2 young candidates have tragically died during army pre-recruitment sorting series in 2006. As part of the classification and characterization of the physical aspects of the training, this experiment was requested.

We aim at determining the characteristics of physical strains in sorting series, by objective and subjective parameters and evaluating the difficulty levels and intensity of those strains.

each subject will perform the following 3 days experiment protocol, consisting of army training exercises:

1. sack carrying exercise; the subjects will go up and down through a steep slope with sand sack on their back (path length is 200 meters,10 repetitions).

   the first day will also include recruitment and medical examination, in addition to the exercise.

2. crawling exercise; the subjects will crawl with knee's protectors back and forth (path length is 20 meters,15 repetitions).

3. combined exercise: sprints session (path length 600 meter, 3 repetitions),15 min break, sack carrying session (same protocol as first day), 45 min break and crawling session (same protocol as the second day).

during all exercises heart rate, core temperature, lactic acid and CPK levels will be monitored continuously.

Inclusion Criteria:

• Aged 18-22 years.
• Healthy civilian volunteers.
• without skeleton-muscle illnesses.
• without Infectious disease 2 weeks prior to the experiment.

Exclusion Criteria:

• any physical condition.
• physician decition.