I know lots of people enjoy and get a lot of value out of doing strength work whilst in a fasted state. But how about sprints or other speedwork? I'm about to add sprinting back into my workout regime after a break, and want to know if it's beneficial to do so fasted or whether it's irrelevant.
I must have heard at least a dozen slightly different versions of what exact activity depletes glycogen and what doesn't. Basically, high intensity heavy breathing type expercise depletes glycogen in the muscles and the fastest way to replace it is via carbs. Hence the idea of carboloading. HOwever, you only really need to eat enough carbs to replenish the glycogen. Beyond that is not going to be good for you. MOre is not always better. For very active athletes, they usually eat more carbs even if they are paleo. They will usually eat things like sweet potatoes and more fruits. But these are elite athlete types. They are constantly depleting glycogen so they need to replenish it ASAP. The body can also replenish glycogen via fat and protein, but it takes a bit longer. If you are just going to do a bit of intermittent sprinting now and then, perhaps a slightly carby thing afterwards might be in order, or save your most carby meal for then. But then again, many regular exercising paleos say they recover fine eating normal paleo. One hint is if you feel like recovery time is longer than normal or if you feel unusually fatigued afterwards, you may want to try upping carbs immediately after sprints. SOme even say a bit of carb before is also good. Really, that is like a huge giant discussion all by itself and seems like everyone reacts differently.
So basically, if the question is about eating and high intensity workout, some feel a bit of added healthier carbs might be good but others feel they personally don't need extra carbs just for maybe like 20 minutes of intermittant sprints. If the question is about do paleos think sprints are a good healthy exercise, then yes, many paleos think highly of occasional sprints as a good healthy exercise.
I do max-intensity sprints once or twice a week at 15-18 hours fasted usually. Skip breakfast and it's easy. I think it feels more natural than doing it sooner after eating and obviously from a practical POV it's good to have the stomach completely empty to avoid nausea but most sprinters know that.
But benefits? I dunno. Unlike cardio sprints are usually over before you've had a chance to metabolize any fat but they do affect EPOC in the hours afterward so you might preferentially burn bodyfat if you keep fasting for a few more hours.
I've seen anecdotal reports (this thead for example, or pretty much anywhere this is discussed) that low-carb/paleo diets are not optimal for sprinting performance. Not everyone agrees, but it makes sense to me. I know back in high school when I ran competitively everyone used to load up on pasta before races and I think it does make a difference. When glycogen is depleted the muscles just won't contract as fast and at sprint speeds there is not enough time for aerobic fat metabolism to help you much.
But if we're just doing it for health benefits (that's my only motivation), performance shouldn't be a concern. And who knows, maybe acute glycogen depletion has metabolic benefits.
I'm sorry to answer with another question. You ask if sprinting while IF is beneficial. Beneficial for what? For sprinting performance, or for inducing certain training and/or metabolic effects?
I really don't know about performance, but I guess that a few sprints will not suffer from IF. Muscle glycogen should be sufficient to do this.
If your concern is health and/or metabolic effects, I think sprinting (like strentgh training) while IF is beneficial.
But, again, if you do it for health, it probably does not matter that much. Power law variation is really important. Sometimes you sprint while IF, sometimes you have eaten a few hours before.
I'm sorry but I can't provide any links or references for now...
I love sprinting while fasting, or even better if I have been fasting for more than 24 hours. I have deep wells of energy when I do that, and it takes more rounds of sprints to wear me out.
This might not work as well at a lower BF%, but I hope to find that out as I lower my own BF%.
I find sprinting to break a fast it great. I usually wait an hour after my sprints to eat (I remember Art De Vany recommending it) Sprinting help deplete the glucose stores in your muscles, this coupled with having your first meal contain no sugar/carbs, really kicks your body into fat burning mode. Since I am really focusing on fat lose, I lose the sprint/fast combo.
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