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Last week I discussed some of the current research presented at this year's ACSM conference in Nashville, Tennessee. With thousands of scientists and practitioners from around the world, however, I've merely scratched the surface. This week I'll review several more abstracts.
First, it's probably most important to define CPK (also sometimes referred to as just CK):
CPK is creatine phosphokinase. CPK is important to catalyze the reversible transfer of phosphate groups between creatine and phosphocreatine as well as between ATP and ADP. Basically, it is necessary for energy production. Most of the CPK resides in skeletal muscle, heart muscle, and in the gastrointestinal tract. CPK enters the blood rapidly following damage to muscle cells (e.g., weight training or other vigorous exercise). CPK used to be thought of as a marker of acute heart attacks, but other skeletal muscle damage can cause CPK levels to rise as well.
Previous work has shown that carb/protein supplements post-workout can attenuate the normally elevated CPK levels vs. carb only supplements. However, there are few studies in this area. Researchers in this study utilized 14-competitive male cyclists as their subjects. The cyclists rode at 75% of their previously tested VO2max until exhaustion to produce glycogen depletion and fatigue. This exercise bout was intended to deplete their glycogen stores (remember that glycogen is the primary fuel source for the body, but stores are limited).
Using a counter balanced, double blind study (see part I for definitions), subjects were given either a carbohydrate only or a carbohydrate/protein beverage every 15 minutes (1.8 mL/kg body weight) during exercise and again 30 minutes post exercise (at 10 mL/kg body weight). Fifteen hours later, subjects had a blood sample drawn to measure CPK levels and then performed a second, more intense ride at 85% VO2max.
Results: CPK levels were significantly lower in the carb/protein vs. the carb only group. This difference appeared to support extended and enhanced performance, as well. Looks like another study to add to the carb/protein "win column." The evidence is mounting and at this point is very clear that protein and carbs together are better than carbohydrates alone.
Take home message: This is one more reason to ensure your post-workout drink has some carbs and protein (in a 3 or 4:1 ratio, respectively). Note: fat-free chocolate milk is a great, inexpensive, post-workout food/meal.
Soccer is considered a power-endurance sport. Power, because it involves a good deal of start and stop sprinting. Endurance, because it also involves a good deal of longer distance continuous movement.
Therefore, soccer players during preseason and in-season training are under a great deal of stress (as are most athletes) as they attempt to maintain high levels of strength and endurance. It is crucial that they are able to perform near maximal capacity in season.
The purpose of this study was to examine the physiological changes and metabolic parameters in collegiate soccer players during preseason training. Twenty four, collegiate, Division I, male subjects underwent testing, including:
- Onset of blood lactate accumulation (which could determine onset of fatigue)
- Time to fatigue
- CK response (see previous abstract for definition of CK)
Athletes were also given a dietary supplement, containing superoxide dismutase, COQ10, and BCAA's or an isocaloric placebo. The particularly dietary supplement is purported to enhance some of the measurements utilized in this study.
Results: There were significant changes in all measurements utilized, which is not surprising after preseason training-VO
2max, onset of blood lactate accumulation, and time to fatigue, were all significantly improved in these athletes.
CK levels also increased, meaning muscle breakdown was higher; this is not surprising since the athletes were undergoing tremendous levels of training. There also appeared to be modest differences between the experimental and control group (supplement vs. non-supplement, respectively).
The researchers drew the conclusion that this particular combination of ingredients may enhance some of the parameters measured; however, they noted the short term effects were moderate.
Take home message: more research is necessary with this particular concoction of ingredients; this is one, small pilot study. The effects were only moderate, at best.
Caffeine is a known ergogenic aid. It has been shown through numerous studies to enhance endurance performance, increase mental focus and ability, speed among other things. This study took it one step further; knowing of caffeine's positive effect on the aforementioned parameters, the researchers here thought they would examine if caffeine also has an effect on athletic agility and, therefore, overall anaerobic performance.
Sixteen adult men performed two trials, separated by 2-3 days each, of two drills: pro-agility run test (to measure agility) and the 30 second Wingate test (to measure anaerobic power). Subjects were not blinded for this study; they all received 6 mg/kg of caffeine before one of the testing days, then a placebo on the other day. The order they received the supplement was random.
Results: The researchers found no significant differences between either the placebo or caffeine trials in either of the outcome measurements. They suggested a number of possible limitations to this study, however; caffeine dosage may have been too low, habitual caffeine use (e.g., if subjects were accustomed to drinking caffeine vs. being caffeine naive), and subject training status all could have influenced the results.
Take home message: Caffeine does work, but further studies need to be conducted addressing the limitations with this study, to determine if it has an ergogenic effect on other parameters.
Abstracts, Not Full Manuscipts
This wraps up the second part of the ACSM review. It is also important to note that what I have presented here are only abstracts, meaning the actual studies discussed have not yet undergone the rigors of peer review and have not yet been published as full length manuscripts. Some of the studies discussed and presented at ACSM will be published as full length manuscripts, but many will not.
Abstracts are not weighted as highly as peer reviewed manuscripts, so what I've presented here should just be considered introductory information. Stay tuned for more future summaries of more abstracts, presentations, and study reviews.
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