Whether you're putting on your first pair of running shoes or learning to lift a barbell, starting a new fitness routine is an exciting time. Consider it like the first day of school: you get to buy new clothes, invest in new equipment, and potentially meet new people.
Furthermore, the positive changes you'll notice in your mental and physical state will be extremely motivating. According to the Centers for Disease Control and Prevention, regular exercise can help lower your risk of type 2 diabetes, obesity, and arthritis, as well as increase your energy and help you sleep better. Exercise is also a key component in fat loss and weight management.
But what exactly is happening in your body as these changes occur? "It really depends on the type of exercise, duration, and whether or not you've previously exercised," says Douglas Comeau, MD, a sports medicine specialist at Boston Medical Center. However, you will generally notice muscle growth, an increase in energy, a stronger immune system, and an increase in energy levels.
When it comes to when you should expect to see the benefits, some will be noticeable right away, such as an increase in energy. Others, such as muscle gain or fat loss, may take a few weeks to start to show results. "Improvements in body composition (your muscle-to-fat ratio) can be seen in the first month or two of a resistance training programme," says Dr. Comeau.
If you're wondering how and why all of these changes happen, experts break down a behind-the-scenes look at what happens all over your body — inside and out — when you start exercising below.
How exercise impacts your Heart.
Aerobic adaptations are caused by physical activity and help increase blood flow through your heart, delivering more oxygen to your organs and muscles. According to the American Heart Association, working out can also improve your blood pressure, lower your resting heart rate, and lower your cholesterol levels, all of which help reduce your risk of dying from cardiovascular disease.
How exercise impacts your Muscles.
If you've never worked out before (or are returning after a break), you're likely to feel achy. Soreness will result from engaging muscles you haven't used in a while or in a way you haven't used them before. But pain is not the same as soreness.
"If you do have muscle soreness, you can use ice to reduce inflammation, and light stretching can also help," Dr. Comeau says. If you are in pain, stop whatever exercise you are doing and contact your healthcare professional or make an appointment if the pain does not go away.
Regular exercise improves muscle gain while also making you feel a little sore (looking at you, abs). According to the Cleveland Clinic, exercise causes micro-tears in your muscle fibres and connective tissues. But don't be alarmed; this is a good thing! With rest and proper nutrition, these small tears heal and strengthen your muscles, making them stronger — and more defined.
Your Brain on exercise.
Exercise is beneficial to your brain for a variety of reasons. According to a 2019 study published in BMC Public Health, physical activity increases blood flow, particularly to the brain, which can lower your risk of dementia.
Your Immune System on exercise.
Though exercise reduces your risk of developing heart disease, its relationship to the common cold is less clear. One theory suggests that increased circulation (and thus antibodies and white blood cells) can help the body detect and fight off invaders faster.
How exercise impacts your Hormones.
You're exercising more than you used to, so you should be able to eat more, right? Dr. Comeau says it depends on your level of exercise and your goals, such as weight loss or weight maintenance.
"If you're used to eating a lot and not exercising," he says, "you might not be as hungry in the middle of the day as you used to be." However, if you do feel hungry, make sure you aren't misinterpreting thirst pangs, and don't overeat simply because you feel like you're burning a lot of calories.
According to Hundt, exercise can stimulate the metabolism when you're first starting out, but your metabolism adapts over time. For example, someone who has been sedentary but begins walking daily will notice an increase in calorie burn, but after a while, you will no longer burn the same amount of calories. She suggests varying your workouts on a regular basis and adjusting your nutrition accordingly in order to continue adapting to aerobic training.
According to Hundt, women in particular may experience an increase in sweet cravings as a result of the stress of working out. She claims that an hour-long walk in the park does not cause stress in the body, but an hour-long run can cause metabolic stress and cravings.
Your Energy Levels on Exercise.
After a good sweat, do you feel like the Energizer Bunny? According to Dr. Comeau, if you're a regular exerciser, and you just crushed a workout, you might feel a burst of pep right after. "If you haven't been exercising, you may feel fatigued at first, but that energy will surge and you'll feel more productive from working out," he says.
The benefits of exercise are life changing, and will positively impact every aspect of your life. Now let’s take a look at what happens to the body when you don’t exercise…
What Happens to Your Body When You Don't Work Out.
It's easy to succumb to the siren song of your comfy couch after a long day at work or caring for the kids. And it's becoming more common for people to lead sedentary lives with little to no exercise.
According to a Centers for Disease Control and Prevention report from January 2020, approximately 15% of Americans are physically inactive. This doesn’t mean that 15% of Americans don’t exercise, it means that 15% of us literally don’t move. With 80% of the population now overweight or obese, the lack of adequate physical movement is creating a long list of negative health consequences.
"There are many types of exercise, and all of them have health benefits," says Lynn Marie Morski, MD, a board-certified family medicine and sports medicine physician. The combination of no exercise and a sedentary lifestyle increases your risk of developing a slew of potentially fatal conditions. "Evidence suggests that sedentary lifestyle may predict mortality more strongly than some of the well-known causes of mortality, such as smoking and high blood pressure," Dr. Morski says.
Here's what your body goes through when you don't exercise.
Your Heart when you don’t exercise.
Physical activity puts a high demand on your heart to pump blood to your working muscles, and many of the benefits of exercise can be attributed to better cardiovascular health.
Dr. Morski explains that "aerobic exercise has been shown to improve circulation, blood pressure, and cardiac output, which is a measure of how well the heart pumps blood to the rest of the body."
The heart, like any other muscle, strengthens in response to the strain of exercise. You are not providing the stimulus your heart requires to grow stronger if you do not exercise, and this can have a negative impact on your health. "In recent studies, increased sedentary time has been associated with features of metabolic syndrome, such as increased waist circumference and insulin resistance," Dr. Morski says. "It has even been linked to an increased risk of cardiovascular disease and all-cause mortality, as well as an increased risk of type 2 diabetes."
Researchers discovered that sedentary behaviour is one of the leading preventable factors worldwide associated with increased cardiovascular disease and all-cause mortality in a February 2019 study published in Circulation Research.
Your Brain when you don’t exercise.
Every part of the body, including the brain, is susceptible to the effects of ageing. According to a January 2020 study published in the Mayo Clinic Proceedings, aerobic exercise helps slow brain ageing and cognitive decline. Your brain may be more vulnerable to the effects of age-related decline if you do not exercise.
Furthermore, aerobic exercise may aid in memory and learning. Regular aerobic exercise was shown to significantly increase hippocampal volume in elderly women in a February 2015 study published in the British Journal of Sports Medicine. This suggests that the brains of sedentary people and those who exercise regularly have structural differences.
Your Mood when you don’t exercise.
Sedentary behaviour not only affects the way your brain functions in general, but it also changes the chemistry of your brain. Sedentary behaviour for more than three hours per day was linked to an increased risk of depressive symptoms in a study published in the International Journal of Behavioral Nutrition and Physical Activity in August 2018.
In a September 2018 study published in Preventive Medicine Reports, researchers discovered that changes in sedentary behaviour strongly predicted changes in mental wellbeing — with increased sedentary behaviour being associated with decreased mental health.
Your Joints and Bones when you don’t exercise.
You might associate high-impact workouts or sports with an increased risk of bone and joint injuries, but the opposite is true if you play it smart.
Dr. Morski says, "Weight-bearing exercise has been shown to help prevent osteopenia and osteoporosis." "Maintaining flexibility can also help prevent falls and keep people able to perform daily activities for much longer."
In a January 2018 study published in Rambam Maimonides Medical Journal, researchers discovered that weight-bearing exercises reduced bone mass loss and increased bone stiffness, both of which act as a barrier to the development of osteoporosis.
Your waistline when you don’t exercise.
You probably already know this, but sitting on the couch with Netflix and chips isn't doing your midsection any favours. Sedentary behaviour was linked to increased waist circumference and cardiovascular disease risk in a 2017 May study published in the International Journal of Obesity. On average, the more sedentary a person is, the larger their waistline will be.
Leading a sedentary lifestyle reduces the total number of calories you burn. According to an August 2018 study published in Cardiovascular Diabetology, consistently burning fewer calories can lead to weight gain and increase your chances of developing insulin resistance — a condition that causes high blood sugar levels — which can lead to and predict cardiovascular disease.
Your Cancer risk on zero exercise.
While researchers haven't figured out all of the intricacies of cancer and its risk factors, one thing is becoming increasingly clear: if you don't exercise, your risk of certain types of cancer rises.
Cancer, which is currently the world's second-leading cause of death, is caused by changes to DNA within cells, according to a World Health Organization report published in September 2018. (also known as gene mutations). Researchers discovered a link between sedentary behaviour and an increased risk of several cancer types in a December 2017 review published in Sedentary Behaviour Epidemiology.
Sedentary behaviour was associated with an increased incidence of endometrial and ovarian cancers, as well as potentially breast, colorectal, and lung cancers, according to the findings of 25 studies that looked at 17 cancer types.
Regular exercise, on the other hand, appears to be linked to a lower risk of cancer. Researchers discovered a strong link between increased physical activity and a lower risk of several types of cancer in a June 2019 study published in Medicine & Science in Sports & Exercise, which included several million study participants.
Bottom line: Exercise on a regular basis.
It's critical to stay physically active if you don't want to increase your chances of experiencing the negative effects of a sedentary lifestyle.
Exercise does not have to be punishing or take more than 15 minutes per day if you are doing the right type of exercise at the level that is appropriate for your fitness level. Here is a great article that explains why experts agree that 10-15 minutes of ful body, strength training mixed with HIIT is enough to shed excess fat, lose weight and get in the best shape of your life.
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