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Why Cardiovascular Drift is something you should know about

Cardiovascular drift refers to the increase in heart rate that occurs during prolonged endurance exercise with little or no change in workload. During steady-state aerobic exercise, heart rate should reflect the intensity of the work being performed. If intensity (workload) remains constant, heart rate should remain constant as well. With prolonged exercise, however, it is common to see heart rate "drift" upward during the workout, even with no increase in workout. Sometimes the increases can be significant. 

Cardiovascular drift is mostly caused by increased body core temperature. This increases heart rate, but decreases stroke volume so that cardiac output (and oxygen uptake) remain the same. The effect can be enhanced by the decrease in plasma volume that is caused by water loss during exercise. Both causes of cardiovascular drift will be more pronounced when exercising under thermal stress--e.g. hot room, high humidity. The effect can be blunted somewhat by ingesting sufficient fluid during the workout. 

It is important to emphasize that cardiovascular drift results in an increased heart rate WITHOUT AN ASSOCIATED INCREASE IN OXYGEN UPTAKE OR CALORIES BURNED. You can observe this phenomenon by paying attention to your breathing during a longer, low to medium intensity cardio workout. If you are attuned to your breathing pattern, you will notice that, even though heart rate increases steadily during the workout, breathing remains relatively constant. 

I tend to "run hot" during exercise and lose a decent amount of water weight (3-4 lbs/45 min) so I have been aware of this phenomenon for many years. I was thinking about it again last night during my workout. I try to include one (relatively) extended, lower-intensity (50%-60%) cardio workout every week. Sometimes it 's hard to do because you really have to force yourself to stay at a low level and just grind it out, but it is an important part of an overall conditioning program. Since last October, I have been kind of spinning in circles due to a variety of physical and life issues. For the past month or so I have gotten back on track and have started ramping my program back up. 

Last night I did 60 minutes on the cross trainer, with a goal intensity of 50%. I kept the workload constant the entire time (that's what I mean by "grinding it out"). Once I steadied out, my heart rate settled at around 113, right in my goal of 110-115. As expected, at around 20 min it started to drift upward. Because my endurance levels are still relatively untrained (I had only been beyond 30 min twice in the previous 2 months), the increase was larger than usual. After 30 min the HR went up even more and by the end I was pushing 140. 

So that was the "drift"--113 to 140, with no increase in workload and no significant change in breathing. Consistency of workload is demonstrated by the calories burned shown on the machine display: 434 the first 30 min, 441 the second 30. 

So what are the practical implications of cardiovascular drift and why should you even pay attention? 

One goes back to some of my issues with HRM calorie totals. Since HRMs only measure heart rate and estimate calories based on heart rate, an increased heart rate with no increase in oxygen uptake (as occurs during cardiovascular drift) could cause an HRM to OVERestimate exercise calories. This was clearly demonstrated during my workout. I wear a Polar F11. The HRM calorie number for the 1st 30 min of my workout was 353, for the 2nd 30 min 460. That's a 30% difference--with NO change in workload intensity. Just one more reason why one must exercise caution when incorporating HRM exercise calorie estimates into an eating plan. 

Two: Cardiovascular drift is the main reason why I advise clients NOT to use HR-controlled programs on cardio machines. Cardio programs use the HR data from the machine sensors or a chest strap to automatically adjust workout to keep you in a specific HR "target" range. On paper, it sounds like a great idea--let the machine automatically keep you in your desired "zone". However, in reality, once you reach your target and "drift" above it, the machine will start to reduce your workload, thus steadily decreasing the quality of your workout. Workload intensity is the stimulus that produces the results you want (whether the goal for the day is easy, hard or in between). You can use heart rate to help gauge and control intensity, but you don't want to reduce intensity solely on inflated HR numbers 

Three: since cardiovascular drift is enhanced by thermal stress, any activity that occurs under those conditions (e.g. "hot" yoga, working out in sweatsuits) will result in exaggerated and overestimated calorie counts that are virtually useless. 

Bottom line: Don't be a slave to your HRM numbers --either heart rate or calories. As your progress in your workout program, learn to use breathing as a way to intuitively assess your intensity and use that along with heart rate to control your overall effort.

Why I don't count exercise calories

Or--why I don't count them that much.  
Sometimes it seems like half the comments on these boards are concerned with estimating, tracking, and logging exercise and activity calories. At any given time of day or night one can find the topic "what kind of HRM should I buy?" on the first page of the "Fitness and Exercise" Message Board. 

I am going to propose a different approach. This is in keeping with some of my other recent posts in which I am recommending a more simplified strategy for weight loss, one that has more emphasis on focusing one's efforts in a few key areas rather than getting too caught up in what I consider peripheral items. 

This approach is based on my background and personal exeperience with my own weight loss; it has been reinforced by my experience with the weight loss program run by the medical fitness center where I have worked for 16 months now. 

I don't mean to assert or imply that this is the ONLY approach, or even that it is the best approach for everyone. Ultimately, the overall strategy is not that different--it's another means of managing energy output vs energy intake. It is also meant primarily for those starting a program, with a high level of body fat. 

Here it is in a nutshell: Increase your daily calorie intake and stop including exercise calories routinely into your eating plan (i.e. "eating back exercise calories"). REFUEL after your workouts (carb/protein snack, 150-400 calories, depending on length/intesnity/calories expended during workout), but not more than 1/2 the exercise calories and do not bother with tracking recreational or activity calories (cleaning, dog walking, yardwork, wearing high heels, golf, etc. And get out of the 1200 calorie/day herd. 

Here are some of my reasons: 

1. Our methods of estimating calories expended during exercise are imprecise at best. I've explained this in detail on numerous occasions. Sometimes the number you get is no more accurate than just making one up out of thin air--at best they are no more than 75%-80% accurate. 

2. Even if you do calculate an accurate BMR and could accurately calculate exercise calories, a good 20%-30% of your daily total energy expenditure (TEE) comes from casual activty and other physical factors. And that number is not only just a rough estimate, it can also vary widely from day to day. So despite our best efforts, most of us only have a vague idea of what we are burning every day. 

3. Most people starting a weight loss program can and should be eating  more than 1200 calories per day.  In our program, the minimum calorie expenditure recommended by our dietitians is 1600 for females, 1800 for males. I think you can be a little more aggressive than that, but anyone over 180 lbs should do just fine on 1500 calories per day. 

4. If you are eating a decent number of calories (1400-1800/day), and you are starting out, and you have a high level of body fat, the chances of going into "starvation mode" are low to nonexistent, in my experience. And that is true even with calorie deficits of over 1,500 per day. 

Again, this is as much an accounting strategy as anything else. One could say "well, I start at 1200 calories/day and then just add exercise and activity and get to the same place". 

And if that works for you, that is fine. What I am trying to do is take away a lot of the arithmetic and research that I think is unnecessary. For beginners, there is no need to be that precise about your energy output. As long as you are eating a minimum number per day, and incurring a defict, you should have success. To me, that is a lot easier than trying for the 500th time to figure out the number of calories burned in a Zumba class. I also think that routinely trying to eat 1200 calories a day is more stressful and can be counterproductive at times. 

There are reasons to track exercise calories--since calories expended during a workout can represent the total amount of aerobic work performed, tracking your calories can be used to set goals and monitor fitness improvement. Heart rate monitors are excellent tools for improving and maintaining the quality of your workouts and training program. 

But if you want to try a more streamlined approach, consider setting your daily calories a little higher, and working out and being as active as possible. I think it is more important to focus on calorie intake than it is to count every exercise/activity calorie because you are worried about starvation mode. 

Starting a Weight Loss Program? Keep it Simple.

MFP attracts a lot of new users who are primarily interested in losing weight. The forums--both here and on other sites--are full of ideas, tips, "rules", etc, for shedding those unwanted pounds. 

Because fitness and weight loss are big business, the internet and mass media are also sources of a seemingly endless stream of information and advice. Well-intentioned beginners come here with a new resolve and determination to "follow all the rules" and finally make some positive changes. 

I look at the many posts in the forums and read the many questions that newcomers have and, overall, I have one thing to say:

Weight loss is hard. Don't make it harder by overcomplicating the process. 

You may have heard of the "80/20 Rule" which says that we tend to spend 80% of our time and effort on things that only produce 20% of the results. Whatever the percentage, I think that many beginners focus too much time and energy on trivia and this lowers their chances of long-term success. 

For some, it's with the best of intentions. As I said: they are motivated and want to do "everything" right. Others are the types who feel they just haven't found the "perfect" program, so they hop from program to program, and diet to diet.

Most beginners will see more results from following a few key guidelines consistently rather than trying to construct the "ideal" program with a long list of "rules". 

I can tell you there is no one eating plan or exercise program that is the best for everyone and that will guarantee success. Try focusing on a few important guidelines and following them consistently. 

NOTE: I am targeting this advice for BEGINNERS, esp those who have not been working out and are in the 40+% BF range for females, 30+% for males. The recommendations may not be applicable to other groups. 

1. Energy Needs: Calculate your BMR and add in a reasonable activity factor. Or, simplify it even more--if you are female and over 200lbs, just go with 1600 calories per day. 

2. Portion Control: Weigh, measure, and log everything.

3. Protein intake: 1.0 to 1.5 g per kg of body weight ( or minimum 100g). 

4. Fat intake: 25% of total calories

5. Carbs: whatever is left: focus on whole grains and fiber; avoid processed foods and sugars. 

6: Aerobic exercise: Yes. Try to average 5 days/wk, 30-60 min per session. At first, just "capture the distance"--build up your endurance. After that, include different intensities--some days long and easy, others shorter with more challenging intervals. Any aerobic exercise will work--do what you like.   

7. Resistance training: Yes. 2 Days per week. If you are just starting out and have a higher percentage of body fat, choose weights that you cause you to reach a fatigue point in 45-60 seconds of controlled lifting. Choose 6-10 exercises that involve larger muscles and do 3 quality sets of each one. Don't waste time with small-muscle exercises such as biceps curls, triceps extensions and most ab exercises. Those can come later. A body-weight squat will do more to train your "core" at this point than dozens of ab crunches. 

(In terms of exercise in general, I personally prefer to have my clients stick with relatively simple and straightforward routines. I am not a big fan of workout videos or exercise classes for beginners, however I understand that often those are the only options for some people, and that some people find them very motivating. I guess my advice would be to find classes/videos that feature simpler movements and are longer in duration. Nothing is impossible, but I feel that programs like 30 Day Shred and P90X significantly reduce the odds of long-term success for beginners). 

8. Eating back exercise calories: I think most beginners need to exercise extreme caution when doing this. First of all, our estimates of calories expended during exercise are, at best, only 80% accurate. Secondly, our amount of non-exercise activity varies widely--and tends to be affected by our workout sessions. So, you might "calculate" that you burned 500 calories in a workout and eat them all back, yet it turns out that you only burned 400 and then afterwards reduced your daily activity by another 100 calories because you were tired from the workout. In my experience the risks of overestimating calories and overeating far, far outweighs the risk of "starvation mode". 

To me a better strategy is to get off the 1200 calorie hamster wheel, eat more calories every day (see above--1600 or so) and not regularly count exercise calories at all. If you do a longer or more strenuous workout, then "refuel" the workout by adding a post-workout snack of 100-300 calories on those days only. 

9. Non-exercise activity: move as much as possible. Look for opportunities to take stairs, park in a distant part of the parking lot, see household chores as "calorie gifts", etc. 

Things NOT to be concerned with: 

1. Workout timing--do it when you can. 

2. Meal timing and frequency--do whatever makes you happy. 

3. Water intake--drink how much you want--don't obsess over it. 

4. Any supplements. 

5. Any "diet" with a name. 

6. Any oddball diet "strategy"--e.g. food combinations, "zig-zag" dieting, etc. 

7. Heart rate monitors--unless you are using it to monitor your heart rate and thus improve the quality of your workouts. 

8. Shoes or other informercial gadgets. 

9. Looking for any type of "magic bullet", i.e. the new, unique program that will automatically succeed where the others have failed. It doesn't exist. Never has, Never will. 

I tried to keep this relatively simple--I hope it comes across that way. I think the guidelines make for a relatively streamlined approach, but that is in the eye of the beholder, I guess. It is an approach we use with the weight-loss program at our facility. It is a 12-week supervised program. It doesn't have any frills or exotic interventions--just a lot of structure and hands-on attention to keep people focused on these key concepts. After 15 months and almost 120 participants, the avg 12-wk weight loss achieved has been about 22 pounds. A few have not been that successful and others have "overachieved" and lost 30-35 pounds. And, quite frankly, most are older and less fit than the average person on MFP. 

Again, I emphasize that this is mainly for beginners. As you make progress and reduce body fat %, then the approach must change and things get more complicated. However, by that time you will have more experience and familiarity, so it will not be a big distraction.

But if you are just starting, or if you have tried a lot of plans in the past and felt like you were spinning your wheels, consider a more "minimalist" approach. 
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