We know exercise is the key to longevity — helping to strengthen bones, increase muscle, and improve balance. Yet most aging adults still shy away from new workout routines. Fear of injury, or worsening a current health condition, are enough motivation to avoid exercise altogether.

If your muscles have a lot of mileage on them, here are the top three exercises that cause more harm than good:

Sit-ups

Most exercisers pull on their neck muscles rather than their abdominal muscles during this move, resulting in strains, tension headaches and a totally ignored core. Save yourself a royal pain in the neck by nixing sit-ups entirely.

For abdominal muscle definition, a strong lower back, balance and stability, opt for this total body exercise.

Try this instead: planks

  • Begin by lying on your stomach with your body weight propped up on your forearms.
  • Push through your forearms and toes to bring your body into a plank position, forming a straight line from your head to your heels. Your shoulders should be aligned directly above your elbows.

Hold for 30 to 60 seconds, for a total of three sets.

Behind-the-neck lat pull-downs

This exercise should be avoided at any age. When creating a fitness routine, it is best to strengthen muscles used in your everyday activities. How often are you pulling heavy weights down behind your neck?

Not only does this exercise put stress on the neck muscles, it can compress arteries in the neck which can lead to dizziness and fainting — two side effects that can easily cause falls.

Try this instead: overhead shoulder press

  • Find a set of free weights that are slightly challenging. The last few repetitions of your set should be the hardest.
  • Sit on a sturdy chair or bench with both feet firmly planted on the ground. If possible, use a seat that does not have back support to encourage core strength and stability.
  • Hold a dumbbell in each hand and elevate the arms until the elbows form a 90-degree angle.
  • Keep your core tight and neck relaxed as you push the weights up until your arms are straightened above your head. Slowly return to the 90-degree angle starting position.

Repeat 10-12 times, for a total of three sets.

Leg extensions

Most of us don't realize how crucial this joint is until we start to experience aches and pains from years of overuse and misuse. While leg extension machines are great for targeting the quadriceps, improper form and inaccurate seat adjustments can easily jeopardize knee safety.

Try this instead: reverse lunges

  • If your balance is not strong, stand next to a steady object such as a chair, wall or railing so you can steady yourself if needed. Otherwise, place hands on hips as shown.
  • Keep your shoulders back and core muscles engaged as you take a step back with the right leg. Lower the body so the front and back knee form a 90-degree angle. The left knee should be aligned above the heel, while the back knee is directly below the hip.
  • Recruit your quad, glute and hamstring muscles by pushing through your front heel and returning the right leg to the starting position.

Repeat 10 times on each leg, for a total of three sets.

Growing older doesn't mean you can't grow stronger.

Ashley B. Greenblatt is a certified personal trainer and wellness coach. To learn more, visit ashleyblakefitness.com.