Some of the most commonly used antagonist muscle pairs in the human body include quadriceps/hamstrings, biceps/triceps, shins/calves, pectorals/latissimus dorsi and trapezius/deltoids, according to MIT. Other antagonist muscle pairs involve two types of deltoids, abdominals versus spinal erectors, two types of oblique muscles and two forearm muscle pairs.
Agonists create the normal range of motion of a joint, while subsequent antagonists return the joint to its normal position, notes MIT. Agonists and antagonists usually exist on opposite sides near a joint, such as the biceps and triceps with the elbow as well as the hamstrings and quadriceps at the knee.
The biceps are the front of the upper arm, and the triceps are in the back, states the BBC. When the biceps muscle contracts and the triceps relaxes, the forearm moves up. When the triceps muscle contracts and the biceps relaxes, the forearm moves down. Every human joint is controlled by multiple muscles, and each joint has antagonistic pairs to allow complete freedom of movement.
Abdominal muscles, together with erectors, bend the spine forward and backward. Hip abductors and adductors move the legs together and apart. Iliopsoas and gluteals lift the knee, explains Los Angeles Trade-Tech College. Quadriceps and hamstrings straighten the knee, while deltoids and latissimus dorsi muscles lift and lower the entire arm at the shoulder.