What Happens When You Stop Training- Endurance & Muscles Turning Into Fat
Part 2 of 2
There is usually a reason why people stop training and while lack of time ranks up there as reason number one, injury is often to blame as well. In this the second of a two part series on what happens when you stop training, we will take a look at how our bodies change when we stop training in terms of endurance and the critical role that workout intensity plays in maintaining the health benefits of exercise. Keeping injury as a possible factor in layoffs we will discuss the importance of not spending too much time lying down and why it’s always best to get back on your feet as quickly as possible. We will also tackle the well told myth of muscle turning to fat in those who stop working out, an observation that claim to have seen when regular gym going athletes stop training and put on weight. There is more to it than meets the eye and an understanding of what really happens can give you some insight as to what you can do as well to minimize unwanted weight gain when you stop training. Thanks as always for reading, and I encourage you to ‘like’, ‘retweet’ and share as much as possible.
What Happens When You Stop Training: Endurance
When you stop training one of the first things you will notice is a decrease in your endurance. Running up the stairs or making a dash for the train may still be something that you can do, but you will very soon feel a difference as you don’t seem to have the ‘wind’ that you used to and have to stop and catch your breath a little more than you used to. Unlike strength losses, which are mostly psychological, endurance does decline relatively soon after stopping training. One of the adaptations from intense exercise is a marked increase in aerobic capacity or peak oxygen uptake- (commonly referred to as VO2 max). This value goes up thanks in part to increases in your heart’s capacity to pump blood and the volume of blood sent out with each heartbeat (cardiac output and heart stroke volume respectively) as a result of regular intense exercise.[1,2] This increased efficiency translates into a tangible increase in endurance- however in keeping with the reversibility concept, these increases deteriorate over time and unlike strength losses from detraining, it occurs fairly quickly. A rapid decline of on average 7% of peak oxygen uptake was observed in a study of experienced athletes undergoing detraining within the first 12 to 21 days, with a further drop in VO2 max values of 9% during the following 21- 84 days of inactivity. The initial 7% decline during the first 12 days of inactivity was linked to a reduction in maximal heart stroke volume whereas the decrease in VO2 max during the 21-84 day period was associated with a decline in maximal arteriovenous oxygen- (which is the technical way of referring to the maximum amount of oxygen is present in your blood).
What is fascinating about the initial drop in VO2 max over the first few days of detraining is that while it is associated with reduced heart stroke volume, this drop in performance has little to do with any loss of cardiovascular function as it occurs as a result of a reduction in blood volume. You might not be aware of it, but intense exercise usually results in an increase in blood volume by about 500ml from an expansion in plasma volume.[5,6] It’s an adaptation that occurs fairly quickly after only a few sessions of intense physical activity  and the increased blood volume means more oxygen rich blood is available to needy muscles when they are hard at work. The decrease in blood volume from detraining means your heart will (obviously) pump less blood with each stroke. However this isn’t a sign of any deterioration in cardiovascular ability as decreases in VO2 max and stroke volume are reversed when blood volume expands to pre-detraining values. Consequently, individuals engaged in high intensity training for several years suffer little if any real reduction in heart function during short periods of inactivity.
What Happens When You Stop Training: Endurance & The Importance Of Intensity
Intensity plays a major part in how much our exercise induced adaptations are reversed over time, both in terms of strength and endurance (See part 1 What Happens When You Stop Training) as the more intense your workouts were, the more you retain when you stop training, even for prolonged periods of time. Among those training at high intensities, studies show that levels of mitochondrial enzyme activity remains 50% higher than that of sedentary individuals, skeletal muscle capillarization is maintained at high levels and both VO2 max and maximal arteriovenous oxygen levels stabilize to a point 12-17% higher than untrained individuals even after 84 days of inactivity. Detrained athletes who trained at high intensities also maintain higher exercise tolerance levels when compared to those who never exercised before. Not only do they have peak oxygen uptake levels significantly above untrained values but they also are able to exercise at a high percentage of their VO2 max before lactic acid accumulates in their blood. So they can do far more before becoming appreciably exhausted. Among those engaging in regular low to moderate intensity exercise, the long term benefits are not as promising. A study of male subjects engaging in low intensity aerobic exercise for 20 minutes three times a week reported quite positive increases in VO2max values of 6% to 8% above untrained levels after 7 weeks. However these gains were completely reversed after 8 weeks of inactivity. Moderate intensity exercise fares no better as even though such activity has been shown to increase VO2max by 10 to 20% or more, these values fall off rapidly during the first month of detraining and at a slower rate during the second and third month as they revert to pre-training levels.[8,9,10] It is interesting to note that the very low to moderate intensity protocols used for the studies mimic universal recommendations for aerobic exercise, a form of training that research continues to show may not be the best option for those seeking long term health benefits.[cardio vs high intensity training] (See my article Rethinking The Need For Cardio)
What Happens When You Stop Training: The Negative Effects Of Bed Rest
Since injuries are often the cause of you having to take time away from the gym, an article on detraining would be incomplete without some discussion of what happens when a well trained individual becomes bedridden. In the olden days bed rest was cited as the best treatment for just about everything[11,12] but time has shown quite the contrary and that laying down for prolonged periods can do more harm than good.  In fact prolonged bed rest brings about severe cardiovascular deconditioning, reductions in muscle size, strength and maximal oxygen consumption as well as reduced bone mass. [13, 14] It used to be that when you had a procedure done at a hospital you would spend a lot of time laying down, but today many remark at how aggressive hospital staff tend to be in terms of getting you back on your feet. You see both our cardiovascular and muscular systems operate best while counteracting gravity in an upright position . A coordinated interaction between the cardiovascular and nervous systems ensures that your brain and other organs have a steady supply of blood. However fluid shifts and changes in blood pressure brought on by extended periods in a reclined position can bring about severe cardiovascular deconditioning in as little as 2-3 weeks.[15, 16]. We know for a fact that it is the position itself and not inactivity per se that is a causative factor of heart dysfunction as studies have been able to replicate deterioration in heart function in volunteers to the degree observed over 2-3 weeks of bed rest after as little as 20 hours of in a reclined position with the head tilted downwards. Like detraining, blood volume is also reduced during periods of inactivity, but unlike detraining normal heart function is not restored when blood volume returns to normal [15,16]
Thanks to these bed rest induced changes, studies have found that maximal oxygen consumption decreases at a rate of just under 1% per day over 30 days of bed rest. That is a significant loss of function over time and it happens regardless of age and gender. [17,18,19] The bad news is that being in good shape doesn’t make it any better, in fact the more physically fit you are, the greater your absolute VO2max decreases daily when compared to less fit individuals. [17,18,20, 21] Most hospitals and rehabilitation facilities are pretty good at getting you up and moving and special pressure sleeves are often used with individuals forced to stay in bed as a way of minimizing dangerous fluid shifts over time.
What Happens When You Stop Training: Muscles Turning To Fat
The commonly held notion is that when someone who is highly muscular stops training, the muscle will eventually turn to fat. This rather idea has discouraged many from working out for fear that if they stop training they would be doomed to have all those muscles become blobs of adipose tissue. It is physically impossible however as muscle tissue and fat tissue are completely different and one can’t turn into the other any more than lead can turn into gold. The misunderstanding comes from the layman’s observation of what APPEARS to happen to most athletes who stop training completely, but it has nothing to do with muscle turning to fat. Let’s say for example that you weigh 200 lbs, are very well muscled, have a very low body fat percentage and engage in intense regular training. At that weight you would need anywhere in the ballpark of about 3,600 k/calories a day just to keep your body weight steady- which by the way is one of the great benefits of being active and having significant amounts of lean muscle mass. You can eat more and still stay in great shape.
However, if you stop training, as we have described in detail in part 1 of our series on detraining, over time those muscles will atrophy. Since lean fat free muscle tissue is responsible for the lion share of calories your body burns each day, with out it and a reduced activity level, your energy requirements will drop to anywhere between 2,000 to 2,600 k/calories per day depending on how inactive you become. That’s a huge drop in food intake from 3,600 k/calories and if you were used to eating that much for years on end, it would prove very difficult to suddenly stop. That being said, most former athletes keep eating pretty close to what they ate while they were actively training and in so doing can easily gain significant amounts of body fat over time. While on the outside it might look like the muscles are turning into fat what, is really happening is a slow reduction in muscle mass and a slow increase in body fat both happening at the same time.
What To Do When You Stop Training: Best Practices to Not Gain Weight
Now that we understand the dynamics behind weight gain when regular training is stopped, the most important thing you can do during a layoff is to gradually reduce your calorie intake. It isn’t always an easy thing to do as millions can attest to the fact that eating less can be frustratingly difficult, however it is the only way to compensate for decreased activity levels and possible loss of metabolically active lean fat free muscle tissue over time. The more muscular you are and those who engage in high volumes of intense exercise need to pay particular attention to this recommendation as the more muscle you have the less you’ll need to eat, and it goes without saying that stopping extreme amounts of exercise will mean reducing calories to suit. Those who are injured are also at risk as your activity level may be far less than it would be if you weren’t injured in terms of everyday activity, so concessions must be made to keep your food intake on par with your needs and not what you were used to eating while actively training.
If at all possible, try to always do something. It might not be the same as an intense workout nor might it yield that satisfying feeling that comes after true exertion, but a walk here and there can do you some good and keep you from becoming too depressed when by your situation. Depression can be a common problem among those forced to stop training against their will, and movement will do you some good psychologically, and keep you from spending too much time laying in bed. Another good strategy is to fidget as much as you can. It might not seem like much but some studies have found some increased calorie expenditures among individuals who move around and fidget regularly when compared to more stationary individuals. You won’t burn a ton of calories, but if you stand when you can sit and make a point to get up and move around every couple of minutes instead of always staying in one place, it will help some. You have to be practical about your layoffs if they are going to last for more than 3-4 weeks and understand that losing some of your hard earned fitness markers is inevitable, but that doesn’t mean that you can’t do your best to minimize those losses.
An important lesson we can take away from detraining is the importance of having a sustainable exercise program. Many athletes, from bodybuilders, to dancers and fitness models rely on excessive amounts of exercise and activity to keep their body fat levels down. This may work in the short term, but in the event of injury (which is often inevitable with extreme amounts of exercise) or simply life getting in the way of spending hours exercising; it will do more harm than good. The bottom line is that one day you will have to stop and when you do it will be very difficult to eat significantly less calories than you are accustomed to eating. Thus gaining weight is usually how the story ends. It makes sense then to always follow a workout program that you can reasonably follow long term, one that doesn’t call for hours upon hours of training that can increase your likelihood of sustaining a stress injury. Combine that with learning to eat well and you’ll have the best chances of getting into great shape and staying there. In the end, layoffs aren’t always a bad thing, so that vacation you took away from the gym for a couple of weeks shouldn’t leave you miserable and depressed. A layoff can mean greater gains down the road and even if you are forced to stop for a significant amount of time, keep in mind that any losses in strength, conditioning and or muscle mass will be quickly reversed when you resume training. Stay strong!
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