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Comment by antisthenes | Hacker News Reader

In my experience lifting weights helps you grow enough muscle to actually be able to do 600 minutes of cardio.

With small/insufficient muscle size, you simply run out of stored glycogen before you get tired cardiovascularly.

> Because if you need to fit 560 minutes of cardio and then also fit weight lifting 3 times a week that's a lot of time working out

Proper exercise is absolutely a lifestyle change and a big commitment. Not only do you have to exercise several hours a week, but also eat healthier macros and fix your sleep to make sure most of the benefits stick and aren't wasted.

People try to half-ass it all the time by doing weird diets or going on 15 minutes walk during their lunch break, and yes it's better than nothing, but not by much.

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I don't understand how walking in the study is considerate moderate.

Like my heartrate for sure goes higher when lifting weights than when I walk. If I walk fast, it might get closer, but I am not that confident.

300 minutes of HIIT per week are equal to 10 HIIT sessions per week, I would argue that's outright impossible, the body cannot handle that, I don't think even an Olympic athlete can handle more than 3 times per week HIIT.

Vigorous might be possible, that's still 5 times 1 hour cardio sessions, on top of which you have to add 3 sessions of weight lifting for bone density, on top of which you have to add balance training and stretching.

There isn't enough time in a day to do that if you work, let alone if you have kids

HIIT is far beyond vigorous.

Vigorous would be Z2/3 cardio, so like 120-160 BPM for most adults. Moderate would be Z1 90-120.

Once you are capable of doing cardio consistently in Z4/5 with HIIT and tempo training you really don't need to worry about "am I doing enough exercise."

I mean, according to this study I would still need that. I can average 165 BPM (because I'm trained, used to average 175) and max 180 in a session. But that's all the cardio I get. I walk 20 minutes per day to bring the kids to school, and lift weight.

Weight lifting doesn't count, but I tested yesterday and I average 110 bpm during a workout (it's constant ups-and-downs). Based on that, it would count for moderate exercise.

The time investment is steep if we cannot count weight lifting, there is no escape.

>With small/insufficient muscle size, you simply run out of stored glycogen before you get tired cardiovascularly.

You can eat carbs during cardio ("fueling") though it's unlikely an issue doing 600 mins a week. Muscles store 15g of glycogen per 1kg (more for trained athletes) , which amounts to 60 (k)calories. In aerobic process with COP ~ 25% these nicely convert to output energy of 60 kJ. To produce this much output over 90 minutes you need to push power of ~11 watt. Elite athletes have FTP (functional threshold power) around 6 w/kg. It's over the entire body mass, not just muscle, but even if you are pushing 50% body fat, you can be pretty confident you have enough glycogen for 90 min of aerobic exercise at your FTP (also liver holds/can produce on demand quite a lot of glycogen and aerobic process will use fat for energy as well). Even if you do 200 minutes 3 times a week instead of doing 90 minutes every day you can get by staying in under 3 w/kg power zone, which is still greater than most people's FTP (and even fewer people can hold this power over 3 hours).

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