Updated: Mar 3, 2019
Have you ever decided to start an exercise program but when the time comes to actually do it you hear that little voice in your head saying, “I’m so tired and I’d much rather sleep in today?” Most exercisers skip a workout occasionally. You may be traveling, fall ill, or have an unusually heavy work deadline that keeps you from the gym. Sometimes you simply lack the motivation to work out, sometimes you feel pulled in multiple directions by family and they always come before you, right? That happens to everyone, but most exercise enthusiasts get back to it as soon as they can. But if your siesta from exercise leads to another skipped workout or two, you need to be aware of the consequences.
First, skipping workouts is not the same as spacing your workouts appropriately. In the case of high-intensity interval training (HIIT), you need the rest in order to recover. These type of workouts should only be done two to three times a week anyway. That’s because the intensity is so high your body needs the rest to recuperate.
But, if skipping workouts becomes a habit, your body, and your fitness level will suffer, with negative changes occurring faster than you might think. Not only that, your age might make a difference in the speed at which you lose that fitness level. To understand this better, let’s look at what we might expect as we age.
The 20’s through the 30’s
Ah, the years of youth. The years when we experience a coming of age into adulthood finds the body at the end stage of its growth spurts and riding a metabolic high. Never again will the body be so finely tuned from youth where skipping exercising does not affect it significantly (yet). But, during the decade after we turn 20 until we reach 30, that finely tuned metabolism begins to slow down. Over the next few decades, it will slow at a rate of 2-3% per decade causing a systematic drop in lean mass of 5-7 pounds per decade of life. Remember, your muscle burns fat and keeps you active and functional. While you may not notice the gradual loss of metabolism, by your 30’s you would have gained 10-15 pounds of fat because of that slowing metabolism. Of course, this does not have to happen but if nature takes its course it certainly will. To avoid this, research finds that active people who strength train lose very little muscular and metabolic function as they age (remember this as you read this blog).
It is during these years that people who do start to exercise push themselves the hardest. There’s no doubt that they can, recovery from hard training only takes 24-48 hours, so you can push yourself harder and recover faster. But don’t mistake youth for indestructibility! The last thing you want to do is become hampered by a bad injury.
Some of you know what I’m talking about. That old football injury, that torn meniscus, back injury, or ankle injury. They don’t go away! They wait for you to get older and then they let you know they are still there. The fact is the older you get the harder it is to recover from such setbacks. Because of this, your goals during this period are simple. Don’t do anything crazy stupid that you will regret the rest of your life! Don’t be an over enthusiastic risk taking over the top exerciser that believes that over training, over dieting or flipping large tractor tires does not have consequences. Oh and, by the way, sleep is super important too.
The muscles you develop during these years should be functionally trained, balanced, and performed with good mechanics. Rounding the back on those squats, jumping on those plyo-boxes and doing too much weight on those shoulder presses will haunt you one day. Learn from all those who have gone before you and who will be quick to tell you, everything you do in this decade counts, good and bad. Take the time to learn the correct execution of an exercise. Or do things that are safer, such as whole body vibration training which limits joint stress while optimizing muscle development.
Do you progress slower if you exercise safer? A little, but research shows that those who take a safer path end up stronger and in less pain than those who over train, get injured, recover then over train again. The resistance you use is not as important as you think as long as you properly stress the muscle. But, if you herniate that disc, tear a tendon or damage your shoulder, it will be something you will deal with for the rest of your life!
The facts are simple. Every aspect of your life is easier in the 20-30’s. Take advantage of it, but don’t destroy yourself in the process.
The 30’s through the 40’s
During this period, your metabolism begins to slow a little more. Another 3-4% equating to the loss of another 5-7 pounds of lean mass (without exercise) and 12-15 pounds of fat. By around age 40, almost everyone will begin reaching for reading glasses (or deny they actually need any), some can postpone this until their mid-50’s if they keep themselves hydrated and their sugar intake low, but few escape the dreaded readers.
By age 35, without strength training our bones will show the signs of aging. Throughout our life, old bone is broken down by cells called osteoclasts and replaced by bone-building cells called osteoblasts - a process called remodeling. Children's bone growth is rapid - the skeleton takes just two years to renew itself completely. In adults, this can take ten years.
Until our mid-20s, bone density is still increasing. But at 35, bone loss begins as part of the natural aging process. This becomes more rapid in post-menopausal women and can cause the bone-thinning condition called osteoporosis, especially if lots of fructose or fizzy sodas are involved. The shrinking in size and density of bones begins the slow loss of height which does not become evident for another two decades.
By the end of your 40’s your growth hormones will fall off without strength training, falling about 14 percent per decade after the age of thirty. By the age of eighty, without strength training, your production of HGH (human growth hormone) has been reduced to 5% of what it was at the age of twenty.
The 40’s through the 50’s
Starting at around 40, the heart pumps blood less effectively around the body because without conditioning it cannot do the job it could at 20. This is, in part, because blood vessels become less elastic while arteries can harden or become blocked because of fatty deposits forming on the coronary arteries. But, this is not an aging process, this is more an eating and inactivity process. Years of eating processed carbs, sugar, and poor nutrition foods, coupled with a lack of sleep is the main culprit. The blood supply to the heart begins to be reduced eventually leading to fatigue, and heart disease. Men over 45 and women over 55 are at greater risk of a heart attack. Not because of their age, but because they don’t exercise.
A study in the UK found the 'heart age' of inactive people five years older than their chronological age, probably due to obesity and lack of exercise. Their conclusion was that inactivity is a greater risk than even smoking.
Around 50, the kidneys begin to show their age. The number of filtering units (nephrons) that remove waste from the bloodstream starts to reduce. Not because it’s an aging thing, but more because we have lived a life of partial dehydration and lack of adequate sleep. The bladder has shrunk (atrophied) a little and is less elastic causing the inability to turn off urine production at night, causing frequent trips to the bathroom. The kidneys of an inactive 75-year-old person will filter only half the amount of blood that a 30-year-old will.
By 50, we have begun to slow the metabolism a little more, losing another 5-7 pounds of lean mass, that’s as much as 21 pounds of muscle since our 20’s. We gain about 15 pounds of fat (or 45 pounds since our 20’s). For many 50-year-olds they are faced with the contemplation of middle age and the struggle they have to sleep better, have more energy and hold onto their youth, but without strength training it will be nearly impossible.
It’s not too late though. A study conducted by scientists at the University of Oklahoma found that men aged 18 to 22 and 35 to 50 who followed the same weightlifting routine for 8 weeks had nearly identical strength gains. Meaning that your ability to gain muscle is no different from your younger you. It’s true, as you get older your muscles do become more susceptible to muscle damage and that takes longer to repair than in your 20-30’s. In your 50’s you may require 48-72 hours of rest for recovery between exercise bouts if those sessions are high intensity.
There is no evidence that your metabolism can be significantly hindered at this point in your life if you have avoided unnecessary injuries in your 20’s and if you have avoided severe calorie restriction diets which can have a lasting metabolic effect.
Why, then, do so many people gain weight as they age if it is not physiological decline? The answer is pretty easy, and you likely have already guessed by now that maintaining your strength as you age is the key is aging slowly and keeping the weight off. Eat a reasonable diet, strength train, and get plenty of sleep and you will do well. The only exception of course is if you have lost muscle through endless starvation diets and you have been avoiding exercise.
You will have a reduction in growth hormone production as you age, which is natural, but research finds that the inevitable decline associated with age is more due to inactivity and muscle loss. Research also shows that the loss of sleep and use of medications contribute to the decline.
Of course, there are ways to naturally improve your hormone profile as well, with the most effective ways being high-intensity training such as strength training or Sprint 8 training.
This is the age when most women move into menopause when the progesterone, testosterone, and estrogen levels begin to decrease.
What many people do not realize is that the absence of sufficient quantities of progesterone derived steroids can produce aches and pains in the joints, chronic fatigue, depression, sleep disturbances and anxiety. The decreasing amount of progesterone in the body can also be attributed to weight gain (in the form of fat and cellulite around the hips and thigh area), low libido, water retention, and indirectly cause hypertension.
Although thought of as a male hormone, testosterone has shown to be of benefit to women, especially those who have had a hysterectomy. Testosterone in women will assist in weight loss, mood stability, libido, concentration, and focus, increased energy levels, and a boosted immune system. Both men and women have this hormone, men simply have more of it.
Interestingly, estrogen is responsible for over 300 functions in the human body, including the health and maintenance of bones, skin, hair, nails (all of which tend to dry out), memory, mood and heart function. But too much estrogen and too little testosterone causes weight gain which is hard to undo, even with exercise. Carbohydrates tend to boost estrogen levels in the body. So as we age it’s a good idea to lower your intake of carbs and eat more vegetables in their place.
The 50’s through the 60’s
Things begin to change a little more rapidly at this time of life, but keep in mind that the norm is based on inactive populations, not active ones. An individual who has been inactive will find their rate of cellular loss accelerating as does the rate of muscle loss. In the 50’s you can lose double the mass than you did by not exercising in your 20’s. This could easily equate to a 7-12 pound loss of lean mass and a 15-20 pound gain in fat weight. Without exercise, adequate sleep and nutrition your rate of recovery is slower than it was in your 40’s. The good news is you need less to get more since your recovery rate is closer to 72 hours now.
The 60’s through the 70’s
During this period of time, we find that diminishing hormone-insulin-like growth factor (IGF-1) drops off rapidly and is likely responsible for the accelerated loss of muscle mass and thinning of the skin. The rate of loss accelerates due to a lack of strength training, which is ultimately your only means to preserve your mass. Without exercise, you would have lost 40 pounds of muscle since your 20’s and gained 55-60 pounds of fat without exercise.
The extra weight coupled with the lack of muscle (strength) begin to make it difficult to do the things you took for granted in your 20’s. It’s harder to walk upstairs, harder to pick things up, and you have less energy to do it too. That’s because your muscles store glucose or immediate energy. Without the muscle, you simply don’t have the storage space.
The extra weight is also hard on the joints, increasing the wear and tear. Typically a lifetime of dehydration and magnesium deficiencies will cause the muscles to weaken more, spasm more and exert more pressure on the joints, leading to accelerated arthritic changes.
The good news, there's no hard and fast rule about how long it takes to lose your fitness edge. The bad news, it accelerates without a fitness program. If you're very fit to begin with, your body will remain in a fitter state longer than someone who's not fit, even as your workouts cease. But the benefits of fitness have a limited time period if you stop. But what about skipping your workouts every now and then? Does that make a difference?
A study in the Journal of Applied Physiology suggested that skipping workouts for just two weeks can significantly reduce your cardiovascular fitness, lean muscle mass, and insulin sensitivity. But things change at various rates. In the body, we tend to measure things in something called a half-life. Half-life describes a tissue or cell undergoing constant exponential decay. The decay or loss is constant over the lifetime of the cell. The term "half-life" is used to refer to any period of time in which a quantity falls by half, even if the decay is not exponential. So how long does it take to make something, and how long does it take to lose it.
Your mitochondria (the things that make energy in the muscle) have a 10-day half-life. In other words, in ten days you can lose half of that which you have built up during your exercise career! Your heart can take as long as three months to begin to lose condition, and your strength can take 6 months to completely undo half your gains.
So, when you skip too many workouts, the strength of your heart and lungs will fade first. One study found that after just 12 days without exercise, VO2 max, a measure of cardiovascular endurance, dropped by 7 percent, while blood enzymes associated with endurance performance dropped by 50 percent.
In another study, four weeks of inactivity among endurance cyclists resulted in a 20 percent decrease in VO2 max. Keep in mind that this is for trained athlete. Among those new to exercise, gains in VO2 max completely disappeared after only four weeks of inactivity.
Strength tends to hold a little longer with inactivity. Studies show newly made gains tend to hold on even after months of inactivity. Among previously untrained men who engaged in a 15-week strength-training program, taking a three-week break in the middle had no impact on strength levels at the end of the study.
Loss of muscle is different based on fiber types too. Your body has three basic types of muscle fibers (actually 14, but it can be summarized into three): slow aerobic twitch (SO), fast aerobic twitch (FO), and fast anaerobic twitch muscles (FG).
Slow-twitch muscles are the red muscles (SO, FO). They are used primarily in aerobic or cardiovascular events. The fast twitch (FG) are typically called white muscle fibers, and these are only activated during high-intensity interval exercises or sprints. Medicine and Science in Sports and Exercise journal published a review of several studies on the subject that looked at runners, rowers, and power athletes. They concluded that muscular strength fibers appear not to change, even after a month of inactivity, but endurance fibers do change in as little as two weeks.
This is further complicated because with age and inactivity we tend to lose most of our muscle from the fast twitch fibers, which after several decades of inactivity reduce our strength to miniscule amounts.
Some things change more rapidly. Cholesterol for instance (HDL) immediately improves with either strength or cardiovascular exercise, but begins to drop off again after 48 hours, indicating that exercise every other day appropriately keeps us protected from heart disease.
The good news is that you can get your fitness back at any time in your life. Obviously, the longer you wait, the longer it takes, and some losses may be too great to fully restore due to injury and lifestyle choices.
So, your age plays a role. The older you get, the faster your muscles atrophy. In addition, it will take you longer to gain it back if you lose it. When comparing 20- to 30-year-olds with 65- to 75-year-olds, the older groups lose strength nearly twice as fast during six months of inactivity and find it more difficult to get it back, but they can restore most of it if they stick to their exercise plan.
Bottom line. It’s never too late to get back into the swing of exercise and begin a sensible strength training program again. This is especially important if you are trying to lose weight. Research published in the journal Cell Metabolism showed that when healthy but inactive people exercise intensely, even if the exercise is brief, it produces an immediately measurable change in their DNA.
In fact, several of the genes affected by exercise are genes involved in fat metabolism. Specifically, the study suggested that when you exercise your body almost immediately experiences genetic activation that increases the production of fat-busting (lipolytic) enzymes. Keep in mind that if something changes immediately with exercise then it can also reverse quickly without exercise. So if you want to lose fat, exercise is the key along with your dietary choices.
Another study found that unfit but otherwise healthy middle-aged adults were able to improve their insulin sensitivity and blood sugar regulation after just two weeks of interval training (three sessions per week). A follow-up study also found that interval training positively impacted insulin sensitivity, even in those with diabetes. Yet other studies find that in just 14 weeks you can undo decades of strength loss.
From this, we can ascertain the importance of maintaining your strength throughout your entire life, and if you are older, it’s not too late. If you get sick or go on vacation there are losses within two weeks, but one of the many benefits of being fit is that you can take time off and recover and use the reserves that you have built up to help you recover. Generally speaking you could take a week off without much impact to your health or your body.