Who Should Go Low?
Low-impact exercises are most appropriate for beginners, as well as people with arthritis or osteoporosis and older adults, individuals who are obese, pregnant women, and people with bone, joint, connective tissue injuries. That's because low-impact exercise tend to be less jarring on the body and joints, and less intense overall (more on that below). According to the American Council on Exercise, keeping at least one foot on the ground at all times also reduces your risk of musculoskeletal injury.
Who Should Aim High?
High-impact exercises tend to be more intense overall and therefore burn more calories. They may even strengthen bones better than lower impact options, but any impact can help with that, even if it's light. These types of exercises should be reserved for people who already have a baseline of fitness and are at low risk for joint problems because they pose a higher risk for injury, especially to the ankle, knee and hip joints as well as the spine. How?
If you remember high school science class, Newton's third law (the law of impact and reaction forces) explains why. For every action (force applied by one body to a second), there is an equal and opposite reaction (the second applies an equal force on the first but in the opposite direction). Whew! What that means as that your body must absorb the impact forces during high-impact moves. The force on your body while running (high impact) can be more than twice that of walking (low impact). A 150-pound person who runs will land on one foot with about 300 foot pounds of pressure on the ankle, knee and hip joints. This can result in overuse and stress injuries, especially in larger people and at fast speeds.
21 Low-Impact Workouts That Are More Effective Than You Think
Today we're going to show you 21 low- (or no!) impact exercises to keep things varied, safe and full o’ fun.
1. Walking

2. Elliptical
Sorry treadmill, elliptical takes the cake when it comes to putting less stress on those legs.
3. Stairmaster
Not all gyms have staircases, but they probably have a Stairmaster. (Which is obviously way more exciting than a treadmill.) No gym nearby? No problem. Hit the real stairs.
4. Strength training
5. Cycling
Thank mom and dad for teaching us to take off the training wheels. Hopping on the bike is a fun way to fit in some exercise, with a lower chance of damaging the joints. And you don't even need to sign up for a spin class.
6. Rowing machine
Spice up the cardio routine and bring the water sports to the gym? Yes, please. The rowing machine (impact not included) is an intense and fun way to work those arms, back, legs, and core. Score!
7. Kayaking

8. Tai Chi
Try some meditation in motion to give those bones a break. This gentle, fluid movement may also help ward off headaches, helping to improve flexibility, too . (Whether that includes a hangover headache is unclear.)
9. Hiking
Another way to spice up a walk is to add some hiking terrain (opt for flatter areas, though, to keep impact to a minimum). Ready to strap on the boots and hit the woods?
10. Rock climbing
To take off some stress, head to the nearest wall (err, rock wall, that is!). Climbing movements are typically slow and controlled, which works the muscles without the added strain.
11. Yoga

12. Pilates
High-impact sports won’t magically give us six-pack abs, that we know. The potential solution? Just roll out the mat for a quick Pilates session to strengthen the core and help increase flexibility.
13. Total Body Resistance Training
Also known as "TRX", it is a strap suspension system (say that three times fast) that’s easy on the joints but a serious challenge for your whole body.

15. Water aerobics
If laps in the pool gets repetitive, bring the aerobics class to the water. Some gyms even offer treadmills in the pool to really keep things interesting.
16. Snowshoeing
For a different kind of walk in the park, snowshoeing is the way to go. Working against the resistance of the snow will expend more energy than walking on dry land.
Step aerobics is a form of aerobic power distinguished from other types of aerobic exercise by its use of an elevated platform (the step). The height can be tailored to individual needs by inserting risers under the step.
Take a tip from Dancing With the Stars. Not only is dancing super sexy, it’s often easy on the body and a guaranteed great workout . So go grab a partner and give those dips, twirls, and whirls a spin!
19. Rollerblading
Let’s take a trip back to the 90s. Gliding on pavement won’t fail to burn calories while putting less stress on limbs. Now, if only stopping was that easy…

21. Golf
Now, now—golf isn’t just for the pros (or the retired). Take a trip to the fairway and get that swing on. Bonus points for skipping the golf cart and walking the course!
REFERENCE: http://greatist.com/fitness