The lowest risk to high burn ratio is probably swimming in a non-heated pool. Whether a person can burn that many calories doing that, depends on the lenght of the session, and their body and muscle mass. The heavier a person is, the more calories they burn just by breathing. Same with muscle.
Thanks to some people, a calorie as defined in the SI is 1/1000 a CAL as written in food packaging. So people keep saying calories when actually talking about kilocalories. So by breathing for a couple of minutes an adult burns about a 1000 calories (or 1 CAL or 1 kcal).
There is no completely safe activity. You can pull a muscle just by laying on a sofa, or get back pain from sitting incorrectly.
Exercise mitigates these risks and increases others. The sweet spot for adults, as per the WHO, is between 2.5 to 5 hours of aerobic exercise per week, and about 2 hpk of strength exercise. More than that and injuries outweigh benefits.
Can anyone lose a 1000 kcal per day extra by exercising? Probably. Can anyone spend two or three hours doing laps at the pool, daily, for the foreseeable future? Doubtful.
As long as you're otherwise healthy and use proper technique there is no reliable evidence that more than 5 hours per week of aerobic exercise increases risk of injuries more than benefits. In fact the WHO states that more than 5 hours per week provides "additional health benefits".
The injury risk comes not from hours per se but from impact and intensity. For example, a 1 hour running intervals workout will generally carry a much higher injury risk than a 1 hour cycling tempo workout.
Thanks to some people, a calorie as defined in the SI is 1/1000 a CAL as written in food packaging. So people keep saying calories when actually talking about kilocalories. So by breathing for a couple of minutes an adult burns about a 1000 calories (or 1 CAL or 1 kcal).
There is no completely safe activity. You can pull a muscle just by laying on a sofa, or get back pain from sitting incorrectly.
Exercise mitigates these risks and increases others. The sweet spot for adults, as per the WHO, is between 2.5 to 5 hours of aerobic exercise per week, and about 2 hpk of strength exercise. More than that and injuries outweigh benefits.
Can anyone lose a 1000 kcal per day extra by exercising? Probably. Can anyone spend two or three hours doing laps at the pool, daily, for the foreseeable future? Doubtful.