Twelve weeks. Three days a week. Ten one-minute sprints at 90% HR max on a stationary bike.

That’s the protocol Chilean researchers dropped on 18 unsuspecting dudes (Caparrós-Manosalva et al., 2023).

Nine were young stallions (21 yrs).
Nine were older warhorses (66 yrs).

And the results? A metabolic mosh pit.

Young Bloods (21 years old)

  • Strength ↑ 10.4% — statistically real, no fairy dust.
  • Power ↑ ~12% — enough to make your quads whisper, “more plates, please.”

Older Iron Veterans (66 years old)

  • Strength ↑ 3.7% … but statistically meh. Think: fart in a hurricane.
  • Power ↑ ~35% — beastly on paper, but the variability was insane. Some lit up like Thor’s hammer. Others flatlined.

Body Comp Reality Check

Forget abs popping through your lifting belt. Only the non-dominant leg gained lean tissue:

  • +2% (young)
  • +0.6% (older)

Everywhere else? Nada. Your biceps remain lonely spaghetti noodles.

Nerd Chute Tangent (Strap In)

  • Early explosive strength (RFD 0–50 ms): the “get off the toilet without a lifeline” kind of force → improved in both groups.
  • Power: went up, especially in the older dudes. But variability = chaos.
  • Asymmetry: red flag for fall risk. Bilateral training (like cycling) isn’t always the symmetry fix you think. Sometimes it just widens the gap.

Translation: keep unilateral training in your program, Brosefus.

The Takeaway

HIIT is the wasabi shot on your sushi roll.
Sharp. Fiery. Clears your sinuses. Maybe makes you cry in the bathroom mirror.
But it’s not the meal.

  • If you’re young: HIIT can sneak in some bonus strength and power.
  • If you’re older: it might help… or it might just make you wobblier than a drunk uncle at a wedding.

Solid programming with violent consistency wins again — sprinkled with some true HIIT work.
Just don’t major in HIIT.

Much love and metabolic mayhem,
Dr. Mike

Note: The accompanying image was generated using AI to visually represent the concepts discussed in this article. It is not a real photograph or depiction of actual events.

P.S. Want to put this into practice?

If you’re ready to train smarter (not longer) and build a physiology that can handle anything—from short sprints to savage lifts—check out my Meathead Cardio Course.

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Reference (for the nerds who demand receipts)

Caparrós-Manosalva, C., Garrido-Muñoz, N., Alvear-Constanzo, B., Sanzana-Laurié, S., Artigas-Arias, M., Alegría-Molina, A., Vidal-Seguel, N., Espinoza-Araneda, J., Huard, N., Pagnussat, A. S., Sapunar, J., Salazar, L. A., & Marzuca-Nassr, G. N. (2023). Effects of high-intensity interval training on lean mass, strength, and power of the lower limbs in healthy old and young people. Frontiers in Physiology, 14, 1223069.