Brief, high intensity exercise to save your body and your brain.

Why are marathoners and fit older folks both so skinny?

Because long cardio workouts and aging both have similar effects on your fast twitch muscle fibers (these are what give you speed and power). Distance runners live in a catabolic state - they lose fat AND fast twitch fibers to get lighter and faster. Similarly, as your body ages, the amount of fast-twitch muscle fibers decreases, which contributes to a major decrease in muscle bulk and strength. After your mid-30s, you can lose an average of 3-8% lean muscle mass per decade. And fast twitch - speed and power - muscle fibers are what you are losing!

You may think, “I don’t care how big my muscles are.” But trust us, yes you do! In the short term, losing this type of muscle negatively impacts your metabolism and physical performance. Later in life, those who lose speed and power need help to get out of a chair. People don’t suddenly go from normal function to off balance, weak, and falling. It takes years and years of muscle loss to end up unable to care for themselves, living in a nursing home.

This is completely avoidable.

We recently posted an Instagram reel on the benefits of sprinting. We may like running sprints, but we understand most people probably don’t. That is okay because many other forms of high-intensity interval training (HIIT) can bring almost all of the same benefits. The key to HIIT is to push yourself hard (about 80-90% of max heart rate) for brief periods, rest for a specific amount of time, and then push yourself again. Your max heart rate is approximately 220 - your age. Then multiply that by 0.8 or 0.9 to get your target heart rate for HIIT.

Just a few of the benefits of interval training:

• Rapidly improve cardiovascular fitness and VO2 max

• Build and maintain power/speed fast twitch muscle fibers

• Build muscle in your legs, core, and upper body

• Increase brain-derived neurotrophic factor (BDNF) for increased mental focus

• Increase bone density due to high-impact exercise

• Increase metabolic rate for the remainder of the day

• Strengthen tendons to reduce the risk of injuries

• May be a powerful tool you can use to delay or prevent Alzheimer’s.

One nice benefit is that HIIT sessions are shorter in duration than resistance training or cardio. You get a ton of bang for your buck (time investment) with these workouts, as evidenced by the findings of this study. The entire workout they used takes only 10 minutes, and can be done cycling, running, or on a rowing machine. A description of their SIT workout is provided below.

Example exercises that are great for HIIT:

• Cycling outside or inside on an exercise bike

• Rowing machine

• Running

• Weight circuit training

Example work/rest duration:

• Always stretch, roll out with a foam roller, and warm up. Then repeat afterward.

• 6 x 1 minute

  • One minute of exercise at 90% of maximum heart rate

  • One minute of rest

  • Repeat for 6 efforts

• 4 x 4 minute

  • Four minutes of exercise at 80-90% of max heart rate

  • Four minutes of rest

  • Repeat for 4 efforts

• 40 seconds on and 20 seconds off circuit training

  • Create a circuit of 8-10 exercises, such as push-ups, sit-ups, wall sits, or different weight exercises

  • Forty seconds of effort, doing as many reps as you can in that time

  • Twenty seconds of rest

  • Move on to the next exercise

  • Go through the whole circuit 2 or 3 times

• Sprint Interval Training (SIT) on a bike, rowing machine, or running

  • Three 20 seconds all-out efforts (warm up before, 2-minute walk or slow cycling recovery between, then cool down after)

  • Only one minute at max effort for the whole workout!

  • Entire workout takes only 10 minutes

  • Just 3 sessions per week shows major improvement in metabolism and cardiovascular fitness

  • Goal is to get above 95% max HR for these very short efforts

As we mentioned . . . we think running sprints is fantastic for all of the reasons mentioned in our Instagram post. If you are interested, try this.

Sample easy 15-minute sprint running workout for grown-ups:

• Always stretch well and use a foam roller to roll out your glutes, hamstrings, quads, and calves before AND after your workout

• Slow jog for 5 minutes to warm up

• 100-meter sprint (these can be at 60-70% of top-end speed for beginners)

• Slow jog for 3 minutes

• 100-meter sprint

• Slow jog for 3 minutes

• 100-meter sprint

• Slow jog for 3 minutes to warm down