Sunday, May 23, 2010

Weight Loss Ups your Power - if you're a competitive cyclist and not going nuts with the CR.

ResearchBlogging.orgThere's been a debate for some time as to whether or not "fasted cardio" is ok. There's a "fasted cardio roundtable" at t-nation discussing this, and good arguments on either side. The title of a recent article made me think "great - a specific study on fasted cardio with elite athletes" Here's the title: "Effects of caloric restriction and overnight fasting on cycling endurance performance." But alas, it's not about fasted cardio: it's about doing an exertion test after ONE night of fasted cardio after having been on a calorie restricted diet.

Not the most usual circumstance. Indeed, the study is interesting nonetheless for a couple of other related reasons: it's looking at the effects on performance of a protocol often used by cyclists before competetive race season when they need to drop some weight to improve their Power to Weight Ratio (PWR) - lighter on the bike but still driving the same power means get there faster, if not fasted.

So not exactly fasted cardio - as in regularly doing cardio in a fasted state.  But there are *some* findings that may reasonably be extended - maybe - around fasted cardio. In particular the effects shown around perceived exertion in this condition and intriguingly fat utilization.

Here's the abstract

J Strength Cond Res. 2009 Mar;23(2):560-70.
Effects of caloric restriction and overnight fasting on cycling endurance performance.
Ferguson LM, Rossi KA, Ward E, Jadwin E, Miller TA, Miller WC.
Department of Exercise Science, The George Washington University, Washington, DC, USA. Abstract:

In addition to aerobic endurance and anaerobic capacity, high power-to-weight ratio (PWR) is important for cycling performance. Cyclists often try to lose weight before race season to improve body composition and optimize PWR. Research has demonstrated body fat-reducing benefits of exercise after fasting overnight. We hypothesized that fasted-state exercise in calorie-restricted trained cyclists would not result in performance decrements and that their PWR would improve significantly. We also hypothesized that substrate use during fasted-state submaximal endurance cycling would shift to greater reliance on fat. Ten trained, competitive cyclists completed a protocol consisting of baseline testing, 3 weeks of caloric restriction (CR), and post-CR testing. The testing sessions measured pre- and post-CR values for resting metabolic rate (RMR), body composition, VO2, PWR and power-to-lean weight ratio (PLWR), and power output, as well as 2-hour submaximal cycling performance, rating of perceived exertion (RPE), and respiratory exchange ratio (RER). There were no significant differences between baseline and post-CR for submaximal trial RER, power output, VO2, RMR, VO2max, or workload at VO2max. However, RPE was significantly lower, and PWR was significantly higher post-CR, whereas RER did not change. The cyclists' PWR and body composition improved significantly, and their overall weight, fat weight, and body fat percentage decreased. Lean mass was maintained. The cyclists' RPE decreased significantly during 2 hours of submaximal cycling post-CR, and there was no decrement in submaximal or maximal cycling performance after 3 weeks of CR combined with overnight fasting. Caloric restriction (up to 40% for 3 weeks) and exercising after fasting overnight can improve a cyclist's PWR without compromising endurance cycling performance.
Doesn't the above sound to you like the cyclists were doing both caloric restriction for three weeks AND doing fasted cardio at the same time? Well it turns out the only time we know that  they did fasted cardio was on two test occaisions: before the diet started and at the end of the three week period

Here's the actual protocol during the study:
For the CR period, subjects followed a fixed-macronutrient, calorie-restricted diet [this was set carbs, fats, proteins equivalent to a 40% reduction in total calories -mc] while maintaining their normal exercise training routines. None of the athletes were actively involved in strength training. Individual training plans typically involved base miles and some interval work, as it was still the off-season. Training was not standardized among athletes, because each athlete was a seasoned cyclist, accustomed to his or her own training regimen, and making changes to those plans could have produced chronic fatigue, muscle soreness, or altered the training volume to which each cyclist was accustomed-any of which could have led to unfavorable temporary adaptations that would have confounded their performance in their paired time trials.
In other words, they were doing big calorie restriction and that's the only change to their training.  We don't know if training actually changed in any way during this period - though participants were asked to keep things the same during the study as before in terms of these workouts. Ok, let's say that's all fine, then.

In the lab: the athletes did a submaximal two hour endurance ride (with ipods and music of their choice if they wished) on lab bikes set up just like their racing bikes with the following condition:
A metronome was used to ensure that subjects cycled at a constant 50 rpm to allow for consistent evaluation of workload. Subjects warmed up for 5 minutes at 100 W for men and 75Wfor women. The workload was incrementally increased by 50 Wevery 2.5 minutes. When HR reached 35 bpm below age-predicted maximal HR (220 bpm 2 age), or when the respiratory quotient exceeded 1, the workload was only increased by 25 Wevery 2.5 minutes until exhaustion. The subject cycled to exhaustion, ending the test voluntarily when he or she could no longer pedal or keep the 50-rpm cadence. Each subject wore a mouthpiece and nose clip, and ventilatory air was continuously analyzed forO2 consumption and CO2 production using the ParvoMedics system. Also, HR, RPE, and power output were recorded at the end of each stage throughout the test.

over the 25 days of their CR, they lost weight - in particular their body fat dropped but their lean mass was maintained. They had a 1.7 plus or minus. 5kg body weight loss, with a drop in bf% of 2.1 (plus or minus .4) %. Lean mass increased by 2.1%. No muscle mass loss. That's a plus of exercise while doing calorie reduction: lean mass hangs in.

in the lab: the fasted, post CR test showed no statisitcal difference in power output, Vo2max, resting metabolic rate (RMR), revolutions per minute. In otherwords, nothing performance wise changed - in particular, nothing changed netgatively - as a result of the CR and fasted state of the test.

One place there was a difference: PWR at 90 and 100% vo2max was significantly different post CR (it went up), though no PLWR (power to lean weight ratio) changes.

The authors suggest:
The increase in PWR was influenced by the significant decreases in body weight and percent body fat. Because there was no significant loss of lean body mass, the PLWRwas maintained. Thus, power was maintained not simply because of weight loss but because of the maintenance of fat-free mass. This increase in power output at high intensity levels, accompanied by a decrease in body weight, will provide the cyclist with more energy and power for improved uphill cycling performance.
Overall then, the cyclists did get what they wanted: an improved Power to Weight Ratio: their power stays the same, but at a lighter weight. That translates potentially into getting the bike moving down the road faster. 

Two notable changes/surprises: first, that perceived exertion was LOWER after the CR period. And second, that despite doing a heavy work load after an 11 hour fast, fat oxidation (using fat as the main fuel for the workout) did not change from baseline. Now me, i must be missing something because both base line test and re-test post CR were the same: post 11 hour fast. But here's what the authors say about the fat oxidation non-change:
Although we hypothesized that we would find a greater reliance on fat oxidation post-CR, particularly because RER [respiratory exchange rate - seeing which fuel is used more, carbs or fat -mc] - measuring has been previously shown to be lower in the fasted state (Aragón-Vargas LF 93, Knapik JJ88 ), this was not statistically supported. ...A possible explanation for the lack of a significant shift to fat metabolism is that the subjects were all highly trained endurance cyclists already and, as such, were able to use fat as a fuel more efficiently than if they had been untrained subjects.
Hmm. Makes ya wonder.

Practical Applications
The authors have some cautiously positive effects to report
[The study results] suggests that CR (up to 40% for 3 weeks) and exercising after fasting overnight can improve a cyclist’s PWR without compromising endurance cycling performance. Furthermore, this study demonstrates that a shortterm period of moderately severe CR is not detrimental to the conditioning process. Athletes can continue to prepare for the upcoming race season in terms of endurance training while dieting to reduce body weight without losing significant muscle mass in the process. However, it is not known what would happen to performance if an athlete were to prolong his or her exposure to the CR beyond 3 weeks, or to repeat the 3-week exposure to CR with short intervals of balanced energy intake in between. The current data suggest that a protocol such as the one outlined in this report would be most appropriate if used in the off-season to increase PWR or during the season before a competition.

 In other words, there's some good results in terms of body comp and PWR from a pretty intense caloric restriction for three weeks, but we don't know what would happen if this was strung out or for that matter repeated at intervals anywhere into competetive season. This ain't a license to go nuts.

And it's also not much help when thinking about fasted cardio as a regular practice.What i'm not sure this study says is what the authors state in the abstract: that "Caloric restriction (up to 40% for 3 weeks) and exercising after fasting overnight can improve a cyclist's PWR without compromising endurance cycling performance" Caloric restriction for three weeks with regular workouts, sure, but one session of fasted endurance work? Maybe i'm reading this wrong, but that seems a bit of a stretch. All it seems one can say is that after three weeks of caloric restriction, a sub max endurance workout in a fasted state when done by elite athletes doesn't have any negative effects - on them.

On the plus side: one can work to weigh less and maintain power, thereby increasing power. And for sports, like life, where better body comp has a host of benefits, a three week nutritionally balanced calorie cut with maintained workouts - at least for seasoned athletes - can be effective. Does this approach transfer to non-competetive athletes? May be worth investigating.

Ferguson LM, Rossi KA, Ward E, Jadwin E, Miller TA, & Miller WC (2009). Effects of caloric restriction and overnight fasting on cycling endurance performance. Journal of strength and conditioning research / National Strength & Conditioning Association, 23 (2), 560-70 PMID: 19197210

Aragón-Vargas LF (1993). Effects of fasting on endurance exercise. Sports medicine (Auckland, N.Z.), 16 (4), 255-65 PMID: 8248683

Knapik JJ, Meredith CN, Jones BH, Suek L, Young VR, & Evans WJ (1988). Influence of fasting on carbohydrate and fat metabolism during rest and exercise in men. Journal of applied physiology (Bethesda, Md. : 1985), 64 (5), 1923-9 PMID: 3292504

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