Muscle power training has proven to be an effective intervention to prevent sarcopenia and frailty in old people. In the last decade, new concepts related to the functionality of old people have been generated, such as muscle quality and functional capacity.

The power training consists of rapid movements of short duration that imply a more specialized neuromuscular response and that improve the functional response reflected in activities of daily life that demand a certain manifestation of muscular power (stand up of a chair, climbing stairs, rebalance, accelerate suddenly, among others). Therefore, it is important to investigate the dose-response relationships in power training in older people and establish how possible improvements in muscle quality can be reflected in functional capacity.

The aim of this study is to compare the effects of power training at two different loads on muscle quality and functional capacity in women aged 65-75

Fifty-six women will be randomly assigned to one of two muscle power training supervised for a physical activity instructor with different velocity loss (VL) thresholds: 10% (VL10) and 30% (VL30). Subjects followed a muscle power training for 8 weeks (2 sessions per week on alternate days) using the leg extension exercise, with similar relative intensity (50% 1RM). Between weeks one and four two series will be performed per session. Then the number of series will increase to three per session. The inter-set recovery period will be always of 2-min.

Before and after the muscle power training the following tests will be performed: 1) measure of body composition with dual-energy x-ray absorptiometry for determining the lean mass of thighs; 2) three functional test (chair stand test, time up go test with cognitive task and gait speed test); 3)Progressive loading test in a leg extension machine until finding the mean muscle power corresponding to 50% of 1RM (speed of concentric phase of 6.67 ± 0.04 m/s measured using a camera-based optoelectronic system).

Inclusion Criteria:

• Women 65 to 75 years.
• Healthy volunteers.
• Have not perform muscle power training in the last six months.

Exclusion Criteria:

• History of asthma.
• History of uncontrolled diabetes.
• History of uncontrolled hypertension.
• History of cardiovascular disease.
• History of coronary heart disease.
• Smoker.
• Arrhythmias.
• Personal history of surgical procedures in the last three months.
• Uncontrolled non-communicable diseases.
• Psychological, sensitive, cognitive, neuromotor and/or osteo-muscular conditions that may affect participation in an exercise program.
• Under medical treatment with anticoagulants, bronchodilators, and/or steroids.