Electrical stimulation in soccer players

The objective of this study is to assess the efficacy and safety of NeuroMuscular Electrical Stimulation (NMES) program applied in soccer players - 6 months after anterior cruciate ligament (ACL) reconstruction - on the quadriceps muscle. The primary study endpoint is comparison of the change in muscle strength between the stimulated and control group. The secondary end point is the analysis between groups of the change of quadriceps muscle circumference and other measured parameters as predictors of safety (whether are any pathological changes in knee function) after NMES therapy. Intevention: NMES procedure is on both right and left quadriceps (two electrodes on the muscle attachment sites). A portable electrical stimulator delivers biphasic symmetric rectangular pulses (frequency of impulses 2500 Hz, train of pulses frequency 50 Hz). The stimulus output is interrupted every 10 ms to create “bursts” of stimulation every second. The 10 ms off period is not detectable by the subject. A total of 10 maximal contractions sustain for 10 seconds each, with a 50 second off time defined a treatment session. The intensity is between 55 to 67 mA. Stimulation is performed with a current which produced strong, visible motion effects. Electrodes are made of conductive carbon rubber (8 x 6 cm). Before application of electrodes the skin is cleaned in use of alcohol. The total time of single procedure is 30 minutes. Quadriceps is stimulated at 60 degree of knee flexion. The procedures are repeated three times daily (3 hours break between treatments), 3 days a week (Tuesdays, Thursdays and Saturdays), for one month. All procedures are administered by a physiotherapist in sports clinic. The measurements: 1. Measurements of muscle strength is performed by a tensometer, composed of resistance lever, roller and electronic momentum meter. The spectrum of measurement is between 0 and 500 Newton meters [Nm]. The magnitudes of force moment are converted into Newtons [N]. The tested legs are at 60 degrees of knee flexion. 2. Change of muscle circumference is measured by a “tailor tape” 10 cm above the patella on the quadriceps. The measurements are performed before and after experiment (the measurements are in a supine position before first and after the last NMES procedure). 3. The goniometry pendulum test is composed of a peripheral device and a personal computer with software. The peripheral device consisted of a goniometry compass and an interface system – transducer cooperate with the computer. The goniometry compass is composed of two thin metal arms. One of the arms (immobile) is fixed in a special outlet that allowed for changing the angle and length. The mobile arm is connected to the athlete’s leg. The motion of the compass is measured by a mini – optoelectronic transducer. The position of the transducer is measured (with a resolution of 12 bytes [B] on one revolution) and coded in a range from 0 to 360 degrees (exact to 0.088) The signal is transmitted to the interface. The software allow readings of 100 positions of the compass per second. Using the pendulum test, the spectrum (range) and ease of motion in knee (whether the movement was smooth, physiological and free in examined axis) are measured and determined the following parameters: n – number of oscillations, t – whole time of oscillations, T – period of oscillations (T=t/n), lambda – logarithm decrement of suppression (lambda=ln X2/X4, where X2 is a second amplitude during oscillations and X4 is a fourth amplitude during oscillations, beta – suppression index (beta= lambda/T). The number of oscillations (n) and whole time of oscillations (t) describe the ease of knee motion. The period of oscillations (T) and suppression parameters (lambda and beta) assess the spectrum of knee motion. The goniometry pendulum test is performed for analysis of NMES safety (to assess whether an increase in muscle mass and strength will change in the mechanics of the knee joint).