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Do Motivational Placebo Cues Influence Resistance Training Adaptations?
Roberto Moriggi Júnior1, Denis Fabrício Valério1, Felipe Damas1
1Universidade Estadual de Campinas, School of Physical Education, Department of Sport Sciences, Campinas, Brazil.
Perceptual and Motor Skills
|March 19, 2026
Summary
External motivational feedback did not enhance resistance training outcomes. This study found no placebo effect on muscle strength or lean mass gains in untrained individuals following a 14-week program.
Area of Science:
- Exercise Physiology
- Sports Science
- Psychobiology
Background:
- The placebo effect influences physical performance, but its role in resistance training (RT) outcomes is understudied.
- Few investigations explore placebo effects on RT-induced muscle strength and mass.
- Understanding placebo effects can optimize training interventions.
Purpose of the Study:
- To investigate if external motivational feedback strategies influence RT effectiveness.
- To determine if a placebo effect enhances muscle strength and lean mass gains in untrained individuals.
- To analyze the impact of motivational feedback on RT adaptations.
Main Methods:
- Thirty-one untrained volunteers participated in a 14-week RT program.
- Participants were divided into a PLACEBO group (with feedback) and a N-PLACEBO group (without feedback).
- Muscle strength (1RM) and lean mass (DEXA) were measured pre- and post-training.
Main Results:
- Both groups showed significant increases in 1RM strength and lean mass over time (p < 0.001).
- No significant group-by-time interaction was observed for strength or lean mass.
- External motivational feedback did not lead to additional gains compared to the control group.
Conclusions:
- External motivational feedback strategies did not augment RT-induced muscle strength or lean mass gains.
- No placebo effect was detected for the measured outcomes in this study.
- Motivational strategies may not be sufficient to enhance RT adaptations in untrained populations.
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