The aim of this observational study Is to examine the validity of the Smartphone application (VO2max calculator) in calculating VO2max in elderly population.

Research hypotheses:

this study will test the following null hypothesis: (Vo2max calculator) application will not have criterion validity in estimating VO2max values in the elderly population.

Research question:

Is the Smartphone application (VO2max calculator) considered a valid tool for estimating accurate values of VO2max in the elderly population in comparison to the golden standard method?

Although maximal oxygen consumption (VO2max) is growing in evidence as a powerful indicator of several health conditions it's rarely used in clinical practice due to the high expense, requirement of specialized equipment, and related risks of maximal exertion. So, we aim to develop a simpler method for estimating VO2max using modern smartphone technologies.

Method: participants of this study will be divided into 2 equal groups. The first group will perform a gold standard treadmill-based VO2max measurement and the other group will perform a smartphone based 1-mile walk test for VO2max estimation.

Inclusion Criteria:

• Elderly subjects aged from (65 to 75) years.
• BMI 18.5-29.9 kg/m2
• Answer (NO) to all of the questions in the Physical activity readiness questionnaire (PAR-Q)
• Do not have any absolute or relative contraindications for exercise testing according to the American Heart Association (AHA) statement.

Exclusion Criteria:

• Recent surgical conditions.
• Skeletal deformities.
• Blood pressure regulating medication intake.
• Any respiratory disorders.
• Back, hip, knee or ankle pain within last month.
• Any neurological or psychiatric conditions.
• Implanted pacemaker.
• Anemic patients.

(52) Male and female participants will be recruited from the out clinic customers, and workers at the faculty of physical therapy Delta University at ELmansoura governorate.