If you look at supplemental table S6 (which is admittedly inconvenient because it's a separately downloaded MS Word document) you get this:

S6. Summary of indoor cycling (Peloton) workouts by year (2018–2025)

  2018 (age 70): 11 workouts, 20 min, 171 watts
  2020 (age 71): 14 workouts, 60 min, 175 watts
  2021 (age 72): 140 workouts, 30 min, 177 watts
  2022 (age 73): 164 workouts, 20 min, 167 watts
  2023 (age 74): 73 workouts, 30 min, 187 watts
  2024 (age 75): 59 workouts, 45 min, 165 watts
  2025 (to march): 69 workouts, 30 min, 165 watts

In 2021-2022 the patient was doing 2-3 workouts a week on a stationary bicycle. And 177 watts for 30 minutes is solid, at age 72.

Going up to 5-6 workouts per week is a step up, but this wasn't an inexperienced rider. And who knows how much outdoor cycling they did, which the Peloton wouldn't have recorded?

76 (already a good age) with an existing heart condition and increases HIIT exercise frequency by 25%.

I wonder if they consulted their physician before doing that, and what they recommended?