The effects of carbohydrate and caffeine on self-paced intermittent exercise

The aim of this study was to examine the effect of adding caffeine to a carbohydrate electrolyte drink during a modified Loughborough Intermittent Shuttle Test (LIST), which incorporates an element of self-pacing (Part B). Ten recreationally active (age 21.8 ± 1.5 years, stature 183.9 ± 5.5 cm, mass 86.1 ± 5.9 kg, estimated VO2max 48.5 ± 3.4 ml/kg•min-1) team sport players performed three trials of the modified LIST. Each participant performed the LIST (single blind) after ingesting carbohydrate (CHO, 6.4 %) only, caffeine (CAF, 4 mg/kg/BM) only, or carbohydrate with caffeine (CHO+CAF, 6.4 % + 4 mg/kg/BM) in a volume of 5 ml/kg/BM one hour prior to testing and 2 ml/kg/BM after every 15 minute block. Movement demands and heart rate were measured using GPS, with physiological (Countermovement jumps, Blood lactate) and perceptual (RPE, gut fullness) measures being taken throughout. Analysis indicated no significant differences between trials (P > 0.05) therefore, effect sizes (Cohen, 1977) were used to detect possible differences between variables. During block 6, participants covered more distance (d = 1.60), sprinted faster (d = 0.23), and had a faster average speed (d = 0.48) in the CHO+CAF trial as opposed to the CHO trial (P > 0.05). Participants clearly engaged in separate pacing profiles throughout both parts of the LIST. Although effect sizes indicated some notable differences, it was concluded that the addition of CAF to CHO did not provide any significant (P < 0.05) ergogenic benefits compared with ingestion of CAF or CHO alone