Choosing a Machine continued...
Every time your foot hits the ground, says Alexander, "the impact forces are 3.7 times your weight just walking on the planet."
Since a treadmill is moving under you, the impact may be slightly less than that. But if it doesn’t feel right -- particularly on your knees or lower back -- choose another machine.
One more thing to keep in mind: Treadmills can pose a real balance challenge for new exercisers or those who haven't worked out in a while, says Matthew Vukovich, exercise physiologist and associate professor at South Dakota State University.
2. Elliptical Machines and Stair Steppers
These machines pack a little less punch on the joints, and either can be a good alternative to the treadmill, says Vukovich.
Because you use them in a standing position, you're using lots of muscle mass, so the calorie burn rate is still pretty high.
Elliptical machines with arm components can further increase the numbers of calories you burn, says Stamford. But if you're a beginner, he doesn’t recommend using your arms at first.
3. Stationary Bikes
All our experts agree that the stationary bike offers the workout with the least impact on the joints. People with knee pain are often steered toward these bikes, since the impact of body weight is not a concern as it is on a treadmill, elliptical trainer, or stair stepper.
But to avoid knee strain, you must make sure the bike is adjusted to fit your body, Vukovich says.
"Nine times out of 10, people get on a bike and are not fitted to the bike," he says.
When adjusting the seat height, he says, make sure that when you’re sitting on the seat with the ball of your foot on the pedal, there is a very slight (5- to 10-degree) bend in your knee.
Most people sit too low, meaning their knees flex too much as they pedal. This can put too much pressure on the knee and result in soreness, warn Vukovich.