According to the Healthy Living Index on AZ Central, treadmills provide an effective cardiovascular workout that helps strengthen the muscles of the legs and buttocks to include quadriceps, hamstrings, calves and glutes. A treadmill routine that involves walking uphill backwards engages the core abdominal muscles and improves balance.
Jenny Sugar of PopSugar Fitness claims that using the upper body by pumping the arms while running on the treadmill actually tones biceps, triceps and shoulders. Back muscles can be strengthened as well during a run on the treadmill. Interval training stimulates the muscle memory, helping exercisers make the most out of their treadmill workouts.