Strength & Conditioning

Document Type



Instability resistance training (RT) or exercising within an unstable environment is a popular training modality and frequently used in training, rehabilitation and prevention settings. Yet, due to the reported reduced force output during exercising within unstable condition, instability RT is said to lack the necessary overload to induce meaningful effects. However, empirical evidence of interventions suggests otherwise. The aim of this study was to systematically analyse instability RT vs. stable RT and discuss potential mechanisms. Therefore, we analysed squats within unstable and stable environments and calculated transversal and vertical forces. Greater transversal plane ground reaction forces were observed while performing squats on the unstable surface (p = .013; d = 1.88, CI-95% [0.33, 3.39]). In contrast, vertical force output remained similar for both conditions (p = .764; d = 0.14, CI-95% [-0.77, 1.02]).