A new study suggests that slightly faster lowering during squats, paired with explosive lifting, may be the most effective tempo for boosting strength, sprint speed, and jumping ability in resistance-trained athletes.
Study: The effect of squat training with different eccentric contraction tempos on lower limb muscle strength. Image credit: Photology1971/Shutterstock.com
Researchers investigated the effect of squat training with different eccentric contraction speeds on lower-limb muscle strength and explosive performance. They published the study in PLOS ONE.
Why squat tempo influences strength and power
Squat training is a dynamic strength training exercise that requires coordinated functioning of lower- and upper-body muscles. This type of resistance training promotes adaptive changes in the nervous system and structural changes in muscles that support strength development.
Among various types of squats, the back squat is considered the most effective exercise to strengthen lower-limb muscles. It follows a joint-by-joint training approach that emphasizes the integrated mobility and stability of the ankle, knee, hip, and core structures to optimize strength development while reducing injury risk.
Movement tempo is a vital parameter in this type of exercise, which defines the speed of a movement repetition. It is typically a 4-number code that represents the duration of different phases of muscle contraction. A movement tempo of 4/0/1/0 indicates a 4-second eccentric contraction (muscle lengthening under load; lowering phase), 0-second isometric contraction (no change in muscle length; holding phase), 1-second concentric contraction (muscle shortening under load; lifting phase), and the pause duration between the end of the concentric phase and the beginning of the next repetition.
Any changes in movement tempo can affect muscle contraction duration. A slower movement tempo increases the duration of muscle contraction, leading to the induction of metabolic stress and reduced muscle strength development. Strength training with heavy weight can slow down movement tempo. In that case, a faster and more powerful movement tempo can be achieved by exerting maximum speed and force to pull the weight up (explosive contraction intent), which is vital for gaining muscle strength.
Given the importance of controlling movement tempo in a given contraction phase in strength training, researchers at Shandong Sport University, China, investigated the impact of an 8-week squat training program with different eccentric contraction tempos on maximal squat strength, jump height, and sprint performance among university students majoring in sports training.
Athletes completed eight weeks of tempo-controlled squats
A total of 30 male students majoring in sports training, all of whom had previous resistance training experience, participated in the study. They were randomly assigned to the 4/0/X/0 group, the 2/0/X/0 group, or the self-selected eccentric, isometric, and inter-repetition tempo group (V/V/X/V). The “V” represents a self-selected tempo, and “X” represents the fastest possible contraction speed. In each tempo-specific group, participants performed loaded squat training twice weekly for 8 weeks.
Maximal squat strength, 30-meter sprint performance, countermovement jump height (an explosive vertical jump), and squat jump height were assessed before and after the training.
All squat tempos increased maximal strength
The assessment of maximal squat strength indicated significant improvements across groups after 8 weeks of training. The magnitude of improvement was highest in the 2/0/X/0 group, followed by the V/V/X/V and 4/0/X/0 groups. However, the difference was not statistically significant between the groups.
Regarding 30-meter sprint performance, the analysis indicated a significant improvement in the 2/0/X/0 group and a significant decline in the 4/0/X/0 group after the training. However, no significant change in performance was observed in the V/V/X/V group.
Regarding countermovement jump height, the analysis revealed significant improvements in both 2/0/X/0 and V/V/X/V groups and a significant decline in the 4/0/X/0 group after the training. A similar trend was observed for squat jump height.
Two-second lowering phase maximized explosive performance
The study reveals that a movement tempo comprising a 2-second eccentric contraction, 0-second isometric contraction, and the fastest (explosive) concentric contraction showed the most favorable trend for improving lower-limb maximal strength. It produced the largest strength gains among the three groups, although the differences between groups were not statistically significant. This tempo also resulted in the greatest improvements in 30-meter sprint performance, countermovement jump height, and squat jump height.
In contrast, a movement tempo comprising 4-second eccentric contraction, 0-second isometric contraction, and the fastest concentric contraction is associated with significant declines in explosive performances, despite significant gains in maximal strength.
These findings suggest that the explosive contraction intent during the concentric phase cannot fully offset the negative impact of prolonged eccentric muscle contraction on explosive performance.
The control group in the study, which followed the self-selected eccentric, isometric, and inter-repetition tempos together with the fastest concentric contraction tempo, exhibited superior squat jump performance compared to the group following a 4-second eccentric contraction, 0-second isometric contraction, and the fastest concentric contraction tempo.
These findings further indicate that ultra-slow eccentric contraction speed is not suitable for explosive strength training intervention. The authors note, however, that this conclusion applies specifically to training programs aimed at maximizing explosive strength and power development and does not necessarily rule out slower eccentric training for other objectives.
Given these findings, researchers recommend that strength and conditioning coaches should prioritize squat training with a 2/0/X/0 tempo when designing lower limb strength programs to maximize the benefits for lower limb muscle strength and power development.
The study included only male students majoring in sports training, meaning that they have a basic experience in resistance training. These characteristics of the study population may limit the generalizability of findings to female populations, as well as to those with different kinds of training experiences.
The authors also noted methodological limitations, including restricting arm swing during jump testing, the practical difficulty of perfectly controlling prescribed movement tempos, and unusually similar baseline countermovement and squat jump performances, which may influence the interpretation and generalizability of the explosive performance findings.
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