Bodybuilding.net - Bodybuilding Forum - View Single Post

EricT · 06-11-2006, 03:49 PM

Excerpted from Active Nutrition by Joel Marion

The "When" of Cardiovascular Training

This is probably the most confusing and misunderstood topic when speaking of matters of active nutrition-- when is the best time to consume a meal in relation to cardiovascular activity? In order to answer this question, we must consider the most favorable way to:

Maximize performance. Now, you may be thinking "I don't care about performance; I'm not competing in a race; I just want to lose fat!" This is a very common attitude; however, it's not a very smart one. Exercise intensity is directly related to the amount of calories and fat you burn as a result of a given workout. If your performance is suffering from a lack of proper nutrition, you won't be losing fat at an optimal rate-- period.

Optimize fat loss. Obviously, we don't want to hinder the amount of fat lost either during or after the exercise session. Therefore, we have to consider whether the method we choose to supplement in has any adverse effects on fat loss.

Minimize muscle loss. Many times trainees will compromise large amounts of hard-earned muscle mass while dieting. A major contributor to this sad occurrence is the failure to appropriately time meals to combat the catabolic influences of exercise.

It was originally thought that while consuming a meal before exercise may have a positive effect on performance, it would certainly have an adverse effect on the amount of fat lost as a result of that session. Consequently, consuming a meal prior to exercise was frowned upon and performing cardio in a fasted state became the staple recommendation to optimize fat loss. However, all theory aside, research has shown this not to be the case. Three recent studies directly analyzing the aforementioned variable founded that consuming a carbohydrate containing meal prior to cardiovascular activity had no adverse effect on substrate utilization during exercise (the amount of fat versus carbohydrates used as energy during exercise) (2,3,4)*. Furthermore, the one study analyzing time to fatigue founded that those who did not consume a meal before exercising fatigued faster and performed at a lesser level than those subjects who did eat prior to the session (4).

Also, it should be noted that performing cardio in a fasted state is very catabolic not only to fat stores, but also to muscle protein. Continual use of such a method will likely cause lean tissue loss in dieters who are constantly in a state of negative calorie balance. This is especially true for leaner trainees trying to shed that last bit of fat.

Another common recommendation has been to wait an hour after exercise before eating in order to take advantage of the substantial increase in metabolism that occurs as a result of high intensity exercise. This hypothesis was recently studied by Dr. Lee and the Department of Exercise Science at the University of Se Jong in Seoul, South Korea (1). He and his research team founded that those subjects who consumed a protein and carbohydrate beverage actually increased the amount of calories burned during the hour post-exercise while still having no effect on substrate utilization. Also, proper post-workout nutrition will help prevent lean muscle mass from being catabolized and used as energy during this time frame.

Hopefully by now, it should be easy to see that consuming meals both prior to and immediately following intense exercise is the best way to 1) maximize performance, 2) optimize fat loss, and 3) minimize muscle loss.

"What" and "How Much" of Cardiovascular Training

Because cardiovascular activity generally causes less muscular damage than weight training, pre-/post-workout nutrition does not need to be as strictly calculated. Here are some general guidelines for the two types of cardio sessions mentioned earlier in the article:

For all workouts, pre-cardio nutrition can be as simple as consuming a small whole-food meal containing both protein and moderate GI carbohydrates about an hour prior to your session. An example of this would be to have a cup of oatmeal along with eight egg whites at 7 a.m. and then your session at 8 a.m. If wanting to perform the cardio sooner after your meal, then choose something that is more rapidly digested, such as a 1/2 of a nutrition shake with a cup of skim milk; this can be consumed half an hour prior to your session.

For a moderate intensity, longer duration session, just consume your next whole-food meal shortly after your training; this will suffice for post-workout nutrition.

For all HIIT sessions, consume a rapidly digesting beverage containing quality proteins and carbohydrates immediately after your training. An example of this would be to consume a nutrition shake with two cups of skim milk immediately after your HIIT session.

*Edit - Oops, I forgot to paste in the sources listed above. Here are whole abstracts as per 0311's request:

2. Int J Sports Med. 1999 Aug;20(6):384-9.

Cardiovascular and metabolic responses during 30 minutes of treadmill exercise shortly after consuming a small, high-carbohydrate meal.

Diboll DC, Boone WT, Lindsey LR.

School of Human Performance and Recreation, University of Southern Mississippi, USA. ddiboll@csubak.edu

Fourteen male endurance runners (VO2peak = 64.8 +/- 8.7 ml x kg(-1) x min(-1)) participated in this study to determine the cardiovascular and metabolic responses during 30 minutes of treadmill running at a moderate intensity soon after consuming a small, high-carbohydrate meal (CHO-M). In randomized order on separate days, subjects either consumed the CHO-M (2088 kJ; 77% carbohydrate) 15 minutes prior to running or they fasted (FAST). Data were collected for 5 minutes beginning at 5, 15, and 25 minutes of the 30-minute run. Heart rate (HR) was determined, a metabolic measurement cart was used to determine VO2 and respiratory exchange ratio (RER), and the CO2 rebreathing procedure (Collier plateau method) was used to determine cardiac output (Q). Statistical analyses indicated that the CHO-M did not affect HR, stroke volume, Q, VO2, or RER compared to FAST. However, all grouped CHO-M and FAST variables, except VO2, changed significantly across the 30-minute exercise session. These data suggest that a small, high-carbohydrate meal does not alter cardiovascular and metabolic function during moderate-intensity exercise in endurance-trained subjects.

3. J Appl Physiol. 1999 Feb;86(2):479-87.

Respiratory gas-exchange ratios during graded exercise in fed and fasted trained and untrained men.

Bergman BC, Brooks GA.

Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, California 94720-3140, USA.

We evaluated the hypotheses that endurance training increases relative lipid oxidation over a wide range of relative exercise intensities in fed and fasted states and that carbohydrate nutrition causes carbohydrate-derived fuels to predominate as energy sources during exercise. Pulmonary respiratory gas-exchange ratios [(RER) = CO2 production/O2 consumption (VO2)] were determined during four relative, graded exercise intensities in both fed and fasted states. Seven untrained (UT) men and seven category 2 and 3 US Cycling Federation cyclists (T) exercised in the morning in random order, with target power outputs of 20 and 40% peak VO2 (VO2 peak) for 2 h, 60% VO2 peak for 1.5 h, and 80% VO2 peak for a minimum of 30 min after either a 12-h overnight fast or 3 h after a standardized breakfast. Actual metabolic responses were 22 +/- 0.33, 40 +/- 0.31, 59 +/- 0.32, and 75 +/- 0.39% VO2 peak. T subjects showed significantly (P < 0.05) decreased RER compared with UT subjects at absolute workloads when fed and fasted. Fasting significantly decreased RER values compared with the fed state at 22, 40, and 59% VO2 peak in T and at 40 and 59% VO2 peak in UT subjects. Training decreased (P < 0.05) mean RER values compared with UT subjects at 22% VO2 peak when they fasted, and at 40% VO2 peak when fed or fasted, but not at higher relative exercise intensities in either nutritional state. Our results support the hypothesis that endurance training enhances lipid oxidation in men after a 12-h overnight fast at low relative exercise intensities (22 and 40% VO2 peak). However, a training effect on RER was not apparent at high relative exercise intensities (59 and 75% VO2 peak). Because most athletes train and compete at exercise intensities >40% maximal VO2, they will not oxidize a greater proportion of lipids compared with untrained subjects, regardless of nutritional state.

4. Med Sci Sports Exerc. 1999 Mar;31(3):464-71.

The effect of a preexercise meal on time to fatigue during prolonged cycling exercise.

Schabort EJ, Bosch AN, Weltan SM, Noakes TD.

MRC/UCT Bioenergetics of Exercise Research Unit, Sports Science Institute of South Africa, Newlands.

PURPOSE AND METHODS: Seven subjects exercised to exhaustion on a bicycle ergometer at a workload corresponding to an intensity of 70% maximal oxygen uptake (VO2max). On one occasion (FED), subjects consumed a preexercise carbohydrate (CHO) containing breakfast (100 g CHO) 3 h before exercise. On the other occasion (FASTED), subjects exercised after an overnight fast. Exercise time to fatigue was significantly longer (P < 0.05) when subjects consumed the breakfast (136+/-14 min) compared with when they exercised in the fasted state (109+/-12 min). RESULTS: Pre- and post-exercise muscle glycogen concentrations, respiratory exchange ratio, carbohydrate and fat oxidation, and lactate and insulin concentrations were not significantly different between the two trials. Insulin concentrations decreased significantly (P < 0.05) from 4.7+/-0.05 microIU.mL(-1) to 2.8+/-0.4 microIU.mL(-1) in FED and from 6.6+/-0.6 microIU.mL(-1) to 3.7+/-0.6 microIU.mL(-1) in FASTED subjects and free fatty acid concentrations (FFA) increased significantly (P < 0.05) from 0.09+/-0.02 mmol.L(-1) to 1.4+/-0.6 mmol.L(-1) in FED and from 0.17+/-0.02 mmol.L(-) to 0.74+/-0.27 mmol.L(-1) in FASTED subjects over the duration of the trials. CONCLUSIONS: In conclusion, the important finding of this study is the increased time to fatigue when subjects ingested the CHO meal with no negative effects ascribed to increased insulin concentrations and decreased FFA concentrations after CHO ingestion.