased fatigue of the working muscle (9,30,51,56). This rapid onset of fatigue during work bouts may be attributed to increased fiber activation patterns (16). In both SEMS and anaerobic training, high levels of adenosine triphosphate (ATP) hydrolysis are required by the active muscles to sustain force output. Originally, it was speculated that this energy demand was met exclusively by the ATP–phosphocreatine system; however, studies have reported that significant glycolytic activity does occur in people performing resistance exercise (20,47,50). These studies suggest that decreases in endogenous glycogen stores coupled with hypoglycemia may lead to a reduction in force output during periods of prolonged resistance exercise.
In this regard, an exogenous supply of glucose may delay fatigue (25,43) by lessening the dependency on endogenous muscle glycogen (2,55). The reduced reliance on endogenous muscle glycogen has been found to occur during resistance exercise (19,20), and thus, the consumption of an exogenous carbohydrate supplement before and during an exercise session may attenuate muscle glycogen depletion. However, the literature has yielded conflicting results regarding the ergogenic impact of carbohydrate ingestion during resistance exercise. In 4 studies, the authors reported increases in the amount of work performed during resistance exercise sessions in subjects supplemented with carbohydrates (20,23,36,53). However, these findings are in contrast to those of another study that reported no augmentation in performance measures after carbohydrate supplementation (34). These disparate results may be because of differences in exercise intensity, exercise duration, participant selection criteria, or central nervous system factors (i.e., psychological factors and emotions).
Therefore, the aim of this study was to investigate the effects of supplemental carbohydrate ingestion on blood parameters and total force output during SEMS of the quadriceps muscle in elite weightlifters. We hypothesized that carbohydrate ingestion before and during an isometric resistance exercise protocol coupled with SEMS would lead to greater blood glucose availability, consequently resulting in an increased performance.
This study was conducted in parallel with the prior mentioned publication by Wax et al. (53). This second article uses data from the same experiment but reports the effects of supplemental carbohydrate ingestion during an SEMS resistance exercise protocol on plasma glucose, nonesterified fatty acids, glycerol, and the sum of the total force produced during the submaximal phase, rather than its effects on blood lactate, time to exhaustion, and periodic maximal force output.
Experimental Approach to the Problem
This study was designed as a randomized counterbalanced, double-blind experiment. The protocol employed in this study was based on a prior study (53), which tested the efficacy of carbohydrate (CHO) ingestion on time to exhaustion in a SEMS resistance exercise protocol. The subjects reported to the laboratory 3 times (i.e., visit 1, visit 2, and visit 3) at the same time of the day. Visit 1 was used to obtain anthropometric data and to familiarize the subjects with the experimental techniques. During visit 2, half of the subjects chosen at random consumed a CHO solution, and the other half consumed a placebo (PL) solution before and during the exercise protocol. On visit 3, the subjects consumed the other solution, and the same exercise protocol was performed. There was a 7-day period between visit 1 and visit 2, and between visit 2 and visit 3.
Six apparently healthy male volunteers (age: 29 ± 4 years old, height: 1.79 ± 0.09 m, weight: 102 ± 21 kg, and body fat: 14 ± 9% ) with a minimum of 5 years of continuous competitive bodybuilding and power lifting experience participated in this study. A sample size analysis was performed a priori for force output (primary dependent measure) and showed that for this repeated measures experimental design 6 participants were required to achieve a power of 0.80. All the subjects were national level competitors in their perspective power lifting and bodybuilding sports. The subjects had no lower extremity musculoskeletal injuries in the previous 6 months and were free (self-reported) of any anabolic steroid use for a year before the experimental sessions. This study was reviewed and approved by the Institutional Review Board, and all the subjects completed a health history questionnaire and signed an informed consent before initiation of data collection.
During the CHO condition, the subjects consumed a loading dose of a 10% carbohydrate solution (Carboplex, Unipro Inc., Atlanta, GA, USA) at 1 g of carbohydrate·per kilogram of body mass. The subjects also consumed the same solution at a dose of 0.17 g of carbohydrate per kilogram of body mass before the exercise protocol started and thereafter at 6-minute intervals until the completion of the exercise protocol. Prior data indicate that this concentration of carbohydrate clears from the stomach at a rate comparable with that of water, while maintaining a high rate of carbohydrate availability to the muscle (45). In addition, the carbohydrate intake timing was based on data showing that this amount of carbohydrate increases resistance exercise performance during lower body muscle contractions (36,53). During the PL condition, the subjects consumed a solution that contained saccharin and aspartame that was similar in taste, texture, color, and volume to the carbohydrate solution.
This session was used to determine subjects' anthropometric data. Also, the subjects were instructed to refrain from strenuous leg exercise and caffeine and alcohol intake for 48 hours before each of the following 2 visits. Furthermore, the subjects were asked to maintain a log of their dietary intake 3 days before visit 2 and were instructed to duplicate the nutritional intake before visit 3. In addition, the subjects performed a mock submaximal session to familiarize themselves with the experimental procedures and equipment.
Visits 2 and 3
The subjects reported to the laboratory at the same time of the day for visit 2 and visit 3, after an overnight fast during the morning hours. Upon arrival, the subjects were questioned about their compliance in regard to their activity level and submitted their nutritional journal to a trained evaluator. If a subject failed to meet the pretesting guidelines required for participation in that day's protocol, the session was rescheduled. All the subjects complied with the pretesting criteria and completed their scheduled sessions.
After the evaluator's clearance regarding compliance to the pretesting guidelines, the subjects consumed their assigned solution (CHO or PL; minute 0). Next, electrodes (10.16 × 10.16 cm) were securely placed on the subjects transversely to the proximal (10 cm below the groin) and as close as possible to the motor point of the vastus medialis and vastus lateralis muscles on subjects' perceived dominant leg. The subjects were then seated with the dominant knee secured to a 300-lb load cell strain gauge (Transducer Techniques, Temecula, CA, USA) at an angle between 85 and 90° just above the malleoli. This position mimics a typical seated leg extension model used in training facilities. A restraint was placed around the pelvic region to maintain quadriceps muscle length and to prevent substantial use of hip flexors during exercise protocol.
To determine maximal voluntary force output, the subjects performed an isometric maximal voluntary contraction without SEMS by using their dominant leg (preexercise—minute 10). The subjects performed a series of three, 3-second maximal voluntary contractions. Force output was amplified (Model SGA-6, Advanced Mechanical Technology, Inc., Watertown, MA, USA) by using the signal sent via the load cell and the signal was recorded at 1,000 Hz using DataPac 2000 (Run Technologies, Laguna Hills, CA, USA). Each subject rested between each maximal voluntary contraction for a duration of 90 seconds. The greatest force held for 1 second was deemed to be the maximal voluntary contraction. After determination of maximal voluntary contraction, the subjects underwent transcutaneous muscle stimulation to obtain a level of stimulation they could comfortably tolerate without discomfort (preexercise—minute 20). The quadriceps muscle was stimulated using a transcutaneous electronic muscle stimulator (Dynapulse 8, Health Group, Vista, CA, USA) and pulse waves of 60 Hz lasting 100 microseconds were used. Stimulation intensity was determined by the pain tolerance of each subject. The maximal tolerated intensity varied between 70 and 110 mA. The level of stimulation and electrode placement remained constant for each subject throughout the study, and this stimulation was used to apply SEMS during isometric maximal voluntary contractions. This assured minimal variability in fiber recruitment during each session. No subject reported any serious discomfort during the experiment.
The subjects had a set target force of 50% of their predetermined maximal voluntary contraction and began the exercise protocol (minute 30) by performing repeated isometric contractions. Additionally, visual feedback was provided to the subjects marked on a storage oscilloscope. The subjects generated a continuous pattern of 20-second contractions without SEMS followed by a 40-second rest period (duty cycle 0.20). During the last 3 seconds of the first 20-second voluntary isometric contraction, and thereafter at 5-minute intervals, SEMS was applied during a maximal voluntary contraction in a concomitant manner.
The exercise protocol continued until failure. Failure in this investigation was defined as the inability of a subject to sustain 50% target force output for 5 consecutive seconds. After failure, the subjects remained seated for 5 minutes, and this time point was defined as recovery. Total force output was defined the sum of the force produced during the 50% maximal voluntary contractions for the duration of the exercise protocol. These procedures are summarized in Figure 1.
Blood samples were obtained at minute 10 (pre), within 15 seconds of failure, and 5 minutes after failure (recovery). All blood samples were obtained using a 20-G Teflon cannula placed in a superficial antecubital vein by a registered nurse. The cannula was maintained patent using an isotonic saline solution (with 10% heparin solution) placed in a 3-way stopcock with a male Luer lock adapter. Blood samples for nonesterified fatty acids and glycerol analyses were collected in serum-separator tubes, and blood samples for glucose, hematocrit, and hemoglobin analyses were collected in tubes containing ethylenediaminetetraacetic acid.
Plasma glucose concentration was measured by the hexokinase method as described by Barthelmai and Czok (3), and later modified by Konig et al. (31). Nonesterified fatty acids were determined by in vitro enzymatic colorimetric method (Wako Pure Chemical Industries, Dallas, TX, USA). Glycerol levels were determined by using the modified methods published by McGowan et al. (44). Hematocrit and hemoglobin values (Sigma Diagnostics, St. Louis, MO, USA) were used to determine plasma volume shifts (15) and values for glucose, nonesterified fatty acids, and glycerol were corrected for these shifts changes. Intraassay variance was <5% for all assays.
Total force output data were analyzed using repeated measures t-test. Glucose, nonesterified fatty acids, and glycerol data were analyzed by using a 2 (condition; PL or CHO) × 3 (time; pre, failure, recovery) repeated measures analysis of variance (ANOVA). When the ANOVA was found to be significant, pairwise comparisons were made using repeated measures t-test to deduce differences between groups. All statistical analyses were performed by using analyzed using PASW Statistics 20 (SPSS, Inc., Chicago, IL, USA). Data are reported as mean ± SD.
Dietary intake analysis showed no differences for carbohydrate, protein, fat, or total kilocalories consumed for CHO or PL (p > 0.05).
Total force output (newtons) was significantly increased (p < 0.05) in CHO compared with that of PL. It is important to note that all 6 subjects had a higher total force output when they consumed the carbohydrate solution compared with placebo solution (Figure 2). The correlation coefficient of average measures was 0.85 (p < 0.05).
The average measure of intraclass correlation coefficient of plasma glucose was 0.91 (p < 0.05). A 2-way repeated measures ANOVA indicated a significant interaction effect (p < 0.05) for plasma glucose. The subjects who ingested CHO had significantly higher (p < 0.05) plasma glucose at all 3 time points (pre, failure, recovery) compared with PL subjects (Figure 3). Furthermore, in CHO subjects, plasma glucose was significantly higher (p < 0.05) at recovery compared with failure and pre, and at failure, plasma glucose was statistically higher (p < 0.05) compared with pre. In regard to PL, we observed a significant increase (p < 0.05) in plasma glucose at failure and recovery compared with pre. However, unlike CHO subjects, plasma glucose during the PL condition was not statistically different (p > 0.05) at recovery compared with failure.
The results for serum nonesterified fatty acids and glycerol are presented in Figures 4 and 5, respectively. The average measure of intraclass correlation coefficient of serum nonesterified fatty acids was 0.93 (p < 0.05). Although PL subjects had numerically higher serum nonesterified fatty acids compared with CHO, no statistical differences (p > 0.05) were detected. Also, our data did not show any statistical differences (p > 0.05) for serum glycerol. The average measure of intraclass correlation coefficient of serum glycerol was 0.67 (p < 0.05).
In this study, it was hypothesized that carbohydrate ingestion before and during resistance exercise coupled with SEMS would lead to greater blood glucose availability and higher total force output. Our results clearly indicate that the subjects who consumed the carbohydrate solution generated a greater overall force output during the exercise protocol compared with placebo ingestion. Further, the data also show that plasma glucose remained at significantly higher levels when the subjects consumed the carbohydrate solution compared with when they consumed the placebo solution. The data also show that nonesterified fatty acids and glycerol levels were not altered by the resistance exercise protocol used in this study after either placebo or carbohydrate supplementation.
In this study, an SEMS resistance exercise protocol was used to investigate the potential ergogenic benefits of carbohydrate supplementation during this type of activity. Previous studies have shown increased muscular force generation and anaerobic performance with the application of SEMS in conjunction with voluntary isometric muscle contractions compared with voluntary contractions alone (6,16,49,52). Despite this increase in performance, a single bout of SEMS of the quadriceps muscle—as used in this study—has been reported to induce significant muscle fatigue (∼20% torque loss) and soreness (56). However, these studies did not investigate the possible additional benefits of carbohydrate supplementation on the work performed in conjunction with SEMS. Our study used both of these experimental paradigms, and our main findings are that carbohydrate supplementation provided further ergogenic effect to SEMS.
The increase in force output indicates that resistance exercise performance is affected by decreased muscle glycogen stores and increased blood glucose availability (21). In response to intense bouts of exercise, the body is primarily in a catabolic state. Many of the stress hormones are elevated and important fuel stores (e.g., muscle glycogen) decrease (28). For the body to recover and training adaptations to occur, this process must be mitigated. The supplementation of carbohydrate before, during, and immediately after intense bouts of exercise has been shown to be beneficial during cardiovascular endurance exercises (17,29,37), resistance exercises (20,22,23,34,36), and to a limited extent in electromyostimulation training (53). Exogenous carbohydrate supplementation can inhibit the release of catabolic stress hormones (33), suppress protein catabolism (8), and augment muscle glycogen stores by increasing insulin concentrations (11), resulting in elevated growth hormone levels (32,48), which fosters the creation of an anabolic environment (21). This increase in growth hormone resulting from carbohydrate-induced insulin spikes have been reported to last 5–6 hours postexercise (11). The enhancement of this anabolic state may increase muscular strength and decrease recovery time.
In this regard, the findings from our study are in agreement with the findings of Haff et al. (20,23), and Lambert et al. (36) who reported that carbohydrate supplementation increased muscular performance. Our previous results (53) revealed that the total time to exhaustion and mean force production were significantly higher in the carbohydrate treatment than in placebo treatment when performing SEMS concurrently with isometric leg contractions. This ergogenic effect may be explained by several factors. Specifically, SEMS training concurrently with voluntary isometric exercise results in greater fiber use, thus resulting in greater depletion of muscle glycogen stores. Researchers have postulated that intermittent carbohydrate ingestion during intense resistance exercise would mitigate this glycolytic effect occurring in the muscle by providing an exogenous source of glucose. Because most forms of resistance exercise have intermittent characteristics, carbohydrate ingestion may foster an internal environment within the exercising muscle that augments performance (22). This may be attributed to decreased reliance on muscle glycogen (2,5,20,55) by way of continued delivery of exogenous glucose to the working muscle (12,22,36).
Despite claims that carbohydrate supplementation can augment performance during resistance exercise, the literature has not consistently supported this assertion. This may be related to the nature of subjects selected (i.e., untrained, novice, recreational lifter, trained lifter) and the various resistance exercise paradigms used (21) or the timing of the ingestion of carbohydrate ingestion combined with the length of the resistance exercise session (12,36). It is reasonable to suggest that carbohydrate supplementation before and during resistance exercise may increase plasma glucose availability and improve performance thereby delaying the onset of muscular fatigue. Therefore, the potential ergogenic effects of carbohydrate ingestion would be clearer if trained subjects performed highly intense exercise bouts of high work volumes.
The primary findings of this study reveal that carbohydrate ingestion before and intermittently during an SEMS session of isometric leg contractions at 50% 1 repetition maximum to failure mitigates fatigue factors by providing exogenous glucose to the exercising muscle, eliciting an ergogenic effect by augmenting submaximal force output. Furthermore, the results suggest that practitioners and athletes may find that carbohydrate supplementation above that of their normal food intake may provide ergogenic benefits when ingested before and during high-volume resistance training as performed during muscular endurance and hypertrophy phases of traditional periodization training programs. Consequently, despite these positive findings, there are limitations to our study such as limited number of subjects, homogeneity of subjects used, specific training condition (isometric SEMS of dominant quadriceps muscle), and heterogeneity in individual response to SEMS. Therefore, further investigations are warranted to elucidate the ergogenic benefits of carbohydrate supplementation with various types of resistance training bouts.
No grant support was used to perform this study. The results of this study do not constitute endorsement of any products by the authors or National Strength and Conditioning Association.
1. Babault N, Cometti G, Bernardin M, Pousson M, Chatard JC. Effects of electromyostimulation training on muscle strength and power of elite rugby players. J Strength Cond Res 21: 431–437, 2007.
2. Bagby GJ, Green HJ, Katsuta S, Gollnick PD. Glycogen depletion in exercising rats infused with glucose
, lactate, or pyruvate. J Appl Physiol 45: 425–429, 1978.
3. Barthelmai W, Czok R. [Enzymatic determinations of glucose
in the blood, cerebrospinal fluid and urine.]. Klin Wochenschr 40: 585–589, 1962.
4. Bax L, Staes F, Verhagen A. Does neuromuscular electrical stimulation strengthen the quadriceps femoris? A systematic review of randomised controlled trials. Sports Med 35: 191–212, 2005.
5. Bergstrom J, Hultman E. A study of the glycogen metabolism during exercise in man. Scand J Clin Lab Invest 19: 218–228, 1967.
6. Bigland-Ritchie B, Jones DA, Hosking GP, Edwards RH. Central and peripheral fatigue in sustained maximum voluntary contractions of human quadriceps muscle. Clin Sci Mol Med 54: 609–614, 1978.
7. Billot M, Martin A, Paizis C, Cometti C, Babault N. Effects of an electrostimulation training program on strength, jumping, and kicking capacities in soccer players. J Strength Cond Res 24: 1407–1413, 2010.
8. Biolo G, Williams BD, Fleming RY, Wolfe RR. Insulin action on muscle protein kinetics and amino acid transport during recovery after resistance exercise
. Diabetes 48: 949–957, 1999.
9. Boerio D, Jubeau M, Zory R, Maffiuletti NA. Central and peripheral fatigue after electrostimulation-induced resistance exercise
. Med Sci Sports Exerc 37: 973–978, 2005.
10. Brocherie F, Babault N, Cometti G, Maffiuletti N, Chatard JC. Electrostimulation training effects on the physical performance of ice hockey players. Med Sci Sports Exerc 37: 455–460, 2005.
11. Chandler RM, Byrne HK, Patterson JG, Ivy JL. Dietary supplements affect the anabolic hormones after weight-training exercise. J Appl Physiol 76: 839–845, 1994.
12. Conley MS, Stone MH. Carbohydrate ingestion/supplementation or resistance exercise
and training. Sports Med 21: 7–17, 1996.
13. Currier DP, Lehman J, Lightfoot P. Electrical stimulation in exercise of the quadriceps femoris muscle. Phys Ther 59: 1508–1512, 1979.
14. Currier DP, Mann R. Muscular strength development by electrical stimulation in healthy individuals. Phys Ther 63: 915–921, 1983.
15. Dill DB, Costill DL. Calculation of percentage changes in volumes of blood, plasma, and red cells in dehydration. J Appl Physiol 37: 247–248, 1974.
16. Enoka RM. Activation order of motor axons in electrically evoked contractions. Muscle Nerve 25: 763–764, 2002.
17. Francescato MP, Puntel I. Does a pre-exercise carbohydrate feeding improve a 20-km cross-country ski performance? J Sports Med Phys Fitness 46: 248–256, 2006.
18. Girold S, Jalab C, Bernard O, Carette P, Kemoun G, Dugue B. Dry-land strength training vs. electrical stimulation in sprint swimming performance. J Strength Cond Res 26: 497–505, 2012.
19. Gollnick PD, Armstrong RB, Sembrowich WL, Shepherd RE, Saltin B. Glycogen depletion pattern in human skeletal muscle fibers after heavy exercise. J Appl Physiol 34: 615–618, 1973.
20. Haff GG, Koch AJ, Potteiger JA, Kuphal KE, Magee LM, Green SB, Jakicic JJ. Carbohydrate supplementation attenuates muscle glycogen loss during acute bouts of resistance exercise
. Int J Sport Nutr Exerc Metab 10: 326–339, 2000.
21. Haff GG, Lehmkuhl MJ, McCoy LB, Stone MH. Carbohydrate supplementation and resistance training. J Strength Cond Res 17: 187–196, 2003.
22. Haff GG, Schroeder CA, Koch AJ, Kuphal KE, Comeau MJ, Potteiger JA. The effects of supplemental carbohydrate ingestion on intermittent isokinetic leg exercise. J Sports Med Phys Fitness 41: 216–222, 2001.
23. Haff GG, Stone MH, Warren BJ, Keith R, Johnson RL, Nieman DC, Williams FJ, Kirksey KB. The effect of carbohydrate supplementation on multiple sessions and bouts of resistance exercise
. J Strength Conditioning Res 13: 111–117, 1999.
24. Hainaut K, Duchateau J. Neuromuscular electrical stimulation and voluntary exercise. Sports Med 14: 100–113, 1992.
25. Hargreaves M. Carbohydrates and exercise. J Sports Sci 9: 17–28, 1991.
26. Herrero AJ, Martin J, Martin T, Abadia O, Fernandez B, Garcia-Lopez D. Short-term effect of strength training with and without superimposed electrical stimulation on muscle strength and anaerobic performance. A randomized controlled trial. Part I. J Strength Cond Res 24: 1609–1615, 2010.
27. Herrero AJ, Martin J, Martin T, Abadia O, Fernandez B, Garcia-Lopez D. Short-term effect of plyometrics and strength training with and without superimposed electrical stimulation on muscle strength and anaerobic performance: A randomized controlled trial. Part II. J Strength Cond Res 24: 1616–1622, 2010.
28. Ivy JL, Ferguson LM. Optimizing resistance exercise
adaptations through the timing of post-exercise carbohydrate-protein supplementation. Strength Conditioning J 32: 30–36, 2010.
29. Karelis AD, Smith JW, Passe DH, Peronnet F. Carbohydrate administration and exercise performance: What are the potential mechanisms involved? Sports Med 40: 747–763, 2010.
30. Keeton RB, Binder-Macleod SA. Low-frequency fatigue. Phys Ther 86: 1146–1150, 2006.
31. Konig R, Dauwalder H, Richterich R. [Comparative determinations of glucose
concentrations in the urine with polarimetry and an enzyme method (hexokinase-glucose
-6-phosphate-dehydrogenase)]. Schweiz Med Wochenschr 101: 860–866, 1971.
32. Kraemer WJ, Staron RS, Hagerman FC, Hikida RS, Fry AC, Gordon SE, Nindl BC, Gothshalk LA, Volek JS, Marx JO, Newton RU, Hakkinen K. The effects of short-term resistance training on endocrine function in men and women. Eur J Appl Physiol Occup Physiol 78: 69–76, 1998.
33. Kraemer WJ, Volek JS, Bush JA, Putukian M, Sebastianelli WJ. Hormonal responses to consecutive days of heavy-resistance exercise
with or without nutritional supplementation. J Appl Physiol 85: 1544–1555, 1998.
34. Kulik JR, Touchberry CD, Kawamori N, Blumert PA, Crum AJ, Haff GG. Supplemental carbohydrate ingestion does not improve performance of high-intensity resistance exercise
. J Strength Cond Res 22: 1101–1107, 2008.
35. Lake DA. Neuromuscular electrical stimulation. An overview and its application in the treatment of sports injuries. Sports Med 13: 320–336, 1992.
36. Lambert CP, Flynn MG, Boone JBJ, Michaud TJ, Rodriguez-Zayas J. Effects of carbohydrate feeding on Multiple-bout resistance exercise
. J Strength Conditioning Res 5: 192–197, 1991.
37. Langenfeld ME, Seifert JG, Rudge SR, Bucher RJ. Effect of carbohydrate ingestion on performance of non-fasted cyclists during a simulated 80-mile time trial. J Sports Med Phys Fitness 34: 263–270, 1994.
38. Maffiuletti NA. The use of electrostimulation exercise in competitive sport. Int J Sports Physiol Perform 1: 406–407, 2006.
39. Maffiuletti NA, Bramanti J, Jubeau M, Bizzini M, Deley G, Cometti G. Feasibility and efficacy of progressive electrostimulation strength training for competitive tennis players. J Strength Cond Res 23: 677–682, 2009.
40. Maffiuletti NA, Cometti G, Amiridis IG, Martin A, Pousson M, Chatard JC. The effects of electromyostimulation training and basketball practice on muscle strength and jumping ability. Int J Sports Med 21: 437–443, 2000.
41. Maffiuletti NA, Pensini M, Martin A. Activation of human plantar flexor muscles increases after electromyostimulation training. J Appl Physiol 92: 1383–1392, 2002.
42. Malatesta D, Cattaneo F, Dugnani S, Maffiuletti NA. Effects of electromyostimulation training and volleyball practice on jumping ability. J Strength Cond Res 17: 573–579, 2003.
43. Maughan RJ, Williams C, Campbell DM, Hepburn D. Fat and carbohydrate metabolism during low intensity exercise: Effects of the availability of muscle glycogen. Eur J Appl Physiol Occup Physiol 39: 7–16, 1978.
44. McGowan MW, Artiss JD, Strandbergh DR, Zak B. A peroxidase-coupled method for the colorimetric determination of serum triglycerides. Clin Chem 29: 538–542, 1983.
45. Owen MD, Kregel KC, Wall PT, Gisolfi CV. Effects of ingesting carbohydrate beverages during exercise in the heat. Med Sci Sports Exerc 18: 568–575, 1986.
46. Pichon F, Chatard JC, Martin A, Cometti G. Electrical stimulation and swimming performance. Med Sci Sports Exerc 27: 1671–1676, 1995.
47. Robergs RA, Pearson DR, Costill DL, Fink WJ, Pascoe DD, Benedict MA, Lambert CP, Zachweija JJ. Muscle glycogenolysis during differing intensities of weight-resistance exercise
. J Appl Physiol 70: 1700–1706, 1991.
48. Roth J, Glick SM, Yalow RS, Bersonsa RA. Hypoglycemia: A potent stimulus to secretion of growth hormone. Science 140: 987–988, 1963.
49. Strojnik V. The effects of superimposed electrical stimulation of the quadriceps muscles on performance in different motor tasks. J Sports Med Phys Fitness 38: 194–200, 1998.
50. Tesch PA, Ploutz-Snyder LL, Yström L, Castro MJ, Dudley GA. Skeletal muscle glycogen loss evoked by resistance exercise
. J Strength Conditioning Res 12: 67–73, 1998.
51. Theurel J, Lepers R, Pardon L, Maffiuletti NA. Differences in cardiorespiratory and neuromuscular responses between voluntary and stimulated contractions of the quadriceps femoris muscle. Respir Physiol Neurobiol 157: 341–347, 2007.
52. Valli P, Boldrini L, Bianchedi D, Brizzi G, Miserocchi G. Effect of low intensity electrical stimulation on quadriceps muscle voluntary maximal strength. J Sports Med Phys Fitness 42: 425–430, 2002.
53. Wax B, Brown SP, Webb HE, Kavazis AN. Effects of carbohydrate supplementation on force output
and time to exhaustion during static leg contractions superimposed with electromyostimulation. J Strength Cond Res 26: 1717–1723, 2012.
54. Willoughby DS, Simpson S. Supplemental EMS and dynamic weight training: Effects on knee extensor strength and vertical jump of female college track & field athletes. J Strength Conditioning Res 12: 131–137, 1998.
55. Yaspelkis BB, Patterson JG, Anderla PA, Ding Z, Ivy JL. Carbohydrate supplementation spares muscle glycogen during variable-intensity exercise. J Appl Physiol 75: 1477–1485, 1993.
56. Zory R, Boerio D, Jubeau M, Maffiuletti NA. Central and peripheral fatigue of the knee extensor muscles induced by electromyostimulation. Int J Sports Med 26: 847–853, 2005.
Keywords:Copyright © 2013 by the National Strength & Conditioning Association.
glucose; resistance exercise; isometric contractions; force output