###### Abstract
Deep water movements can help maintain aerobic fitness, but neuromuscular training and movement patterns are very different from normal movements because the forces applied to the body in water are disproportionate to the forces involved in surface movements. An alternative to this type of physical activity may be the use of an anti-gravity treadmill. The Alter-G lower body positive pressure treadmill, also known as the anti-gravity treadmill, is a device dedicated not only to athletes but also to people struggling with overweight or undergoing rehabilitation after lower limb injuries. The anti-gravity treadmill is designed to reduce pressure on joints, tendons, and ligaments while running or walking [22] by limiting the ground reaction forces. It was shown that using the anti-gravity treadmill can effectively preserve the mechanics of gait while reducing the ground reaction forces on lower limbs in postoperative patients. This device is connected to a pressure chamber filled with air, which surrounds an exercising person from the waist down. The anti-gravity treadmill is able to support body weight from 0% to even 100%. The exerciser wears neoprene shorts that are tightly attached to the pressure chamber. After completing all the preliminary steps, the treadmill is calibrated, and the appropriate weight and speed are adjusted. Despite being a relatively new technology, numerous studies have examined the effects of using an anti-gravity treadmill on the runner's body, demonstrating its benefits for injury prevention and rehabilitation. It has been found that the greatest differences in muscle activity were detected after changing running speed, while changes in inclination and body weight had less impact on muscle activity. Lower muscle activation has been reported for all downhill conditions, with more tightly clustered low activation levels that were not affected by incline, speed, and body weight [23]. Some researchers paid more attention to the activation of hamstrings while running on the anti-gravity treadmill. Their results have revealed that increased speed on the treadmill resulted in higher peak activation in all the tested muscles, while body weight had a lower influence on changes in muscle activity. The hamstrings were activated before and after the heel strike during a fast run on an anti-gravity treadmill. The lateral hamstrings were more active than the medial hamstrings throughout the gait cycle, especially in the stance phase [23]. In turn, [PERSON] [24] conducted an experiment which has demonstrated that reducing body weight with the anti-gravity treadmill caused a decrease in muscle activity. In addition, muscle activity increased with higher running speed, maintaining the muscle activity patterns despite changes in speed or weight. If the goal of training on an anti-gravity treadmill was to match the muscle activity to that of running on land, the exercising person would have to run at increased speed with less weight. However, if the aim of exercise on this treadmill is to maintain a specific pattern of muscle activity, then the range of body weight can be set to between 60 and 90%, because body weight does not significantly affect changes in muscle activity patterns during running [24]. Lower extremity muscle activity was also tested by [PERSON] [25] at 20% and 50% of normal body weight. The study found that the activity of the major muscles of the lower extremities decreased as weight decreased and increased as speed increased for all possible body weights. In contrast, the percent change in muscle activity was much smaller compared to the percent change in body weight [26]. The aim of the study was to determine whether the internal structure of running changes under unloaded conditions using an anti-gravity treadmill. It is assumed that conditions of reduced gravity may significantly influence the change in running structure and technique; however, under certain conditions, unloading may have a neutral effect.