2007 ACSM Annual Meeting - Nutrition

[Guest guest]

Members may enjoy reading the following:

Betaine, Hyperventilation, Hyperimmune Egg Protein and Other

Novelties for Performance at the 2007 ACSM Annual Meeting

Will G Hopkins

Sportscience 11, 1-8, 2007 (sportsci.org/2007/wghACSM.htm)

Acute Strategies

http://sportsci.org/2007/wghACSM.htm

Nutrition

The most exciting presentation of the conference for me was on the

performance-enhancing effects of betaine from a group at Bill

Kraemer's lab. Few delegates saw the presentation, because it was

mis-programmed into a session on hydration rather than ergogenic aids

or supplements, and it came right at the end of the last slide

session on the last day in the most remote lecture theater of the

conference center. Betaine, which I had never heard of, turns out to

be a derivative of the amino acid glycine. Plants make and use it

apparently to resist dehydration, but in animals it is involved in

the synthesis of creatine. The subjects in the double-blind

crossover study were 12 men with at least 3 months experience of

resistance training. They did one standardized resistance-training

session a week to maintain fitness during the supplementation and

washout periods, and performance testing was a high-intensity

exercise challenge spread over 2 d to test the ability of betaine to

maintain performance. After 14 d of supplementation (1.25 g, twice a

day), bench-throw power increased by 16% and isometric bench-press

force increased by 28% compared with placebo. Other measures of

performance did not show " significant " changes. In question time I

asked how they thought it might work, but all he could say was that

it appears to used up during exercise–plasma levels fell–which might

explain why it didn't work clearly for the strength-endurance

measures that were assessed towards the end of the challenge.

Compared with a 6% carbohydrate drink alone, addition of 1.2% milk-

protein hydrolysate produced a 35% increase in time to exhaustion at

80% VO2max in 10 cyclists and runners, following an 8-km run and a 50-

km cycle at 80% and 70% of VO2max [904]. Doubling the protein

reduced the benefit to only 9%. It's too difficult to work out the

effect in terms of mean power output in a time trial, but it's

probably something like 1-2% for the lower dose of protein and

negligible for the higher dose.

In a blind crossover of 6 male and 6 female high-level swimmers, a

4:1 carbohydrate-protein supplement in gel form (80+20 g in total)

consumed with 500 ml of water immediately before and during 24 100-yd

sprints produced a gain in swimming speed of ~3% that was apparent by

the fourth sprint and was sustained thereafter [2061]. To convert

percent change in swimming speed or time to percent change in power

output, I've figured out from data in a paper by Toussaint and

Hollander (1994) that you have to multiply by a factor of 2. So the

equivalent gain in power output is a phenomenal ~6%! The same

supplement in drink form produced a 2.3% enhancement in overall

performance time in four 2-km sprints (with 30- to 60-min recoveries)

on a cycle ergometer in a blind crossover with 17 aerobically trained

subjects [2063]. Again, depending on the ergometer, the gain

corresponds to ~5-6% in mean power. I chatted with the principal

investigator, Seifert, who told me that carbohydrate alone was

less effective than carbohydrate plus protein in a subsequent study

with the swimmers…But drinks containing carbohydrate plus protein or

carbohydrate alone had little effect on performance and markers of

muscle damage following unaccustomed eccentric exercise (30 min of

downhill running) in a randomized blind trial of 18 females [2065]….

Caffeine continued to be beneficial at the endurance end of the

performance spectrum or for brief bouts affected by fatigue [698-701,

903, 954], as well as for tennis skill [953]. It helped 15 college-

age males do more reps with less pain than placebo or aspirin in a

resistance-training session, but not without side effects

(restlessness, tremor, stomach distress) [1586]. Caffeine may work

by reducing muscle pain during exercise, at least in 16 college

females, and it reduced pain more in those with less anxiety

sensitivity [1217]. Low doses of caffeine (2-3 mg per kg of body

mass] with 13 male cyclists could be as effective as the more usual

doses (~6 mg.kg?1) in their abstract [701], but the authors reached a

different and wrong conclusion in the podium presentation

after " protecting the p value " . Ever tried desecrating the p value?

It's liberating.

Beta-alanine taken as a supplement gets converted in muscle to

carnosine, a dipeptide that acts probably as buffer for acidity in

intense exercise. It's best to take it many times a day for at least

4 wk [910]. In randomized blind controlled trials, 6+6 elite

cyclists got enhancements in time to exhaustion and isokinetic work

[2069–the data aren't in the abstract and I forgot to get them off

the poster], and 11+11 nondescript women got gains in endurance

performance tests that I can't convert to mean power [2072]. I

chatted with the leading researcher in this field, , and

we worked out that gains in mean power in time trials would be of the

order of a few percent.

Other anti-oxidants featured in several presentations. A 28-wk

course of capsules containing powdered fruit and vegetable juice

produced lower resting protein carbonyls (a measure of oxidative

stress–presumably bad) and TNF-a (a measure of immune activation–good

or bad?) in the blood compared with a placebo in a crossover study of

40 trained men in a special-forces group [1224]. But there was

apparently little effect of or effect on a ride to exhaustion at 70%

of VO2max. On the other hand, protein carbonyls did rise following

exercise and the concentration was higher at rest and in exercise

when the 12 trained males exercised and recovered with a drink

containing carbohydrate, protein, vitamin C and vitamin E than when

the drink contained only carbohydrate [1225]. So, no evidence at

this conference for benefits of anti-oxidants on performance.

Not surprisingly, 9 elite swimmers improved their 200-m freestyle

time by 1.6% when they consumed sodium bicarbonate instead of a

placebo [1462]….

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Carruthers

Wakefield, UK