Intensity and Impact. What is the difference, and why is a little impact good for you?

Intensity and Impact are often misunderstood and confused for each other, but they mean different things.

If someone says they cannot do high intensity exercise due to a joint problem or condition, they most likely mean they shouldn't do high impact exercise. So what is the difference?

Basically, intensity is how hard you work; impact is how much force your body absorbs.

Often, high impact exercise is, by its nature, also high intensity. But high intensity exercise is not necessarily also high impact!

Mostly, impactful exercise involves jumping, where the feet leave the floor and the force of landing is transmitted through the body.

One type of exercise which challenges this is rebounding on a fitness trampoline; the workout can be high intensity - it can make you sweaty and breathless, however, the elasticity of the rebounder surface absorbs the impact, making rebounding actually a low impact form of exercise, despite all the jumping!

On the other hand, you can certainly have high intensity but low impact workouts; intensity is how hard you’re working — think breath rate, sweat, and how much your heart’s pounding. Impact is the physical force your body takes on — the jolt when you land, the load through your bones and joints. They often happen together, but they’re not the same thing, and treating them as interchangeable leads to confusion.

This confusion leads to some people thinking they cannot possibly do a high intensity class due to fear of injury, but high intensity workouts do not always involve jumping and physical force. A high intensity class can be hard work, it can be sweaty, but this does not make it high impact. Avoiding high intensity classes can mean missing out on the cardiovascular benefits and endurance-building results of this type of workout.

Even when people avoid impact exercises due to fear of injury, this can also mean missing out on long-term benefits for functional fitness and bone health. A little impact is generally beneficial for your bones – providing you don’t already have any conditions which could result in injury or pain.

Many adults are worried about participating in moderate or high impact exercise because they feel they need to be careful of their bones and joints, but exercise is vital for keeping your bones strong. In fact, the Royal Osteoporosis Society actually state “The higher the impact, the better for your bones” – providing you are used to exercising and have not experienced fractures.

Small amounts of impact / pressure on the bones can ultimately help maintain them, as can resistance exercise. Bone, just like muscle, is made of living tissue and responds to force placed upon it. As mentioned in my previous post about low/high rep weight training, while older adults generally won’t see a huge increase in bone density, exercise can certainly help prevent bone loss, and also maintain muscle mass to preserve the surrounding bone. Bone mass tends to decline from mid life (and quite rapidly during menopause), so it is never too early to start building up bone density, or at least aiming to maintain your bone mass as much as possible. Strong bones will help you sustain a good quality of life and independence into older age, and of course will help prevent fractures if you fall.

Tendons and ligaments also adapt to progressive force and become more resilient, lowering injury risk over time. Functional strength and balance can also improve when you practise absorbing and producing force, leading to a better quality of life and ease in everyday tasks.

In summary, intensity and impact are related but they are not the same. A little impact, done well (with soft landings, hip/knee alignment, and core bracing) and dosed carefully (with gradual progression), helps most people stay stronger and more capable for longer. So, if you can do it without pain, and you haven't been advised not to - then get those feet off the floor!

Of course, moderate-high impact exercise will not be suitable for everyone and if you’ve been diagnosed with a condition such as osteoporosis or arthritis, or experience any pain during exercise, you should of course consult your doctor before beginning any new exercise programme.