Affiliations: [a] University Outpatient Clinic Potsdam, University of Potsdam, Potsdam, Germany | [b] Department of Computer/Therapy Science, Trier University of Applied Sciences, Trier, Germany
Correspondence:
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Corresponding author: Mina Khajooei, University of Potsdam, %****␣ies-27-ies182206_temp.tex␣Line␣25␣**** Am Neuen Palais 10, 14469 Potsdam, Germany. Tel.: +49 331 977 4916; Fax: +49 331 977 1296; E-mail: khajooei@uni-potsdam.de.
Abstract: BACKGROUND: Compensating unstable situations is an important functional capability to maintain joint stability, to compensate perturbations and to prevent (re-)injury. Therefore, reduced maximum strength and altered neuromuscular activity are expected by inducing instability to load test situations. Possible effects are not clear for induced instability during maximum legpress tests in healthy individuals. OBJECTIVE: To compare isokinetic legpress (LP) strength and lower-leg muscle activity using stable (S) and unstable (UN) footplates. METHODS: 16 males (28 ± 4 yrs, 179 ± 7 cm, 75 ± 8 kg) performed five maximum LP in concentric (CON) and eccentric (ECC) mode. The maximum force (Fmax) and muscle activity were measured under conditions of S and UN footplates. The tested muscles comprised of the tibialis anterior (TA), peroneus longus (PL) and soleus (SOL) and their activity were quantified against the MVIC of each muscle respectively. RESULTS: The main finding revealed a significant reduction in Fmax under UN condition: 11.9 ± 11.3% in CON and 23.5 ± 47.8% in ECC (P< 0.05). Significant findings were also noted regarding the RMS derived values of the EMG of PL and TA. CONCLUSION: Unstable LP reduced force generation and increased the activity of PL and TA muscles which confirmed greater neuromuscular effort to compensate instability. This may have some implications for resistance testing and training coupled with an unstable base in the prevention and rehabilitation of injury to the neuromusculoskeletal system.
