Eight 30-second sprints with just 90 seconds of rest in between are
kind of a heavy load for anyone, let alone a heavily-stressed working
mother. Many of the most effective sprinting studies employ four – not
eight – 30-second sprints with three to four minutes – not 90 seconds –
of rest in between. And the subjects are often young college students
for whom a stressful day means having to wake up before ten o’clock. Oh
how I wish my life were like that again.
Traditional sprinting is far more demanding than the sprint cycling
often used in exercise science. Few studies even use straight on
sprinting unless the subjects are experienced athletes due to the degree
of difficulty required. Sprint cycling also doesn’t really engage the upper body at all, whereas sprinting is a total body endeavor.
All that said: I’m confident you can still sprint and accrue benefits, even undergoing external stress, but you’ll have to change things up and make a few tweaks.
30 second sprints require more rest. Period. Some
people may be able to handle them with truncated rest, and a carefree
relaxed version of you appears to be one of those people, but a
stressed-out time crunched version of you is not. Extend your rest
periods to three or even four minutes instead of a minute and a half. If
that’s “too easy,” you can always slowly reduce your rest as long as
you’re still getting beneficial effects.
Don’t do eight of them. That’s way too many for you. They’re no joke and you don’t need to do eight of them. Heck, in one study, men and women did “just” three 30 second all-out sprint intervals on the stationary bike with 20 minutes of rest in between each sprint and they still got results. I’d say start with four and work up or down based on how you respond.
Try shorter sprints. Try 20 seconds instead of 30.
Even shorter sprints work, too. In fact, a program consisting of three
sets of 5 4-second treadmill sprints with 20 seconds of rest in between
each sprint, done three times per week for four weeks up-regulated molecular signaling associated with mitochondrial biogenesis.
More mitochondria mean greater energy production and consumption,
improved substrate utilization, and overall better metabolic health. Don’t
be afraid to run a series of 4-6 second sprints with minimal rest.
It’ll feel “easy” compared to your normal routine but it’s still
If you’re going to run hills, definitely make the sprints shorter. 30
seconds of sprinting uphill is far more stressful than 30 seconds of
sprinting on flat ground. Whenever I run hills, I knock my normal sprint
time down. Try 15, maybe 20 seconds instead of 30. Remember, the benefits (and stresses) of sprinting depend on effort expended, not the duration.
Find the point where you start to slow down and stop there.
We all have that point. Very few people on the planet can maintain top
speed for 30 seconds. You probably aren’t one of them (I’m certainly
not). And it’s not that continuing to run after you’ve lost your top
gear isn’t useful. It is. It’s just really, really hard on the body.
Since your ability to recover from stress is slightly impaired, you’ll
likely do better with true sprints that stop once you start to slow
down. Besides, as you get stronger, fitter, and faster (from
actually recovering from the sprints now!), you’ll find that you can run
a little longer at your top speed each time.
Whatever tweak you try, use your well-documented powers of observation and interpretation to determine its efficacy. Good luck!