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The Effect of Placebo-Induced Changes in Expectancies on Maximal Force Production in College Students
Journal of Applied Sport Psychology
Abstract
This study used false information about a placebo (milk-sugar tablet) to induce expectancies regarding force production. Forty-two college students were assigned to a placebo/placebo (PP), placebo/no-placebo (PN), or control group, and underwent baseline testing and two trials assessing one-repetition maximum (1 RM) strength on a bench press and seated leg press. The PP and PN groups improved significantly compared to the control at Trial 1 for the bench press (p ≤ .01) and leg press (p ≤ .01). Disclosure of the true nature of the placebo resulted in force production declines in the PN group to levels approximating controls on the bench press (p > .05) and seated leg press (p > .05). The results suggest that placebo-associated expectancy effects played a significant part in the observed changes. Implications include information for coaches, teachers, and fitness enthusiasts about the importance of psychological factors in successful performance.
... [33] Since then, a further 11 experimental studies have been published. [7,32,[34][35][36][37][38][39][40][41][42] This review focuses on the methods and findings of these studies. Data are reported as originally presented, whether in terms of statistical significance or magnitude-based inferences. ...
... Unauthorised copying and distribution is prohibited. Maganaris et al. [39] ( Clark et al. [7] ( Foster et al. [37] ( Beedie et al. [35] ( Kalasountas et al. [38] ( ...
... 2.9 Kalasountas et al. (2007) Again in 2007, and citing the work of Maganaris et al. [39] as a catalyst, Kalasountas et al. [38] examined placebo effects on the weightlifting performance of college students. The authors tested the same hypotheses as had Maganaris et al.: (i) that subjects who received a placebo ergogenic aid would show greater increases in performance than controls; and (ii) that the performance of subjects informed that the substance is no longer effective will return to control levels. ...
The placebo effect, with its central role in clinical trials, is acknowledged as a factor in sports medicine, although until recently little has been known about the likely magnitude and extent of the effect in any specific research setting. Even less is known about the prevalence of the effect in competitive sport. The present paper reviews 12 intervention studies in sports performance. All examine placebo effects associated with the administration of an inert substance believed by subjects to be an ergogenic aid. Placebo effects of varying magnitudes are reported in studies addressing sports from weightlifting to endurance cycling. Findings suggest that psychological variables such as motivation, expectancy and conditioning, and the interaction of these variables with physiological variables, might be significant factors in driving both positive and negative outcomes. Programmatic research involving the triangulation of data, and investigation of contextual and personality factors in the mediation of placebo responses may help to advance knowledge in this area.
... The placebo effect in sports has only become a subject of regular research enquiry in the last 10Á15 years. Despite this slow start, several studies have observed significant increases in endurance (Clark, Hopkins, Hawley, & Burke, 2000) and strength performance (Kalasountas, Reed, & Fitzpatrick, 2007;Maganaris, Collins, & Sharp, 2000), as a result of ingesting a substance with no inherent ability to produce such a positive effect. ...
... Despite suggestions of its existence in sports science, less is known about the nocebo effect (Beedie & Foad, 2009), defined as 'the undesirable effects an individual experiences after ingesting an inert substance'. However, it is axiomatic to propose that the nocebo effect may be just as relevant to sports performance (Kalasountas et al., 2007;Maganaris et al., 2000). For example, Maganaris et al. (2000) and Kalasountas et al. (2007) reported significant decreases in performance when subjects were told that their improvements in weightlifting were the result of a sham anabolic steroid. ...
... However, it is axiomatic to propose that the nocebo effect may be just as relevant to sports performance (Kalasountas et al., 2007;Maganaris et al., 2000). For example, Maganaris et al. (2000) and Kalasountas et al. (2007) reported significant decreases in performance when subjects were told that their improvements in weightlifting were the result of a sham anabolic steroid. Such a suggestion assumes that the nocebo effect is simply reversing a positive outcome, which may underestimate its true potential to negatively impact performance if studied in isolation. ...
Abstract This investigation aimed to explore the effects of inert sugar-free drinks described as either 'performance enhancing' (placebo) or 'fatigue inducing' (nocebo) on peak minute power (PMP;W) during incremental arm crank ergometry (ACE). Twelve healthy, non-specifically trained individuals volunteered to take part. A single-blind randomised controlled trial with repeated measures was used to assess for differences in PMP;W, oxygen uptake, heart rate (HR), minute ventilation, respiratory exchange ratio (RER) and subjective reports of local ratings of perceived exertion (LRPE) and central ratings of perceived exertion (CRPE), between three separate, but identical ACE tests. Participants were required to drink either 500 ml of a 'sports performance' drink (placebo), a 'fatigue-inducing' drink (nocebo) or water prior to exercise. The placebo caused a significant increase in PMP;W, and a significant decrease in LRPE compared to the nocebo (p=0.01; p=0.001) and water trials (p=0.01). No significant differences in PMP;W between the nocebo and water were found. However, the nocebo drink did cause a significant increase in LRPE (p=0.01). These results suggest that the time has come to broaden our understanding of the placebo and nocebo effects and their potential to impact sports performance.
... [33] Since then, a further 11 experimental studies have been published. [7,32,[34][35][36][37][38][39][40][41][42] This review focuses on the methods and findings of these studies. Data are reported as originally presented, whether in terms of statistical significance or magnitude-based inferences. ...
... Unauthorised copying and distribution is prohibited. Maganaris et al. [39] ( Clark et al. [7] ( Foster et al. [37] ( Beedie et al. [35] ( Kalasountas et al. [38] ( ...
... 2.9 Kalasountas et al. (2007) Again in 2007, and citing the work of Maganaris et al. [39] as a catalyst, Kalasountas et al. [38] examined placebo effects on the weightlifting performance of college students. The authors tested the same hypotheses as had Maganaris et al.: (i) that subjects who received a placebo ergogenic aid would show greater increases in performance than controls; and (ii) that the performance of subjects informed that the substance is no longer effective will return to control levels. ...
The placebo effect, with its central role in clinical trials, is acknowledged as
a factor in sports medicine, although until recently little has been known
about the likely magnitude and extent of the effect in any specific research
setting. Even less is known about the prevalence of the effect in competitive
sport. The present paper reviews 12 intervention studies in sports performance.
All examine placebo effects associated with the administration of an inert
substance believed by subjects to be an ergogenic aid. Placebo effects of
varying magnitudes are reported in studies addressing sports from weightlifting
to endurance cycling. Findings suggest that psychological variables such as
motivation, expectancy and conditioning, and the interaction of these variables
with physiological variables, might be significant factors in driving both
positive and negative outcomes. Programmatic research involving the triangulation
of data, and investigation of contextual and personality factors in the
mediation of placebo responses may help to advance knowledge in this area.
... Most studies on the placebo effect on sports domains have been carried out from the perspective of ergogenic aids, such as carbohydrates [4], amino acids [5], or sodium bicarbonate [6]. Nevertheless, the main source of placebo research in sports performance has been associated with caffeine [3], probably due to the well-known ergogenic effects of this substance on sports performance [7][8][9]. ...
... In contrast, the ergogenic properties of caffeine on endurance performance have been well-established for a long time [9,[15][16][17], and athletes in these sports could be more prone to generate expectancies about its positive effects. So, while a few placebo-caffeine-related research studies in the sports context have been focused on strength performance [5,[18][19][20], most studies analyzed this topic on endurance performance [21][22][23][24][25][26]. ...
This study aimed to analyze the placebo effect associated with caffeine ingestion on running performance. Methods: Thirteen recreationally trained males in long-distance running (age: 38.5 ± 11.9 years, 11.0 ± 8.8 years of running experience) performed a 6 min time trial test in each experimental condition (caffeine-informed/placebo ingested (placebo) and non-ingested (control)) separated by 7 days. The total distance covered was measured, and partial times of each 400 m were used to analyze the pacing strategy. Heart rate and kinematic variables were recorded for each split. In addition, the rate of perceived exertion and prevalence of caffeine side effects was measured using questionnaires. Results: Placebo ingestion improved running performance in the 6 min time trial test (1668 ± 139 m placebo vs. 1642 ± 158 m control, t = 2.49; p = 0.03; moderate ES = 0.69), while pacing, heart rate, RPE, and kinematic variables were similar between conditions (p > 0.05 in all cases). Minor side effects were reported. Conclusions: Beliefs of caffeine ingestion can improve running performance at speeds around maximal aerobic speed in recreationally trained runners without affecting pacing strategy so this "nutritional" strategy could be useful in competition scenarios. As a practical application, recreationally trained runners could improve ≈5 s in 1500 m or mile competitions .
... Despite a large body of research on the placebo effect in medicine, there are few studies reporting the magnitude and extent of its effect in sports performance (5). Only recently has empirical evidence emerged in support of the placebo affecting athletic performance, encompassing both endurance- (6,11) and resistance-related (18,26) exercise performance. After being informed that an ergogenic aid was likely to improve cycling time trial performance, the placebo effect has been shown to account for a 3.8% improvement in mean power over a 40-km cycling time trial (11) and a 2.2% increase in mean power over a 10-km cycling time trial (6) when given a carbohydrate and caffeine placebo, respectively. ...
... After being informed that an ergogenic aid was likely to improve cycling time trial performance, the placebo effect has been shown to account for a 3.8% improvement in mean power over a 40-km cycling time trial (11) and a 2.2% increase in mean power over a 10-km cycling time trial (6) when given a carbohydrate and caffeine placebo, respectively. Alternately, both caffeine and amino acid placebos were reported to improve leg extension strength (total work performed during repeated repetitions until fatigue at 60% one-repetition maximum) by 11.8% after 72 h (26) and one-repetition maximum leg press by 21.1% after 48 h (18), respectively. The current study, in comparison, has demonstrated improved maximal (12.6%) and mean torque (13.2%) during an MVC of the quadriceps, 48 h after exercise, when administered to TWP as compared with those in TWI. ...
Despite a general lack of understanding of the underlying mechanisms, cold-water immersion (CWI) is widely used by athletes for recovery. This study examined the physiological merit of CWI for recovery from high-intensity exercise, by investigating if the placebo effect is responsible for any acute performance or psychological benefits. Thirty males (mean ± SD; age 24 ± 5 y; V[Combining Dot Above]O2peak 51.1 ± 7.0 mL·kg·min) performed an acute high-intensity interval training (HIT) session, comprised of 4 x 30-s sprints, immediately followed by one of three 15-min recovery conditions; CWI (10.3 ± 0.2°C), thermo-neutral water immersion placebo (TWP; 34.7 ± 0.1°C) or thermo-neutral water immersion control (TWI; 34.7 ± 0.1°C). An intramuscular thermistor was inserted during exercise and recovery to record muscle temperature. Swelling (thigh girth), pain threshold/tolerance, interleukin-6 concentration, and total leukocyte, neutrophil, and lymphocyte count were recorded at baseline, post-exercise, post-recovery, and 1, 24 and 48 h post-exercise. A maximal voluntary isometric contraction (MVC) of the quadriceps was performed at the same time-points, with the exception of post-exercise. Self-assessments of readiness for exercise, fatigue, vigour, sleepiness, pain, and belief of recovery effectiveness were also completed. Leg strength following the MVC, and ratings of readiness for exercise, pain and vigour, were significantly impaired in TWI compared with CWI and TWP, which were similar to each other. A recovery placebo administered after an acute HIT session is superior in the recovery of muscle strength over 48 h as compared with TWI, and as effective as CWI. This can be attributed to improved ratings of readiness for exercise, pain and vigour, suggesting that the commonly-hypothesised physiological benefits surrounding CWI are at least partly placebo related.
... Kalasountas, Reed and i Fitzpatrick [52] came to similar conclusions in their experiment. The rese-Do podobnych wniosków prowadzą wyniki eksperymentu Kalasountasa, Reeda i Fitzpatricka [52]. ...
... Kalasountas, Reed and i Fitzpatrick [52] came to similar conclusions in their experiment. The rese-Do podobnych wniosków prowadzą wyniki eksperymentu Kalasountasa, Reeda i Fitzpatricka [52]. Badacze podzielili studentów college'u na trzy grupy. ...
The first part of the paper sums up contemporary approaches to the subject of placebo action. The definition of placebo is discussed, as well as the types of its effects and underlying mechanisms. Placebo is defined as a method or an element of the method without any specific activity for the condition being treated. A proposal is discussed to classify the effects of placebo in one coherent system consisted of eight different effects. Also the psychological mechanisms underlying placebo effect are discussed. These include classical conditioning, expectancy and anxiety, and relationships between them. In the second part of the paper,a summary is used for critical analysis of the data from the research on the applications of placebo as an ergogenic aid in sports. Discussion of the research results is focused on the effectiveness of placebo in athletic performance improvement, the influence of the information given to sportsmen on placebo action on its effectiveness, the influence of the information given to sportsmen on active methods action on their effectiveness, and prior experience with active methods as a factor contributing to a placebo effect. The discussed results prove the usefulness of placebo in athletic performance improvement, and this, indicate an important role of the information given to sportsmen in evoking a placebo effect and as a placebo factor modifying action of active procedures. The results of the discussed research suggest that the effects of any ergogenic aid are due to both its active components and psychological factors, e.i., placebo component of any active method.
... Despite a large body of research on the placebo effect in medicine, there are few studies reporting the magnitude and extent of its effect in sports performance (5). Only recently has empirical evidence emerged in support of the placebo affecting athletic performance, encompassing both endurance- (6,11) and resistance-related (18,26) exercise performance. After being informed that an ergogenic aid was likely to improve cycling time trial performance, the placebo effect has been shown to account for a 3.8% improvement in mean power over a 40-km cycling time trial (11) and a 2.2% increase in mean power over a 10-km cycling time trial (6) when given a carbohydrate and caffeine placebo, respectively. ...
... After being informed that an ergogenic aid was likely to improve cycling time trial performance, the placebo effect has been shown to account for a 3.8% improvement in mean power over a 40-km cycling time trial (11) and a 2.2% increase in mean power over a 10-km cycling time trial (6) when given a carbohydrate and caffeine placebo, respectively. Alternately, both caffeine and amino acid placebos were reported to improve leg extension strength (total work performed during repeated repetitions until fatigue at 60% one-repetition maximum) by 11.8% after 72 h (26) and one-repetition maximum leg press by 21.1% after 48 h (18), respectively. The current study, in comparison, has demonstrated improved maximal (12.6%) and mean torque (13.2%) during an MVC of the quadriceps, 48 h after exercise, when administered to TWP as compared with those in TWI. ...
Despite a general lack of understanding of the underlying mechanisms, cold-water immersion (CWI) is widely used by athletes for recovery. This study examined the physiological merit of CWI for recovery from high-intensity exercise, by investigating if the placebo effect is responsible for any acute performance or psychological benefits.
Thirty males (mean ± SD; age 24 ± 5 y; V[Combining Dot Above]O2peak 51.1 ± 7.0 mL·kg·min) performed an acute high-intensity interval training (HIT) session, comprised of 4 x 30-s sprints, immediately followed by one of three 15-min recovery conditions; CWI (10.3 ± 0.2°C), thermo-neutral water immersion placebo (TWP; 34.7 ± 0.1°C) or thermo-neutral water immersion control (TWI; 34.7 ± 0.1°C). An intramuscular thermistor was inserted during exercise and recovery to record muscle temperature. Swelling (thigh girth), pain threshold/tolerance, interleukin-6 concentration, and total leukocyte, neutrophil, and lymphocyte count were recorded at baseline, post-exercise, post-recovery, and 1, 24 and 48 h post-exercise. A maximal voluntary isometric contraction (MVC) of the quadriceps was performed at the same time-points, with the exception of post-exercise. Self-assessments of readiness for exercise, fatigue, vigour, sleepiness, pain, and belief of recovery effectiveness were also completed.
Leg strength following the MVC, and ratings of readiness for exercise, pain and vigour, were significantly impaired in TWI compared with CWI and TWP, which were similar to each other.
A recovery placebo administered after an acute HIT session is superior in the recovery of muscle strength over 48 h as compared with TWI, and as effective as CWI. This can be attributed to improved ratings of readiness for exercise, pain and vigour, suggesting that the commonly-hypothesised physiological benefits surrounding CWI are at least partly placebo related.
... Task expectancies, before and during performance, have also been manipulated by using prescribed substances or placebos. Expectancies are an integral part of the placebo effect (29), and researchers conclude that both positive and negative beliefs associated with placebos and their effects significantly affect performance (12). Psychological variables such as motivation, expectancy, and the interaction of these constructs with physiological variables might be significant factors in driving positive and negative outcomes (12). ...
... There are also many speculative anecdotal examples of what may be legitimate placebo effects (12). Expectations of substance-specific effects seem to trigger many physiological and psychological reactions (30), often independent of the substance given (22,29,63). Within this type of expectancy manipulation, the deception element of the methodology is known, with the participant_s acknowledgment before the investigation of a substance_s possible effects. ...
Athletes anticipatorily set, and continuously adjust pacing strategies prior to and during events, in order to produce optimal performance. Self-regulation ensures maximal effort is exerted in correspondence with the endpoint of exercise, whilst preventing physiological changes that are detrimental and disruptive to homeostatic control. The integration of feedforward and feedback information, together with the proposed brain's performance modifiers, are said to be fundamental to this anticipatory and continuous regulation of exercise. Manipulation of central, regulatory internal and external stimuli has been a key focus within deception research, attempting to influence the self-regulation of exercise and induce improvements in performance. The methods manipulating performance modifiers such as unknown task endpoint, deceived duration or intensity feedback, self-belief or previous experience creates a challenge within research as, although they contextualise theoretical propositions, there are few ecological and practical approaches to integrate theory with practice. Additionally the different methods and measures demonstrated in manipulation studies have produced inconsistent results. This review examines and critically evaluates the current methods of how specific centrally-controlled performance modifiers have been manipulated, within deception studies, to investigate their effects on pacing and performance. From the 31 studies reviewed, 10 reported positive effects on performance, encouraging future investigations to explore the mechanisms responsible for influencing pacing, and consequently how deceptive approaches can further facilitate performance. The review acts to discuss the use of expectation manipulation not only to examine which methods of deception are successful in facilitating performance, but also to understand further the key components used in the regulation of exercise and performance.
... For instance, Ross and colleagues [8] found that a saline injection, labeled as a medication to stimulate red blood cell production, improved endurance runners' performance. Similar effects have been observed in muscle strength; Kalasountas et al. [9] demonstrated that a placebo presented as a potent amino acid combination with immediate strength benefits significantly enhanced college students' performance in bench and leg press tasks. Villa-Sánchez et al. [10] discovered placebo-induced improvements in balancing through a single-legged balance test, where participants believed they had received electrical nerve stimulation to enhance postural control. ...
Studies with adults and school children have shown that placebos can enhance motivation and performance in physical activities. This study aimed to investigate whether similar effects are present in kindergarten-aged children. A total of 101 children (58 girls, 43 boys) aged 3 to 6 years were randomly assigned to one of two groups that either received a deceptive placebo (DP: “magic potion”) or a nondeceptive placebo (NDP: “water”) to enhance physical abilities. Each child completed three tasks (sprinting; balancing: standing on a balance board; strength: using a handheld dynamometer) both with and without the placebo. The variables assessed included task performance, enjoyment, and expected and perceived placebo efficacy (measured with nonverbal pictorial rating scales). Results showed that both the DP and NDP increased speed. For strength, balance, and task enjoyment (which was very high), no placebo-induced changes were observed. Expected efficacy was higher for the DP; perceived efficacy did not differ between DP and NDP. In conclusion, reported outcome expectations indicated that kindergarten-aged children were already able to differentiate between the two types of placebos which exhibited positive effects concerning running performance. This encourages further research on using nondeceptive placebos to enhance physical activity, which is crucial for children’s overall health.
... For example, Duncan [12] found that participants exhibited a 23.8% enhancement in weight lifted during a leg extension task when they received a caffeine placebo. Likewise, Kalasountas et al. [13] reported an 11% rise in weightlifting after participants consumed a placebo believed to contain amino acids. Beedie et al. [14] found that negative information associated with a fictive supplement decreased running speed. ...
Sports performance could be affected by placebo and nocebo effects. The last literature review on placebo and nocebo effects on sports and exercise performance was published in 2019. In the past five years, several new studies have been published. This review aimed to update the previous synthesis and evaluate the results of new studies focusing on placebo or nocebo interventions in sports and exercise by determining the form and magnitude of their effect. Hence, we searched for empirical studies published from 2019 until the end of May 2024 indexed in PubMed, Medline, Web of Science, EBSCO, and Google Scholar databases. The search yielded 20 eligible studies with control or baseline-control conditions, focusing on nutritional, mechanical, and other mixed ergogenic aids. They yielded small to large placebo effects (Cohen’s d) for nutritional (d = 0.86), mechanical (d = 0.38), cream and gel (d = 0.05), and open-label placebo (d = 0.16) interventions. The pooled effect size for placebo effects was moderate to large (d = 0.67), larger than in the earlier review, suggesting that placebo effects can improve motor performance even more than previously reported. However, based on five measures from three studies, the nocebo effects were almost twice as large (d = 1.20). Accordingly, the current findings support and expand the last review in the field by yielding additional support for placebo and nocebo effects in sports and exercise.
... We further speculate that informing participants of the placebo disclosure group that any improvement they noticed was to be traced back to their inherent potential, which was brought to light by the placebo, would cushion the disappointment of expectations due to disclosure while safeguarding their self-efficacy in performing the task. Indeed, being confronted with deception and facing the reality of having received a fake treatment could lead to disillusionment and endanger expectations, thus undermining outcome, especially if no positive suggestions on the efficacy of placebos are deployed (as in classic non-deceptive placebo paradigms) (Kalasountas et al., 2007;Maganaris et al., 2000;Sullivan et al., 2005). Nonetheless, in line with findings that post-disclosure detrimental effects may be circumvented through positive rationales on the placebo (Wei et al., 2018), or even with multiple sessions of conditioning (Schafer et al., 2015), our strategy proved successful in preventing detrimental effects on force in the placebo disclosure group. ...
The present study explores whether a particular style of placebo disclosure could serve as a tool to foster a renewed trust in one's own inherent resources and elicit a meaningful placebo effect. In a motor performance task, two placebo groups received inert transcutaneous electrical nerve stimulation (TENS) in each of four sessions along with information on its force‐enhancing properties. Before the final session, one of the placebo groups was informed about the placebo, which was portrayed as a means to unleash an inherent potential. Along with force, we systematically monitored task‐specific self‐efficacy to test whether this variable would be differentially modulated in the two placebo groups. Compared to two control groups, placebo groups showed higher force and self‐efficacy in the last session. No differences in self‐efficacy were observed in the placebo groups even after revealing the placebo procedure, suggesting that the disclosure was effective in ‘safeguarding’ individuals' self‐efficacy. These findings may have important implications, paving the way for the use of placebos that not only are ethically permissible but also support individuals' self‐efficacy.
... Placebo interventions used in this context range from sham supplements to false information regarding the caloric values of meals or energy expenditure during everyday exercise. Findings of such studies show that placebo interventions can be effective in reducing excess body weight and even the percentage of body fat [27][28][29][30]. On the other hand, some findings suggest the presence of the nocebo effect with the use of pharmacologically connoted interventions (e.g., sham weight-loss tablets), which could be a result of the expectations that participants have towards the supplement [31]. ...
Physical activity is crucial to prevent and reduce excess body mass. The placebo effect can influence the outcomes of fitness-related interventions; however, this topic has not yet been extensively investigated in children. Summarising the data on placebo effects in fitness-related interventions is essential to understand this problem better. A systematic review of PubMed, Cochrane, PsycINFO, PsycARTICLES, TripDatabase and Embase was carried out. A meta-analysis of the results of studies with comparable research plans was performed. There were significant differences, favouring the placebo intervention. At the final follow-up, the children in placebo groups had higher maximal heart rates, shorter recovery times, longer ergometry phases, running time and lower peak and average perceived exertion than the control. The placebo effect is present in fitness-related parameters in children, regardless of the Body Mass Index status. It is crucial, as for youth with excess body mass, it is difficult to be active, especially to show appropriate levels of motivation and involvement. Importantly, the benefits of the placebo were the strongest in the motivation/ engagement-related parameters and self-assessed exertion. Notably, the nocebo effect was not observed, which is advantageous when considering placebo interventions in practice.
... Indeed, an increased dopaminergic response could be expected to enhance motor outputs as clinical treatments to enhance dopaminergic response (i.e., dopamine agonists) led to enhanced force production movement in those diagnosed with Parkinson's disease (Foreman et al., 2014). In fact, a high expectation-essentially a placebo effect-enhanced the level of maximum force production among college students (Kalasountas et al., 2007). Thus, conditions enhancing expectation could neurologically and psychologically facilitate motor performance and learning. ...
The purpose of this study was to examine the effects of different success criteria on motor learning in children. Forty-eight children threw soft-golf balls towards a circular target using their non-dominant arm. On Day 1, they performed six blocks of 12 trials from 5.5 meters. On Day 2, they performed a 12 trial retention test followed by a 12 trial transfer test. Participants were randomly assigned to one of four groups: Difficult Criteria for Success (DS), Relatively Easy Criteria for Success (RES), Easy Criteria for Success (ES), and Control (CON; receiving no success criteria for success) group. Results demonstrated there was a significant difference between the RES and the control groups in their throwing accuracy on the retention and transfer tests, and the RES group had the highest score than the other two groups. This research suggests that providing relatively easy criteria facilitates motor skill acquisition in children.
... On the other hand, findings suggest that psychological variables such as motivation or expectancy might be significant factors in driving both positive (placebo effect) or negative (nocebo effect) outcomes (Hurst et al., 2020). For decades, researchers have shown that the simple suggestion that a drug or supplement will induce some benefit is sufficient for it to occur (Azevedo et al., 2021;Deldicque et al., 2008;Kalasountas et al., 2007;Trojian & Beedie, 2008). ...
The purpose of this study was to test whether believed versus actual acute creatine ingestion impacted resistance exercise performance. Fifteen men (21.9 ± 2.7 years old) completed four bouts of three sets each of squat and bench press to volitional fatigue at a 10RM load with 1-min between-sets rest interval. Thirty minutes prior to each exercise bout, they received the following treatments in a randomized order: 1) nothing (CON); 2) 0.3 g·kg−1 dextrose placebo (PLC); 3) 0.3 g·kg−1 dextrose, identified as creatine (Cr-False); 4) 0.3 g·kg 20 −1 creatine, identified as creatine (CrTrue). Between-treatments comparisons included the total repetitions completed and the rate of perceived exertion. Results revealed (p < 0.05) higher repetitions performed for all treatments versus CON for both squat and bench press. In the squat, more repetitions were performed with Cr-True (p < 0.001) and CrFalse (p < 0.001) than with either CON or PLC. Bayes Factor analyses revealed strong (PLC to Cr-True BF = 19.1) and very strong (PLC to CrFalse BF = 45.3) posterior probability favouring positive effects for both "creatine" conditions over PLC for the squat. In conclusion, in acute measures, belief versus ingestion of creatine yields similar exercise performance. ARTICLE HISTORY
... Various strategies/interventions have been employed to show that motor performance and learning can be enhanced with an enhanced expectation for success. These interventions have included alterations of mindset and ability conceptions (Chiviacowsky & Drews, 2014;Drews et al., 2013;Wulf et al., 2012), presenting participants with visual illusions (Chauvel et al., 2015;Witt et al., 2012), superstition (Damisch et al., 2010;Lee et al., 2011), placebo effect (Kalasountas et al., 2007;Lidstone et al., 2010;Piedimonte et al., 2015), and manipulations of perceived task difficulty (Palmer et al., 2016). Palmer and colleagues (2016) used two different criteria for success for non-golfer participants learning a golf-putting task. ...
The purpose of this study was to examine whether enhancing success expectation by providing relatively easy criteria for success would, in turn, enhance motor learning outcomes. Thirty university student participants threw soft-golf balls towards a circular target, using their non-dominant arm; they performed seven blocks of 12 trials from a distance of 5.5 meters on Day 1, and one block of 12 trials on separate retention and transfer tests on Day 2. After the first block on Day 1, participants were randomly assigned to one of two groups in which they practiced the remaining six blocks of 12 trials: (a) one with relatively easy success (RES) criteria or (b) one with difficult success (DS) criteria. After the practice, we administered a perceived competence scale, a sub-scale of the Intrinsic Motivation Inventory (IMI). On Day 2, participants in the RES group outperformed those in the DS group on both the retention and transfer tests, showing enhanced motor learning. The RES group also self-reported higher perceived competence than the DS group, indicating that the mechanism for benefiting from easier success criteria may have been an alteration in participants' perceived competence.
... A few experiments have shown that providing choice or self-controlled practice conditions increased self-efficacy or perceived competence (Chiviacowsky, 2014;Reeve et al., 2011;Ste-Marie et al., 2013) the relationship between motor performance and self-efficacy has been T. Iwatsuki and M. P. Otten well documented in sports (Feltz et al., 2008;Moritz et al., 2000). In fact, self-efficacy or one's expectation has been experimentally manipulated and those who expected to perform well produced higher performance (Hutchinson et al., 2008;Kalasountas et al., 2007). In addition, the same effect was found under psychological pressure for throwing accuracy (Mckay et al., 2012). ...
The purpose of this present study was to examine whether providing choice would enhance motor performance under psychological pressure. Participants were asked to throw soft-golf balls toward a circular target. The practice phase consisted of 30 trials using three colored balls (i.e., blue, red, yellow) from 5.5 meters. Participants then performed 10 throws from 2 different distances: 5.5 meters (pressure phase) and 6.5 meters (transfer pressure phase) under psychological pressure. Prior to the pressure and transfer pressure phases, the choice group participants were asked to choose the color of the soft-golf ball whereas the control group participants were yoked to their counterpart participant based on the selections of their colored balls. Results demonstrated that despite similar throwing accuracy being produced at the pressure phase between the two groups, the choice group had significantly higher accuracy scores at the transfer pressure phase than the control group. Thus, the autonomy-supportive condition led to enhanced motor performance under psychological pressure.
... For example, placebo effects in sport performance are a well -documented fact. Athletes who ingested placebos in the guise of caffeine (Beedie, Stuart, Coleman, & Foad, 2006;Duncan, Lyons, & Hankey, 2009), anabolic steroids (Maganaris, Collins, & Sharp, 2000), carbohydrate (Clark, Hopkins, Hawley, & Burke, 2000), or amino acids (Kalasountas, Reed, & Fitzpatrick, 2007) performed their sport tasks better than controls. Placebos can also affect pain experience and induce an anaesthetic effect. ...
Research suggests that placebo can reduce the misinformation effect. We aimed to examine for the first time whether placebo administered in the guise of caffeine can reduce the misinformation effect. One hundred and twenty- -three healthy volunteers were randomly assigned to four groups in a 2 Placebo (Present, Not Present) × 2 Narrative (Misleading, Correct) study design. Participants from placebo groups drank 100 ml of placebo solution. They were told that it was water mixed with caffeine which could positively influence their memory. After three minutes, they watched a short movie clip as an original event and read a narrative with misleading details or correct details as a postevent information; they then completed a 22-item, two-alternative forced-choice questionnaire. The results reveal that the misinformation effect occurred. Although participants in the placebo with misinformation group scored better than participants who did not drink placebo and read the narrative containing misleading details, the difference was not statistically significant. Thus, it is concluded that placebo might not be enough to reduce the misinformation effect when it is administered in the guise of caffeine.
... Previous work suggests that consuming placebos believed to be steroids, caffeine, or amino acids improved measures of muscular function compared to control conditions. 8,9,16,17 The handgrip test is simple and does not result in large muscle fatigue. Thus, the handgrip test can be performed prior to a VO2peak test without influencing performance on the VO2peak test. ...
Objectives: The purpose of this study was to examine the effects of both known (“honest”) and unknown (“dishonest”) placebo ingestion on VO2peak to see if placebo ingestion would influence the test outcome by influencing the psychological compo nent of this test. A secondary purpose was to examine these effects on isometric handgrip strength. We hypothesized that placebo (honest or dishonest) ingestion prior to a VO2peak test would increase VO2peak compared to a control condition. We further hypothesized that isometric handgrip strength would be greater during both conditions of acute placebo ingestion compared to a control condition. Design: In a randomized, cross-over, counterbalanced design, subjects performed three trials: exercise tests with honest place bo, exercise tests with dishonest placebo, exercise tests only (control condition). Method: 41 subjects (28 males) aged 24 ± 7 years were tested. RM ANOVAs (3 × 1) were used to analyze VO2peak and handgrip strength across conditions. RM ANOVAs (3 × 1) were used to determine if test order influenced VO2peak and handgrip strength. (Alpha = 0.05.)Results: No differences were found across conditions for either VO2peak (p = 0.360) or handgrip strength (p = 0.474). Further, no differences were found for trial order for either VO2peak (p = 0.766) or handgrip strength (p = 0.067). Conclusions: Administration of both an honest and a dishonest placebo immediately prior to VO2peak and handgrip testing resulted in no differences in performance compared to each other or a control trial. The VO2peak test is a robust exercise test not influenced by immediately-prior pre-workout supplement consumption.
... Recent studies demonstrated that placebos have their own treatment potential 10 and may be used to improve physical exercise results. [11][12][13] While placebo responses in children and specifically in the field of physical exercise are less studied, we recently tested the effect of information placebo on aerobic fitness test results in normal weight 14 and overweight children. 15 We found that the use of deliberate positive information before an aerobic test led to a significant increase in running duration and maximal heart rate and to a significant decrease in recovery time. ...
Background:
The aim of the study was to examine the placebo effect on fitness test results in trained and untrained overweight and obese children.
Methods:
Twenty pre-pubertal overweight children performed two pairs of progressive treadmill exercise tests before and 12 weeks into a multidisciplinary program for the treatment of childhood obesity. In each test pair, at random order, participants received different types of information regarding a water drink consumed prior to testing - standard information (water) versus deliberate positive information (presumed energy drink, placebo).
Results:
The intervention led to a significant change (p<0.05) in BMI%ile (95.6±4.4 versus 93.6±6.9), % fat (35.4±6.0 versus 31.6±5.8), baseline heart rate (104.2±11.6 vs 94.0±7.0 bpm), total leisure activity score-Godin (9.3±8.8 versus 41.5±15.2), total screen time (6.9±5.8 versus 3.1±1.4h/day), running time (434.4±140.3 versus 667.1±176.1sec), peak rate of perceived exertion (RPE) (19.1±1.5 versus 16.9±2.2) and recovery time (133.2±23.7 versus 102.7±18.3 sec). Following the placebo drink, both groups achieved a significantly higher peak heart rate (untrained: 176.1±13.7 versus 167.5±16.8; trained: 170.7±11.6 versus 166.2±11.4bpm), and longer running time (untrained: 559.9±151.0 versus 434.4±140.3 sec; trained: 728.3±177.3 versus 667.1±176.1 sec). Despite longer exercise duration and higher peak exercise heart rate, average, and peak RPE were lower after the placebo drink (untrained: 12.1±2.3 versus 13.6±2.1; trained:10.0±1.8 versus 11.6±2.1), and recovery time was shorter (untrained: 119.2±25.3 versus. 133.2±23.7sec; trained: 92.6±18.9 versus 102.7±18.3sec). The placebo-induced change in running time and peak RPE were significantly greater prior to training.
Conclusion:
The significant information placebo effect is preserved in trained overweight children and may be a useful tool in enhancing physical performance.
... Existe una carencia de literatura científica en relación al papel que pueden desempeñar las expectativas en la modificación de variables físicas tales como la fuerza muscular, la fatiga o el rango de movimiento. Sin embargo, Kalasountas et al. (2007) observaron cómo las expectativas positivas respecto a la toma de un placebo oral ocasionaron un aumento Tabla 1. Estadísticos descriptivos de las variables sociodemográficas. Los datos son presentados como media ± desviación típica o número (%). ...
Objetivo: Evaluar cómo las expectativas, inducidas de forma escrita, influyen en la fuerza de prensión manual, en la intensidad de dolor y en variables somato-sensoriales. Diseño: Ensayo piloto controlado y aleatorizado a simple ciego Marco: Campus Universitario. Participantes: Los criterios de inclusión fueron: sujetos sanos, sin dolor y en edades comprendidas entre 18 y 30 años. Una muestra total de 39 sujetos sanos participaron en el presente estudio piloto y fueron asignados aleatoriamente en tres grupos según la expectativa, la cual podía ser positiva, negativa o neutra, dada por escrito Intervenciones: Tras asignar la muestra de manera aleatoria a los tres grupos de expectativas, se les aplicó una corriente de neuro-estimulación eléctrica transcutánea (TENS) de corta duración y sin efecto terapéutico. Variables: La variable principal fue la fuerza de prensión manual. Las variables secundarias fueron la intensidad de dolor, los umbrales de dolor a la presión y la sumación temporal en zona epicondilar. En primer lugar, se recogieron los valores pre-intervención y tras la intervención, se recogieron los datos de las variables de interés en dos tiempos. Primero, inmediatamente después de la intervención y segundo, a los 5 minutos de la misma. Resultados: No se encontraron diferencias estadísticamente significativas en relación a la influencia de las expectativas con el cambio de la fuerza de prensión manual (p > 0,05). No se encontraron diferencias estadísticamente significativas en la sumación temporal, ni en los umbrales de dolor a la presión. El dolor post-intervención fue mayor en el grupo de expectativas negativas y este fue el único grupo que mantuvo el dolor a los 5 minutos tras finalizar la intervención. Conclusión: A pesar de las tendencias observadas, no se encontraron influencias estadísticamente significativas de las expectativas sobre la fuerza muscular de prensión manual, ni en la intensidad de dolor, ni en variables somato-sensoriales. Las expectativas negativas influyeron en el dolor post-intervención.
... Interestingly, when performance expectations were directly enhanced, for example, by providing positive performance feedback, movement efficiency also increased (e.g., Hutchinson, Sherman, Martinovic, & Tenenbaum, 2008;Montes, Wulf, & Navalta, 2018;Stoate, Wulf, & Lewthwaite, 2012). Furthermore, placebos, which target positive outcome expectations, have been found to enhance force production (Fiorio, Emadi Andani, Marotta, Classen, & Tinazzi, 2014;Kalasountas, Reed, & Fitzpatrick, 2007). Expectations of positive experiences are associated with the release of dopamine (de la Fuente-Fernández, 2009;Lidstone et al., 2010), which has directly or indirectly been shown to enhance movement efficiency and effectiveness (Foreman et al., 2014;Jenkinson & Brown, 2011;Meadows, Gable, Lohse, & Miller, 2016). ...
The purpose of this study was to examine whether conditions that provide performers with a sense of autonomy, by giving them choices, would increase movement efficiency. We evaluated neuromuscular activation as a function of choice, using surface electromyography (EMG), during isometric force production. Participants (N = 16) were asked to perform plantar flexions at each of three target torques (80%, 50%, 20% of maximum voluntary contractions) under both choice and control conditions. In the choice condition, they were able to choose the order of target torques, whereas the order was pre-determined in the control condition. Results demonstrated that while similar torques were produced under both conditions, EMG activity was lower in the choice relative to the control condition. Thus, providing performers with a choice led to reduced neuromuscular activity, or an increase in movement efficiency. This finding is in line with the notion that autonomy support readies the motor system for task execution by contributing to the coupling of goals and actions (Wulf and Lewthwaite, Psychon Bull Rev 23:1382–1414, 2016).
... Most existing reviews and meta-analyses conclude that placebo response rates are higher in children and adolescents compared to adults, while drug responses are roughly equal between the two groups.(13-15) While studies have examined the placebo effect on physical activity in adults, (12,16,17) this was not previously studied in children. ...
Aim:
The aim of the study was to examine the effect of information placebo on fitness test results in normal weight, overweight and obese children.
Methods:
Twenty-four pre-pubertal children with overweight or obesity and 24, age and maturity-matched normal weight children performed a progressive treadmill exercise test twice. Different types of information were randomly provided regarding a water drink consumed prior to testing; standard (water) versus deliberate positive (presumed energy drink, placebo) information.
Results:
Following the placebo drink, both groups demonstrated significantly higher peak heart rate (overweight 165.8 ±16.7 versus 174.2±14.8bpm and normal weight 177.9±13.6 versus 189.8±12.2bpm) and longer time to exhaustion (overweight 396.9±161.9 versus 521.5±182.5 sec; normal weight: 700.1±155.2 versus 893.3±150.1seconds). Despite longer exercise duration and higher peak heart rate, average and peak rate of perceived exertion were significantly lower after the placebo drink (overweight 14.1±2.5 versus 12.5±2.5; normal weight 12.1±1.4 versus 10.7±1.5), with significantly shorter recovery time (overweight 132.2±28.5 versus 118.4±31.6; normal weight: 106.7±18.6 versos 96.7±17.8seconds).
Conclusion:
Our results demonstrate a significant effect of information placebo on fitness test results that is unrelated to body weight. Children with obesity may enhance their physical activity levels and energy expenditure if properly encouraged. This article is protected by copyright. All rights reserved.
... A substantial number of studies have investigated the effect of a verbal suggestion of reduced fatigue or increased performance (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38). In seven of the 13 studies, participants report a lower sense of fatigue while performing a motor task in the placebo condition than in a control condition (25, 28-30, 32, 33, 35). ...
Placebo and nocebo effects are, respectively, the helpful and harmful treatment effects that do not arise from active treatment components. These effects have thus far been researched most often in pain. It is not yet clear to what extent these findings from pain can be generalized to other somatic symptoms. This review investigates placebo and nocebo effects in four other highly prevalent symptoms: dyspnea, fatigue, nausea, and itch. The role of learning mechanisms (verbal suggestions, conditioning) in placebo and nocebo effects on various outcomes (self-reported, behavioral, and physiological) of these different somatic symptoms is explored. A search of experimental studies indicated that, as in pain, the combination of verbal suggestion and conditioning is generally more effective than suggestion alone for evoking placebo and nocebo effects. However, conditioning appears more and verbal suggestions less relevant in symptoms other than pain, with the exception of placebo effects on fatigue and nocebo effects on itch. Physiological measures, such as heart rate, lung function, or gastric activity, are rarely affected even when self-reported symptoms are. Neurobiological correlates are rarely investigated, and few commonalities appear across symptoms. Expectations generally predict placebo and nocebo effects for dyspnea and itch but seem less involved in fatigue and nausea. Individual characteristics do not consistently predict placebo or nocebo effects across symptoms or studies. In sum, many conclusions deriving from placebo and nocebo pain studies do appear to apply to other somatic symptoms, but a number of important differences exist. Understanding what type of learning mechanisms for which symptom are most likely to trigger placebo and nocebo effects is crucial for generalizing knowledge for research and therapies across symptoms and can help clinicians to optimize placebo effects in practice.
... Interestingly, while there was a significant reduction in heart rate at OBLA in the placebo group, there were no measurable improvements in V O 2peak and OBLA. Because the placebo effect, ranging from magnitudes of 1% to 6%, has been implicated in improvements in sports performance (Beedie & Foad, 2009;Beedie, Foad, & Coleman, 2008;Clark, Hopkins, Hawley, & Burke, 2000;Kalasountas, Reed, & Fitzpatrick, 2007), it is plausible this reduction in heart rate, could be a result of a placebo effect rather than an ergogenic effect. ...
Background: Professional and recreational athletes use ergogenic aids to enhance aerobic performance, facilitate training adaptations, and reduce recovery time. While the ergogenic effect of commonly marketed and commercially available ergogenic aids (i.e., sodium bicarbonate and β-alanine) have been investigated extensively, the effectiveness of lactate supplementation on aerobic capacity markers (i.e., V̇O2peak and the onset blood lactate accumulation) has not been thoroughly investigated. Objective: The purpose of this study was to examine the effect of lactate supplementation on V̇O2peak and the onset blood lactate accumulation (OBLA). Methods: Eighteen healthy individuals (14 men and 4 women, age: 24 ± 5 years, height: 171 ± 7 cm, body mass: 76 ± 17 kg) participated in a double-blind-placebo-controlled study and were randomly assigned to one of 2 groups: placebo (PLA, n = 8), or supplement (SUP, n = 10) consisting of a combination of magnesium lactate dihydrate and calcium lactate monohydrate. Prior to and following supplementation, participants performed a cycling graded exercise test to determine V̇O2peak, time to exhaustion, power output, V̇O2 and % V̇O2peak associated with OBLA. Results: There were no statistically significant differences between PLA and SUP in direct markers of aerobic capacity (all p > .05). Heart rate at OBLA was reduced by 6 ± 6% in the PLA group post-supplementation compared to pre-supplementation (p = .03).Conclusions: Lactate supplementation did not present an advantage over a placebo in improving aerobic capacity. The results from this study support those by previous investigators suggesting that there is no physiological rationale for using lactate supplementation to improve aerobic capacity and/or performance.
... From sports medicine it is well known that cognitive strategies like imagery of performance, self-talk, preparatory arousal, and goal setting (Tod et al., 2015), or hypnosis (Barber, 1966), or positions like power-posing (Carney et al., 2010) can increase strength performance. In addition, several studies have tested and demonstrated modulation of the motor system by placebo and nocebo effects (Kalasountas et al., 2007;Bottoms et al., 2014;Carlino et al., 2014;Stoekenbroek and Kastelein, 2017;Butera et al., 2018;Fiorio, 2018). Again, those studies intended to affect sport performance, muscular training, or side effects and diseases that impair movement and muscular functions. ...
Introduction: Nocebo effects are not only seen in studies of pharmacology and placebo/nocebo research but also in clinical everyday situations. For generation of objective and quantitative data on the impact of negative communication we have evaluated the immediate effects of common sentences, non-verbal signals and situations in the medical context on muscular performance.
Methods: In an experimental study, 46 volunteers were tested by dynamometry of the deltoid muscle group to evaluate the maximal muscular strength during arm abduction. Baseline values were compared to performance after exposure to 18 verbal and non-verbal suggestions. Suggestions suspected to be negative were alternated with and compared to positively formulated alternatives.
Results: Verbal and non-verbal communication produced significant effects on muscular performance, resulting mainly in weakening. The decrease in muscle strength after risk information for informed consent (91.4% of baseline) was absent, when benefits of the treatment were named coincidently. The weakening effect of asking about “pain” and “nausea” (89.4%), and of the announcement of medical interventions (91.7%) could be avoided with alternative wording. Impairment of muscular performance was also observed with the nocebo-inducers negative memory (89.5%) or uncertain future (93.3%), in contrast to a positive memory or the orientation into the presence. Non-verbal suggestions like overhead anesthesia induction (89.9%), a transport in strict flat supine position (89.1%), or a view from the window to a parking lot (94.1%) significantly reduced maximal muscle strength, whereas face-to face induction, half-sitting position and a view into the landscape did not. 8 out of 9 tested clinical situations reduced maximal arm muscle strength significantly, whereas alternative formulations did not.
Conclusion: This study describes a quick, simple and uniform test using objective measurement of maximal muscle strength to allow for identification, quantification, and comparison of negative suggestions, regardless of their specific content and effect. Muscle strength is a clinically relevant parameter with regard to early mobilization, risk of falling and sufficient breathing. Furthermore, the observed impairment of muscular performance could reflect a general “weakening effect” of negative suggestions. In addition, the test facilitates development and verification of appropriate alternatives to prevent nocebo effects in patients, thereby improving patient communication.
... We therefore used EEG in this study of the EPR, as it allows the recording of brain activity during high intensity cycling, where the body is stationary while under high physiological stress. EEG activity in the alpha frequency band (8)(9)(10)(11)(12)(13) is inversely related to activation of the underlying cortex 24,25 and builds the basis of the valence motivation model 26 . This model associates dominant left relative to right frontal activation, also known as frontal alpha asymmetry (FAA), with an approach motivational system and positive affect 27 . ...
The performance enhancing (ergogenic) placebo effect is elicited by an inert treatment and caused by positive affective appraisal of effort perception. Frontal alpha asymmetry (FAA) is a neurobiological correlate of positive affect. This study investigates, whether receiving an ergogenic placebo increases FAA and whether scores on the behavioral inhibition and activation system (BIS/BAS) scales affect this increase in FAA. Nineteen competitive male cyclists (37.26 ± 9.82 years) performed two maximum effort time trials. The first served as baseline for the second intervention time trial, where athletes received a placebo ergogenic aid or no treatment. We recorded FAA using EEG throughout all time trials and assessed BIS/BAS by questionnaire. There was a significant difference in change from baseline to intervention time trial in FAA during cycling in response to the placebo ergogenic aid compared to the control group. BIS, the BAS subscale Drive and the BAS-BIS difference score significantly co-varied with the change in FAA from baseline to intervention time trial in response to the placebo ergogenic aid. Administering a placebo ergogenic aid significantly influenced FAA during maximum effort cycling. Those athletes with a more pronounced goal seeking persistence and an overall dominance of the BAS over the BIS showed a significantly greater increase in FAA in response to a placebo ergogenic aid. A more pronounced BIS, however, seems to antagonize the increase in FAA associated with the ergogenic placebo response.
... In two other studies [13,14], weightlifters consumed placebo pills they believed to be anabolic steroids and received positive information stating that the pills would improve motor performance. Later, the researchers revealed to the subjects that they merely received a placebo and not real steroids. ...
Background
The aim of the study was to examine the influence of the placebo effect on the endurance capacity results in normal weight children.
Methods
Twenty-four pre-pubertal normal-weight children aged 6–13 years participated in the study. Subjects underwent anthropometric measurements (weight, height, BMI percentile, and fat percentage), a progressive treadmill exercise test to evaluate endurance capacity, and filled habitual activity questionnaire. The participants were examined twice, in a random order, with each child being compared to him/herself. Different types of information were provided regarding a water drink consumed prior to testing- standard information (water) vs. deliberate positive information (presumed energy drink, placebo).
Results
Following the placebo drink, children demonstrated significantly higher peak pulse (177.9 ± 13.6 vs. 189.8 ± 12.2 bpm), higher stage achieved and longer time of exercise to exhaustion (700.1 ± 155.2 vs. 893.3 ± 150.1 s). Although the exercise duration was longer, stage and heart rate achieved were higher, the reported average, and peak rate of perceived exertion (RPE) were significantly lower for the placebo (18.3 ± 1.4 vs 16.2 ± 1.5). Although the effort was higher while drinking placebo (longer run, higher exercise phase, higher heart rate), recovery time was significantly shorter. The reported differences were not associated with order of tests, age, gender or child activity level.
Conclusion
Our results demonstrate a significant information placebo effect on children’s endurance capacity test results. This highlights the possible role of positive information (placebo) in trying to encourage physical activity in children. Whether this effect could be applied to longer-term interventions has yet to be tested.
Trial registration
ClinicalTrial.gov identifier: NCT03165604, Registered May 24, 2017.
... Indeed, previous research advocates when compared in isolation, the synergistic effect of the pharmacological and psychological influence of nutritional interventions lead to the greatest improvements in sport, exercise and cognitive performance [3,6,30]. Within the context of sport and exercise nutrition, expectancy has been implicated following deceptive administration of anabolic steroids [38,39], carbohydrates [40,41], amino acids [42], sodium bicarbonate [29,30], super oxygenated water [43], and creatine monohydrate [44]. ...
Caffeine (CAF) is widely consumed across sport and exercise for its reputed ergogenic properties, including central nervous stimulation and enhanced muscular force development. However, expectancy and the related psychological permutations that are associated with oral CAF ingestion are generally not considered in most experimental designs and these could be important in understanding if/how CAF elicits an ergogenic effect. The present paper reviews 17 intervention studies across sport, exercise, and cognitive performance. All explore CAF expectancies, in conjunction with/without CAF pharmacology. Thirteen out of 17 studies indicated expectancy effects of varying magnitudes across a range of exercise tasks and cognitive skills inclusive off but not limited to; endurance capacity, weightlifting performance, simple reaction time and memory. Factors, such as motivation, belief, and habitual CAF consumption habits influenced the response. In many instances, these effects were comparable to CAF pharmacology. Given these findings and the lack of consistency in the experimental design, future research acknowledging factors, such as habitual CAF consumption habits, habituated expectations, and the importance of subjective post-hoc analysis will help to advance knowledge within this area.
... This improvement returned to baseline values after the subjects were told the truth about the real inert nature of the substance. As demonstrated in a later study in non-athletes, however, the placebo effect on strength in weightlifting appears to be beneficial even after overt debriefing as compared with the performance of a control group that received no treatment (Kalasountas, Reed, & Fitzpatrick, 2007). A more recent study involving untrained participants further demonstrated the effects of positive and negative expectations for the effect of a drink in modulating the power and perception of discomfort during incremental arm crank ergometry (Bottoms, Buscombe, & Nicholettos, 2014). ...
There is strong behavioral evidence that placebo and nocebo effects can influence aspects of motor performance like speed, force, and resistance to fatigue in athletes and non-athletes alike. These behavioral studies were essential for extending experimental investigation of the placebo and nocebo effects from the pain to the motor domain and to reveal how verbal suggestions and experiential learning are involved in shaping modulatory systems and related behavioral responses. However, the neural underpinnings of these effects in the motor domain are still largely unknown. Studies in healthy subjects demonstrated that the placebo-induced enhancement of force is associated with increased activity in the corticospinal system and that the placebo-induced reduction of fatigue can be disclosed by recording the readiness potential, an electrophysiological sign of movement preparation. Further evidence derives from studies in patients with Parkinson's disease that have directly demonstrated that placebo-induced improvements in motor symptoms are related to changes in subcortical neural firing activity and dopamine release. Future investigations are needed to better clarify the complex neural architecture underpinning the placebo and nocebo effects in the motor domain.
... By using the same experimental paradigm, expectancies have been investigated not only in professional athletes but also in college students. For example, Kalasountas et al. (2007) found that students in the placebo group significantly improved their motor performance (consisting of different lifting exercises) compared to the control group: however, after the placebo was disclosed (thus the expectancy component was removed), control and placebo groups showed approximately the same performance. ...
Due to the recent explosion of placebo research at many levels the Editors believe that a volume on Placebo would be a good addition to the Handbook of Experimental Pharmacology series. In particular, this volume will be built up on a meeting on Placebo which will be held in Tuebingen (Germany) in January 2013, and where the most prominent researchers in this field will present and exchange their ideas. The authors who will be invited to write chapters for this volume will be the very same speakers at this meeting, thus guaranteeing high standard and excellence in the topic that will be treated. The approach of the book is mainly pharmacological, including basic research and clinical trials, and the contents range from different medical conditions and systems, such as pain and the immune system, to different experimental approaches, like in vivo receptor binding and pharmacological/behavioral conditioning. Overall, the volume will give an idea of modern placebo research, of timely concepts in both experimental and clinical pharmacology, as well as of modern methods and tools in neuroscience.
... Before experiment, all participants were informed that IT is highly effective in untrained participants and it is highly likely that this training will be also effective in swimming practice. Kalasountas, Reed, and Fitzpatrick's (2007) study showed that placebo effect can lead to significant increase in the muscle strength estimated by one repetition maximum. On other hand, Wright et al. (2009) showed that placebo effect may be of significant magnitude in endurance exercises but do not change muscle power. ...
The aim of this study was to evaluate the influence of dry-land inertial training (IT) on muscle force, muscle power, and swimming performance. Fourteen young, national-level, competitive swimmers were randomly divided into IT and control (C) groups. The experiment lasted four weeks, during which time both groups underwent their regular swimming training. In addition, the IT group underwent IT using the Inertial Training Measurement System (ITMS) three times per week. The muscle groups involved during the upsweep phase of the arm stroke in front crawl and butterfly stroke were trained. Before and after training, muscle force and power were measured under IT conditions. Simultaneously with the biomechanical measurements on the ITMS, the electrical activity of the triceps brachii was registered. After four weeks of training, a 12.8% increase in the muscle force and 14.2% increase in the muscle power (p < .05) were noted in the IT group. Moreover, electromyography amplitude of triceps brachii recorded during strength measurements increased by 22.7% in the IT group. Moreover, swimming velocity in the 100 m butterfly and 50 m freestyle improved significantly following the four weeks of dry-land IT (−1.86% and −0.76%, respectively). Changes in the C group were trivial. Moreover, values of force and power registered during the ITMS test correlated negatively with the 100 m butterfly and 50 m freestyle swimming times (r value ranged from −.80 to −.91). These results suggest that IT can be useful in swimming practice.
... When external feedback is interpreted in relation to an individual's beliefs in their ability to meet the task demands, it has the potential to elicit positive or negative perceptual experiences (Hutchinson et al., 2008) and performance outcomes (Halson and Martin, 2013). Furthermore, strong beliefs regarding an individual's abilities in their performance have been positively associated with motor performance (McKay et al., 2012), maximal force production (Ness and Patton, 1979;Kalasountas et al., 2007), running efficiency (Stoate et al., 2012), effort tolerance (Hutchinson et al., 2008), and positive affect (McAuley and Courneya, 1992;Stoate et al., 2012). ...
The provision of performance-related feedback during exercise is acknowledged as an influential external cue used to inform pacing decisions. The provision of this feedback in a challenging or deceptive context allows research to explore how feedback can be used to improve performance and influence perceptual responses. However, the effects of deception on both acute and residual responses have yet to be explored, despite potential application for performance enhancement. Therefore, this study investigated the effects of challenging and deceptive feedback on perceptual responses and performance in self-paced cycling time trials (TT) and explored whether changes in performance are sustained in a subsequent TT following the disclosure of the deception. Seventeen trained male cyclists were assigned to either an accurate or deceptive feedback group and performed four 16.1 km cycling TTs; (1 and 2) ride-alone baseline TTs where a fastest baseline (FBL) performance was identified, (3) a TT against a virtual avatar representing 102% of their FBL performance (PACER), and (4) a subsequent ride-alone TT (SUB). The deception group, however, were initially informed that the avatar accurately represented their FBL, but prior to SUB were correctly informed of the nature of the avatar. Affect, self-efficacy and RPE were measured every quartile. Both groups performed PACER faster than FBL and SUB (p < 0.05) and experienced lower affect (p = 0.016), lower self-efficacy (p = 0.011), and higher RPE (p < 0.001) in PACER than FBL. No significant differences were found between FBL and SUB for any variable. The presence of the pacer rather than the manipulation of performance beliefs acutely facilitates TT performance and perceptual responses. Revealing that athletes' performance beliefs were falsely negative due to deceptive feedback provision has no effect on subsequent perceptions or performance. A single experiential exposure may not be sufficient to produce meaningful changes in the performance beliefs of trained individuals beyond the acute setting.
... Specifi cally, researchers in this area have attempted to determine the extent to which strength and performance are due to expectations, self-deception, or self-handicapping. Some of the studies in this category have examined college students (Kalasountas, Reed, & Fitzpatrick, 2007;Nelson & Furst, 1972;Ness & Patton, 1979;Proske et al., 2004), while others have involved powerlifters (Maganaris, Collins, & Sharp, 2000), Olympic weight lifters (Mahoney, 1995), or other athletes (Ariel & Saville, 1972) (see Table 22.5). Most studies have used a quasi-experimental or experimental research design; one study has employed a double-blind methodology (Mahoney, 1995). ...
Resistance exercise has been identified as an important mode of physical activity to maintain and enhance health. Research has been developing regarding psychological alterations during and after resistance exercise. The purpose of this chapter is to briefly highlight the physical health benefits of resistance exercise and then review research in five domains. First it reviews the relationship between resistance exercise and the sensation of effort. Second, it summarizes research that investigates resistance exercise and affect changes. Third, it discusses research regarding resistance exercise and its effects on self-perception. Fourth, it reviews research on the use of "psyching" strategies prior to maximal and submaximal performance of resistance exercise. The chapter concludes with a discussion of the role of expectation in resistance exercise performance.
... By using the same experimental paradigm, expectancies have been investigated not only in professional athletes but also in college students. For example, Kalasountas et al. (2007) found that students in the placebo group significantly improved their motor performance (consisting of different lifting exercises) compared to the control group: however, after the placebo was disclosed (thus the expectancy component was removed), control and placebo groups showed approximately the same performance. ...
In this chapter we present and discuss recent studies on the mechanisms underlying placebo and nocebo effects in physical performance, showing how expectations and both pharmacological and nonpharmacological preconditioning procedures can be very effective in inducing placebo responses, with important implications for sport competitions. Furthermore, we place these findings within the biological model of central governor of fatigue, whose main goal is to protect our body from damage. A crucial aspect of this emerging field of placebo studies is related to the limit beyond which these procedures can be called doping in all respects.
... Whilst this literature is reviewed elsewhere, 43 it suffices to state that placebo effects on sports performance resulting from the belief that an ergogenic substance had been ingested have been reported in 12 well-controlled studies. [5][6][7]39,[43][44][45][46][47][48][49][50] Most of these effects were in the range of 1%-5%. In three studies, nocebo (or negative placebo) effects were observed as the result of subjects either being given negative information about an intervention, 44 having previous negative experience with caffeine, 5 or for reasons that were not entirely clear. ...
The ergogenic effects of caffeine on performance are well documented. These effects are more evident in endurance and short-duration, sustained-effort events than in interactive or stop-go sports. Experimentally-induced placebo effects of caffeine on sports performance have also been observed in a number of recent studies. In the present paper it is argued that, given the nature of the sports in which caffeine effects are observed, the well documented hypoalgesic effects of caffeine, and the fact that pain is highly placebo-responsive, a reduction in perceived pain might be the common factor in both the biologic and placebo ergogenic effects of caffeine on sports performance. This idea is supported by evidence from medicine that suggests placebo effects are often associated with mechanisms similar or identical to those of the substance the subject believes they have ingested. Research findings from both biomedicine and sports medicine that attest to the interaction of biologic and psychologic factors in caffeine and pain responses are briefly reviewed. In conclusion, it is recommended that researchers investigate the pain hypothesis. Furthermore, researchers should consider psychosocial factors that might modulate the pain response as variables of interest in future caffeine and performance research.
... All experimental investigations of treadmill and cycling exercise were reviewed and, whilst articles investigating deception in other exercise modes were noted [37][38][39], they were deemed beyond the scope of this review. Exclusion criteria were also extended to research into the effects of placebos [40,41] and pain manipulation [42,43] with delimitation to the deception of performance, physiological and psychological variable feedback. ...
The aim of an optimal pacing strategy during exercise is to enhance performance whilst ensuring physiological limits are not surpassed, which has been shown to result in a metabolic reserve at the end of the exercise. There has been debate surrounding the theoretical models that have been proposed to explain how pace is regulated, with more recent research investigating a central control of exercise regulation. Deception has recently emerged as a common, practical approach to manipulate key variables during exercise. There are a number of ways in which deception interventions have been designed, each intending to gain particular insights into pacing behaviour and performance. Deception methodologies can be conceptualised according to a number of dimensions such as deception timing (prior to or during exercise), presentation frequency (blind, discontinuous or continuous) and type of deception (performance, biofeedback or environmental feedback). However, research evidence on the effects of deception has been perplexing and the use of complex designs and varied methodologies makes it difficult to draw any definitive conclusions about how pacing strategy and performance are affected by deception. This review examines existing research in the area of deception and pacing strategies, and provides a critical appraisal of the different methodological approaches used to date. It is hoped that this analysis will inform the direction and methodology of future investigations in this area by addressing the mechanisms through which deception impacts upon performance and by elucidating the potential application of deception techniques in training and competitive settings.
... This return to baseline highlights the role of expectation as the main factor involved in the improvement, pointing to the presence of cognitive mechanisms in the generation of the placebo effect. Similar results with an almost identical protocol including a control group and follow-up interviews to chart subjects' expectations were obtained in a bigger trial on college students [66]. ...
Although the great increase in interest in the placebo phenomenon was spurred by the clinical implications of its use, the progressive elucidation of the neurobiological and pharmacological mechanisms underlying the placebo effect also helps cast new light on the relationship between mind (and brain) and body, a topic of foremost philosophical importance but also a major medical issue in light of the complex interactions between the brain on the one hand and body functions on the other. While the concept of placebo can be a general one, with a broad definition generally applicable to many different contexts, the description of the cerebral processes called into action in specific situations can vary widely. In this paper, examples will be given where physiological or pathological conditions are altered following the administration of an inert substance or verbal instructions tailored to induce expectation of a change, and explanations will be offered with details on neurotransmitter changes and neural pathways activated. As an instance of how placebo effects can extend beyond the clinical setting, data in the physical performance domain and implications for sport competitions will also be presented and discussed.
Placebo and nocebo effects have been well documented for nearly two centuries. However, research has only relatively recently begun to explicate the neurobiological underpinnings of these phenomena. Similarly, research on the broader social implications of placebo/nocebo effects, especially within healthcare delivery settings, is in a nascent stage. Biological and psychosocial outcomes of placebo/nocebo effects are of equal relevance. A common pathway for such outcomes is the endogenous opioid system. This chapter describes the history of placebo/nocebo in medicine; delineates the current state of the literature related to placebo/nocebo in relation to pain modulation; summarizes research findings related to human performance in sports and exercise; discusses the implications of placebo/nocebo effects among diverse patient populations; and describes placebo/nocebo influences in research related to psychopharmacology, including the relevance of endogenous opioids to new lines of research on antidepressant pharmacotherapies.
Little is known about the placebo effects when comparing training interventions. Consequently, we investigated whether subjects being told they are in the intervention group get better training results compared to subjects being told they are in a control group. Forty athletes (male: n = 31, female: n = 9) completed a 10-week training intervention (age: 22 ± 4 years, height: 183 ± 10 cm, and body mass: 84 ± 15 kg). After randomization, the participants were either told that the training program they got was individualized based on their force-velocity profile (Placebo), or that they were in the control group (Control). However, both groups were doing the same workouts. Measurements included countermovement jump (CMJ), 20-m sprint, one-repetition maximum (1RM) back-squat, a leg-press test, ultrasonography of muscle-thickness (m. rectus femoris), and a questionnaire (Stanford Expectations of Treatment Scale) (Younger et al. in Clin Trials 9(6):767-776, 2012). Placebo increased 1RM squat more than Control (5.7 ± 6.4% vs 0.9 ± 6.9%, [0.26 vs 0.02 Effect Size], Bayes Factor: 5.1 [BF 10 ], p = 0.025). Placebo had slightly higher adherence compared to control (82 ± 18% vs 72 ± 13%, BF 10 : 2.0, p = 0.08). Importantly, the difference in the 1RM squat was significant after controlling for adherence (p = 0.013). No significant differences were observed in the other measurements. The results suggest that the placebo effect may be meaningful in sports and exercise training interventions. It is possible that ineffective training interventions will go unquestioned in the absence of placebo-controlled trials.
Elhaj, HM, Imam, O, Page, BW, Vitale, JM, and Malek, MH. Perceived consumption of a high-dose caffeine drink delays neuromuscular fatigue. J Strength Cond Res XX(X): 000-000, 2020-The placebo effect is a concept in which a desired outcome arises, mainly from the belief that the treatment (i.e., supplement or drug) was beneficial although no active ingredient was given. The results of studies related to the placebo effect primarily examine functional performance. What remains unanswered, however, is whether these changes in performance are associated with neuromuscular alterations in the exercised muscles. The purpose of the study, therefore, was to determine the influence of the placebo effect on the physical working capacity fatigue threshold (PWCFT) for a continuous exercise paradigm. To achieve this aim, subjects were told that they were participating in a study to determine the dosage response (low or high) of caffeine on neuromuscular fatigue when in fact no caffeine was given during the experiment. We hypothesized that the perceived consumption of the high-dose caffeine drink would result in a higher PWCFT than the perceived consumption of the low-dose caffeine drink and placebo. Secondarily, we hypothesized that the perceived consumption of the high-dose caffeine drink would result in a higher power output than the perceived consumption of the placebo. Nine healthy college-aged men (mean ± SEM: age, 25.7 ± 1.3 years; body mass, 84.4 ± 3.1 kg; and height: 1.82 ± 0.02 m) volunteered to be in the study. For each of the visits, subjects were given an 8 oz. bottle of water with dissolved crystal light. After the drink was consumed, subjects rested in the laboratory for 1 hour before performing the incremental single-leg knee-extensor ergometry. Immediately after the termination of the incremental single-leg knee-extensor ergometry, the subject was asked which caffeine dose (placebo, low, or high) they believed they consumed for that visit. There were no significant mean differences for maximal power output for the 3 perceived conditions (placebo: 62 ± 3, low-dose caffeine: 62 ± 4, and high-dose caffeine: 65 ± 3 W). When the subjects perceived consuming the high-dose caffeine drink, there were significant mean differences (all p-values < 0.01), for PWCFT, between the other conditions (mean ± SEM: placebo: 23 ± 3 W, low-dose caffeine: 26 ± 2 W, and high-dose caffeine: 42 ± 3 W). This corresponded to a significant mean difference (all p-values < 0.01) when the PWCFT was presented as a percentage of the maximal power output (mean ± SEM: placebo: 37 ± 5%, low-dose caffeine: 42 ± 3%, and high-dose caffeine: 64 ± 3%). The application of our results may indicate that the subject's expectancy, to caffeine consumption, plays a critical role in delaying the onset of neuromuscular fatigue despite not receiving any caffeine in their drinks.
Aim
The importance of patient expectations (PEs) on treatment outcomes is poorly understood in clinical practice. The aim of this review is to investigate the evidence behind association between pre‐treatment PEs and treatment outcomes such as pain intensity (PI), level of function (LF) and health‐related quality of life (HRQOL) among individuals with chronic low back pain (CLBP)
Methods
A systematic search was conducted for randomised controlled trials published between 1946 and May 2019 across major databases using the key MeSH terminologies. The association between PEs and PI, LF and HRQOL were extracted and categorized into positive, negative or no association for analysing the data. A descriptive synthesis was conducted and the association between PEs and PI, LF and HRQOL were reported.
Results
Among the total of 7 trials, 2 trials demonstrated a positive association between PEs and PI in short (≤ 6 weeks) and long term (> 6 months), while another 2 trials demonstrated no association at medium term (> 6 weeks ‐ ≤ 6 months). About 4 trials demonstrated a positive significant association between PEs and LF, 2 at medium and 2 at long terms. The only available trial demonstrated no association between PEs and HRQOL at medium term.
Conclusion
PEs is associated with PI at short and long terms. Also, evidence suggests association between PEs and LF at medium and long terms. Currently, there is no evidence of association between PEs and HRQOL. Further studies with valid tools to measure PE are warranted among individuals with CLBP.
The aim of this review was to determine the magnitude of the placebo and nocebo effect on sport performance. Articles published before March 2019 were located using Medline, Web of Science, PubMed, EBSCO, Science Direct, and Scopus. Studies that examined placebo and nocebo effects of an objective dependent variable on sports performance, which included a control or baseline condition, were included in the analysis. Studies were classified into two categories of ergogenic aids: 1) nutritional and 2) mechanical. Cohen’s d effect sizes were calculated from 32 studies involving 1,513 participants. Small to moderate placebo effects were found for both placebo (d = 0.36) and nocebo (d = 0.37) effects and when separated by nutritional (d = 0.35) and mechanical (d = 0.47) ergogenic aids. The pooled effect size revealed a small to moderate effect size across all studies (d = 0.38). Results suggest that placebo and nocebo effects can exert a small to moderate effect on sports performance.
Among the cognitive strategies that can facilitate motor performance in sport and physical practice,
a prominent role is played by the direction of the focus of attention and the placebo effect. Consistent evidence converges in indicating that these two cognitive functions can influence the motor outcome, although no study up-to-now tried to study them together in the motor domain. In this explorative study, we combine for the first time these approaches, by applying a placebo procedure to increase force and by manipulating the focus of attention with explicit verbal instructions. Sixty healthy volunteers were asked to perform abduction movements with the index finger as strongly as possible against a piston and attention could be directed either toward the movements of the finger (internal focus, IF) or toward the movements of the piston (external focus, EF). Participants were randomized
in 4 groups: two groups underwent a placebo procedure (Placebo-IF and Placebo-EF), in which an inert treatment was applied on the finger with verbal information on its positive effects on force; two groups underwent a control procedure (Control-IF and Control-EF), in which the same treatment was applied with overt information about its inefficacy. The placebo groups were conditioned about the effects of the treatment with a surreptitious amplification of a visual feedback signalling the level of force. During the whole procedure, we recorded actual force, subjective variables and electromyography from the hand muscles. The Placebo-IF group had higher force levels after the procedure than before, whereas the Placebo-EF group had a decrease of force. Electromyography showed that the Placebo-IF group increased the muscle units recruitment without changing the firing rate. These findings show for the first time that the placebo effect in motor performance can be influenced by the subject’s attentional focus, being enhanced with the internal focus of attention.
Introduction:
We examined the placebo effect of caffeine and the combined effect of caffeine and caffeine expectancy on maximal voluntary strength.
Methods:
Fourteen men completed 4 randomized single-blind experimental trials: 1) Told caffeine, given caffeine (5mg.kg) (CC); 2) Told caffeine, given placebo (CP); 3) Told placebo, given placebo (PP); 4) Told placebo, given caffeine (PC). Maximal voluntary concentric force and fatigue resistance of the knee flexors and extensors was measured using isokinetic dynamometry.
Results:
A significant and equal improvement in peak concentric force was found in the CC and PC trials. Despite participants believing caffeine would evoke a performance benefit, there was no effect of CP.
Conclusion:
Caffeine caused an improvement in some aspects of muscle strength, however there was no additional effect of expectancy. Performance was poorer in participants who believed caffeine would have the largest benefit, which highlights a link between expected ergogenicity, motivation, and personality characteristics. This article is protected by copyright. All rights reserved.
A brief theoretical discussion of the placebo effect and of some methodological issues of the measurement of it are followed by a narrative review based on the results of our earlier metaanlysis of fourteen published research on the investigation of placebo effect in sports and exercise. Various factors (e.g. personality factors, perceptual characteristics of the applied substance or treatment) of placebo-effect effecting performance in sports and relevant research are also addressed. Absztrakt A placebo-hatás rövid elméleti áttekintését, valamint a placebo-hatás mérésének néhány módszertani problematikájának bemutatását korábbi metaanalízisünkön alapuló, különböző sportokban végzett placebo-hatás vizsgálatok narratív összefoglalója követi. A sportban megfigyelhető placebo-hatás különböző, a teljesítményt is befolyásoló összetevőit (pl. személyiség, az alkalmazott szer perceptuális tulajdonságai) vizsgáló kutatásokat is ismertetünk.
Placebos have been found to affect a number of pathological processes and physiological functions through expectations of clinical improvement. Recently, the study of the placebo effect has moved from the clinical to the physical performance setting, wherein placebos can boost performance by increasing muscle work and by decreasing perceived exertion. However, nothing is known about the neurobiological underpinnings of this phenomenon. Here we show for the first time that a placebo, which subjects believed to be endurance-increasing caffeine, reduces fatigue by acting at the central level on the preparatory phase of movement. In fact, we recorded the readiness potential, which is the expression of the preparatory phase of movement at the level of the supplementary motor area, during repeated flexions of the index finger in a control group that did not receive any treatment and in a placebo group that received placebo caffeine. In the control group, as the number of flexions increased, both fatigue and readiness potential amplitude increased. By contrast, in the placebo group, as the number of flexions increased we found a decrease in perceived exertion along with no increase in readiness potential amplitude. This placebo-induced modulation of the readiness potential suggests that placebos reduce fatigue by acting centrally during the anticipatory phase of movement, thus emphasizing the important role of the central nervous system in the generation of fatigue.
The empirical foundation of the 'placebo effect' is presented briefly, which is followed by the meta-analysis of the relatively few published reports that have investigated placebo effects in sports performance. Based on the analysis of the fourteen studies included in the meta-analysis, an overall medium effect size (0.4, 95% CI ranged from 0.24 to 0.56) was found. Homogeneity of effect sizes (χ 2 (13, N = 196) = 9.35, p = 0.75) and the feasibility of possible explanation models were also tested. In various sports (e.g. cycling, running, weightlifting) the investigation of the placebo effect on various physiological or performance measures (e.g. muscle power, heart rate, running speed) and psychological attributes (e.g. perceived exertion, post-experiment interviews) yielded significant results. Indeed, the common finding of the reviewed studies was that from the point of view of the athletes there is substantial performance enhancement as a result of different forms of placebos. However, the interpretation of some of the results may be limited by methodological shortcomings. Based on the reviewed articles and further questions emerging from them, methodological recommendations as well as possible research ideas are suggested for further inquiries in the area. Placebo-Effekt im Bereich Sport: Metaanalyse: Die Grundlagen der Erforschung des Place-bo-Effekts werden kurz geschildert, sodann werden die Ergebnisse unserer Metaanalyse vorge-stellt, die auf Grundlage einiger Studien zur Untersuchung des messbaren Placebo-Effekts bei Sportleistungen durchgeführt wurde. Auf Grundlage der in die Metaanalyse integrierten 14 Stu-dien wurde eine mittlere Wirkungsgröße festgestellt (0,4, mit 95% CI 0,24–0,56). Es wurden die Homogenität der Wirkungsgrößen (χ 2 (13, N = 196) = 9,35, p = 0,75), sowie die Möglichkeit der *
The power of placebos has long been recognized for improving numerous medical conditions such as Parkinson's disease (PD).
Little is known, however, about the mechanism underlying the placebo effect. Using the ability of endogenous dopamine to compete
for [11C]raclopride binding as measured by positron emission tomography, we provide in vivo evidence for substantial release of endogenous
dopamine in the striatum of PD patients in response to placebo. Our findings indicate that the placebo effect in PD is powerful
and is mediated through activation of the damaged nigrostriatal dopamine system.
Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Sport psychologist, published by and copyright Human Kinetics. Although expectancy has been shown to play a role in the effect of Anabolic Steroids (AS) on behavior, little research has been completed on the potential for parallel effects on performance. This is an important area for investigation because if expectancy effects can be shown to operate by improvements in performance through the administration of a placebo, arguments against the use of AS may be more successfully advanced. Accordingly, the present investigation used the administration of a placebo (saccharine) with competitive power lifters, using false information about the nature of the drug to delineate expectancy effects. The pervasiveness of these effects was further examined by disclosing the true nature of the drug to half of the participants, midway through the investigation. Notable improvements in performance associated with the belief that AS had been administered largely dissipated when athletes were informed as to the true nature of the drug. Results indicated that expectancy played a notable role in performance enhancement. Implications for this work include more effective use of such investigations in the fight against doping in sport.
The use of anabolic-androgenic steroids (AS) is perceived by the media, by segments of the sports medicine and athletic communities, and by the public to have grown to epidemic proportions. Unfortunately, the incidence and prevalence of AS use among elite, amateur, and recreational athletes is poorly documented. This study was designed to help identify AS use patterns among the male portion of the general adolescent population. The overall participation rate on a schoolwide basis was 68.7% and on an individual basis reached 50.3%. Participants in this investigation were 12th-grade male students (N = 3403) in 46 private and public high schools across the nation who completed a questionnaire that established current or previous use of AS as well as user and nonuser characteristics. Results indicate that 6.6% of 12th grade male students use or have used AS and that over two thirds of the user group initiated use when they were 16 years of age or younger. Approximately 21% of users reported that a health professional was their primary source. The evidence indicates that educational intervention strategies should begin as early as junior high school; the intervention should not be directed only toward those individuals who participate in school-based athletics.
Distinguishes between primary assessments, which measure the direct effects of expectancies associated with the placebo, and secondary assessments, which measure S's inferences about underlying dispositions that are not believed to be directly affected by the placebo (inductive effects). Placebos whose alleged impact will counteract the recipient's symptoms (counteractive expectancies) are distinguished from placebos whose alleged effects will parallel the recipient's symptoms (parallel expectancies). Research findings are reviewed and classified into 1 of 4 cells produced by a combination of these 2 factors. Standard placebo effects (changes in the recipient's condition in accordance with the placebo's alleged impact) were found to be most common on primary assessments of counteractive expectancies placebos; reverse inductive effects (altered inferences about an underlying disposition, in the direction opposite to the placebo's alleged impact) were most common on secondary assessments of parallel expectancies placebos. Psychological processes that underlie these effects and implications for clinical practice are considered. (94 ref)
The intensity and spatial distribution of functional activation in the left precentral and postcentral gyri during actual motor performance (MP) and mental representation [motor imagery (MI)] of self-paced finger-to-thumb opposition movements of the dominant hand were investigated in fourteen right-handed volunteers by functional magnetic resonance imaging (fMRI) techniques. Significant increases in mean normalized fMRI signal intensities over values obtained during the control (visual imagery) tasks were found in a region including the anterior bank and crown of the central sulcus, the presumed site of the primary motor cortex, during both MP (mean percentage increase, 2.1%) and MI (0.8%). In the anterior portion of the precentral gyrus and the postcentral gyrus, mean functional activity levels were also increased during both conditions (MP, 1.7 and 1.2%; MI, 0.6 and 0.4%, respectively). To locate activated foci during MI, MP, or both conditions, the time course of the signal intensities of pixels lying in the precentral or postcentral gyrus was plotted against single-step or double-step waveforms, where the steps of the waveform corresponded to different tasks. Pixels significantly (r > 0.7) activated during both MP and MI were identified in each region in the majority of subjects; percentage increases in signal intensity during MI were on average 30% as great as increases during MP. The pixels activated during both MP and MI appear to represent a large fraction of the whole population activated during MP. These results support the hypothesis that MI and MP involve overlapping neural networks in perirolandic cortical areas.
We investigated the mechanisms underlying the activation of endogenous opioids in placebo analgesia by using the model of human experimental ischemic arm pain. Different types of placebo analgesic responses were evoked by means of cognitive expectation cues, drug conditioning, or a combination of both. Drug conditioning was performed by means of either the opioid agonist morphine hydrochloride or the nonopioid ketorolac tromethamine. Expectation cues produced placebo responses that were completely blocked by the opioid antagonist naloxone. Expectation cues together with morphine conditioning produced placebo responses that were completely antagonized by naloxone. Morphine conditioning alone (without expectation cues) induced a naloxone-reversible placebo effect. By contrast, ketorolac conditioning together with expectation cues elicited a placebo effect that was blocked by naloxone only partially. Ketorolac conditioning alone produced placebo responses that were naloxone-insensitive. Therefore, we evoked different types of placebo responses that were either naloxone-reversible or partially naloxone-reversible or, otherwise, naloxone-insensitive, depending on the procedure used to evoke the placebo response. These findings show that cognitive factors and conditioning are balanced in different ways in placebo analgesia, and this balance is crucial for the activation of opioid or nonopioid systems. Expectation triggers endogenous opioids, whereas conditioning activates specific subsystems. In fact, if conditioning is performed with opioids, placebo analgesia is mediated via opioid receptors, if conditioning is performed with nonopioid drugs, other nonopioid mechanisms result to be involved.
It has been suggested that placebo analgesia involves both higher order cognitive networks and endogenous opioid systems.
The rostral anterior cingulate cortex (rACC) and the brainstem are implicated in opioid analgesia, suggesting a similar role
for these structures in placebo analgesia. Using positron emission tomography, we confirmed that both opioid and placebo analgesia
are associated with increased activity in the rACC. We also observed a covariation between the activity in the rACC and the
brainstem during both opioid and placebo analgesia, but not during the pain-only condition. These findings indicate a related
neural mechanism in placebo and opioid analgesia.
Administration of placebo can result in a clinical response indistinguishable from that seen with active antidepressant treatment. Functional brain correlates of this phenomenon have not been fully characterized.
Changes in brain glucose metabolism were measured by using positron emission tomography in hospitalized men with unipolar depression who were administered placebo as part of an inpatient imaging study of fluoxetine. Common and unique response effects to administration of placebo or fluoxetine were assessed after a 6-week, double-blind trial.
Placebo response was associated with regional metabolic increases involving the prefrontal, anterior cingulate, premotor, parietal, posterior insula, and posterior cingulate and metabolic decreases involving the subgenual cingulate, parahippocampus, and thalamus. Regions of change overlapped those seen in responders administered active fluoxetine. Fluoxetine response, however, was associated with additional subcortical and limbic changes in the brainstem, striatum, anterior insula, and hippocampus, sources of efferent input to the response-specific regions identified with both agents.
The common pattern of cortical glucose metabolism increases and limbic-paralimbic metabolism decreases in placebo and fluoxetine responders suggests that facilitation of these changes may be necessary for depression remission, regardless of treatment modality. Clinical improvement in the group receiving placebo as part of an inpatient study is consistent with the well-recognized effect that altering the therapeutic environment may significantly contribute to reducing clinical symptoms. The additional subcortical and limbic metabolism decreases seen uniquely in fluoxetine responders may convey additional advantage in maintaining long-term clinical response and in relapse prevention.
Using the ability of [11C]raclopride to compete with dopamine for D(2)/D(3) receptors, we investigated by positron emission tomography the effect of placebo (saline) injection on dopamine release in the ventral striatum of patients with Parkinson's disease. We found evidence for placebo-induced dopamine release of similar magnitude to that reported in healthy volunteers after amphetamine administration. However, in contrast to the dorsal striatum, there were no differences in [11C]raclopride binding potential changes between patients who experienced the reward (those who reported placebo-induced clinical benefit) and those who did not. We conclude that the release of dopamine in the ventral striatum (nucleus accumbens) is related to the expectation of reward and not to the reward itself. These observations have potential implications for the treatment of drug addiction.
The authors review the literature on the 2 main models of the placebo effect: expectancy theory and classical conditioning. A path is suggested to dissolving the theoretical impasse that has long plagued this issue. The key is to make a clear distinction between 2 questions: What factors shape placebo effects? and What learning mediates the placebo effect? The reviewed literature suggests that classical conditioning procedures are one shaping factor but that verbal information can also shape placebo effects. The literature also suggests that conditioning procedures and other sources of information sometimes shape conscious expectancies and that these expectancies mediate some placebo effects; however, in other cases conditioning procedures appear to shape placebo effects that are not mediated by conscious cognition.
Disruption of motor cortex activity is hypothesized to play a major role in the slowed movement (bradykinesia) associated with reduced dopaminergic function. We recorded single neurons in the motor cortex of free-moving rats performing a forelimb-reaching task. The same neurons were examined before and after induction of bradykinesia with the D2 dopamine receptor antagonist haloperidol. Within-cell changes in the firing rate and firing pattern of individual cells and the correlation between simultaneously recorded cells after injection of haloperidol were statistically compared with vehicle-only control experiments. During haloperidol-induced bradykinesia (mean movement time increase, +231%), there was an average 11% decrease in baseline firing rate. Movement-related peaks in firing rate were more dramatically affected, with an overall reduction in peak amplitudes of 40%. Bradykinesia was also associated with decreased intensity of bursting and amplitude of cross-correlation peaks at rest. The results show for the first time that significant reductions can be detected in motor cortex activity at rest in animals with impaired ability to generate movements induced by reduced dopamine action and confirm that impaired movements are associated with reduced cortical activation. Together, these changes in neural activity may reduce recruitment and rate modulation of motor units in the spinal cord.
This article outlines and assesses the main theories of the placebo effect and suggests how they might sit together in a larger model of placebo etiology. Among the approaches considered are expectancy theory, emotional change theory, classical conditioning, and the biological approach. Although these are sometimes assumed to be competing models, in many cases they shed light on different pans of the placebo puzzle. Expectancies are the core of most placebo effects in human beings. The effects of expectancies are sometimes unmediated but in other cases are mediated by changes in emotional state, immune system function, perception, or behavior. Although expectancies are implicated in most placebo effects, a small number of placebo effects may be solely attributable to nonconscious contingency learning.
There are an estimated 3.3 million boys and 1.8 million girls participating in interscholastic athletics. Although the preparticipation athletic examination (PAE) has traditionally focused on ensuring the health of the athlete, there has been growing interest in using the PAE to also screen adolescents for their involvement in health-threatening behaviors, such as smoking, drinking, drug use, and unsafe sexual practices. For 80% to 90% of adolescents, the PAE substitutes for a routine physical examination. Adolescent athletes may use alcohol and other drugs for three reasons: (1) They experiment with alcohol and other drugs as part of the larger youth culture. (2) They use ergogenic agents to enhance their athletic performance. (3) They use diuretic agents, emetic agents, or other excessive mechanisms to control weight. The American Medical Association concludes that administration of the PAE is an appropriate time to investigate involvement in health-risk behaviors and to provide adolescent health information.
Based on a national sample of over 16,000 public and private high school students (the 1997 Youth Risk Behavior Survey), we used logistic regression analysis to examine relationships among anabolic-androgenic steroid use and other problem behaviors for female and male athletes and nonathletes. After controlling for age, race/ethnicity, parental educational attainment, urbanicity, and recent exercise, users had significantly greater odds of engaging in other illicit drug, alcohol, and tobacco use, fighting, suicide attempts, sexual risk taking, vehicular risk taking, and pathogenic weight loss behavior, suggesting that steroid use is part of Jessor's problem behavior syndrome for adolescents. Despite the stereotypical images of the male athlete user, both nonathlete and female users also faced elevated risks of multiple drug use and other health-compromising behavior. Thus this study rejects the view of steroid use as merely a logical extension of the male athletic cultural imperative.
Identical experimental pain stimuli were applied to the right and left index fingers of 56 university students, following the application of a placebo in the guise of a topical anesthetic to one of the fingers The pain stimuli were administered simultaneously to treated and untreated fingers for half of the subjects and sequentially for the others Significant and equivalent reductions in pain were reported in both conditions as a function of placebo administration These data indicate that reductions of experimental pain produced by placebos presented in the guise of local anesthetics are not mediated by such global mechanisms as anxiety reduction or the release of endogenous opioids
Based on the authors' lifelong study and clinical research,
The Powerful Placebo is a comprehensive and scholarly examination of the placebo effect. The authors begin by surveying the use of placebos from antiquity to modern times. They also examine the development, use, and validity of the double-blind, controlled clinical trial. And they present their own study of the placebo effect in hundreds of patients.
Demonstrating both the magnitude and the limitations of the placebo effect, the book helps to clarify knotty issues ranging from the evaluation of therapies to the ethics of conducting controlled studies in which patients are deliberately given placebos. With the renewed interest in the mind–body relationship as well as in the role of placebos in new and alternative medical procedures and therapies, the findings of this book are timely. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Fifteen male varsity athletes were informed that some of them would be selected to receive an anabolic steroid (Dianabol). Instead, six selected subjects were given placebo pills. Taking the placebo apparently supplied the psychological inducement to increase strength gains above and beyond reasonable progression. Greater training gains were made during the placebo period in three out of four weight lifting exercises. The gains were statitsically significant when comparing the two regression lines for the pre-placebo and placebo periods.
(C)1972The American College of Sports Medicine
We review three possible theoretical mechanisms for the placebo effect: conditioning, expectancy and endogenous opiates and consider the implications of the first two for clinical research and practice in the area of pain management. Methodological issues in the use of placebos as controls are discussed and include subtractive versus additive expectancy effects, no treatment controls, active placebo controls, the balanced placebo design, between- versus within-group designs, triple blind methodology and the double expectancy design. Therapeutically, the possibility of shaping negative placebo responses through placebo sag, overservicing and the use of placebos on their own are explored. Suggestions for using conditioned placebos strategically in conjunction with nonplacebos are made and ways of maximizing the placebo component of nonplacebo treatments are examined. Finally, the importance of investigating the placebo effect in its own right is advocated in order to better understand the long-neglected psychological aspects of the therapeutic transaction.
The present article presents an integrative theoretical framework to explain and to predict psychological changes achieved by different modes of treatment. This theory states that psychological procedures, whatever their form, alter the level and strength of self-efficacy. It is hypothesized that expectations of per- sonal efficacy determine whether coping behavior will be initiated, how much effort will be expended, and how long it will be sustained in the face of ob- stacles and aversive experiences. Persistence in activities that are subjectively threatening but in fact relatively safe produces, through experiences of mastery, further enhancement of self-efficacy and corresponding reductions in defensive behavior. In the proposed model, expectations of personal efficacy are derived from four principal sources of information: performance accomplishments, vicarious experience, verbal persuasion, and physiological states. The more de- pendable the experiential sources, the greater are the changes in perceived self- efficacy. A number of factors are identified as influencing the cognitive processing of efficacy information arising from enactive, vicarious, exhortative, and emotive sources. The differential power of diverse therapeutic procedures is analyzed in terms of the postulated cognitive mechanism of operation. Findings are reported from microanalyses of enactive, vicarious, and emotive modes of treatment that support the hypothesized relationship between perceived self-efficacy and be- havioral changes. Possible directions for further research are discussed.
We review three possible theoretical mechanisms for the placebo effect: conditioning, expectancy and endogenous opiates and consider the implications of the first two for clinical research and practice in the area of pain management. Methodological issues in the use of placebos as controls are discussed and include subtractive versus additive expectancy effects, no treatment controls, active placebo controls, the balanced placebo design, between- versus within-group designs, triple blind methodology and the double expectancy design. Therapeutically, the possibility of shaping negative placebo responses through placebo sag, overservicing and the use of placebos on their own are explored. Suggestions for using conditioned placebos strategically in conjunction with nonplacebos are made and ways of maximizing the placebo component of nonplacebo treatments are examined. Finally, the importance of investigating the placebo effect in its own right is advocated in order to better understand the long-neglected psychological aspects of the therapeutic transaction.
Subjects were given varying doses of a placebo, consisting of decaffeinated coffee, with double-blind or deceptive instructions. Deceptive administration simulated clinical situations in that subjects were led to believe that they were receiving an active drug. In contrast, subjects in double-blind conditions were aware that they might receive a placebo. Double-blind and deceptive administration of the placebo produced different, and in some instances, opposite effects on pulse rate, systolic blood pressure, and subjective mood. Deceptive administration produced an increase in pulse rate, whereas double-blind administration did not. A theoretically predicted curvilinear effect on systolic blood pressure, alertness, tension, and certainty of having consumed caffeine was confirmed with deceptive administration, but not with double-blind administration. Double-blind administration produced curves in the opposite direction on each of these variables. The effects of the placebo on motor performance varied as a function of subject's beliefs about the effects of caffeine. These data challenge the validity of double-blind experimental designs and suggest that this common method of drug assessment may lead to spurious conclusions.
Statistical regression to the mean predicts that patients selected for abnormalcy will, on the average, tend to improve. We argue that most improvements attributed to the placebo effect are actually instances of statistical regression. First, whereas older clinical trials susceptible to regression resulted in a marked improvement in placebo-treated patients, in a modern series of clinical trials whose design tended to protect against regression, we found no significant improvement (median change 0.3 per cent, p greater than 0.05) in placebo-treated patients. Secondly, regression can yield sizeable improvements, even among biochemical tests. Among a series of 15 biochemical tests, theoretical estimates of the improvement due to regression by selection of patients as high abnormals (i.e. 3 standard deviations above the mean) ranged from 2.5 per cent for serum sodium to 26 per cent for serum lactate dehydrogenase (median 10 per cent); empirical estimates ranged from 3.8 per cent for serum chloride to 37.3 per cent for serum phosphorus (median 9.5 per cent). Thus, we urge caution in interpreting patient improvements as causal effects of our actions and should avoid the conceit of assuming that our personal presence has strong healing powers.
To examine whether manipulating self-efficacy affects strength performance on a bench press, and to see if these situation-specific changes would affect levels of physical self-efficacy, 24 undergraduates untrained in weightlifting were randomly assigned to three groups: 'light', who lifted less weight than they believed; 'heavy', who lifted more weight than they believed; and control, for whom there was no manipulation. Self-efficacy measures were taken before and after the manipulation. Physical self-efficacy was measured using the Physical Self-Efficacy Scale (PSE). 'Light' subjects lifted significantly greater increases in weight than the other subjects. 'Heavy' subjects significantly decreased self-efficacy following the manipulation. Initial self-efficacy was found to be a significant predictor of baseline maximum, while manipulated self-efficacy was significant for performance change. The PSE scores did not change pre- to post-study. The results suggest that self-efficacy is a situation-specific construct which can be manipulated, and which relates to both past performance experience and future performance.
Placebo is a widespread phenomenon in medicine and biology and its mechanisms are understood only partially. Most of our understanding of placebo comes from studies on pain. In particular, placebo analgesia represents a situation where the administration of a substance known to be non-analgesic produces an analgesic response when the subject is told that it is a pain killer. Several theories try to explain this effect by means of anxiety mechanisms, cognitive processes and classical conditioning. However, the placebo response is bidirectional, i.e. analgesic and algesic. In fact, if a subject is told that the ineffective substance is a hyperalgesic drug, a pain increase may occur. The negative effects of placebo are called nocebo and, in extreme cases, they lead to severe pathological conditions. The neurobiology of placebo was born when some authors discovered that placebo analgesia is mediated by endogenous opioids. This claim comes from the observation that the opioid antagonist naloxone can reverse placebo analgesia. On the basis of the discovery of the anti-opioid action of the neuropeptide cholecystokinin, recent studies demonstrate that the blockade of cholecystokinin receptors potentiates the placebo analgesic response, thus suggesting an inhibitory role of cholecystokinin in placebo analgesia. Thus, by antagonizing the anti-opioid action of cholecystokinin during a placebo procedure, a potentiation of the endogenous opioid systems can be obtained.
To determine, the prevalence of doping in sport as it was reported by the athletes during surveys, and to try to isolate risk factors to resort to doping.
Medline, Pascal and Embase search for the period from 1980 to 1996.
Of the 44 studies produced, 15 were not included in the detailed data summary because they reported statistical data from antidoping controls, they were not enough specific, or they concerned horse races.
Details of study design, drugs studied, prevalence. When available, were also noted: the sport practiced and the motives for doping.
Among children, doping prevalence in around 3-5%. Among adults, in self-reported use studies, doping prevalence may be estimated at 5-15%, where projected use studies report a mean prevalence near 15-25%. Studies provide few data about the sports that produce drug users.
The extent of sport doping and its potential risks for health must make it to be considered as a problem of public health. This means that physicians must, at last, consider it as any other problem and change their behaviour against doping, in order not to reduce the subject to the sole list of prohibited substances. As for sports federations, they must, as last, recognize that prevalence of doping is high. Lastly, new studies are essential to determine motives for doping and to institute the predictable factors for this practice, what will perhaps make efficient the prevention campaigns.
To examine the trends in anabolic steroid use among adolescents in the United States between 1988 and 1996.
Computerized and manual literature searches were performed, and the resultant local, state, and national cross-sectional surveys of illicit anabolic steroid use by adolescents were reviewed. Trends in steroid use were evaluated using state and national studies administered in multiple periods. Various sampling procedures were employed, and all surveys used anonymous questionnaires. The national studies used for this analysis included the Monitoring the Future (MTF) study, the national component of the Youth Risk and Behavior Surveillance System, and the National Household Survey on Drug Abuse.
Most of the surveys described were self-administered in school classrooms. The National Household Survey on Drug Abuse was administered in the respondent's home.
Most survey respondents were junior high an high school male and female students aged 12 to 18 years.
Individual state studies (ie, a single point in time) provide evidence of continued steroid use throughout the United States despite educational and legal interventions. The findings of multiyear state-level studies show a decrease in lifetime steroid use rates between 1988 and 1994 for male and female adolescents, although no tests of statistical significance were conducted. At the national level, a significant decline (P < .01) in lifetime steroid use has taken place from 1989 to 1996 for male and female students (MTF data). However, since 1991, lifetime steroid use by male students, as measured by 2 of the 3 national surveys, has been generally stable. The third survey, MTF, shows a significant decrease (P < .05) in use from 1991 to 1996. Likewise, from 1991-1996 use of anabolic steroids during the past year (MTF data) was stable for 10th and 12th grade males; use among eighth grade males decreased significantly (P < .01). Since 1991, data from the 3 national surveys indicate an increase in lifetime anabolic steroid use among adolescent females, although only 1 of these increases is statistically significant. Furthermore, past year use of steroids (MTF data) increased for females in the 8th (P < .05), 10th (P < .05), and 12th (ns) grades.
A long-term comparison of anabolic steroid use (from 1989-1996) indicates that use among adolescent males and females has decreased significantly (P < .05). However, for females the low point in lifetime steroid use was reached in 1991, with subsequent significant (P < .05) increases in use being reported in several national data sets. For adolescent males, after declining sharply between 1989 and 1991, steroid use has generally been stable since 1991. Moreover, based on the 1995 estimates of high school students and Youth Risk and Behavior Surveillance System data, approximately 375,000 adolescent males and 175,000 adolescent females in public and private schools in the United States used anabolic steroids at least once in their lives. These results suggest that prevention, intervention, and regulatory efforts to reduce steroid use at the local, state, and national levels should be reassessed, especially those efforts that focus on adolescent female steroid use.
An athlete may think that if a small amount of a chemical helps his or her performance, more will work better. The most appealing supplements are those that claim to help build muscle, improve endurance, and reduce body fat. Widespread acceptance of herbal of "natural" alternatives to mainstream medicine (especially nutritional supplements) is increasing, and the market is largely unregulated. The authors summarize the facts and fiction surrounding the use of popular products that may be found at the pharmacy and health food store that are being used in the locker rooms of high schools, colleges, and gyms in the U.S. They urge clinicians to stress the value of a well balanced diet to their active adolescent patients and not to encourage supplement use.
To examine the frequency, temporal development, and stability of objectively derived motor changes during placebo treatment in PD and to define the clinical domains and demographic groups most affected.
Placebo effects are documented in neurology, but the timing and specific disabilities most susceptible to changes during placebo treatment in PD have not been examined.
The authors examined the placebo-treated group from a randomized, multicenter, placebo-controlled clinical trial of monotherapy ropinerole in PD patients without motor fluctuations. In 105 patients, they evaluated placebo-associated effects on the motor section of the Unified Parkinson's Disease Rating Scale (UPDRS), dividing the motor examination into four categories: tremor, bradykinesia, rigidity, and gait/balance/midline functions. The motor UPDRS and its subscales were compared over time (at baseline and at 4, 12, and 24 weeks) using Wilcoxon's signed rank test. They applied a rigorous definition of placebo-associated improvement as an improvement over baseline score in motor UPDRS of at least 50% or a change in at least two motor items at any one visit by > or =2 points.
During the 6-month study, 16% of subjects improved on placebo treatment. The prevalence of response was steady (8 to 9%) at any one visit without a predominance of an early effect. No patient showed a placebo-associated improvement on all visits. All domains of parkinsonian disability were subject to placebo-associated improvement, with a trend toward more response in bradykinesia and rigidity than in tremor or gait/balance/midline function. Gender, age, disease duration, and baseline disability score did not influence the likelihood of improvement in association with placebo treatment.
Based on a rigorous definition of placebo-associated improvement, prominent improvements in objective measures of PD disability occur during clinical trials. Because placebo-associated improvements occur throughout a 6-month trial, placebo-controlled studies in PD should be at least 6 months to capture early as well as late improvements.
To identify risk factors associated with anabolic-androgenic steroid (AAS) use among adolescents, computerised and manual literature searches were performed and the resultant local, state, national and international reports of illicit AAS use by adolescents that referenced risk factors were reviewed. Results indicate that adolescent AAS users are significantly more likely to be males and to use other illicit drugs, alcohol and tobacco. Student athletes are also more likely than non-athletes to use AAS, and football players, wrestlers, weightlifters and bodybuilders have significantly higher prevalence rates than students not engaged in these activities. Currently, only a partial profile can be created to characterise the adolescent AAS user. Further research will be needed before associations can be made with a reasonable degree of confidence regarding risk factors such as athletic participation, ethnicity, socioeconomic status and educational level. More importantly, to improve prevention and intervention strategies, a better understanding of the process involved in initiating AAS use is needed, including vulnerability factors, age of initiation and the use of other illicit drugs.
Force and electromyographic (EMG) activity of the biceps and triceps brachii were measured in 15 strength-trained men during maximal isometric action of the forearm flexors, with the elbow at 90 degrees, following 20-s periods of psyching (PSY), reading aloud (RA), and mental arithmetic (MA). Perceived arousal and attentional focus ratings for PSY were greater than those obtained for RA and MA, which were undifferentiated. Perceived effort, biceps and triceps EMG, and maximal force did not differ across conditions. Therefore, in highly trained men under conditions of brief exertion, when the biomechanics of the muscular action were controlled, psyching resulted in a perception of enhanced readiness but did not influence force or muscular activation differently from psychological states that were preceded by distraction.
"Ergogenic aid" is defined as any means of enhancing energy utilization, including energy production, control, and efficiency. Athletes frequently use ergogenic aids to improve their performance and increase their chances of winning in competition. It is estimated that between 1 and 3 million male and female athletes in the United States alone have used anabolic steroids. In response to the problem of drug use, many athletic organizations have established policies prohibiting the use of certain pharmacologic, physiologic, and nutritional aids by athletes and have implemented drug testing programs to monitor compliance. Therefore, it is important for physicians to be knowledgeable about the available ergogenic aids so they can appropriately treat and counsel the athletic patient.
Intense debate persists about the need for placebo-controlled groups in clinical trials of medications for major depressive disorder (MDD). There is continuing interest in the development of new medications, but because effective antidepressants are already available, ethical concerns have been raised about the need for placebo groups in new trials.
To determine whether the characteristics of placebo control groups in antidepressant trials have changed over time.
We searched MEDLINE and PsychLit for all controlled trials published in English between January 1981 and December 2000 in which adult outpatients with MDD were randomly assigned to receive medication or placebo. Seventy-five trials met our criteria for inclusion.
Data were extracted from the articles by 2 of the authors and discrepancies were resolved via discussion and additional review by a third author.
The mean (SD) proportion of patients in the placebo group who responded was 29.7% (8.3%) (range, 12.5%-51.8%). Most studies examined more than a single active medication, and, in the active medication group with the greatest response, the mean (SD) proportion of patients responding was 50.1% (9.0%) (range, 31.6%-70.4%). Both the proportion of patients responding to placebo and the proportion responding to medication were significantly positively correlated with the year of publication (for placebo: n = 75; r = 0.45; 95% confidence interval [CI], 0.25-0.61; P<.001; for medication: n = 75; r = 0.26; 95% CI, 0.03-0.46; P =.02). The association between year of publication and response rate was more statistically robust for placebo than medication.
The response to placebo in published trials of antidepressant medication for MDD is highly variable and often substantial and has increased significantly in recent years, as has the response to medication. These observations support the view that the inclusion of a placebo group has major scientific importance in trials of new antidepressant medications and indicate that efforts should continue to minimize the risks of such studies so that they may be conducted in an ethically acceptable manner.
Social foundations of thought and action: A social cognitive theory The neurobiology of placebo analgesia: From endogenous opioids to cholecystokinin