Sometimes, during strenuous aerobic activity, activity ceases only when the discomfort that follows lack of oxygen would be intolerable. Reaching this fatigue condition can cause organ damage, muscular damage and / or in different tissues of the body. In this study, investigators aim at developing new indexes, based on hemodynamics measurements from the peripheral micro - circulation system, for the benefit of early detection of fatigue during accelerated physical activity.

14 healthy volunteers, 7 males and 7 females, aged 18-30 will participate in this study.The study includes 2 stages: In the first stage, aerobic capacity of the subjects will be measured by measuring maximum oxygen consumption (VO2max test). This phase will be conducted to determine physical measurements that could indicate different stages in muscle fatigue (anaerobic threshold, maximum oxygen consumption, heart rate and breathing indices).

In the second phase, the subjects will perform the same physical effort protocol that carried out at the first stage. Non- invasive measurements of leg muscles activity during aerobic exercise and at rest (before and after activity), will be carried out using a wireless EMG. Additionally, hemodynamic measurements of oxygen levels in the skin and skin perfusion monitoring before and after strenuous activity will be performed using two optic sensors.

Inclusion Criteria:

• Aged 18-30 years.
• Healthy civilian volunteers.
• Without known medical illness or medication use that might endanger the participants.

Exclusion Criteria:

• The existence or suspicion of existing cardiac or respiratory disease.
• Any metabolic disorder.
• Any muscles or skeleton condition.
• Any neurological condition.
• the physician decision.