Importance of rest in your exercise routine

 This study compared the effect of rest intervals on isokinetic knee exercise in physically active younger and older women.

Isokinetic exercises use an apparatus that provides “variable resistance” (photo). Regardless of the effort exerted, movement occurs at a constant speed. This technique is used to improve muscular strength and endurance, especially after injury.

First, the details.

• 20 young (average 22 years) and 16 older (71 years) women performed 3 sets of 8 maximum repetitions of knee extension/flexion (straightening/bending) at 60 degrees.
• The rest interval between sets was 15, 30, and 60 seconds, and was randomly assigned over 3 testing days.

And, the results.

• There was a significant decline in the force (torque) required to straighten the knee when 15- and 30-second rest intervals were used between sets, but not a 60-second rest interval.
• There was no significant decline in the force required to bend the knee in the older women following a 30-second rest interval vs a 60-second rest interval in younger women.
• Active younger and older women required similar rest intervals between sets of a knee straightening exercise (60 seconds) for complete recovery.
• However, older women recovered faster (30 seconds) than younger women (60 seconds) between sets of a knee bending exercise.
• The exercise-to-rest ratio for knee straightening was similar for both groups (1:2).
• Old women required only a 1:1 exercise-to-rest ratio for knee bending recovery, whereas younger women required a 1:2 ratio.

Is that clear?

The bottom line?
The authors concluded, “Practitioners should consider age and gender when prescribing rest intervals between sets.”

OK, but I come away thinking that 30 seconds between sets is about right — 60 seconds for young women during bending exercise. Maybe a physical therapist out there can provide perspetive.

An earlier study concluded, “During a common isokinetic strength testing protocol a between set rest period of at least 60 seconds is sufficient for recovery before the next test set.” However, it was designed to evaluate longer time intervals — between 60 and 300 seconds.

10/13/08 17:17 JR