1.Machine Leg Extension
How often do you just sit around and kick out your legs? Probably not often—if ever. So why do so in the gym? "There's no functional benefit to leg extensions,(Functional exercises use your body's natural movement in ways that apply to real-world motions.) Plus, your knees aren't designed to carry weight from that angle, which could cause injury. While your injury risk is low if you have otherwise healthy knees, why take the risk if the exercise isn't even functional to begin with?
Better Moves:
Squats, deadlifts, step-ups, and lunges are all great for training your quads. Not to mention, they simultaneously strengthen your glutes, hamstrings, and smaller stabilizing muscles. Since these are all functional exercises, tapping your body's natural movement patterns, your knees are designed to take their weight.
2. Behind The Bar Pulldown

When performing lat pulldowns, the bar should always stay in front of your body. As in,always. "Otherwise it's a shoulder injury waiting to happen," says women's strength expert Holly Perkins, CSCS. Pulling the bar down and behind your head and neck places extreme stress and strain on the front of the shoulder joint.
Better Moves:
Pulldowns are still your traps' main move—just focus on aiming the bar toward your collarbone. You don't need to bring the bar all the way to your chest, but you should move in that direction.
3. Smith Machine Squats

Squatting on a Smith machine might look like a safe alternative to the squat rack. In reality, it's anything but. When you lower into a squat using a Smith machine, your back stays straight and almost perfectly perpendicular to the ground, which compresses and stresses the vertebrae, Also, since using the Smith machine requires leaning back into the bar, you overly stress your knees, never fully contract your glutes or hamstrings, and don't train your core.
Better Moves:
Both body-weight and weighted squats (e.g., goblet, barbell, and dumbbell variations) train your entire lower body functionally, effectively, and without overstressing your joints, Schuler says. Plus, since you're not relying on the stability of a machine, these exercises also work your core.
4. Superman

The amount of force and compression that gets placed on the vertebrae of the low back is unreal,Yes, you're working your spinal erectors and many stabilizing muscles throughout the back and core, but you're placing a ton of force and stress on a very sensitive and specific area in the body.
Better Moves:
Get on all fours with the bird-dog exercises . The yoga staple strengthens the same muscles, while placing less force on the spine. Good mornings, deadlifts, and floor bridges are also great alternatives.
5. Triceps Dips

It's meant to train your triceps, but it can easily end up overloading the small muscles that make up your shoulder's rotator cuff. "It's a risk to lift your bodyweight
when your upper arms are behind your torso,Damage those muscles and even everyday tasks—like washing your hair—can become painful.
Better Moves:
Tone your trieps while keeping your arms in front of your body, Schuler suggests. Try cable pushdowns, triceps pushups, and close-grip bench presses.