After Skipping a Day of Working Out, Why Is It So Hard to Start Again?

Exercising is hard, but it’s harder to resume the activity after taking a break, but why is that? There are a few reasons for that, from our inherent laziness to not getting enough rest.

Do you feel guilty about missing your scheduled morning run, or your weightlifting session in the gym? Or are you worried that the calories you burnt from your previous exercise session might be in vain because of this break in routine?

Young woman pressing snooze button on early morning digital alarm clock radio - Image( Elena Elisseeva)s

It may seem difficult resuming exercise (Photo Credit : Elena Elisseeva/Shutterstock)

Don’t worry. Stay in bed for a few more minutes and instead work on understanding the reason behind that guilt!

There’s a good reason that people exercise as the first step towards their fitness goals, but sometimes they may find themselves unable to continue their workout routine that they’ve set, especially after taking a short break. The question is… why it is so hard to resume exercising after a break?

Before jumping into the crux of the matter, let’s address some underlying biochemical and physiological processes involved in exercise.

Energy For Exercise

All physical activity requires some form of muscle contraction and relaxation, and the muscles require energy to sustain these bio-mechanical processes. The molecule responsible for providing energy is called adenosine triphosphate (ATP), which is the energy currency of the cell. There are two biochemical pathways for ATP formation, depending on the type of respiration being used in that exercise—aerobic and anaerobic. They are discussed below in brief.


ATP provides energy for muscle contraction, nerve impulse propagation, chemical synthesis in the body among others (Photo Credit: Wikimedia Commons)


Aerobic Anaerobic
  • Aerobic exercise comprises physical activity that generates energy by using oxygen. Aerobic exercises raise the heart rate and breathing over an extended period of time, which boosts the oxygen intake (due to elevated breathing rate) and the oxygen supply (due to elevated heart rate) to the muscle tissues. Glycogen and fat react with Oxygen to produce ATP, with water and CObeing the byproducts.
  • Regular aerobic exercise stimulates the cardiovascular system by forcing the heart to pump a greater volume of oxygenated blood to the tissues.


  • Anaerobic exercise comprises all physical activity that generates energy without oxygen, using anaerobic respiration. This energy sustains short, intense bursts of activity. Muscle glycogen breaks down in the absence of oxygen to produce ATP, with lactic acid being the byproduct.
  • Regular anaerobic exercise causes micro-tears to the muscle fibers. The body adapts to the stress by fusing satellite cells to the injury site to form more muscle fibers, resulting in an increase in muscle mass.

It is clear from the above points that exercise requires energy and has physiological benefits, but that doesn’t mean that there are no downsides. When you take a day or two away from exercising, do you feel energized or lethargic? 

If the answer is the latter, there are a few reasons for this feeling. The tiredness that you feel is partly psychological and partly physiological. 

Sore Muscles And Weakened Bones

Doing exercises like running uses a significant amount of glycogen and fat, while intermittent high-intensity exercise like sprinting or weightlifting depend primarily on glycogen for their energy. Thus, glycogen reserves are depleted after intense or long exercise sessions. Rebuilding glycogen reserves is a slow process, so it’s important to add the right amount of carbohydrates in your diet and consume them regularly.

Studies have shown that a state of glycogen depletion is associated with muscle fatigue, although the exact biochemical link between fatigue and glycogen supply is still under investigation.

Further evidence  shows that some muscle protein is broken down along with glycogen and fat, due to stress placed on them during exercise. This damage may continue for hours after the exercise session is over. Protein and amino acid supplements assist in muscle growth and are recommended to be consumed, along with carbohydrates.

Joints such as the elbows, ankles and knees, which take the bulk of bio-mechanical stress, need time to adapt to the physical stress and repair from previous damage, at times causing stress fractures.

Mental Fatigue

Exercise also requires mental effort, as we must concentrate on every move and follow a routine. Concentrating for long durations can cause mental fatigue. Mentally tired people think that they exert greater effort than their non-tired counterparts (also called Rate of Perceived Exertion). Thus, mentally tired people may spend less time exercising in order to get more rest.

We also experience psychological resistance to change from current habits. This is known as cognitive inertia. This effect causes people to continue their present resting state and may be partly responsible for the struggle to resume exercise after a break. 

Evolutionary Reasons

Thousands of years ago, our ancestors lived as hunter-gatherers. Hunting and foraging required spending energy. Going on a hunt but failing to catch any prey put them in a net energy deficit. Over time, this could lead to weakness and death via malnutrition. As a consequence, they also evolved to minimize energy loss during all non-essential activities by resting as much as possible. 

Food sources became abundant and stable when humans transitioned from hunting and gathering to agriculture. Consequently, finding food required considerably less energy.

However, we still possess the genes of our hunter-gatherer ancestors. The body, to an extent, still hoards excess energy and prefers not spending energy on unnecessary activities, like exercise.

The Verdict

Therefore, difficulty resuming exercise after a day or two is due to a combination of physiological and psychological factors. Deteriorating physical health due to poor nutrition, over-exercise and a lack of rest affects physical health and mental health. These are the primary reasons for that feeling of difficulty getting out of the bed after a rest day. 



The balanced triad of exercise, nutrition and rest ensures that you can resume workouts without any serious lagging (Photo Credit : Elizabeta Lexa/Shutterstock)

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If you find it difficult to resume exercise after that well-deserved rest day, recognize that it’s your body’s way of telling you that some ingredient is missing from your fitness goal. This can derail the journey towards a fitter you, so get over that  guilt, take some rest, eat properly, and break your personal record!

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About the Author

Argha has a Bachelors in Physics, Chemistry and Mathematics from University of Delhi, India. He enjoys discussing STEM topics and football. With a belief that studying science should be enjoyable and not scary, he wants to play his part in a changing world.

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