Effects of a Motion-Triggered Neuromuscular Electrical Stimulation Strength Program on Shoulder Strength and Throwing Velocity in Elite Handball Players

Abstract

Background: To evaluate the effects of a motion-triggered neuromuscular electrical stimulation (NMES) shoulder strengthening program on rotational shoulder strength and throwing velocity in healthy, elite-level handball players. Methods: Fourteen male handball players were randomly allocated (1:1) to either the NMES or control group. Participants were assessed by a blinded investigator at baseline and after 6 weeks for clinical status, isometric dynamometer-based external (ER) and internal rotational (IR) maximal shoulder strength, and handball endurance and maximal throwing velocity (7 m free throw). Between time points, NMES subjects completed a standardized motion-triggered NMES shoulder strengthening program (3 sessions/week, 30 min for 6 weeks), whereas controls performed a conventional standardized strength program. Results: After completion of the motion-triggered NMES program, all NMES participants (100%) demonstrated significant gains in isometric ER strength (+1.4 ± 1.1 kg, p = 0.016) compared with 43% of controls, who demonstrated no overall improvement (-0.2 ± 1.8 kg, p = 0.740). Similarly, a significantly greater proportion of NMES participants improved endurance throwing velocity compared with controls (100% vs. 29%, p = 0.004), with a mean increase of +2.9 ± 2.8 km·h^-1 (p = 0.0.56). Maximum throwing velocity showed no between-group differences in the proportion of athletes with improved results (p = 0.899). Conclusions: A six-week motion-triggered NMES shoulder strengthening program improved external rotation strength and increased the proportion of athletes demonstrating enhanced endurance throwing velocity under fatigued conditions. However, when compared with conventional exercise alone, NMES did not confer additional benefits for maximal throwing velocity in this study. Therefore, NMES should be regarded as a complementary modality rather than a substitute for established shoulder strengthening exercises.

Keywords: athletic performance; motor control; shoulder instability.

Figure 1

Handball throwing velocity testing setup. A player performing an overhead throw from behind the 7 m free-throw line (black arrow). The radar gun (gray arrow) was positioned behind the net to record the throwing velocity.

Figure 2

Isometric hand-held dynamometer external and internal rotation maximal shoulder strength testing setup. Participants were positioned supine with 90° shoulder abduction and 90° elbow flexion. The hand-held dynamometer was fixed to the goal post (gray arrow) to measure maximal (A) external and (B) internal rotational shoulder strength.

Figure 3

Shoulder pacemaker electrode placement. Electrodes were positioned as specified by the manufacturer: electrode 1, inferior to the spina scapulae (stimulating the infraspinatus, teres minor, and posterior deltoid) and electrode 2, medial to the scapula border (stimulating the lower trapezius and rhomboids).