Correlation Between Cardiopulmonary Metabolic Cost and Lower Limb Muscle Activity

Inclusion Criteria: * Between 65 and 84 years elderly without neurological effects * Ability to independent gait at least 16% inclined treadmill * High levels of physical performance (SPPB \> 7) Exclusion Criteria: * Severe visual impairment or dizziness that increases the risk of falls * Serious cardiac conditions (hospitalization for myocardial infarction or heart surgery, history of congestive heart failure, documentedserious and unstable cardiac arrhythmias, hypertrophic cardiomyopathy,severe aortic stenosis, angina or dyspnea at rest or during activities ofdaily living) * Difficult to understand experimental tasks because of extremely severe cognitive impairment * Recent acute injuries such as fractures within 6 months, or experience in orthopedic surgery such as artificial joint replacement * Acute injuries such as fractures within 6 months or orthopedic surgery such as artificial joint replacement