How Much Physical Activity Do We Need?

How Much Physical Activity Do We Need

This reference helps you talk about what you have learned with others. Talking Points also serve as a reminder for when, in the future, you want a refresher on the main highlights of this course. Schedule tea with a friend and have a conversation about this subject!

Are exercise and physical activity basically just the same thing?

Physical activity is any movement that increases our energy expenditure above laying still. As you can imagine, there's a wide range of intensities of physical activity, from barely doing anything all the way to some maximal-effort activity like a sprint.

Exercise, however, is a specific form of physical activity: It's any effortful activity carried out specifically to sustain or improve health and fitness. In other words, it's movement done with the intention to promote health.

Do we need to exercise?

For many, modern life doesn't require much physical activity. But during the course of evolution a regular amount of physical activity was necessary just for survival, and so our genes are adapted for a certain level of physical activity, and when we aren't getting the right amount, our health starts to fail us.

If you look at modern-day hunter-gatherers, they don't formally exercise but they certainly have a high level of physical activity as a part of normal life, and as a result, on average these populations are very fit.

For many of us that don't have physically demanding jobs, exercise provides an efficient way to achieve recommended amounts of physical activity for optimal health. I strive to maintain a physically-active life - which can mean taking the stairs over the escalator or walking instead of driving - but I also mix different forms of exercise into my week.

Every day some have some physical activity.

What does it mean that exercise is a hormetic stressor?

Think of the Goldilocks principle; there is the right amount, too little and too much. That's what we're dealing with here. Hormesis is a term in toxicology that refers to an inverted U- shaped dose-response curve. In hormesis there is a dose of an acute stressor that is beneficial, too little or too much outside this range is not beneficial or harmful.

In the short term exercise causes inflammation, oxidative stress, increased stress hormones and muscle damage. But the adaptation to the stress makes the body able to handle more next time.

The window of stress you can handle depends very specifically on you, your fitness, and your recent activity. This is why many people who go from being a couch potato to running a marathon end up getting injured. They tried to push their training faster than what their body can handle in that moment. Keep this in mind when you're considering how much exercise to do today.

By the way, this even applies to very fit people who, let's say, get sick for a few weeks then get back into exercise. To do that effectively, they need to scale back how much exercise they do When they start up again and build back up to the previous training level. This might all sound simple but not being mindful of this principle is a common reason for injury and people disliking exercise. Being patient, listening to your body, and maintaining the long view are all keys to long-term success with exercise.

I know exercise makes me strong and improves my endurance. Does it actually affect my lifespan and how long I stay healthy?

Yeah, big time. In fact, aerobic capacity is the strongest known predictor of longevity. On the other hand, a sedentary lifestyle is a risk factor for over 35 chronic diseases including heart disease and diabetes. In one study, going from unfit to fit cut the risk of death in the time period studied by nearly half, and if you were in the fittest 20% in that group, your risk for early death was 300% lower than the people in that group with the lowest fitness.

Strength is another marker of fitness and also predicts mortality, future disability and cognitive decline. For example, fifty year old males in the top 30% for strength for their age group, are two and a half times more likely to make it to their 100th birthday. So, as you can see here, there is a huge impact of fitness with health and longevity.

I care to be physically active but how do I know if I'm getting enough or too much?

The US guidelines for weekly physical activity - which by the way, are very similar to guidelines from many other countries - recommended aiming for moderate intensity activity done for 150 to 300 minutes per week. Or, you could ramp up the intensity and by doing so, you cut the amount of time you need to exercise in half. So, if you're doing vigorous activity, they recommend you aim for 75 to 150 minutes per week. Obviously, you can do a combination of moderate to vigorous activity to get in the right zone. But note, they also recommend getting in two sessions per week of whole-body muscle strengthening exercise, like resistance training of body weight calisthenics.

It's kinda hard to keep track of all this which is why I'm grateful for the humanOS Activity tracker. It looks at all the activity you've done over the last 7 days. This includes steps if you have a step counter connected to the system and also exercise entered in the activity tracker, and it converts all of that into one score. If your score is between 100% and 200%, you're meeting the guidelines.

Is exercising more than the national guidelines even better?

To a degree, yes, once you're acclimated to that level of activity. But important, remember the inverted U-shared curve we discussed earlier; that appears to be true here, too. So, if you look at how levels of physical activity correspond with reduced mortality, you have the steepest benefit simply going from sedentary to getting some exercise. That should be motivating for anyone who is sedentary now. After that, getting into the zone of what the national guidelines recommends is a great goal for most people. From there, even doubling that amount of activity seems to offer some more benefit in terms of reduced risk of early death, but there are signs that there could be such a thing as too much of a good thing. If you look at the curve of mortality risk, once people start to get up to 10x the national guidelines, you clearly see that their risk of early death starts to go back down again, meaning you get less benefit to health than you were with less exercise. Keep that in mind!

The main point here is that we have a huge range for physical activity that we can participate in to get health benefits. Keeping track of it on humanOS has really helped me not only understand my current levels of physical activity on a day to day basis, but has also helped motivate me to achieve my goal of staying in my target zone.