Scholarly article on topic 'Effects of carbohydrate and protein supplementation during resistance exercise on respiratory exchange ratio, blood glucose, and performance'

Effects of carbohydrate and protein supplementation during resistance exercise on respiratory exchange ratio, blood glucose, and performance Academic research paper on "Educational sciences"

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{Insulin / Diabetes / Lipolysis / Squat / "Bench press"}

Abstract of research paper on Educational sciences, author of scientific article — David M. Laurenson, Danielle Jane Dubé

Abstract Introduction Athletes must determine whether they will benefit most from exercise in the fasted or fed state when discussing variables such as substrate oxidation, muscle anabolism, and performance. Objective To determine the effects of a carbohydrate plus protein (C + P) beverage consumed during resistance exercise on respiratory exchange ratio (RER), blood glucose, and performance. Methods Ten resistance trained male subjects completed two bouts of exercise consisting of seven sets of squats and bench presses using 60% of their one repetition maximum (1RM). Subjects consumed C + P during one trial, and a non-caloric placebo (P) in the other. Six sets of each exercise were performed for a predetermined number of repetitions, followed by a seventh set of each exercise for as many repetitions as possible, performed as explosively as possible. Power was measured during the final set of each exercise. Glucose was measured pre, during, and post exercise. RER was measured seven times during each session. Results No significant difference in power was found. C + P resulted in significantly greater work in the bench press (p < 0.05), with no difference in the squat (p = 0.10). Post-exercise glucose was significantly greater (p < 0.05) in C + P vs. placebo. In C + P, post-exercise glucose was significantly greater (p < 0.05) than before or during exercise. For RER, a significant effect was found for time (p < 0.05), with no difference between conditions. Conclusion In active males, C + P ingestion during resistance exercise improved bench press performance and increased blood glucose, but does not appear to affect RER.

Academic research paper on topic "Effects of carbohydrate and protein supplementation during resistance exercise on respiratory exchange ratio, blood glucose, and performance"

H ~~~

Journal of CLINICAL and TRANSLATIONAL ENDOCRINOLOGY

Accepted Manuscript

Effects of Carbohydrate and Protein Supplementation During Resistance Exercise on Respiratory Exchange Ratio, Blood Glucose, and Performance

David M. Laurenson , Ph.D., Danielle Jane Dube , B.S.

PII: S2214-6237(14)00042-8

DOI: 10.1016/j.jcte.2014.10.005

Reference: JCTE 39

To appear in: Journal of Clinical & Translational Endocrinology

Received Date: 4 June 2014 Revised Date: 22 October 2014 Accepted Date: 27 October 2014

Please cite this article as: Laurenson DM, Dubé DJ, Effects of Carbohydrate and Protein Supplementation During Resistance Exercise on Respiratory Exchange Ratio, Blood Glucose, and Performance, Journal of Clinical & Translational Endocrinology (2014), doi: 10.1016/j.jcte.2014.10.005.

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1 Effects of Carbohydrate and Protein Supplementation During Resistance Exercise on Respiratory

2 Exchange Ratio, Blood Glucose, and Performance.

4 David M. Laurenson1, Ph.D.

5 Danielle Jane Dube2, B.S.

7 iSpringfield College, Springfield Massachusetts

8 2University of Connecticut

10 David M. Laurenson 219 York St. Stoughton, Ma. 02072 (781)-975-1202 (no fax #)

11 DaveLaurenson@hotmail.com

13 Word count:

14 Abstract- 260

15 Text excluding abstract, tables and references- 2770

16 Number of references- 23

17 Number of tables- 5

2 0 Disclosure Statement: The research presented is original and is not being considered for

21 publication elsewhere. The authors do not report any conflicts of interest.

24 Abstract

25 Athletes must determine whether they will benefit most from exercise in the fasted or fed

26 state when discussing variables such as substrate oxidation, muscle anabolism, and performance. 2 7 OBJECTIVE: To determine the effects of a carbohydrate plus protein (C + P) beverage

2 8 consumed during resistance exercise on respiratory exchange ratio (RER), blood glucose, and

2 9 performance. METHODS: Ten resistance trained male subjects completed two bouts of exercise

3 0 consisting of seven sets of squats and bench presses using 60% of their one repetition maximum 31 (1RM). Subjects consumed C + P during one trial, and a non-caloric placebo (P) in the other. Six 3 2 sets of each exercise were performed for a predetermined number of repetitions, followed by a

3 3 seventh set of each exercise for as many repetitions as possible, performed as explosively as

34 possible. Power was measured during the final set of each exercise. Glucose was measured pre,

3 5 during, and post exercise. RER was measured seven times during each session. RESULTS: No

3 6 significant difference in power was found. C + P resulted in significantly greater work in the

3 7 bench press (p < .05), with no difference in the squat (p=.10). Post-exercise glucose was

3 8 significantly greater (p < .05) in C + P vs. placebo. In C + P, post-exercise glucose was

3 9 significantly greater (p < .05) than before or during exercise. For RER, a significant effect was

4 0 found for time (p < .05), with no difference between conditions. CONCLUSION: In active 41 males, C + P ingestion during resistance exercise improved bench press performance and

4 2 increased blood glucose, but does not appear to affect RER.

44 Key Words: insulin, diabetes, lipolysis, squat, bench press

4 5 Abbreviations: RER- respiratory exchange ratio, C+P- carbohydrate plus protein 46

4 8 Introduction

4 9 Many athletes consume nutritional supplements in an effort to maximize the results from

5 0 their exercise training. Proper nutrient intake is vital in attaining optimal adaptations to exercise,

51 with the greatest benefits seen when nutrients are ingested in close proximity to the exercise bout

52 (1, 2, 3). When carbohydrates and amino acids are consumed immediately before resistance

53 exercise, protein synthesis following exercise is greater compared to when carbohydrates and

54 amino acids are consumed immediately following resistance exercise (4). Consuming a pre-

55 workout supplement containing carbohydrate and protein provides additional fuel for the athlete

56 while simultaneously increasing levels of blood glucose and insulin (5). Insulin serves several 5 7 roles in the body, including the stimulation of cellular glucose uptake (6), increasing the rate of 58 protein synthesis (7), and inhibiting protein breakdown (8). Such effects may be viewed as

5 9 positive among athletes, especially those involved in strength and power sports.

6 0 Another role of insulin is to inhibit lipolysis (9), which may be viewed as a negative

61 consequence among individuals attempting to decrease body fat as a primary objective of their

62 exercise program. Carbohydrate supplementation 1 hour prior to endurance exercise (10), or 4

63 hours prior (11) results in increased insulin along with increased carbohydrate availability, which

64 causes the body to favor carbohydrate over lipid as a fuel source. A beverage containing a 4:1 6 5 carbohydrate to protein ratio administered immediately before and during endurance exercise

6 6 leads to higher rates of carbohydrate oxidation and lower rates of lipid oxidation (12). Miller et

6 7 al. demonstrated an attenuated rise in plasma free fatty acids when subjects ingested

68 carbohydrate or non-fat milk during endurance exercise, compared to placebo (13). Athletes and

69 recreational exercisers may experience a dilemma in deciding whether or not to supplement

70 during their workout, depending on their priorities regarding promoting muscle anabolism and

71 accelerating recovery from exercise, or maximizing lipolysis and lipid oxidation in an effort to

72 decrease body fat. The purpose of the present investigation was to examine differences in

73 performance, blood glucose, and respiratory exchange ratio (RER) which may occur when

74 carbohydrates and protein are consumed during an acute bout of resistance exercise compared to

75 when the same exercise bout is conducted while consuming a non-caloric placebo. Variables

76 measured included power output, total volume of work, blood glucose, and RER. Blood glucose

77 measurements were taken immediately before, once during, and immediately after two identical

78 resistance training protocols. RER was measured during each of the two exercise sessions

79 (supplement vs. placebo) at seven time points.

81 Methods

82 Subject characteristics are presented in Table 1. Subjects completed an informed consent

83 and medical history questionnaire and were free of any medical conditions including diabetes.

84 RER was measured using the Cosmed K4B2 portable metabolic system (Cosmed USA, Chicago, 8 5 IL). Blood glucose was measured using the Bayer Contour blood glucose monitor (Bayer Health 8 6 Care, Mishawaka, IN). Blood samples were taken from the fingertip via capillary puncture.

8 7 Power output was measured using the Tendo Unit (Tendo Sport Machines, Trencin, Slovak

8 8 Republic). The supplement used in the present study was an 8% solution of glucose and

8 9 hydrolyzed whey protein at an approximate 3:1 carbohydrate to protein ratio. The serving

9 0 administered during the supplement trial (48g dissolved in 600 mL of water) provided

91 approximately 36g of carbohydrate and 12g of protein (approximately 392 kcal). During the

92 placebo trial, subjects ingested the same volume of a non-caloric naturally flavored placebo

93 beverage. Both the supplement and placebo were flavored with non-caloric natural orange cream

94 flavoring. The beverages were consumed in two equal doses of 300 mL each at 12 and 26

95 minutes into exercise. Both the supplement and placebo were manufactured by True Protein

96 Laboratories Inc. (Oceanside, CA).

97 Exercise Protocol

98 Subjects completed three visits to the laboratory for testing. The first session was to

99 determine their 1RM on the back squat and bench press. 1RM refers to the maximum resistance

100 with which an individual can perform a single repetition. The other two testing sessions involved

101 multiple sets with 60% of their predetermined 1RM, once while consuming C+P, and once while

102 consuming a placebo. Glucose was measured before, during, and following exercise. RER was

103 measured before, three times during, and three times following exercise, for a total of 7 RER

104 measurements. Power and work were measured during the final set of each exercise. Power was

105 calculated with the Tendo unit, and work was calculated by multiplying resistance by repetitions.

107 The exercise protocol was as follows:

108 -10:00 Pre-exercise RER measurement (RER T1)

109 -07:00 Pre-exercise glucose measurement (Glucose T1)

110 -05:00 Dynamic Warm-up

112 (All exercises performed using 60% 1RM;

113 each set was estimated to be approximately 30 seconds in duration; subjects rested for two

114 minutes between sets unless otherwise noted)

116 00:00 Squats x 12

117 02:30 Bench x 12

118 05:00 Squats x 11

119 07:30 Bench x 11

121 08:00 Six Minute rest- RER measured over min 1 -4 (RER T2)

122 Glucose measured at minute 4 (Glucose T2)

123 First half of the beverage consumed during minutes 4-6

12 5 14:00 Squats x 10

12 6 16:30 Bench x 10 12 7 19:00 Squats x 9

12 8 21:30 Bench x 9 129

13 0 22:00 Six Minute rest- RER measured over min 1 -4 (RER T3)

131 Second half of the beverage consumed during minutes 4-6

133 28:00 Squats x 8

134 30:30 Bench x 8 13 5 33:00 Squats x 7 13 6 35:30 Bench x 7 137

13 8 36:00 Six Minute rest- RER measured over min 1 -4 (RER T4)

13 9 42:00 Squats x Max Power and Reps (up to 15) (5 min rest)

14 0 48:00 Bench x Max Power and Reps (up to 15) (exercise concluded) 141

14 2 RER measurement over min 1-4 post-exercise (RER T5)

14 3 Glucose measured at min 4 post-exercise (Glucose T3)

144 RER measurement over min 12-15 post-ex (RER T6)

14 5 RER measurement over min 27-30 post-ex (RER T7) 146

14 7 Statistical Analyses

14 8 Two repeated measures t-tests were performed to examine differences in power output

14 9 during the final set of squats and bench presses between the supplement and placebo conditions.

150 Two additional repeated measures t-tests were performed comparing the total volume of work

151 (resistance in kg x number of repetitions) subjects were able to complete during the final set of

152 each exercise between the two conditions. A 2 X 3 repeated measures Analysis of Variance

153 (RM-ANOVA) was used to assess differences in blood glucose between conditions and across

154 time periods. The three time periods were pre, during (12 min into exercise), and post exercise

155 (53 min from the start of exercise; or 4 min post exercise). A 2 X 7 RM-ANOVA was performed

156 to assess differences in RER between conditions and across time. RER was measured at seven

157 time points during each exercise session. One measurement was taken pre-exercise; three

158 measurements were taken during exercise (min 12, 26, and 40); and three measurements were

15 9 taken during recovery from exercise (min 4, 15, and 30 post exercise). 160

161 Results

162 POWER: No significant mean difference was found in peak power for squats between the

163 supplement (M = 1083 ± 290) and placebo (M = 1061 ± 271) conditions (p = .45). No significant

164 mean difference was observed in peak power for bench presses between the supplement (M =

165 552 ± 151) and placebo (M = 544 ± 138) conditions (p = .70). Results for power are presented in

166 table 2.

167 WORK: When comparing the volume of work between conditions, no significant

168 difference was found in total work (resistance in kg x reps) for squats between the placebo (M =

169 909 ± 472) and supplement (M = 1009 ± 433) conditions (p = .10). However, subjects performed

170 significantly more work in the bench press in the supplement (M = 921 ± 365) versus the placebo

171 (M = 783 ± 332) condition (p = .01). Results for work are presented in table 3.

172 BLOOD GLUCOSE: A 2 X 3 RM-ANOVA was used to examine differences in blood

173 glucose between conditions (supplement vs. placebo) and across time points (pre, during, and

174 post exercise). The supplement was distributed following the second blood glucose

175 measurement. A significant interaction was found between condition and time period for blood

176 glucose (p = .008). A simple effects test was computed to determine where the significant mean

177 differences occurred. When comparing time differences for the supplement condition, no

178 significant mean difference was found between pre vs. mid exercise (p > .05). In contrast, blood 17 9 glucose was significantly higher post exercise compared to both pre (p = .003) and during (p =

180 .001) exercise. No significant mean differences were found when comparing differences in blood

181 glucose among the three time points for the placebo condition (p > .05). No significant mean

182 difference in blood glucose was found between conditions for pre (p = .63) or during (p = .21)

183 exercise. However, blood glucose was significantly higher following exercise in the supplement

184 compared to placebo condition (p = .01). Results for blood glucose are presented in table 4.

185 RER: A 2 X 7 RM-ANOVA was computed to examine differences in RER over time and

186 between conditions. RER was measured pre-exercise, three times during exercise, and three

187 times following exercise. No significant interaction was found between condition and time for

188 RER (p = .51). No significant mean difference was found between conditions for RER (p = .44). 18 9 A significant mean difference for RER was found across time points (p = .00). RER was

190 significantly higher at time 1 compared to time 7 (p < .05), and significantly lower than times 2,

191 3, 4, and 5 (p < .05). RER at time 1 was not significantly different from time 6 (p > .05). RER at

192 time 2 was significantly higher than times 3, 4, 5, 6, and 7 (p < .05). RER at time 3 was

193 significantly higher than times 4, 6, and 7 (p < .05), and not significantly different from time 5 (p

194 > .05). RER at time 4 was not significantly different from time 5 (p > .05), but was significantly

195 higher than times 6, and 7 (p < .05). RER at time 5 was significantly higher than times 6 and 7 (p

196 < .05). RER at time 6 was not significantly different from time 7 (p > .05). Results for RER are

197 presented in table 5.

199 Discussion

2 00 Some researchers have reported no performance benefit of supplementation during an

2 01 acute bout of resistance exercise (14, 15), whereas Haff et al suggested an ergogenic benefit of

2 02 consuming nutrients during resistance exercise (16). In the present study, the only performance

2 03 benefit seen was an increase in work capacity for the bench press. The additional fuel provided

2 04 by the supplement may have aided performance, perhaps by sparing muscular glycogen. The

2 05 difference in work capacity for the squat did not reach statistical significance (p = .10). Perhaps

2 06 the results would have been different if the timing and amount of supplement ingested were

207 changed. Also, the exercise type and duration, as well as initial glycogen levels, are likely to

208 impact whether or not performance differences can be seen with supplementation.

209 Blood glucose was well maintained during exercise in the placebo condition, and

210 increased in response to C + P ingestion. Blood glucose is regulated by glucose release into the

211 blood stream, either from digested carbohydrates or hepatic glucose production, and glucose

212 disposal, or uptake by cells. Glucose was measured via capillary puncture. Having subjects

213 consume a beverage containing labeled glucose would have provided a more detailed picture of

214 the contribution of the ingested beverage to changes in blood glucose. Since blood glucose was

215 well maintained during the placebo condition, one may infer that the exercise protocol was not

216 long or intense enough to threaten blood glucose homeostasis. In the present study, liver glucose

217 output, whether from glycogenolysis or gluconeogenesis, was able to meet the demands of

218 exercise during the placebo condition. Subjects were instructed to fast for at least 8-10 hours

219 prior to testing, and to record and match their food intake for 72 hours prior to each testing

2 2 0 session. Perhaps if the exercise bout had been greater in duration and/or volume, and if subjects

2 21 were glycogen depleted at the beginning of exercise, a greater performance difference may have

2 2 2 been observed. Also, the addition of an aerobic portion following the resistance exercise protocol

2 2 3 would have offered another way to compare performance differences. During the placebo

2 24 condition, no nutrients were consumed and thus blood glucose was maintained by glycogenolysis

2 2 5 and gluconeogenesis. The increase in blood glucose seen after subjects consumed the supplement

2 2 6 may have been due to increased glucose release from splanchnic tissue. In retrospect, a fourth

2 2 7 glucose measurement taken 30 min following exercise may have helped to determine if glucose

2 2 8 levels would return to baseline after 30 min of recovery in the supplement condition, and if 30

2 2 9 min of recovery would have led to any glucose changes in the placebo condition.

230 RER is a widely used measure in studies examining aerobic exercise, and has been

2 31 examined less in studies involving resistance exercise (17-20). In the present study, RER was

232 measured throughout exercise in an effort to examine potential differences in fuel oxidation

233 when nutrients are consumed during resistance exercise versus when no nutrients are ingested.

234 One aim of the study was to examine if the supplement would improve performance at the

235 expense of limiting lipid oxidation. Many people who engage in physical activity are concerned

236 more with changing body composition than with exercise performance. RER can provide us with 2 3 7 an estimate of how much relative fuel is being oxidized from carbohydrates vs. lipids. RER

2 3 8 changed significantly over time in both conditions, although the conditions were not statistically

2 3 9 different from one another. The first RER measurement was taken before the start of exercise.

24 0 The second was taken after two sets of each exercise, but before any beverage was consumed.

241 The third was taken following two more sets of each exercise, and one half of the beverage. The

24 2 fourth was taken following two more sets of each exercise, and the second half of the beverage.

24 3 The fifth was taken following the final (7th) set of each exercise (conclusion of exercise). The

244 sixth and seventh RER measurements were taken following 15 and 30 minutes of recovery from

24 5 exercise, respectively. As expected, RER rose from rest to exercise during both the supplement

24 6 and placebo trials, and returned towards normal during recovery. However, no differences in

24 7 RER between conditions was found, suggesting that the supplement did not cause a statistically

24 8 significant difference in fuel oxidation between the two conditions.

24 9 Results from the present study are in agreement with Ormsbee et al., who reported a

2 50 decrease in RER from before to after resistance exercise, indicating a shift towards greater lipid

2 51 oxidation during recovery from exercise compared to pre-exercise (20). In the present study,

2 52 RER was significantly lower 30 min following exercise compared to pre-exercise. At 30 min

2 53 post-exercise, RER in the placebo condition was 0.70 ± .032 compared to 0.76 ± .029 in the

2 54 supplement trial, suggesting a greater reliance on lipid oxidation during recovery in the placebo

2 55 trial, however no statistical significance was found. Following the 2x7 ANOVA, a repeated

2 56 measures /-test was used to examine for differences at time 7 only. However, no significant

2 57 difference was found. Perhaps if a third portion of the beverage had been consumed immediately

2 58 following exercise, or if RER was measured beyond 30 minutes of recovery, perhaps for 1-2

2 5 9 hours post exercise, we may have witnessed an elevated recovery RER compared to placebo by

2 60 allowing ample time for the ingested glucose to be metabolized. Although RER during exercise

2 61 was not statistically different between trials, RER values during exercise were higher in the

2 62 present study compared to other studies. Other researchers have reported slight differences in

2 63 respiratory measurements when comparing the portable Cosmed K4b2 system to laboratory

2 64 based metabolic carts (21-23).

2 65 Several possibilities exist for future research. Measuring insulin and indicators of

2 66 lipolysis such as glycerol would help to determine the effects of nutrient ingestion during

2 67 resistance exercise on lipolysis. A longitudinal study would be interesting as well. Subjects could

2 68 be divided into two groups and perform identical exercise programs for several weeks. One

2 6 9 group could exercise while fasted, while the other group could supplement during exercise.

2 70 Researchers could compare differences in body composition and performance improvements

2 71 over time, as well as indicators of overall health such as insulin sensitivity, and markers of

2 72 inflammation. Also, similar studies on diabetic and pre-diabetic patients could provide

2 73 information regarding proper dietary and exercise prescriptions in order to manage blood glucose

2 74 during and following exercise. In conclusion, in healthy active males, nutrient ingestion during

2 75 resistance exercise improved upper body muscular endurance, but had no effect on power or

276 substrate use as indicated by RER. The question remains as to whether supplementation during

277 exercise will improve performance at the expense of lipid oxidation, and whether exercise in the

278 fasted state will enhance lipid oxidation at the expense of limiting performance.

2 80 Dr. David Laurenson contributed to the study design, subject recruitment, and ran all exercise

281 testing sessions. Danielle Dube was responsible for data recording, instrumentation, and

282 preparation and administration of the test beverages.

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Table 1

Descriptive Statistics for Subjects

Variable Mean s N

Age (yrs) 25.3 6.07 10

Weight (lbs) 184.2 28.86 10

Height (in) 70.0 3.71 10

1RM Squat (lbs) 300.5 70.65 10

1RM Bench (lbs) 236.5 52.50 10

Table 2

Descriptive Statistics of Mean Values of Muscular Power Output for the Squat and Bench Pressa

Exercise Placebo Carbohydrate + Protein

Mean SD Mean SD

Squat 1060.8 271.3 1082.9 289.6 Bench Press 543.6 138.0 552.1 150.7

aPower represents the average of the best 3 repetitions performed in each set reported in Watts.

Table 3

Descriptive Statistics of Mean Values for Total Volume of Work Completed (Resistance in kg x Number of Repetitions) in the Squat and Bench Press

Exercise Placebo Carbohydrate + Protein

Mean SD Mean SD

Squat 909 472 1009 433

Bench Press 783 332 921* 365

*Total volume of work in the bench press significantly higher in the supplement condition (p=01).

Table 4

Descriptive Statistics of Mean Values for Blood Glucosea

Time Placebo Carbohydrate + Protein

Mean SD Mean SD

Pre Exercise 75.7 7.8 76.9 9.3

Mid Exercise 81.3 12.9 77.5 11.3

Post Exercise 84.9 18.9 110.1*" 21.2

aGlucose = mg/dL

Significantly greater than pre exercise in the C + P condition (p=.003) fSignificantly greater than mid exercise in the C + P condition (p=.001) ^Significantly greater than post exercise values during the Placebo condition (p=.01).

Table 5

Descriptive Statistics of Mean Values for Respiratory Exchange Ratioa

Time Placebo Carb + Pro Overall

Mean SD Mean SD Mean SD

1. Pre Ex 0.79 0.05 0.82 0.05 * 0.81 0.01

2. Min 12 Ex 1.31 0.08 1.28 0.13 1.30t 0.03

3. Min 26 Ex 1.16 0.09 1.20 0.11 1.18$ 0.02

4. Min 40 Ex 1.10 0.09 1.11 0.10 1.10s 0.02

5. Min 4 Rec 1.08 0.12 1.12 0.09 1.101 0.03

6. Min 15 Rec 0.77 0.11 0.78 0.10 0.77 0.02

7. Min 30 Rec 0.70 0.10 0.76 0.09 0.73 0.02

aRespiratory Exchange Ratio average values over one minute. Time 1 significantly less than times 2, 3, 4, 5, and 7. ^Time 2 significantly greater than times 3, 4, 5, 6, and 7. $Time 3 significantly greater than times 4, 6, and 7. §Time 4 significantly greater than times 6, and 7. ^Time 5 significantly greater than times 6, and 7. All (p<. 05)