Journal of Strength and Conditioning Research Publish Ahead of Print DOI: 10.1097/JSC.0000000000000220
The Effect of Caffeine Ingestion on Delayed Onset Muscle Soreness Caitlin F. Hurley, Disa L. Hatfield, Deborah Riebe Human Performance Laboratory Department of Kinesiology University of Rhode Island South Kingston, RI 02881, USA
A
C C
EP
TE
Correspondence To: Disa L. Hatfield, Ph.D. Human Performance Laboratory Department of Kinesiology University of Rhode Island South Kingston,RI 02881 Phone: 401-874-5183 Fax: 401-874-4215 E-mail: [email protected]
D
Running Head: caffeine and delayed onset muscle soreness
Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
ABSTRACT
The beneficial effects of caffeine on aerobic activity and resistance training performance are well documented. However, less is known concerning caffeine’s potential role in reducing perception of pain and soreness during exercise. In
D
addition, there is no information regarding the effects of caffeine on delayed onset muscle soreness. The primary purpose of this study was to examine the effect of
TE
caffeine ingestion on muscle soreness, blood enzyme activity, and performance following a bout of elbow flexion/extension exercise. Nine low caffeine consuming males (body mass: 76.68 ± 8.13kg; height: 179.18 ± 9.35cm; age: 20 ±
EP
1 yr) were randomly assigned to ingest either caffeine or placebo one hour prior to completing 4 sets of 10 bicep curls on a preacher bench, followed by a fifth set in which subjects completed as many repetitions as possible. Soreness and soreness
C C
on palpation intensity was measured using three, 0-10 visual analog scales prior to exercise, and 24, 48, 72, 96 and 120 hours post exercise. Following a washout period, subjects crossed-over to the other treatment group. Caffeine ingestion resulted in significantly (p ≤0.05) lower levels of soreness on day 2 and day 3
A
compared to placebo. Total repetitions in the final set of exercise increased with caffeine ingestion compared to placebo. This study demonstrates that caffeine ingestion immediately before an upper-body resistance training out enhances performance. A further beneficial effect of sustained caffeine ingestion in the days following the exercise bout is an attenuation of delayed onset muscle
2 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
soreness (DOMS ). This decreased perception of soreness in the days following a strenuous resistance training workout may allow individuals to increase the number of training sessions in a given time period.
A
C C
EP
TE
D
Keywords: Caffeine; delayed onset muscle soreness; DOMS; resistance training; performance
3 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
INTRODUCTION As much as 90% of the population ingests caffeine on a regular basis and caffeine is the most popular stimulant used by athletes to enhance sport performance (3, 15). The endurance performance enhancing effects of caffeine
D
have been well documented (25, 32). Several potential mechanisms exist that may explain this increase in performance, including the release of cortisol and
TE
beta endorphins (12, 16, 32). Caffeine ingestion also increases lipid oxidation, thus resulting in muscle glycogen sparing (20, 28, 29, 46). In addition to these physiological effects, these hormonal and endorphin mechanisms may account for
EP
decreased perception of fatigue during physical activity (16).
Less is known about the effect of caffeine ingestion on muscular strength and endurance. To date, the results from studies that examine caffeine’s effect on muscle strength is equivocal. Some studies have found a significant gain in
C C
muscle strength with caffeine ingestion (26, 28) while other studies report no significance (5). Since resistance training and other short term, high intensity activities do not require such high concentrations of glycogen, further research on
A
additional mechanisms in which caffeine affects the muscle function have emerged (5, 20). There has been some speculation on potential mechanisms in which caffeine affects resistance training performance (5, 20). Caffeine may increase the muscles ability to recruit motor units, increasing the force of a muscle contraction (28, 29). In addition to the benefits on performance, caffeine is an adenosine antagonist. By blocking adenosine receptors, caffeine may enhance
4 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
sympathetic nervous system response, including reduced feelings of pain and soreness (2, 13, 17, 36). In turn, these reduced feelings of pain and soreness may play a role in enhanced performance through increased ability to do work. However, some investigators report no effect of caffeine ingestion on perceived
D
effort (4). Differences in dosage, timing of caffeine ingestion, mode of exercise, subject population, and acute nature of individual studies may account for the
TE
varied results on performance and perceptual indices. Resistance training
In addition to pain and soreness scores, activity of muscle enzymes also acts as an indirect marker of muscle damage (9, 11, 33, 42). Further, to date,
EP
only one study has examined caffeine’s effects on physiological markers of muscle damage such as creatine kinase (CK) that are associated with higher levels of pain perception after an acute bout of resistance exercise (35). Investigators in that study reported that caffeine does not attenuate CK levels immediately after a
C C
resistance training session. However, peak level of blood CK activity and corresponding peak of delayed onset muscle soreness (DOMS) and pain occurs between 24-48 hours following exercise (10, 41). Currently, no study has
A
investigated how caffeine affects either physiological markers like CK or perception of pain in the days following an acute bout of resistance exercise, when muscular soreness is at the highest levels. Without this information, the practicality of ingesting caffeine in order to decrease feelings of pain cause by DOMS is unknown.
5 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
Therefore, the primary purpose of this investigation was to examine both perceptual and physiological markers of muscle damage and soreness for several days following resistance exercise with and without ingestion of caffeine. Given the conflicting research, a secondary purpose was to examine the effect of
D
caffeine ingestion on upper-body muscular strength performance. Our hypothesis is that caffeine ingestion will increase upper-body resistance training performance
TE
and, through caffeine’s role as an adenosine antagonist, will attenuate perception of DOMS.
METHODS
EP
Experimental Approach to the Problem
In order to test this hypothesis, healthy, college-age, recreationally trained men were recruited to participate in this double blind, within subject, crossover design, placebo controlled study during the spring semester at the University of
C C
Rhode Island.
Subjects were required to complete three testing sessions. The first testing
session that consisted of informed consent, anthropometric measures, and a 1-
A
repetiion maximum bicep curl test. Following this, subjects participated in two experimental exercise trials in which they ingested either caffeine or placebo then underwent a strenuous upper body exercise protocol. Each subject also completed two follow up periods of five days after each experimental trial in which they evaluated soreness and fatigue using scales. The experimental trials were completed two weeks apart at approximately the same time of day.
6 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
Subjects Twelve healthy, resistance-trained males aged 18 – 25 years who were familiar with the biceps curl exercise volunteered for this study. Resistance trained was
D
defined as taking part in a regular (at least twice a week) resistance exercise regime for the past six months (31). Prior training experience in the bicep curl
TE
exercise was thought to be important to ensure that learning effects did not did not influence the results. Subjects were asked to refrain from caffeine 7 days prior to the start and for the entire duration of the study. This eliminated any possible
EP
tolerance to caffeine and its effect on pain and soreness after exercise. Subjects maintained their normal dietary habits but were advised to refrain from exercise, alcohol and nicotine consumption at least 48 hours prior to exercise testing sessions. For the duration of the study, subjects were to refrain from upper body
C C
resistance training and the use of pain relievers and analgesics. Subjects kept a dietary log of all items ingested during the 48 hour time period prior to each exercise session.
A
Prior to participation, each subject gave written informed consent and
completed a medical history, exercise history and nutritional questionnaire. Procedures were approved by the Institutional Review Board at the University of Rhode Island. Subjects were of age 20 ± 1 year, body mass 76.68 ± 8.13kg, and height 179.18 ± 9.35cm. Percent body fat as measured by skinfold calipers was 9.64 ± 4.86%.
7 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
Procedures During the familiarization session, anthropometric measurements were taken, BMI was calculated, percent body fat was measured, and one repetition The 1-RM test
D
maximum (1-RM) for the bicep curl exercise was determined.
was performed on a preacher bench (Yukon Fitness Equipment). The 1RM was
TE
measured using a standard 1-RM protocol from Kraemer and Fry (31). After testing, subjects were carefully instructed on how to use the muscle soreness scales.
EP
Following this preliminary testing, subjects underwent two sessions of testing. The testing sessions were separated by seven days, and each took place at the same time of day. Previous studies have suggested that a seven day washout period is long enough to ensure that caffeine is no longer in one’s system (46).
C C
Subjects were instructed to eat the same or similar meals two days before each testing session. This was done to help eliminate the chance of an increase in carbohydrate intake and potential affect on muscle glycogen stores and to check
A
that they didn’t ingest caffeine-containing foods or beverages. All testing sessions took place in the same location, which were supervised by the same investigators. Care was taken to ensure that all subjects received the same verbal encouragement and instructions for all exercises to negate potential differences in state of arousal.
8 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
All experimental trials were performed in the morning, after a twelve hour fast, excluding water. Time of day was standardized (± 1hour) to avoid confounding influences of diurnal hormonal variations and subjects were asked how sleep they got the night before to ensure the same amount of rest was had
D
before each trial. Additionally, subjects were instructed to drink ~1 liter of water the night before and the morning of the experimental trials to ensure adequate
TE
hydration. Hydration state was determined prior to exercise and caffeine or placebo ingestion via urine refractometry. Following a resting blood draw,
subjects ingested a capsule containing five mg/kg body weight of caffeine or a
EP
placebo with approximately 500mL of water. Each subject then sat quietly for one hour, a time frame that allows for a peak plasma caffeine concentration (39). Following the rest period, subjects completed five sets of a bicep curl performed on a preacher bench with the non-dominant arm using a weight equal to 75% of
C C
each subject’s predetermined 1RM. Subjects were instructed to complete 10 repetitions during the first four sets and as many repetitions as possible during the last set. A metronome cadence of 30 was used to control the motion to ensure
A
proper speed of the movement. The Borg CR-10 scale was used after completion of each set to score perception of effort and soreness (8). Subjects were provided with soreness scales to take home and use to report levels of soreness during the five day follow up by marking the proper line on the visual analog scale. Scales were returned to investigators at completion of follow up. Subjects reported back
9 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
to the exercise science laboratory 48 hours following the experimental trials for a second blood draw.
Follow Up
D
Days 1-5: On days one-five (24-120 hours) following experimental trials, subjects evaluated level of muscle soreness using the specific instructions received.
TE
Subjects also ingested the appropriate capsule at the same time of day on these follow up days. Phone call reminders were sent to subjects during follow up to remind subjects to evaluate muscle soreness and to ingest the appropriate capsule.
EP
Completed scales were collected at completion of each follow up period. On day two, subjects also reported to laboratory for a second blood draw.
Caffeine and Placebo Administration
C C
Caffeine (USP grade, Wilken Scientific, Pawtucket RI) and placebo was
prepared in capsules by the Pharmacy Department at URI. Five mg/kg BW was used to determine the total dose for each subject. This dosage is equal to
A
approximately two and one-half cups of brewed coffee and is consistent with several past studies examining the effect of caffeine on exercise (27, 36, 39). Placebo capsules were filled with flour, which resembles caffeine in color and texture. Caffeine or placebo was ingested one hour prior to experimental trials, 24 hours following the experimental trials and every day for four days thereafter. Subjects ingested the caffeine or placebo at the same time of day for the entire
10 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
study. An individual who was not involved in data collecting or data analysis was responsible for the assignment of caffeine and placebo to protect against the expectancy effect by the subjects and investigators. Subjects were provided with
D
soreness scales to take home.
Study Measures
TE
Anthropometric Measurements
Body weight was measured to the nearest 0.1 kg using a digital read scale (Tanita BF-556, Arlington Heights, IL.) Height was measured by use of a
EP
stadiometer (Seca, Hamburg, Germany) to the closest 0.5 cm. BMI was calculated as weight (kg) divided by height (m) squared. Body fat percentage was determined from skinfold measurements of the chest, abdomen and thigh (Lange Skinfold Caliper, Cambridge, MD). The three-site skinfold equation was used to
C C
determine body density (24). Body fat was converted from body density using a population specific formula for white males age 20-80 years (44).
A
Muscle Soreness: Instructions on the use of three scales was read to all subjects; Overall Soreness Scale, Overall Fatigue Scale, and a Soreness on Palpation Scale. Subjects rated their level of muscle soreness by selecting a number of the continuous scales. Ratings for each scale were as followed: 0 no soreness/fatigue; 1 very light soreness/fatigue; 2 moderate soreness/fatigue; 3 light (weak) feelings of soreness/fatigue; 5 (heavy) strong feelings of soreness; 7 very heavy feelings of
11 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
soreness; 10 maximal soreness. This type of scale is a valid and reliable measure that has been used in multiple studies regarding muscle soreness and pain (22, 37, 38). Blood Profile: All blood draws were obtained by venipuncture on subject’s
D
dominant arm due to the fact that each subject performed the bicep curl on their non-dominant arm. A resting blood draw was taken prior to both experimental
TE
trials and during the second day of follow up of each trial. Whole blood was collected and transferred into appropriate tubes in order to obtain serum and
plasma. Blood was centrifuged at 1500g for 15 minutes at 4°C. Resulting serum
EP
and plasmas was aliqouted and stored at -80°C for analysis. Serum Creatine Kinase (CK) was measured using colorimetric procedures at 340nm.
Statistical Analysis
C C
All results are reported as mean ± SD. A 2 x 2 (trial x time) repeated
measures ANOVA was used to analyze the CK data, a 2 x 6 (trial x time) used to analyze the soreness and fatigue resting data from the exercise trial day to Day 5,
A
and 2 x 5 (trial x sets) used to analyze the CR10 Borg scale ratings collected after each set of bicep curls. A paired-sample t-test was used to analyze the repetition number for the last set of bicep curls in the two trials. Linear assumptions were tested for and met. In the case of a significant F score in the ANOVAs, a Bonferroni Post Hoc test was performed to determine where significant differences lay. Significance for all analysis was set a p≤ 0.05. Based on previous
12 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
studies it was determined that an n of 10 was adequate to defend the 0.05 alpha level of significance with a Cohen probability level of 0.8 (G-Power software,
RESULTS
D
version 3.1.2, Kiel University, Germany).
TE
In general, this study demonstrated that caffeine ingestion has beneficial effects on ratings of muscle soreness, perceived exertion and performance
Soreness
EP
surrounding an acute bout of resistance exercise.
Soreness values at day 1 and day 2 were significantly different than pre exercise values with caffeine and placebo ingestion. Caffeine produced a
C C
significantly lower soreness value on day 2 and day 3 post exercise when
A
compared to placebo. Values for overall soreness can be seen in Figure 1.
Figure 1 about here
Change in Soreness Change in soreness values are shown in Figure 2. Increase in soreness
from pre exercise to day 2 of follow up was significantly higher under both conditions, however there were no between group differences.
13 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
Figure 2 about here
Soreness on Palpation
D
A significant difference was demonstrated in soreness on palpation values with caffeine ingestion on day 2 of follow up compared to soreness with placebo
TE
ingestion. Soreness on palpation values on day 1, 2, 3 and 4 for caffeine and days 1, 2, and 3 for placebo were significantly different than the pre-exercise soreness
EP
on palpation value. These values are shown in Figure 3.
Figure 3 about here
C C
Change in Soreness on Palpation
Figure 4 shows change in soreness on palpation values. A significant
increase was observed in changes in soreness on palpation values from preexercise to day 1 and day 2 of follow up with both conditions in addition to day 3
A
with caffeine ingestion. There was also a significant difference in soreness on palpation values on day 4 of follow up between conditions.
Figure 3 about here
14 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
Performance (Repetition Number) There was a significant increase (p
The Effect of Caffeine Ingestion on Delayed Onset Muscle Soreness Caitlin F. Hurley, Disa L. Hatfield, Deborah Riebe Human Performance Laboratory Department of Kinesiology University of Rhode Island South Kingston, RI 02881, USA
A
C C
EP
TE
Correspondence To: Disa L. Hatfield, Ph.D. Human Performance Laboratory Department of Kinesiology University of Rhode Island South Kingston,RI 02881 Phone: 401-874-5183 Fax: 401-874-4215 E-mail: [email protected]
D
Running Head: caffeine and delayed onset muscle soreness
Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
ABSTRACT
The beneficial effects of caffeine on aerobic activity and resistance training performance are well documented. However, less is known concerning caffeine’s potential role in reducing perception of pain and soreness during exercise. In
D
addition, there is no information regarding the effects of caffeine on delayed onset muscle soreness. The primary purpose of this study was to examine the effect of
TE
caffeine ingestion on muscle soreness, blood enzyme activity, and performance following a bout of elbow flexion/extension exercise. Nine low caffeine consuming males (body mass: 76.68 ± 8.13kg; height: 179.18 ± 9.35cm; age: 20 ±
EP
1 yr) were randomly assigned to ingest either caffeine or placebo one hour prior to completing 4 sets of 10 bicep curls on a preacher bench, followed by a fifth set in which subjects completed as many repetitions as possible. Soreness and soreness
C C
on palpation intensity was measured using three, 0-10 visual analog scales prior to exercise, and 24, 48, 72, 96 and 120 hours post exercise. Following a washout period, subjects crossed-over to the other treatment group. Caffeine ingestion resulted in significantly (p ≤0.05) lower levels of soreness on day 2 and day 3
A
compared to placebo. Total repetitions in the final set of exercise increased with caffeine ingestion compared to placebo. This study demonstrates that caffeine ingestion immediately before an upper-body resistance training out enhances performance. A further beneficial effect of sustained caffeine ingestion in the days following the exercise bout is an attenuation of delayed onset muscle
2 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
soreness (DOMS ). This decreased perception of soreness in the days following a strenuous resistance training workout may allow individuals to increase the number of training sessions in a given time period.
A
C C
EP
TE
D
Keywords: Caffeine; delayed onset muscle soreness; DOMS; resistance training; performance
3 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
INTRODUCTION As much as 90% of the population ingests caffeine on a regular basis and caffeine is the most popular stimulant used by athletes to enhance sport performance (3, 15). The endurance performance enhancing effects of caffeine
D
have been well documented (25, 32). Several potential mechanisms exist that may explain this increase in performance, including the release of cortisol and
TE
beta endorphins (12, 16, 32). Caffeine ingestion also increases lipid oxidation, thus resulting in muscle glycogen sparing (20, 28, 29, 46). In addition to these physiological effects, these hormonal and endorphin mechanisms may account for
EP
decreased perception of fatigue during physical activity (16).
Less is known about the effect of caffeine ingestion on muscular strength and endurance. To date, the results from studies that examine caffeine’s effect on muscle strength is equivocal. Some studies have found a significant gain in
C C
muscle strength with caffeine ingestion (26, 28) while other studies report no significance (5). Since resistance training and other short term, high intensity activities do not require such high concentrations of glycogen, further research on
A
additional mechanisms in which caffeine affects the muscle function have emerged (5, 20). There has been some speculation on potential mechanisms in which caffeine affects resistance training performance (5, 20). Caffeine may increase the muscles ability to recruit motor units, increasing the force of a muscle contraction (28, 29). In addition to the benefits on performance, caffeine is an adenosine antagonist. By blocking adenosine receptors, caffeine may enhance
4 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
sympathetic nervous system response, including reduced feelings of pain and soreness (2, 13, 17, 36). In turn, these reduced feelings of pain and soreness may play a role in enhanced performance through increased ability to do work. However, some investigators report no effect of caffeine ingestion on perceived
D
effort (4). Differences in dosage, timing of caffeine ingestion, mode of exercise, subject population, and acute nature of individual studies may account for the
TE
varied results on performance and perceptual indices. Resistance training
In addition to pain and soreness scores, activity of muscle enzymes also acts as an indirect marker of muscle damage (9, 11, 33, 42). Further, to date,
EP
only one study has examined caffeine’s effects on physiological markers of muscle damage such as creatine kinase (CK) that are associated with higher levels of pain perception after an acute bout of resistance exercise (35). Investigators in that study reported that caffeine does not attenuate CK levels immediately after a
C C
resistance training session. However, peak level of blood CK activity and corresponding peak of delayed onset muscle soreness (DOMS) and pain occurs between 24-48 hours following exercise (10, 41). Currently, no study has
A
investigated how caffeine affects either physiological markers like CK or perception of pain in the days following an acute bout of resistance exercise, when muscular soreness is at the highest levels. Without this information, the practicality of ingesting caffeine in order to decrease feelings of pain cause by DOMS is unknown.
5 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
Therefore, the primary purpose of this investigation was to examine both perceptual and physiological markers of muscle damage and soreness for several days following resistance exercise with and without ingestion of caffeine. Given the conflicting research, a secondary purpose was to examine the effect of
D
caffeine ingestion on upper-body muscular strength performance. Our hypothesis is that caffeine ingestion will increase upper-body resistance training performance
TE
and, through caffeine’s role as an adenosine antagonist, will attenuate perception of DOMS.
METHODS
EP
Experimental Approach to the Problem
In order to test this hypothesis, healthy, college-age, recreationally trained men were recruited to participate in this double blind, within subject, crossover design, placebo controlled study during the spring semester at the University of
C C
Rhode Island.
Subjects were required to complete three testing sessions. The first testing
session that consisted of informed consent, anthropometric measures, and a 1-
A
repetiion maximum bicep curl test. Following this, subjects participated in two experimental exercise trials in which they ingested either caffeine or placebo then underwent a strenuous upper body exercise protocol. Each subject also completed two follow up periods of five days after each experimental trial in which they evaluated soreness and fatigue using scales. The experimental trials were completed two weeks apart at approximately the same time of day.
6 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
Subjects Twelve healthy, resistance-trained males aged 18 – 25 years who were familiar with the biceps curl exercise volunteered for this study. Resistance trained was
D
defined as taking part in a regular (at least twice a week) resistance exercise regime for the past six months (31). Prior training experience in the bicep curl
TE
exercise was thought to be important to ensure that learning effects did not did not influence the results. Subjects were asked to refrain from caffeine 7 days prior to the start and for the entire duration of the study. This eliminated any possible
EP
tolerance to caffeine and its effect on pain and soreness after exercise. Subjects maintained their normal dietary habits but were advised to refrain from exercise, alcohol and nicotine consumption at least 48 hours prior to exercise testing sessions. For the duration of the study, subjects were to refrain from upper body
C C
resistance training and the use of pain relievers and analgesics. Subjects kept a dietary log of all items ingested during the 48 hour time period prior to each exercise session.
A
Prior to participation, each subject gave written informed consent and
completed a medical history, exercise history and nutritional questionnaire. Procedures were approved by the Institutional Review Board at the University of Rhode Island. Subjects were of age 20 ± 1 year, body mass 76.68 ± 8.13kg, and height 179.18 ± 9.35cm. Percent body fat as measured by skinfold calipers was 9.64 ± 4.86%.
7 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
Procedures During the familiarization session, anthropometric measurements were taken, BMI was calculated, percent body fat was measured, and one repetition The 1-RM test
D
maximum (1-RM) for the bicep curl exercise was determined.
was performed on a preacher bench (Yukon Fitness Equipment). The 1RM was
TE
measured using a standard 1-RM protocol from Kraemer and Fry (31). After testing, subjects were carefully instructed on how to use the muscle soreness scales.
EP
Following this preliminary testing, subjects underwent two sessions of testing. The testing sessions were separated by seven days, and each took place at the same time of day. Previous studies have suggested that a seven day washout period is long enough to ensure that caffeine is no longer in one’s system (46).
C C
Subjects were instructed to eat the same or similar meals two days before each testing session. This was done to help eliminate the chance of an increase in carbohydrate intake and potential affect on muscle glycogen stores and to check
A
that they didn’t ingest caffeine-containing foods or beverages. All testing sessions took place in the same location, which were supervised by the same investigators. Care was taken to ensure that all subjects received the same verbal encouragement and instructions for all exercises to negate potential differences in state of arousal.
8 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
All experimental trials were performed in the morning, after a twelve hour fast, excluding water. Time of day was standardized (± 1hour) to avoid confounding influences of diurnal hormonal variations and subjects were asked how sleep they got the night before to ensure the same amount of rest was had
D
before each trial. Additionally, subjects were instructed to drink ~1 liter of water the night before and the morning of the experimental trials to ensure adequate
TE
hydration. Hydration state was determined prior to exercise and caffeine or placebo ingestion via urine refractometry. Following a resting blood draw,
subjects ingested a capsule containing five mg/kg body weight of caffeine or a
EP
placebo with approximately 500mL of water. Each subject then sat quietly for one hour, a time frame that allows for a peak plasma caffeine concentration (39). Following the rest period, subjects completed five sets of a bicep curl performed on a preacher bench with the non-dominant arm using a weight equal to 75% of
C C
each subject’s predetermined 1RM. Subjects were instructed to complete 10 repetitions during the first four sets and as many repetitions as possible during the last set. A metronome cadence of 30 was used to control the motion to ensure
A
proper speed of the movement. The Borg CR-10 scale was used after completion of each set to score perception of effort and soreness (8). Subjects were provided with soreness scales to take home and use to report levels of soreness during the five day follow up by marking the proper line on the visual analog scale. Scales were returned to investigators at completion of follow up. Subjects reported back
9 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
to the exercise science laboratory 48 hours following the experimental trials for a second blood draw.
Follow Up
D
Days 1-5: On days one-five (24-120 hours) following experimental trials, subjects evaluated level of muscle soreness using the specific instructions received.
TE
Subjects also ingested the appropriate capsule at the same time of day on these follow up days. Phone call reminders were sent to subjects during follow up to remind subjects to evaluate muscle soreness and to ingest the appropriate capsule.
EP
Completed scales were collected at completion of each follow up period. On day two, subjects also reported to laboratory for a second blood draw.
Caffeine and Placebo Administration
C C
Caffeine (USP grade, Wilken Scientific, Pawtucket RI) and placebo was
prepared in capsules by the Pharmacy Department at URI. Five mg/kg BW was used to determine the total dose for each subject. This dosage is equal to
A
approximately two and one-half cups of brewed coffee and is consistent with several past studies examining the effect of caffeine on exercise (27, 36, 39). Placebo capsules were filled with flour, which resembles caffeine in color and texture. Caffeine or placebo was ingested one hour prior to experimental trials, 24 hours following the experimental trials and every day for four days thereafter. Subjects ingested the caffeine or placebo at the same time of day for the entire
10 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
study. An individual who was not involved in data collecting or data analysis was responsible for the assignment of caffeine and placebo to protect against the expectancy effect by the subjects and investigators. Subjects were provided with
D
soreness scales to take home.
Study Measures
TE
Anthropometric Measurements
Body weight was measured to the nearest 0.1 kg using a digital read scale (Tanita BF-556, Arlington Heights, IL.) Height was measured by use of a
EP
stadiometer (Seca, Hamburg, Germany) to the closest 0.5 cm. BMI was calculated as weight (kg) divided by height (m) squared. Body fat percentage was determined from skinfold measurements of the chest, abdomen and thigh (Lange Skinfold Caliper, Cambridge, MD). The three-site skinfold equation was used to
C C
determine body density (24). Body fat was converted from body density using a population specific formula for white males age 20-80 years (44).
A
Muscle Soreness: Instructions on the use of three scales was read to all subjects; Overall Soreness Scale, Overall Fatigue Scale, and a Soreness on Palpation Scale. Subjects rated their level of muscle soreness by selecting a number of the continuous scales. Ratings for each scale were as followed: 0 no soreness/fatigue; 1 very light soreness/fatigue; 2 moderate soreness/fatigue; 3 light (weak) feelings of soreness/fatigue; 5 (heavy) strong feelings of soreness; 7 very heavy feelings of
11 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
soreness; 10 maximal soreness. This type of scale is a valid and reliable measure that has been used in multiple studies regarding muscle soreness and pain (22, 37, 38). Blood Profile: All blood draws were obtained by venipuncture on subject’s
D
dominant arm due to the fact that each subject performed the bicep curl on their non-dominant arm. A resting blood draw was taken prior to both experimental
TE
trials and during the second day of follow up of each trial. Whole blood was collected and transferred into appropriate tubes in order to obtain serum and
plasma. Blood was centrifuged at 1500g for 15 minutes at 4°C. Resulting serum
EP
and plasmas was aliqouted and stored at -80°C for analysis. Serum Creatine Kinase (CK) was measured using colorimetric procedures at 340nm.
Statistical Analysis
C C
All results are reported as mean ± SD. A 2 x 2 (trial x time) repeated
measures ANOVA was used to analyze the CK data, a 2 x 6 (trial x time) used to analyze the soreness and fatigue resting data from the exercise trial day to Day 5,
A
and 2 x 5 (trial x sets) used to analyze the CR10 Borg scale ratings collected after each set of bicep curls. A paired-sample t-test was used to analyze the repetition number for the last set of bicep curls in the two trials. Linear assumptions were tested for and met. In the case of a significant F score in the ANOVAs, a Bonferroni Post Hoc test was performed to determine where significant differences lay. Significance for all analysis was set a p≤ 0.05. Based on previous
12 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
studies it was determined that an n of 10 was adequate to defend the 0.05 alpha level of significance with a Cohen probability level of 0.8 (G-Power software,
RESULTS
D
version 3.1.2, Kiel University, Germany).
TE
In general, this study demonstrated that caffeine ingestion has beneficial effects on ratings of muscle soreness, perceived exertion and performance
Soreness
EP
surrounding an acute bout of resistance exercise.
Soreness values at day 1 and day 2 were significantly different than pre exercise values with caffeine and placebo ingestion. Caffeine produced a
C C
significantly lower soreness value on day 2 and day 3 post exercise when
A
compared to placebo. Values for overall soreness can be seen in Figure 1.
Figure 1 about here
Change in Soreness Change in soreness values are shown in Figure 2. Increase in soreness
from pre exercise to day 2 of follow up was significantly higher under both conditions, however there were no between group differences.
13 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
Figure 2 about here
Soreness on Palpation
D
A significant difference was demonstrated in soreness on palpation values with caffeine ingestion on day 2 of follow up compared to soreness with placebo
TE
ingestion. Soreness on palpation values on day 1, 2, 3 and 4 for caffeine and days 1, 2, and 3 for placebo were significantly different than the pre-exercise soreness
EP
on palpation value. These values are shown in Figure 3.
Figure 3 about here
C C
Change in Soreness on Palpation
Figure 4 shows change in soreness on palpation values. A significant
increase was observed in changes in soreness on palpation values from preexercise to day 1 and day 2 of follow up with both conditions in addition to day 3
A
with caffeine ingestion. There was also a significant difference in soreness on palpation values on day 4 of follow up between conditions.
Figure 3 about here
14 Copyright Ó Lippincott Williams & Wilkins. All rights reserved.
Performance (Repetition Number) There was a significant increase (p
