Q: "I have a question about exercise. I try to do two pump classes a week, and sometimes include a kick-boxing class; all around 50 minutes long. I also try and go for a run at least twice a week. I run about 5km in 30 minutes. Would it make much difference if instead of running I went for an hour's walk twice or three times a week? I would love to know if there's a difference between running and walking fast for your body?"
A: Kristen MacKenzie, health and nutrition consultant at Millennium Institute of Sport & Health, responds:
"Current guidelines encourage us to do a minimum of 30 minutes of physical activity each day. So well done with your current programme! Before changing, it is important to recognise the difference between these forms of exercise.
While walking is glorified as being the right intensity for 'fat burning', in reality for each minute of running you still burn a greater amount of energy. Therefore running is a preferred option for greater fitness benefits and to use more energy (and burn more fat) for a shorter time investment. This is as long as you are relatively injury-free, as running is high impact. Running also burns more energy after you finish exercise as an added bonus. However, walking is an excellent low-impact, whole-body exercise which is strongly recommended if you are starting an exercise programme or are unfit.
A greater amount of time is required to burn as much energy through walking compared to running. In your case, switching 2 x 30-minute runs to 2 x 1-hour walks may burn a similar amount of energy (depending on the intensity) but your heart doesn't have to work as hard so you won't get as much of a fitness benefit. You need to decide why you want to make the change and consider time and injury factors.
Another option is doing a combination of walking and running, for example one walking hill session, a long run and a fartlek* run. The more active we are on a daily basis the better, so focusing on walking more in our everyday tasks such as at work, when shopping and around the house, while aiming for some high intensity exercises such as running or kick-boxing will ensure we get the benefits from both of these exercise types."
*Fartlek training is Swedish for speed play or alternating pace during continuous exercise. The aim of the training is to merge moderate intensity exercise with higher intensity exercise, thus moving the athlete out of a predominantly aerobic zone into an anaerobic zone and lifting their metabolic training rate.
As an example: after 10-15 minutes of moderate pace running, every 4th power pole you come to would require you to sprint to the next one, with the next 4 poles being recovery. This might continue for a total of 8 sets of 5 power poles, followed by 10 minutes at a walk or slow jog.