Comparing the effects of plyometric and isometric strength training on dynamic and isometric force-time characteristics

Abstract

The purpose of the study was to compare the change in dynamic and isometric force-time characteristics after plyometric (PLYO) or isometric strength training (ISO). Twenty-two endurance runners (age = 37 ± 6 years, stature = 1.71 ± 0.05 m, body mass = 62.7 ± 8.6 kg, weekly mileage = 47.3 ± 10.8 km) performed a countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) test during pre- and post-tests. They were then randomly assigned to either PLYO or ISO group and completed 12 sessions of intervention over six weeks. The PLYO included drop jump, single leg bounding and split jump, and the ISO included IMTP and isometric ankle plantar flexion. Significant and large time x group interactions were observed for CMJ countermovement depth ( P = 0.037, ƞ² p = 0.21) and IMTP and relative peak force (PF) ( P = 0.030, ƞ ² p = 0.22). Significant and large main effects for time were observed in CMJ height, peak power, propulsive phase duration, countermovement depth, reactive strength index modified, IMTP PF and relative PF ( P < 0.05, 0.20 ≤ ƞ² p ≤ 0.65). Effect for time showed small improvement in CMJ height for both PLYO ( P < 0.001, d = 0.48) and ISO ( P = 0.009, d = 0.47), small improvement in CMJ PP in PLYO ( P = 0.020, d = 0.21), large increase in countermovement depth ( P = 0.004, d = 1.02) and IMTP relative PF ( P < 0.001, d = 0.87), and moderate increase in propulsive phase duration ( P = 0.038, d = 0.65) and IMTP PF ( P < 0.001, d = 0.55) in ISO. There were large differences between groups for percentage change in countermovement depth ( P = 0.003, d = 0.96) and IMTP relative PF ( P = 0.047, d = 0.90). In conclusion, both PLYO and ISO improved CMJ jump height via different mechanisms, while only ISO resulted in improved IMTP PF and relative PF.

Comparing the Effects of Long-Term vs. Periodic Inclusion of Isometric Strength Training on Strength and Dynamic Performances

“…The positive effects of IST on CMJ performance have been evident in several studies (4,25,26). However, only one group of researchers has reported the effects of IST on CMJ forcetime data (26).…”

“…The positive effects of IST on CMJ performance have been evident in several studies (4,25,26). However, only one group of researchers has reported the effects of IST on CMJ forcetime data (26). It was reported that significant increases in CMJ height and countermovement depth were observed after performing IMTP and isometric ankle plantar flexion for 12 training sessions over 6 weeks.…”

“…The improvement in maximum strength has often been attributed as one of the reasons for the improvement in sprinting and jumping performances (25,26,35). Results from recent studies on IST have also reported the concurrent improvement in strength with sprinting and jumping performances (25,26). In addition, it has also been reported that the inclusion of IST resulted in greater strength increases compared with performing heavy weight training alone (24).…”

“…For example, athletes could replace half the volume of dynamic back squat with isometric squat (ISqt) performed at the joint position that corresponds to the sticking point of back squat so as to enhance their force generation capability at that joint position. However, it is important to note that IST alone may not be sufficient to optimize adaptations to improve dynamic movement (20,22,26). For example, Lee et al (20) reported that IST resulted in less improvement in jump performance than dynamic resistance training.…”

“…Researchers have also reported that IST was beneficial in improving various dynamic performances such as jumping (25,26), sprinting (25), cycling (17), endurance running (2), ball kicking (4), and sprint kayaking (24). These improvements in dynamic performances were attributed to improved maximal strength, rate of force development, or tendon stiffness, or a combination of these factors (2,17,24).…”