52. THE KEY TO DESIGN YOUR AEROBIC HIGH INTENSITY TRAINING WORKOUTS!

Photo by Simon Breau on Unsplash

High intensity Training (HIT) is a widely used strategy to stimulate positive physiological adaptations for endurance performance. It represents performing intervals at an intensity above the second threshold/critical power/FTP (so zone 4 high, and zone 5 in a five training zones model). HIT sessions are a powerful adaptive stimulus which leads to positive adaptations very fast, however they are also demanding from both a physiological and psychological point of view. So, as already noted in previous KisW Research Notes, they should be carefully dosed (that is usually no more than 2/3 HIT session per week). As a consequence, it is very important understanding how to perform HIT sessions to get the most from this powerful but limited use weapon.

Intuitively, accumulating as much time as possible at high percentages of maximal oxygen consumption can be the key to optimize aerobic adaptations. Is it really so?

Is accumulating as much time as possible at high fraction of VO2max (maximal oxygen consumption) the key to optimize HIT aerobic adaptations?

A hot of the press study published by Odden and Colleagues (Inland Norway University of Applied Sciences, Lillehammer, Norway) published on European Journal of Sport Sciences in 2024 tried to answer this question. (1)

Proving this principle can be crucial to give us the criteria to design effectively the intervals of our high intensity training sessions.

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WHAT DID THEY DO?

• 30 trained cyclists (~21 years old, ~70 VO2max) trained all similarly for 9 weeks.

  The training program consisted in:

  • ~9 hours per week in total

  • 21 HIT sessions over the 9 weeks (so 2/3 HIT per week).

    Three different HIT formats were alternated:

    1. 5x8min alternating 30-s at 118% of PO40min and 15-s at 60% of PO40min

    2. 5x8min alternating 60-s at 110% and 90% of PO40min

    3. 5x8min constant at 100% of PO40min.

In all the 3 formats, the recovery between the 5x8min efforts was 3min at 35% of PO40min.
PO40min is the personal best mean power output for 40min.

• After the 9 weeks (to perform the data analysis) cyclist were split into two groups:

  • high fraction of VO2max group (HVO2): that was composed by the 15 cyclists (50% of the participants) who recorded the highest average oxygen consumption (measured as fraction of VO2max) throughout all the HIT sessions over all the 9 weeks.

  • low fraction of VO2max group (LVO2): the other half of the participants who scored a lower average oxygen consumption (measured as fraction of VO2max) throughout all the HIT sessions over all the 9 weeks.

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WHAT DID THEY FIND?

• The cyclist who recorded a higher fraction of VO2max (HVO2) during the HIT sessions improved more their aerobic physiological and performance parameters compared to the cyclists who recorded a lower fraction of VO2max (LVO2) during the HIT sessions:

  • V̇O2max:

    5.2±2.8 vs 1.8±1.7 mL/min/kg

  • Power output at 4mmol of blood lactate concentration:

    0.3±0.2 vs 0.1±0.2 W/Kg

  • Average power on 15min time trial:

    0.3±0.2 vs 0.2±0.2 W/kg

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PRACTICAL TAKEAWAYS:

• Sustaining a higher fraction of maximal oxygen uptake (V̇O_2max) during HIT sessions leads to superior improvements in aerobic physiological and performance.

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GABRIELE’S COMMENT:

• These data clearly show us that sustaining a higher fraction of maximal oxygen uptake (V̇O_2max) during HIT sessions is the key to get the most from HIT sessions for what concern aerobic adaptations and performance.

• While this study was just to show the general concept and all the cyclists performed similar HIT sessions, we can use this information to choose the right intervals formats to design our HIT sessions.

  How? Using physiological principle and previous studies that recorded oxygen consumption during different HIT formats.

  Basing on these principles, here the HIT formats (in order of effectiveness) you should pick if you want to optimize HIT’s derived aerobic adaptations:

  1. Intermittent short intervals: