Accentuated eccentric training: effects on horizontal jump distance and muscle strength among young adults

Efficient and effective training methods are continually sought after by physiotherapists, coaches, and athletes to enhance sports performance,1 Resisted movement training is used in athletic conditioning to enhance power and athletic performance by executing a movement important to sport with added resistance that is not excessive and does not adversely affect the movement pattern. Traditional weight training exercises performed slowly with heavy resistance are well suited to enhance strength but may not be optimal for power development requiring higher velocity because there are considerable portions of deceleration during the motion, whereas resisted movement training can allow for acceleration throughout the range of motion.2 Eccentric exercises are frequently applied in strength and conditioning program by giving external resistance to the targeted muscles in the direction which is opposite the muscle pull. According to,3 eccentric exercises improve maximal and explosive muscle strength, shift the optimal muscle length, improve muscle coordination and induce muscular adaptations. There are few different training modalities derived from eccentric exercises such as “pure eccentric” and “coupled eccentric‒concentric” manner. Accentuated eccentric loading (AEL) is one of the extended concepts from eccentric exercises. Accentuated eccentric loading is a training method in which greater load is applied during eccentric phase in comparison to concentric phase of a coupled eccentric‒concentric action. The aim of this study was to evaluate the training effects of accentuated eccentric load countermovement jump on horizontal jump distance and maximum muscle strength of lower extremity among young adults. According to,4 AEL was described as magnitude of eccentric load is higher than that of concentric load while maintaining the natural mechanism of movements involving concentric and eccentric action. It means that an additional load is applied during eccentric phase in comparison to concentric phase of a movement. It is hypothesized that a greater concentric force will be developed through higher loading in eccentric action. It is believed that AEL involving coupled concentric and overloaded eccentric muscle actions could optimize the effects of stretch‒shortening cycle (SSC). An additional mechanical stimulus was given during eccentric phase in order to produce greater force and power output during concentric phase in SSC activities. AEL augments the negative work of eccentric phase, thereby increasing the positive work of concentric phase to overcome the negative work. Countermovement is described as a movement in a direction opposite to the goal direction. Some tasks such as throwing and jumping start with countermovement in order to improve performance. Countermovement is commonly observed in actions involving SSC. The pre‒stretch in countermovement leads to higher speed and greater force production in athletic performance. The spring‒like mechanism found in SSC actions,5 could be applied to explain the superior results gained in actions involving countermovement. The coil of spring immediately rebounds and jumps off the surface in an opposite direction after it is released from compression. The spring jumps higher or farther by increasing the compression speed and compression force applied on the spring. This is known as the “rate of loading”. Studies related to the acute and chronic effects brought by AEL were inconclusive, mostly due to differences in selecting subjects, exercise, load prescription, and method of providing AEL.5 some studies demonstrated that the AEL protocol could acutely enhance athletic performance while some studies showed the contrary results. Therefore, further research should be conducted to evaluate the training effects of AEL among untrained subjects because training the untrained individual is the initial step of novice training programs. Moreover, there is lack of study conducted to investigate the effects of AEL on standing long jump (broad jump) performance. Standing long jump is an athletic event and becomes one of the annual events