A sticking point occurs when the weight feels heaviest in a certain area for the range of motion. Your strength fails to overcome the resistance at that point, and you miss the rep. Had you blasted past it, the rest of the range of motion would have felt easier, and you likely would have finished the rep. The sticking point occurs because muscles struggle with poor leverage or when they function weakly. Throughout an exercise, leverage and muscle strength change. Not all positions tax your muscles the same.
Imagine a bench press. About halfway down, your elbows flare out away from your shoulders. You will feel this as a sticking point. At the top and bottom of the movement, your elbows are closer to your shoulders. These positions give better leverage, so you feel stronger.
You feel the most strong at the top since your elbows extend fully. The moment arm becomes zero or close to it, meaning the best possible leverage. At the bottom on the movement, your muscles stretch. This makes them weak. You may have better leverage compared with the middle portion, but not as good as you have at the top, so it feels hard here as well. This means the bench press will feel hardest at the bottom through the middle of the exercise, not because you have a weakness. This happens due to mechanics and physiology that applies to everyone, without exception. Keep in mind you can also fail at any point due to fatigue from the set.
Your body developed logically. The hardest point in most motions occurs when your muscles function strongest. They work best at the mid-range. They form more connections here due to optimal overlap of the muscle filaments. At the endpoints of any motion, the sites that allow connections overcrowd or reside too far apart. This means that although you may feel stronger or weaker at the endpoints, these positions always involve less tension. Tension is the main stimulus for size and strength. Therefore, training must focus on the mid-point of any exercise.
Try this to demonstrate the concept. Drop your arm to your side and flex your arm. Next, bring the arm up to a 90° bend at the elbow and flex your arm. Finally, bend your elbow as far as possible so that your hand is near your head then flex. You will notice that while flexing with the 90° bend, you felt the most tension in your arms. You may have also noticed that with the other two options at the bottom and top, that you felt it more in the elbow joint. Not only do these positions generate less tension, they also use your force less efficiently because some of the force directs into the elbow.
Many powerlifting variations on exercises aim to beat the sticking points. They often use boards, chains, bands, etc. to make the exercise feel harder at the top or the lockout. They call this accommodating resistance. It aims to match the weight with the strength curve of your body or address a weakeness. These tools make it feel heavier at the top with the simple logic that you feel stronger there.
Here lies the problem. You feel strong at the top or lockout not due to muscular strength, but because of the small moment arm and thus the best possible leverage. This does not occur because your muscles act strongly near the top. As mentioned, the filaments start to overcrowd here, so they work weakly. Your feeling of strength here deceives you. Making an endpoint more difficult completely goes against how your body evolved to handle resistance.
Advocates may argue that using bands and chains teach acceleration. Since the weight grows heavier as you lift, this forces you to attempt to move fast. Although this may seem helpful, the intention itself makes the biggest difference. You simply need to tell yourself to move faster with your normal weight.
Others may argue that these tools work because some of the elite use them and therefore need no explanation. Consider that they work only because they do not detract from the other important work powerlifters and athletes do. Perhaps it even gives their muscles a break without them realizing it, since it challenges them less.
Why should you find this important? These tools complicate training in a way that actually reduces your results. You will not teach your muscles to overcome sticking points.
Instead, overcome a sticking point through speed. Your body has a natural mechanism to reduce weakness at the bottom of any exercise. At the bottom of a bench press, even though your muscles weaken, you can use stored energy to get a boost on the way back up. Imagine when someone tries to jump as high as possible. They always do a quick counter-movement downward, before exploding into the air.
Move the weight smoothly but quickly as you lift. Do this after lowering the weight in control and while staying tight. Do this regardless of how heavy it feels. You do not need to use less weight and perform speed work. You do not need to strengthen specific muscles. You just need to do the basic lifts with the right speed.
During a non-uniform lift, such as a barbell dead-lift, overloading a point may make some sense. This occurs as muscle groups do not play an equal role throughout the range of motion. A basic squat, bench press, and row or pull-up represent uniform lifts. In these exercises, the resistance moves in a linear path. The prime movers involved contribute near equally. These exercises work better than non-uniform options, since they balance the stress evenly across the joints and muscles. As long as you choose a medium grips, widths, and positions, no muscle alone will cause you to fail.
Powerlifters use specialized equipment to lift incredible weights. This will change the strength curves for exercises in an unnatural way. They also use form to maximize leverage which may overload certain muscles and neglect others. This creates different sticking points compared with raw lifters that train normally.
Practice basic exercises over a normal range of motion. Push, pull, and squat using medium positions to balance the stress on the joints and muscles. If you encounter a sticking point, make sure you perform the exercise properly. Transition out the bottom of any movement smoothly but quickly. Stay tight on the way down and come back up quickly to best use this stored tension. Ignore special exercises and tools for sticking points.