Author(s): MAROCOLO, M., FERRAUTI, A., MONTEIRO, L.O.S., OLIVEIRA, G.T., MEIRELES, A., ARRIEL, R.A., HOHL, R., HURST, P., SOUZA, H.L.R., Institution: FEDERAL UNIVERSITY OF JUIZ DE FORA, Country: BRAZIL, Abstract-ID: 383

INTRODUCTION:
The placebo effect refers to positive changes in outcomes following the administration of a placebo, while the nocebo effect pertains to negative changes. Ischemic preconditioning (IPC) involves intermittent blood occlusion followed by reperfusion of skeletal muscle, performed either before or after exercise or test. The mechanism for its purported benefit is questioned, with many have reporting that changes in performance are the result of placebo effects (1-2). Given that one major factor mediating placebo and nocebo effects is the expectation evoked after receiving an intervention (3), we investigated the placebo effect associated with IPC. This was accomplished by manipulating subjects expectations following the application of a sham-IPC intervention.
METHODS:
Thirty-five healthy men, experienced in resistance exercise (RE), were randomly assigned to one of the following conditions: positive (POS), negative (NEG), or no verbal manipulation (CON). No participants reported prior pneumatic cuff experience. In the 1st and 2nd visit a familiarization with maximal voluntary isometric contraction (MVIC), lower limb muscle power output, and 10RM test and retest were performed. On the 3rd visit, three maximum sets with a 10RM load were performed, representing the baseline moment. Finally, on the 4th visit, sham-IPC with either POS, NEG or CON manipulations preceded performance tests. All tests were performed unilaterally, on the subjects dominant limb. The sham-IPC intervention consisted of 3 cycles of 5-minute cuff administration (positioned on the proximal region of thigh) set at 20 mmHg of the subjects, followed by 5 minutes of "pseudo-reperfusion" at 0 mmHg, totaling 30 minutes of intervention. The CON intervention involved no cuff application, while subjects remained in a supine rest position for 30 minutes.
RESULTS:
Differences were observed for the number of repetitions (POS: 29.6±4.0; NEG: 24.9±4.4; CON: 26.9±2.7; p=0.019), whereby those who received positive information about IPC, significantly improved than those who received negative-information (p=0.01; ES: 1.11). No changes in MVIC peak force were found between groups (POS: 646.6±81.9; NEG: 642.3±90.9; CON: 599.5±56.5 N; p=0.06), and peak muscle power was similar across all groups (POS: 531.4±99.0; NEG: 632.7±111.1; CON: 538.5±69.4 W; p=0.11).
CONCLUSION:
The use of sham-IPC cuff intervention linked to positive or negative manipulation, influenced the maximum number of repetitions during a leg-extension task. Our results have important implications for researchers measuring participant expectations about their intervention, which can significantly influence performance outcomes.
REFERENCES:
(1) Souza, et al. 10.1371/journal.pone.0250572;
(2) Marocolo, et al. 10.1007/s00421-022-05109-9;
(3) Brietzke, et al. DOI:10.1007/s00421-022-05029-8
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