I may have to make this a bi-weekly feature after last weeks novel of an answer...but look out class...this is a REALLY good one...
Q: I tend to feel that unless I push myself really hard that I have not had a workout. To do that I feel like I need a big chunk of time (at least 1.5 hours) and will therefore talk myself out of a workout altogether. My question: What are the physiological pros and cons of doing frequent shorter, "easier" workouts versus longer, "more intense" workouts less often? IE: 5 x 1/2 hour workouts a week versus 2 or 3 x 1 1/2 hour ones.
A: Thank you for your question Janet! I am sure there are many people who are wondering the same thing as you are!
As discussed last week, individual goals will dictate how the FITT principle is followed to determine the Frequency, Intensity, Time and Type of Activity that one should choose. Athletes with specific sport goals will have a much more specific FITT principle to ensure they reach their sport specific outcomes. 'Lifestyle' athletes have a bit more room to play with when it comes to exercise prescription as many different exercises will have benefits for overall health and wellness goals.
That being said: The intensity and duration of exercise that you work at will result in specific physiological changes in your body. There are lots of amazing things going on inside your body during your workout...
Calories: First and foremost, all exercise will burn calories as your body uses up energy to perform the movements required of it. Secondly, the harder you work the more you burn. Period. So, if your goal is caloric expenditure then you need to work on total output. This can be accomplished through intensity or duration. The lower the intensity, the longer you need to work out in order to burn the same amount of calories. The higher the intensity, the more calories you will expend in any given time. BUT how long can you last at full tilt? Not very long. So...this is where the balance between intensity and duration come together.
Endurance: In order to build your aerobic endurance you must work longer...not harder. So, the benefits of the longer workouts are seen in your aerobic endurance. When you train at a lower intensity for a longer period of time (more than 1-2 hours) some amazing things occur in your body: Your little energy factories, mitochondria, increase in number in your muscles, your red blood cells increase their ability to carry more oxygen, your body actually makes more blood capillaries to feed the working muscles, and your oxygen absorption becomes more efficient in the muscle cells all to create a higher oxygen utilization capacity...resulting in you becoming a super efficient aerobic endurance machine! Which in turn results in a lower heart rate as your heart no longer has to beat as many times to get the same job done. WOW. AND the bonus of endurance training: Your body learns to burn more fat as a fuel source so it can save the energy in your muscles for the long workout. Yup. Endurance training makes you a fat burning machine too.
High Intensity: The shorter more intense workout has additional benefits and the specific heart rate intensity (based on percentages of your maximum heart rate) determines the specific system being worked. To keep things simple higher intensity exercise ,or anaerobic interval training, will increase your speed & power and decrease your fatigue level at higher intensities. You will be able to work harder without getting tired. AND you will teach your body to deal with the bi-products of high intensity exercise: hydrogen and lactic acid. WOW. AND the bonus of interval training: You will burn more calories per minute during the workout AND your post exercise metabolic rate will be elevated resulting in more calories burned for the remainder of the day after your workout! Yup. Anaerobic interval training will make you a super duper calorie burning machine.
So, the short answer is both types of training , endurance and interval training, have amazing benefits for the human body. And you should be including both types into your weekly training plan!