Streptococcus bovis - Gundersen Lutheran Health System

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Authors: Glenn Wright, PhD John P. Porcari, PhD, RCEP Carl C. Foster, PhD Heidi Felker, MS Ashley Kosholek, MS Jennifer Otto, MS Erik M. Sorenson, MS Brian E. Udermann, PhD, ATC, FACSM Department of Exercise and Sport Science University of Wisconsin–La Crossse Address for correspondence: Glenn Wright, PhD Department of Exercise and Sport Science University of Wisconsin–La Crossse 1725 State Street La Crosse, WI 54601 email: wright.glen@uwlax.edu Placebo Effects on Exercise Performance AbStrACt The concept of controlling for placebo effects during experimental and clinical intervention studies is well established. The power of the placebo effect has been recognized in the literature, with the general expectation that about 33% of experimental subjects or patients will respond solely on the basis of the placebo effect. 1 Well-documented effects related to subjective outcome measures, 2 depression, 3 pain relief, 4 symptom relief, 5,6 blood pressure reduction, 7 and asthma relief 8 have been reported. Although virtually all exercise intervention studies include control groups to account for the placebo effect, data documenting the magnitude of the placebo effect during exercise are limited. Accordingly, the purpose of this study was to assess the magnitude of the placebo effect during exercise, with particular reference to the type of exercise (aerobic vs anaerobic) and exerciser (athletes, healthy nonathletes, patients). MethodS Approach to the Problem This study was designed to test the hypothesis that there would be a significant placebo effect during exercise in different types of exercise and in different types of exercisers. It was conducted in 3 distinct parts. In all parts of the study, subjects provided written informed consent, and the study protocols had been approved by the university Institutional Review Board. In all parts of the study, the subjects had performed a practice trial of the criterion task to ensure that they were fully task habituated. Placebo and control studies were performed in random order with ≥ 48 hours without heavy exercise prior to each trial. Despite the routine use of placebo control in exercise intervention studies, there is inadequate information about the magnitude of the placebo effect and how it might respond during different types of exercise. This study was designed to evaluate the placebo effect in different populations and in different types of exercise. In a 3-part study the effect of purported nutritional ergogenic aids was measured in: (A) trained runners in a 5-km time trial, (B) physical education students during a high-intensity cycle sprint test, and (C) in clinically stable patients during a 6-minute walk test. In A, performance was improved by 83 seconds (6.5%), with a larger placebo effect in the slower runners. In B, there was no significant effect on peak or mean power output, or on the pattern of fatigue. In C, although there was no significant difference in the distance completed in the 6-minute walk test, there was a significant trend (P = .08) for patients to walk faster during the first minute of the test. The results suggest that the placebo effect may be of significant magnitude, particularly during more prolonged tasks, and may influence both athletes and patients. 9 -14 SubJeCtS In Part A, healthy, well-trained competitive runners ranging from university to recreational class (23 men, mean [SD] age 28 [13] years; 9 women, mean [SD] age 30 [13] years) were studied during 5-km running time trials. In Part B, healthy physical education students (8 men, mean [SD] age 20 [1] years; 10 women, mean [SD] age 21 [1] years) were studied during highintensity sprint cycling (Wingate Test). In Part C, patients with stable cardiovascular disease who were participants for longer than 1 year in a community-based exercise program (6 men, mean [SD] age 62 [10] years; 4 women, mean [SD] age 64 [8] years) were studied while performing the 6-minute walk test. proCedureS In all 3 parts of the study, subjects were intentionally misinformed of the purported beneficial effects of the placebo agent by having them view a video (Part A = super-oxygenated water), by having them attend a graduate class on ergogenic aids (Part B = fastacting creatine monohydrate), or by having them read a brochure purporting to report results of previous studies (Part C = Peligrino Spa water). In all cases, subjects were given an inactive agent (tap water) in both the placebo and control conditions. We deliberately let the subjects know when they were receiving the “active” agent, so that they would be expecting an ergogenic benefit. Polling of the subjects indicated that they generally felt that the “active” agent (ie, placebo) was likely to help their performance. In Part A, the subjects ran two 5-km time trials (running without the benefit of other competitors) on an indoor 200-m track. The warm-up before each run was based on the normal pre- Gundersen Lutheran Medical Journal • Volume 6, Number 1, June 2009 3
competition practice of each subject, and was consistent between trials within each subject. During the trial, the time for each lap was called to the subject to facilitate pacing, which is a common practice during competitions. Prior to the warm-up (~30 minutes prior to the beginning of the time trial) each subject consumed 300 ml of tap water. In the placebo trial, the water was labeled “super-oxygenated water” in order to create the impression that subjects were consuming an ergogenic aid. In the control trial, the water was correctly labeled as “water.” During the time trials, running time was recorded for each of the 25 laps, and heart rate was recorded using radio telemetry (Polar Electro OY, Finland). Within 60 seconds of completing the trial, blood lactate concentration was measured in capillary blood using an enzyme electrode system (YSI Sport, Yellow Springs, OH), and the rating of perceived exertion (RPE) was measured using the Borg category ratio scale (CR10 Scale). 15 In Part B the subjects performed 2 Wingate anaerobic tests 16 on an electronically braked cycle ergometer (LODE Excalibur, Netherlands), with the resistance set at 75 g.kg -1 body weight. These tests were performed at least 3 days apart. The warm-up was standardized for each subject and consisted of continuous cycling at 75 watts (W) for 10 minutes. During the last 5 minutes of the warm-up, the subjects accelerated to maximal power output for ~5 seconds on 2 occasions in order to ensure that the subject had a sense of the feeling of the power output required during the test. Following the warm-up the subjects recovered by pedaling at 25 W for 5 minutes. The protocol of the test was controlled by software in the cycle, with a 30-second countdown prior to the test initiation. The subjects began maximal acceleration of the pedals at -3 seconds, and rapid adjustment of the resistance was performed by the ergometer software, such that the required resistance was achieved at the start of the 30-second Wingate test protocol. Subjects were verbally encouraged to pedal at maximal pedal revolutions (ie, the highest possible power output) throughout the test. The ergometer recorded the power output during each second of the test. In order to create the impression that they were taking an ergogenic aid, subjects in the placebo group were instructed to report to the laboratory to mix and consume 300 ml of water with 5 g of white powder labeled “alpha-hydroxycreatine” (placebo as maltodextrin) approximately 24 hours prior to the test, while the control group subjects consumed 300 ml of known water. An Lap Velocity, m.s -1 5 4.5 4 3.5 C ontrol Placebo Lap Velocity 0 1000 2000 3000 4000 5000 Distance, m additional dose of the placebo or control beverage was consumed prior to the warm-up of the respective trial approximately 30 minutes prior to the test. In Part C the subjects performed two 6-minute walk tests in a 36-m hallway. An investigator positioned at the midpoint of the hall timed the subjects each time they touched the wall or passed the midpoint of the hallway, allowing velocity to be calculated over every 18 m. This was later converted to average velocity over every 30 seconds of the test. Heart rate was determined using radio telemetry. RPE was measured using the Category Ratio RPE scale. Prior to performing the test, subjects had walked for 10 minutes at their normal exercise training pace and had rested for 5 minutes immediately prior to beginning the test. In order to create the impression that they were taking an ergogenic aid, subjects in the placebo group were instructed to consume 300 ml of a liquid labelled “Pelegrino Spa Water” approximately 30 minutes before the warm-up, while the control group consumed 300 ml of a liquid labelled “water.” StAtiStiCAL AnALySiS For all parts of the study, outcome measures were analyzed using repeated measures analysis of variance (ANOVA) for an intervention by serial measurement design. Post hoc analyses were performed using the Tukey test when justified by ANOVA. Statistical significance was accepted when P < .05. reSuLtS All tests were completed without complication by all subjects. Questioning of the subjects indicated that the procedures used to create the expectation that the intervention beverage would confer an ergogenic effect were effective. pArt A On average, subjects ran the placebo trial significantly faster (83 seconds faster, 6.5%) than they ran the control trial (mean [SD] 19:41 [2:32] minutes vs 21:04 [3:34] minutes). Average running velocity, distributed fairly evenly within the trial, was 0.23 m.s -1 faster during the placebo trial (Figure 1 left). Heart rate (HR) (mean [SD] 179 [13] beats.min -1 vs 179 [11] beats.min -1 ), figure 1. (Left) Running velocity per lap during 5-km time trials in the control (solid circles) and placebo (open circles) conditions. (Right) Comparison of total running time for 5 km during the placebo and control trials. There was a significant overall effect (83 seconds) attributable to the placebo, but a proportionally larger placebo effect in the slower (> 1200 seconds) runners compared with the faster runners (2:22 ± 1:02 vs 0:28 ± 1:08). 4 Gundersen Lutheran Medical Journal • Volume 6, Number 1, June 2009 Placebo Time, s 1800 1700 1600 1500 1400 1300 1200 1100 1000 900 Control vs Placebo Time 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 Control Time, s
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