The use of infantry helmets under heavy heat stress conditions, during physical exertion, may hinder the body's ability to effectively dissipate heat from the head area, thereby damaging the soldier's function. Therefore head cooling may potentially enable a longer duration of activity until reaching fatigue. An improvement in function may also be possible.The purpose of this research is to determine the extent of the cognitive and physiological strain caused by wearing a helmet under exertional conditions while exposed to heavy heat stress and to evaluate the effect of a unique ventilation system connected to the helmet on strain reduction.

12 young, healthy civilian volunteers, aged 21-28 will participate in the study. Following a day of examinations and 6 days of acclimatization in a climatic chamber in accordance with a well accepted protocol, the subjects will undergo 3 days of experiment that will include exposure to hot environmental conditions with different helmet-wearing scenarios, while wearing uniform and a combat vest: (a) without a helmet (b) with a helmet (c) with a helmet connected to a ventilation system. All 3 scenarios will include a two hour effort (walking on a treadmill) in heavy heat stress in the climatic chamber at our institute (the Heller institute of medical research).

Inclusion Criteria:

• healthy civilian volunteers
• aged 21-28
• without known medical illnesses or medication use

Exclusion Criteria:

• the existence of or suspicion of existing cardiac or respiratory disease
• hypertension
• diabetes
• any hormonal disease or any other chronic illness that may inhibit participation in the experiment
• infectious disease 3 days prior to the experiment.