The duration of an exercise repetition is typically 2-5 seconds depending on the exercise. About half of this time is spent on the concentric phase and the other half is spent on the eccentric phase. A recent study published in the Journal of Sports Sciences examined if improvements in muscle strength are influenced by the durations of the concentric and eccentric phases used in training.
Women aged 18 to 35 were randomly assigned to one of three groups. One group performed leg extension exercise with a 5-second concentric phase and a 1-second eccentric phase (5CON-1ECC). A second group performed leg extension exercise with a 3-second concentric phase and a 3-second eccentric phase (3CON-3ECC). A third group performed leg extension exercise with a 1-second concentric phase and a 5-second eccentric phase (1CON-5ECC). A resistance of 50% of maximum was used by all participants, and 3-5 sets of 6 repetitions were completed in each exercise session. All participants performed the exercise 3 times per week for 10 weeks. The study also included a group of control participants who did not perform resistance training. Before and after the 10-week training program, muscle strength of the quadriceps was assessed with the one repetition maximum (1RM) test and various isometric tests.
Individuals in the 1CON-5ECC group showed the greatest improvements in 1RM strength. They improved their 1RMs by an average of 22%. Individuals in both the 5CON-1ECC and 3CON-3ECC improved their 1RMs by an average of 14%. However, isometric muscle strength improved equally in all three groups. Control participants did not experience any changes in muscle strength over the 10-week study period.
Results from the study demonstrate that 10 weeks of leg extension exercise improves muscle strength of the quadriceps. These improvements occurs with various combinations of eccentric and concentric contraction durations that total a 6-second repetition. However, repetitions performed with longer eccentric phases (5 seconds) coupled with shorter concentric phases (1 second) appear to be the most effective at increasing 1RM strength, whereas all contraction durations appear equally effective at increasing isometric muscle strength.
To apply the results from the study to the V-Form Trainer:
1) attach the ankle strap to the V-Form Trainer
2) select the “leg extension” exercise
3) select “focused” mode
4) select 6 repetitions
5) select a resistance that is moderately challenging
6) set the movement range of motion in the first 3 calibration repetitions
7) let the entire resistance stack on at the top of the movement (fully extended knee position)
8) try to resist the cable pulling the leg down for 5 seconds
9) once at the bottom of the movement extend the leg back up as quickly as possible
10) repeat until set is finished
11) switch to the other leg and repeat above steps
12) keep switching between legs until 3-5 sets have been completed for each leg
13) repeat this exercise 3 times per week for 10 weeks
Ribeiro Diniz RC, et al. Resistance training intervention performed with different muscle action durations influences the maximal dynamic strength without promoting joint-angle specific strength gains. Journal of Sports Sciences, 2021. DOI: 10.1080/02640414.2021.1934287.