Vibrational-proprioceptive Resistance Exercise Training Versus Neuromuscular Electrical Stimulation Training in Elderly People With Muscle Weakness

Inclusion Criteria: * age related muscle weakness * age between 65-85 years * all inclusion criterias must be fullfilled Exclusion Criteria: * recent hip or knee endp-prosthesis (within last 2 years), longstanding immobility * body mass index greater than 40 * acute thrombosis in lower extremity (within last 3 weeks) * severe articular effusion * acute infection * known myopathy * relevant neurological diseases with gait disorders (e.g. poly neuropathy, Parkinson's disease) * dementia, impaired cognitive abilities * diseases of the vestibular system causing vertigo or impairing balance * symptomatic cardio pulmonal diseases within the last 6 months * not or insufficient treated hypertonia * rheumatic diseases * other relevant functional impairment of the musculo-skeletal system caused by surgery, trauma or degenerative diseases * pain in the lower extremity (VAS \> 5) * if one of the above criteria applies the subject will be excluded from the study