Ultimate frisbee requires endurance, sprinting, and quick changes of direction. Movements that require fast starts and stops can cause injury to the leg muscles in the glutes, thighs, and calves. Build balanced strength and flexibility of leg muscles to avoid injury.
Knee injuries (such as ligament tears, meniscus injury) can happen during pivoting, change of direction, landing from a jump, or overuse while running. Unlike other joints, the knee only moves in one direction. It can become susceptible to pain and injury if surrounding joints and muscles lack mobility and strength. Build mobility in hips and ankles and strength in muscles around the knee to reduce the risk of pain and injury.
Quick stops in ultimate frisbee require leg muscles to contract rapidly. If your leg muscles are not strong enough, the stress of the rapid movements transfers to the foot and ankle and can cause injuries such as sprained ankles (the most common injury in ultimate frisbee overall), plantar fasciitis, and injuries to the Achilles tendon (more common in older athletes).
Repetitive overhead throws can lead to strains and tears in the muscles around the shoulder (such as the rotator cuff). Shoulder injuries are also common during layouts. Work on your mobility and shoulder strength to reduce the risk of shoulder injury.