A former roommate of mine was very into lifting
weights. He would lift weights
several times each week and before every workout I always saw him drinking a
pre-workout mix. I never
understood the logic behind pre-workout formulas. My roommate claimed he used it to “wake him up” before every
workout. This made sense because
just about every pre-workout mix contains some amount of caffeine. However, this seemed counterintuitive
to me. I would never drink a soda
or a cup of coffee before working out so why would I want to drink a
pre-workout mix that had caffeine?
Certainly there had to be other ingredients in the supplement besides
caffeine.
Glycine Propionyl-L-Carnitine (GPLC), the active ingredient
in many pre-workout formulas, has been found to increase nitric oxide
metabolites at rest. Several
studies have been done assessing the effect increased nitric oxide metabolites
have on exercise performance. One
such study assessed the effect GPLC by having subjects perform five 10-second
Wingate sprints, with a one-minute recovery time between each sprint. The
experiment recorded peak power, mean power, decrement in power output,
lactate levels, and heart rate.
GPLC was found to increase peak power, while also decreasing lactate
levels four and fourteen minutes post exercise. The proposed mechanism by which GPLC works is that
increasing NO synthesis results in vasodilation. Vasodilation causes capillary beds to swell increasing the
interface with skeletal muscle.
I admit that while I never understood why my roommate always
drank pre-workout, I still tried it several times. I liked that I seemed more awake after taking it, and I felt
as though I was able to lift more weight for longer periods of time. I suppose now that I have found actual
evidence showing pre-workout has beneficial effects on exercise I will have to
quit giving my former roommate a hard time for always taking it before he works
out.
Jacobs, P.,
Goldstein, E., Blackburn, W., Orem, I., & Hughes, J. (2009). Glycine
propionyl-l-carnitine
produces enhanced anaerobic work capacity with reduced
lactate accumulation in resistance trained males. Journal of the International Society of Sports Nutrition, 6(9).
I wonder what wins out, the vasodilation of GPLC or vasoconstriction from the caffeine.
ReplyDeleteYou are talking about GPLC in terms of weight lifting and sprinting, both of which use type II fast twitch fibers. Many articles online about GPLC are also focusing on type II fast twitch fiber exercises. On the contrary, long distance running uses type I slow twitch fibers. I was curious as to whether this made a difference in the effect of GPLC. Your study highlights how GPLC increases peak power, however, in long-distance running, you need more endurance than you do power. I found an article from a marathon runner: http://sportsnutritioninsider.insidefitnessmag.com/3013/5-must-take-supplements-for-optimum-marathon-performance. This article states GPLC as an excellent supplement to take throughout long-distance running as it increases endurance, stamina, and recovery via increased blood flow and oxygen delivery due to vasodilation and increases mitochondrial production of ATP. The article also states that GPLC helps with recovery during and after a long run because of its antioxidant properties. As your blog states, most of these are due to the increase of nitric oxide metabolites.
ReplyDeleteAfter looking at all of these pros, I was curious about the cons. Men's fitness (http://www.mensfitness.com/nutrition/supplements/glycine-propionyl-l-carnitine) states that the possible side effects of GPLC include nausea and diarrhea, sleeplessness, increased appetite, body odor and rash.
During my research, I came across an article by Smith et al. (2008) that states that GPLC has no effect on anaerobic OR aerobic exercise. The researchers looked at muscle carnitine (vastus lateralis), VO(2peak), exercise time to fatigue, anaerobic threshold, anaerobic power, and total work before and after and 8-week aerobic training program in a placebo control group and a GPLC supplemented group and they found no statistical significance in performance between the two groups.
It looks like there is still much research that need to be done on this type of supplement. I am certainly curious and willing to give it a try.
Reference:
Smith WA, Fry AC, Tschume LC, Bloomer RJ. 2008. International Journal of Sport Nutrition and Exercise Metabolism. 18(1):19-36.
Pseudoscience is my favorite kind of science. Workout supplementation might be one of the biggest versions of that. But my personal favorite is the newer "ultra concentrated" pre-workout mixes. These things are strong. Mine is Neurocore. By the name it already sounds like it will make you stronger, or have your brain explode
ReplyDeletePeople take anywhere from 4-16 grams. And the ingredient list is formidable:
For a 12.6g serving...
Caffeine - 330mg - Same as a Starbucks Grande Coffee
Beta-alanine - 3.2g - Supporting skeletal muscle Carnosine levels (an antioxidant) purportedly reducing fatigue rates.
L-Citruline - 3.0g - fatigue reduction, vasodilator
Creatine Monohydrate - 3.0g - supplementation supposedly promotes ATP synthesis above the bodies typical capacity.
Geranium extract - 531mg - Antidoping agency banned. Unstudied. Supposedly increases norepinephrine release
Rhondiola extract - 100mg - hardly studied. Supposed NO promoter, and antioxidant
Deanol bitartrate - 50mg - used as an attention enhancing drug.
Vinpoceteine - 5mg - vasodilator, cerebral metabolism enhancer.
+Color, sucralose and vit C.
They are really all fantastic for you as you can tell. If it is not obvious, many of these substances are poorly studied at best. Most studies utilize tiny sample sizes (10 people) and are often not repeated.
What does it feel like? Nobody who tries something like this can deny its intense stimulatory effects. Sometimes you feel like Bruce Banner. Other times you feel sick until you work out. Regardless, you work out and you work out hard. And when you walk away it feels like every energy supplying chemical is gone from your body. So I think it speaks to Candice's point that it might not be useful in long endurance exercise. I think this is certainly true. The feeling is as if every metabolic pathway has been exhausted.
Tim's roommate is right. It most certainly wakes you up. So does a large cup of coffee, and I have friends who will merely drink a large cup of coffee before the gym.
I think there ends up being a couple of camps among users of pre workout mixes. There are those who know nothing about the contents and merely the name Super-Concentrated Pre-Workout Stimulant NEUROCORE, convinces them of the beneficial effects. There are those who read every pseudoscience fact from the "clinical studies" and buys them because of that. Myself, I accept that this is amount of stimulant is terrible for me, but I crave that absolute feeling of exhaustion. Honestly, there are times that I wouldn't get up from TV without the massive stimulant rush. I think that might be where Tim's roommate is. Despite the aggressive rush it gives you, it is really the psychological effect that promotes exercise.
Then again, I haven't touched the stuff in months.