CARBOHYDRATE SUPPLEMENTATION FAILS TO REVERT THE EFFECT OF ENDURANCE EXERCISE ON SUBSEQUENT STRENGTH EXERCISE PERFORMANCE

Abstract

Previous studies indicated that endurance exercise might have an adverse effect on subsequent strength exercise performance. The decrease in strength performance might be related to the changes promoted by endurance exercise in energy metabolism. PURPOSE Our aim was verify if carbohydrate (CHO) feeding can attenuate the effects of endurance exercise on strength development. METHODS Six female university students (164±2.5cm;64.9±4.4kg) with strength training experience were submitted to a VO2max test (44±1.9ml.min−1) and an 1-RM test in the leg press (186±9.8kg) followed by a maximum repetitions test (2 sets of leg press exercise performed at 70% of 1-RM value until exhaustion, 1st set 21±1.2 reps and 2nd set 11±0.9 reps) in different days. In a double-blind design, the subjects were submitted to 2 different trials, receiving placebo (P) or CHO beverages (1L of P or 6% CHO solutions), 60 min before (500ml) and during (500ml) endurance exercise bout. These bouts were performed in a treadmill at 70% of VO2max for 45 minutes. Subsequently, the subjects performed an 1-RM test followed by a maximum repetitions test. RESULTS No changes were observed in 1-RM test. There was a similar decline in maximum repetitions test (an index of muscular endurance) in both trials (P- 1st set 13±1.6 reps and 2nd set 6±0.9 reps CHO- 1st set 15±1.2 reps and 2nd set 7±0.8 reps, P < 0.05). CONCLUSIONS In the 1-RM test, the additional participation of fast-twitch fibers IIa and IIb might overcome the effect of endurance exercise, thus contributing to the lack of alteration in this parameter. Muscular endurance tasks relied in the recruitment of slow- twitch fibers, we believe that the decrease seen in maximum repetitions test was due to a reduction of muscle glycogen in these fibers induced by endurance exercise. No differences were observed in glycaemia in both trials, suggesting a greater participation of intramuscular substrates. In conclusion, CHO supplementation was inefficient to revert the deleterious effect of endurance exercise on maximum repetitions test.