Acute Effects of Partial Range of Motion Resistance Training and Increases in Blood Lactate Impact Accuracy of Penalty Kicks in Soccer Players

Abstract

The purpose of this investigation was to assess the acute effects of partial range of motion (pROM) exercises, on the accuracy of soccer penalty kicks on goal. This method limits the joint from moving through the complete length of a motion, creates an occlusion effect, and thus causes the type 1 muscle fibers to work anaerobically. Thirty-six soccer players, with 5-8 years of soccer playing experience, were pretested for accuracy then retested ( $\text{rtt}=0.92$ ) and divided into random groups from the Associação Banco do Brasil Futebol Clube—Group A, Paraná Futebol Clube—Group P, and Coritiba Futebol Clube—Group C. Groups were composed of 12 people performing full range of motion (fROM) exercises or pROM exercises. Both groups performed 5 sets of back squats at 50% of body weight in sets of 40 seconds with metronome tempo of 56 bpm for an average of 10-12 repetitions per 40-second set. Blood samples were collected post-warm-up, after the 3rd set, and following the 5th set for both groups, within 3–5 minutes of cessation of exercise. Athletes performing fROM exercises showed increased blood lactate from $2.69\pm 0.2$ to $4.0\pm 1.2$  mmol/L ( $p<0.05$ ), and in pROM, blood lactate increased from $2.48\pm 0.42$ to $10.29\pm 1.3$  mmol/L ( $p<0.001$ ). In fROM, accuracy decreased from $42.96\pm 13.39$ % to $41.37\pm 17.25$ % ( $p>0.1$ ), a slight decrease, while in the pROM groups, accuracy decreased from $45.42\pm 14.93$ % to $24.53\pm 10.2$ % ( $p<0.001$ ). The calculations demonstrating average percentages of accuracy are presented in the tables. These findings support that pROM exercises significantly increase blood lactate resulting in a reduction in soccer kick accuracy. This decrease in accuracy directly correlates to the accumulation of lactic acid and hydrogen ions (H+) and demonstrates that pROM strength training should not be utilized prior to a sport-specific session in order to avoid interference with the development of special skills.