Neuromuscular Performance of Explosive Power Athletes versus Untrained Individuals

TILLIN, N. A., P. JIMENEZ-REYES, M. T. G. PAIN, and J. P. FOLLAND. Neuromuscular Performance of Explosive Power Athletes versus Untrained Individuals. Med. Sci. Sports Exerc., Vol. 42, No. 4, pp. 781-790, 2010. Purpose: Electromechanical delay (EMD) and rate of force development (RFD) are determinants of explosive neuromuscular performance. We may expect a contrast in EMD and RFD between explosive power athletes, who have a demonstrable ability for explosive contractions, and untrained individuals. However, comparison and the neuromuscular mechanisms for any differences have not been studied. Methods: The neuromuscular performance of explosive power athletes (n = 9) and untrained controls (n = 10) was assessed during a series of twitch, tetanic, explosive, and maximum voluntary isometric knee extensions. Knee extension force and EMG of the superficial quadriceps were measured in three 50-ms time windows from their onset and were normalized to strength and maximal M-wave (M-max), respectively. Involuntary and voluntary EMD were determined from twitch and explosive voluntary contractions, respectively, and were similar for both groups. Results: The athletes were 28% stronger, and their absolute RFD in the first 50 ms was twofold that of controls. Athletes had greater normalized RFD (4.86 +/- 1.46 vs 2.81 +/- 1.20 MVC.s(-1)) and neural activation (mean quadriceps, 0.26 +/- 0.07 vs 0.15 +/- 0.06 M-max) during the first 50 ms of explosive voluntary contractions. Surprisingly, the controls had a greater normalized RFD in the second 50 ms (6.68 +/- 0.92 vs 7.93 +/- 1.11 MVC.s(-1)) and a greater change in EMG preceding this period. However, there were no differences in the twitch response or normalized tetanic RFD between groups. Conclusions: The differences in voluntary normalized RFD between athletes and controls were explained by agonist muscle neural activation and not by the similar intrinsic contractile properties of the groups.