Biomechanical and Neuromuscular Comparison of Horizontal and Vertical Squat Jumps

ABSTRACT: Trama, S, Macchi, R, Pâris, B, Bertin, D, Regnaud, J, Nicol, C, and Hays, A. Biomechanical and neuromuscular comparison of horizontal and vertical squat jumps. J Strength Cond Res XX(X): 000-000, 2026-Compared with the vertical squat jump (VSJ), the horizontal squat jump (HSJ) offers a safer alternative, as the jumper performs it while lying down, which also eliminates landing impact. The aim of this study was to investigate the mechanical outputs from each test, with the potential to guide future applications in training and rehabilitation programs. Sixteen male athletes performed VSJ at body mass (BM) and HSJ on a frictionless sled at 0, 20, 40, 60, 80, and 100% BM. Force plates and linear encoders were used to measure peak force/BM, mean force/BM, mean net force, net impulse, rate of force development (RFD/BM), time to peak force, velocity at takeoff (Vto), mean linear velocity (Vmean), peak power/BM, and push-off distance (Hpo). Hip, knee, and ankle angular velocities were recorded in parallel with the surface electromyographic (EMG) activity of 7 lower-limb muscles. All HSJ conditions showed lower Vto, Vmean, and peak power/BM than VSJ (p < 0.001), mainly due to a shorter Hpo (p < 0.001). In terms of force production, HSJ had higher values for mean net force, RFD/BM, Fmax/BM (40-100% BM), and Fmean/BM (80-100% BM) than VSJ (p < 0.05). Regardless of the load, the slope of EMG activity of all lower-limb extensors increased more sharply in the HSJ than in the VSJ, particularly for the gluteus maximus (GMax). In rehabilitation or training contexts, the HSJ should be prioritized to enhance explosive strength and motor unit recruitment, whereas the VSJ may be more suitable for improving force production at higher velocities than in the HSJ. In addition, the HSJ appears to be a promising exercise for activating the GMax.