Thought this was too good to stay just a journal post, pasting it here.
T0ddday if you think it is incomplete or misleading please edit/add what is needed.
Remember that the main benefit to sprinting for fat loss is muscle-sparing despite low bodyfat levels. So, it's a great tool for men at or below ~10% bf or women at or below ~18% bf***. One effect of the muscle sparing nature of sprinting i
As you move farther away from these body fat levels a calorie deficit will result in primarily fat loss as long as nutrition is adequate. It's not that sprinting won't help the overweight BUT sprinting does involve a lot more shock and there is increased injury risk relative to walking/cycling/etc. IMO it's still always better than jogging though!
**Note that the effectiveness of sprinting has some people who look at the scale too much actually become disappointed. The reason being that if you are lean (say 8% bf) and start to sprint for fat loss you will not lose weight as quickly as if you do a lot of marathon jogging... But that's because you lose weight slower when it's primarily bodyfat!
That said for a woman I would probably time here in an all out 100m sprint. If her fastest 100m is between 20 and 25 seconds I would have her do something like the following at a track:
1) Run 100m in under 30 seconds. Walk 300m in under 2.5 minutes. Repeat. Thats a 12 minute mile pace. Work up to the ability to do this for about an hour at which case there will be 5 miles completed in 1 hour which includes "20" sprints. The benefit here is the total distance but for someone this slow there they are probably not super lean OR they are so inexperienced in running that they shouldn't use it until they have a tiny bit of efficiency. If they are even slower I would reduce total distance modify the goals (eg run 100m under 40 seconds, walk 300m under 3 minutes).
For everybody faster than that (given that they are not actual sprinters and don't compete in a power/explosive activity) I would recommend the following:
Calculate your distances ran with time but do your workouts with distances. We don't want to prescribe specific distances because energy systems are largely time dependent rather than distance dependent. That means someone doing 200m repeats in 25 getting into moderate lactate while someone doing them in 45 seconds is deep into aerobic respiration. This is why Clyde Hart has his world class 400m men running 350's while the women run 300's. Keeping them at a distance which they can keep under 40 seconds allows repeats to be run at a high intensity (once you approach 50 seconds aerobic respiration produces so much h+ that the lactic acid is paralyzing). So that said here is the basic guide to energy systems and sprinting for fat loss:
1) Under 6 seconds = alactic anerobic respiration (free ATP, creatine phosphate)
2) 6-15 seconds = initial stages of fermentation (lactate) that can be cleared with moderate rest
3) 15-25 seconds = significant lactate produced so without longer rest intervals each rep will effect the next
4) 25-40 seconds = lactate threshold reached and aerobic respiration starts to contribute
5) Above 40 seconds = Aerobic respiration becomes primary pathway. If intensity is high enough to produce lactate then the bout may be somewhat paralyzing without a rest interval too long to include in a single workout.
* Note that the second pathway (fermentation) can be skipped. If you run a lap at 50% your body will use alactic anerobic respiration (ATP stores) first, there is no way around this (that's why even distance runners always run fast for the beginning of race - they say first 6 seconds are free). However, after it exhausts free ATP it will only go into fermentation IF the demand for ATP is great (you are running fast). If your going at 50% you body will just shift to aerobic respiration and produce slow consistent ATP which it can keep up for a good 2 hours until you hit the wall... Since there isn't any lactate produced this won't be painful. This is why all distance runners follow the same strategy - run very fast for 6 seconds, run the pace just slow enough to keep lactate from creeping up, and then with about 20 seconds to go GO all out and just fight the lactate because your almost done. If they ran the first lap hard and got into lactate the acid produced from aerobic respiration would be paralyzing... Our goal is designing training is to never skip lactate, we define sprinting as the use of the energy systems in the following order (alactic anaerobic, lactate) if we go alactic anaerobic to aerobic we are jogging.
**Also Understand that these times are variable and trainable (especially time #3 and #4 - you can increase lactate tolerance and efficiency to a great degree).
Given those rules we want to rule out any repeats of over 40 seconds because learning to do multiple reps efficiently will be achievable only by jogging. However, that doesn't mean we can't do 1-2 reps at the end of a practice session.
I think the information provided here is enough for you to design a template. Here is a sample template for fat loss from sprinting that occurs 3x a week.
1) Find the distances you can cover in a sprint for 10,15...45 seconds. Or just run a 100m, 150m, 200m, 300m, 400m. Assume you get the following times:
100m = 12.5
150m = 20
200m = 27
300m = 50
400m = 66
Your distances would be 100m (< under 15 seconds) , 150m (< 25 seconds) and 250 (< 42 seconds). Here is a MWF template:
M: 1x100m time trial THEN 4x2x150 under 25 seconds, rest 5-10 minutes between sets, walk half the curve between reps in 30 seconds or less. Total workout should be about 35 minutes and total distance covered is 1 mile. Time the 100m and watch it drop slowly each week.
W: 3x4x100m attempt under 15 seconds for each 100m, rest 5-10 minutes between sets, walk the curves in 1-1.5 minutes between reps, total workout should take around 45 minutes, total distance ~ 1.5 miles.
F: 3 x (250, 100) 1x400. Run a 250 in under 42 seconds. Rest for 15 seconds. Run a 100m in under 16 seconds. Or try. Rest for 5-10 minutes between repts. Then rest 15 minutes. Run an all out 400m. Then recover with the weekend. Time the 400m and watch it drop quickly each week. Whole workout will be about a mile and should take about an hour.
That's a protocol you can't go wrong with.
