Isotonic contractions are split into two Concentric contractions Eccentric contractions
Concentric contractions
Concentric contractions are the contractions which cause the muscle to shorten as it contracts. Concentric contractions are the most common type of muscle contraction and occur frequently in daily and sporting activities.
A sporting example of this contraction would be lifting a weight, bending the elbow from straight to fully flexed.
Eccentric contractions
Eccentric contractions are the opposite of concentric and occur when the muscle lengthens as it contracts. This contraction