Keywords

Open-label placebo; maximal voluntary isometric contraction; neuromuscular fatigue

Abstract

Placebo treatments have long been used to study the psychological effects of expectancy and conditioning on an inert intervention. Interestingly, open-label placebo treatments (i.e., directly telling subjects they are receiving an inactive intervention) have recently shown promise in minimizing pain in clinical patient populations. We utilized a repeated measures design to examine the acute effects of placebo, open-label placebo, and control treatments on muscle strength and voluntary activation (Experiment #1), as well as neuromuscular fatigue (Experiment #2). Twenty-one untrained males (n=11) and females (n=10) visited the laboratory on three occasions to receive each treatment in a randomized, counter-balanced manner. All visits involved a pretest, 15-minute intervention period, and posttest. In Experiment #1, knee extensor maximal voluntary isometric contraction (MVIC) peak torque and percent voluntary activation were evaluated. In Experiment #2, subjects performed 20, six-second MVICs while surface electromyographic signals were detected from the vastus lateralis. Subjective assessments of energy and perceived exertion were also examined. In Experiment #1, no differences among interventions were demonstrated for peak torque or voluntary activation, but a main effect revealed that energy levels increased following each treatment (p = .016, η2 = .257). Experiment #2 demonstrated that placebo and open-label placebo treatments had no influence on neuromuscular fatigue, but there were main effects for declines in absolute (p = .001, η2 = .675) and normalized peak torque (p = .001, η2 = .765), electromyographic mean frequency (p = .001, η2 = .565), neuromuscular efficiency (p = .001, η2 = .585), and energy levels (p = .006, η2 = .317). Collectively, placebo and open-label placebo treatments had minimal influence on strength, voluntary activation, and fatigue resistance in untrained subjects. We speculate that our subject population and study design intricacies that are unique to placebo trials may explain our findings.

Notes

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Graduation Date

2018

Semester

Summer

Advisor

Stout, Jeffrey

Degree

Master of Science (M.S.)

College

College of Education and Human Performance

Department

Educational and Human Sciences

Degree Program

Sport & Exercise Science

Format

application/pdf

Identifier

CFE0007254

URL

http://purl.fcla.edu/fcla/etd/CFE0007254

Language

English

Release Date

August 2021

Length of Campus-only Access

3 years

Access Status

Masters Thesis (Open Access)

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