Welcome to day tow of our 3-day exercise question and answer session in honor of World Physical Activity Day!

Today’s Question:  Is exercising harder and faster always better?

Shows like the Biggest Loser give many the impression that the only way to lose weight or
get in shape is with the “go hard or go home mentality.” I think that saying was actually meant for game-day motivation, but has become the mentality of many exercisers.

High intensity exercise certainly has its place in weight loss, strength training, and endurance building. However, it’s important to build a strong aerobic base and then alternate high intensity workouts with recovery or lower intensity days.

Too much high intensity exercise makes you want to do this the next day:

While taking some continuing education courses to keep my spinning instructor certification current, I had the opportunity to learn more about the benefits of exercising at an aerobic level. When exercising, your body either makes energy aerobically (using oxygen) or anaerobically (without oxygen). When in anaerobic mode, your body primarily uses fat as its energy source, though some glucose (read: carbohydrates) is used. When exercising at anaerobic levels, the muscles switch modes to use glucose; this can also lead to a build up of lactic acid, which gives you that burning sensation in your muscles and often results in fatigue. It’s the high intensity exercise that usually leads to anaerobic exercise (think sore muscles and very heavy breathing). Anaerobic exercise is not sustainable for long periods of time, which is why long-distance athletes work so hard to stay right below that aerobic threshold.

Interestingly, when you spend too much time in the anaerobic phase, your body begins to prefer glucose as a source of energy and puts less emphasis on fat usage, even when you are not exercising. This can be dangerous because your brain relies solely on glucose as an energy source, while the rest of your body normally prefers fat as fuel. Taking glucose away from your brain can lead to mood swings, energy fluctuations, and ultimately sugar cravings!

And then you become the tired, cranky sugar monster…

On the opposite side of this, building an aerobic base and continually exercising at an

anaerobic level will train the body to use fat as a primary fuel source, which will regulate mood, energy, and appetite. It can ultimately lead to loss of body fat (think of how lean those long-distance runners are – they have trained their body to prefer fat as an energy source).  It also allows you to exercise for longer periods of time because your body naturally stores more energy as fat than sugar. Exercising at an aerobic level will also lead to a stronger immune system, fewer injuries, and better overall performance (you build endurance).

With that said, interval and anaerobic training sessions do have their place, but it’s important to include lower intensity training in your schedule as well.

How do you know if you are training aerobically or anaerobically?

The best way is by using a heart rate monitor (see yesterday’s post!). Generally training between 65-80% of your max heart rate is aerobic training, while anything above 80% will turn to anaerobic.

If you don’t have a heart rate monitor, you can use perceived exertion. The American College of Sports Medicine provides the following guidelines

You are training aerobically between 12-16 (you can hold a short conversation and maintain your pace for a long time) and anaerobically 17-20 (very little talking).

If you’re new to exercise, it’s especially important to start off slow with lower intensity exercise to build your aerobic base. After about 2 months, start to add in interval and higher intensity training sessions.

Have more food or fitness questions? Email them to me at Sarah@foodandfitnessfriend.com

And don’t forget to check back tomorrow for part 3 of the World Physical Activity Day Celebration!

- your food and fitness friend