EFFECTS OF PRE-EXERCISE CAFFEINE SUPPLEMENTATION ON THE PSYCHOPHYSIOLOGICAL RESPONSES TO HIGH-INTENSITY INTERVAL TRAINING: A SINGLE-SUBJECT RANDOMIZED EXPERIMENT

EFFECTS OF PRE-EXERCISE CAFFEINE SUPPLEMENTATION ON THE PSYCHOPHYSIOLOGICAL RESPONSES TO HIGH- INTENSITY INTERVAL TRAINING: A SINGLE-SUBJECT RANDOMIZED EXPERIMENT ABBATE, S., MARCORA, S.M. ALMA MATER STUDIORUM - UNIVERSITÀ DI BOLOGNA INTRODUCTION: Caffeine is well known to reduce perceived effort in athletes, but its effects in unfit people are not clear and may not be as pronounced [1]. This single-subject randomized controlled study aimed to preliminarily investigate the effects of pre-exercise caffeine supplementation on perceived effort, affective valence and enjoyment in unfit adults partic- ipating in high-intensity interval training (HIIT) to improve their cardiorespiratory fitness. METHODS: An unfit adult female (baseline VO2max 26 ml/kg/min) participated in a single-subject randomized experi- ment involving two conditions: caffeine supplementation (3 mg/kg) 60 min prior to exercise and a placebo condition. The participant visited the lab for: a) Baseline VO2max test, b) Three HIIT sessions for familiarization, c) Eight HIIT sessions (4 caffeine, 4 placebo in random order), d) Follow-up VO2max test. The HIIT protocol consisted of uphill walking on a tread- mill with 4 min at 85% VO2max followed by 3 min at 55% VO2max repeated four times (4 x 4 protocol). During exercise, the participant was asked to rate her perceived exertion (6-20 RPE scale) and affective valence (Feeling Scale, FS). Heart rate (HR) was continuously recorded with a HR monitor. Enjoyment was measured after each HIIT session with the Physical Activity Enjoyment Scale (PACES). Randomization tests [2] were used to assess for mean differences between the Caffeine and Placebo conditions. Data are presented as mean + SD of the values recorded at the end of the 4th interval (HR, RPE, FS) or after exercise (PACES). Statistical significance was set at p < 0.05. RESULTS: After 5 weeks of training, VO2max increased to 29 ml/kg/min. Pre-exercise caffeine supplementation did not have a significant effect on HR (Caffeine 173 + 2 vs Placebo 172 + 1 beats/min, p > 0.05) but significantly reduced RPE (Caffeine 16.5 + 0.4 vs Placebo 17.3 + 0.5 a.u., p < 0.05). Caffeine also increased the FS score (Caffeine -1.3 + 0.5 vs Place- bo -3.0 + 0.9 a.u., p < 0.05) and the PACES score (Caffeine 55.8 + 2.9 vs Placebo 47.3 + 5.0 a.u., p < 0.05). Discussion: These findings provide preliminary evidence that pre-exercise caffeine supplementation can make vigorous exercise feel less effortful and more pleasant while maintaining the same level of physiological intensity in an unfit adult subject. If replicated in a large randomized controlled trial, these beneficial psychological effects of pre-exercise caffeine supplementation may result in improved adherence to HIIT programs that are highly effective in improving cardiorespira- tory fitness and metabolic health but challenging from a motivational point of view. References 1. Doherty M, Smith PM. Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a me- ta‐analysis. journal of medicine & science in sports. 2005. 2. Dugard P, File P, Todman J, Todman JB. Single-case and Small-n Experimental Designs: A Practical Guide to Randomi- zation Tests, Second Edition. Routledge; 2012.