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Think about what you feel when you lift. The portion of the range of motion where the weight feels the heaviest is the peak in the resistance curve. You'll feel the least strong in this area because this is where the joints are at the their greatest disadvantage in relation to the load being applied to them. It's often what lifters call their "sticking point."
Every exercise has a resistance curve. This defines how much force is being applied to a muscle. Every movement also has a strength curve. This is how much force those muscles can produce at a certain joint angle.
The strength curve and resistance curve are inversely proportionate. When resistance is low, strength is higher. When resistance is high, strength is lower.
But the highest point of resistance/tension isn't uniform across all exercises. Tension increases and decreases at certain points during a movement. Knowing this will help you manipulate the resistance curve to create more continuous tension, and thus, more gains.
Know Your Curves, Love Your Curves
There are three types of curves. The hip-to-waist ratio curve, lower back to perky glutes curve, and her smile. Feminists have none of these. That's a joke. Laugh now.
Ascending, descending, and bell-curve are the three curves of strength training.
1. Ascending Resistance Curve
The weight gets harder to lift as you get closer to the completion in the range of motion. Difficulty is highest at the top, and your strength descends as you lift (descending strength curve). Dumbbell lateral raises are an example of this.
2. Descending Resistance Curve
Difficulty is highest at the beginning of the movement, and the weight gets easier to lift as you get closer to the completion in the range of motion (ascending strength curve). Incline dumbbell curls are an example of this.
3. Bell-Shaped Resistance Curve
The resistance, and thus difficulty, is greatest at the mid-point in the exercise, which is also where the strength curve is at its lowest point. A standing barbell curl is a great example of this.
The Case for Accommodating Resistance
When you modify the resistance curve, you modify the strength curve of that exercise. The resistance curve you get from machines vary greatly because they're engineered differently. A leg curl designed by one company many have a descending resistance curve, where another has an ascending resistance curve.
Muscles experience the greatest amount of tension where the resistance curve is at its peak in the concentric point in the movement. Tension is the stimulus for growth because, after all, if the muscles are never placed under tension then they have no reason to adapt and grow.
This is why we see bodybuilders that are far more jacked than Olympic lifters. While there's all sorts of velocity and power involved in the snatch and the clean & jerk, the muscles involved don't spend very much time under tension. You need time under tension for maximal muscle growth and the purpose of Olympic lifts are to move explosively.
So tension can be manipulated in order to spur new mass gains. One way to do that is to raise the resistance curve at the point where it starts to decline so that the muscles are at a disadvantage for a longer period of time. This is where accommodating resistance comes into play.
You can use bands and chains to increase the resistance where it normally would descend. Without these tools, tension diminishes as the strength curve increases. You can probably think of common compound movements (like squats and presses) that lifters often do with accommodating resistance. Here are a few others that become far more productive with the addition of bands or chains.
Use a band. This eliminates the need for a training partner to apply manual resistance at the top portion of the movement. Wrap the band around your back, or even below the bench (all depending on the strength of the band), to keep tension more constant through the movement.
The old Nautilus pullover machine might be the best overall lat movement that exists. Don't have access to one? Then the dumbbell pullover is a solid alternative. Problem is, once the dumbbell crosses over your face there's basically zero resistance in the movement. So add bands to it, increase the resistance through the movement, and get a similar affect as you would with the pullover machine.
Dumbbell Preacher Curl
The chest pad works as your built-in counterbalance against gravity, so you're forced to stay strict. Get a band and angle it so that it provides maximum resistance at the top of the movement when the bicep is completely shortened.
Get some really strong bands to get the full effect. The best part is that even if you were to do as little as a two-inch range of motion, you'd still get tension on that miniscule ROM. I'm not advocating using such a short range of motion, but even for those that cut the ROM pretty short, this exercise becomes far more effective.
Bands make the leg press an exceptionally productive exercise because if the band tension is tweaked up correctly, it'll start kicking in right where the resistance curve would normally descend.
Bands around your neck will naturally bend you forwards and cause the pecs to get into a very deep stretch. They'll also create more tension at the top of the rep.
Stiff-Legged Deadlift or Romanian Deadlift
Try dumbbell stiff-legged deadlifts with bands around your neck. It's just easy to setup that way. Or do Romanian deadlifts. If you don't have a platform that has band hooks, you can simply wrap them around your feet and the bar.
Add chains so that the tension remains as your hands rise. Chains also make this move more elbow-friendly.
Normally, triceps extensions are hard on the joints. But don't lower the bar to your forehead. When you do there's a tremendous amount of stress placed directly onto the elbow joint. Remember, tension is distributed throughout many areas (ligaments, tendons, bones), not just the muscle. When you lower the bar directly to the forehead, rather than behind the head, the elbows hog a lot of that tension and stress. So correct your form before you do any variation of skull crusher.
When you add chains to skullies, the weight will deload onto the floor during the concentric, which also means less stress on the elbows even when the movement is being performed in a more joint-friendly manner, where there's more shoulder flexion involved. So if you had to drop these due to elbow irritation, then start back up again with this variation in order to avoid that issue.
Close-Grip Bench Press
This is a great triceps developer, but it can be improved with the use of chains. Why?
Because the triceps come more into play in the lockout portion. With chains (set up so that the majority of the chain weight comes off the floor near the lockout), you can make the triceps work a lot harder in the range of the movement where they do the majority of the work.
I also like the Swiss bar (or football bar) here because you can use a neutral grip. A trap bar may work as well. That automatically puts you into a natural position of tucking the elbows in to your sides, again, bringing more of the triceps into play.
The shorter the range of motion in a lift, the less likely it is you'll need to add accommodating resistance. Movements like calf raises, shrugs, and wrist curls don't need it because there's a high degree of tension throughout the movement. The "longer" a movement becomes, the greater the curve is. Without accommodating resistance, there's a lot of "space" in the big movements where tension isn't very high.
This doesn't mean to throw the baby out with the bath water and slap bands and chains on every exercise you do. That's silly. What's important is to understand how to apply them to rid specific movements of their points with low degrees of tension, so that more time is spent in the growing zone.
Don't Overdo It
Standard barbell and dumbbell exercises without bands and chains should be the bread and butter of your gym time, but adding some accommodating resistance is highly productive if you do it right and in moderation. Just remember the whole point: to remove the wasted range of motion that offers little to no resistance or tension on the muscles being worked.
You'll also need to find the appropriate bands for each lift. You don't need a million pounds of band tension to do dumbbell curls, but you'll need more than the Wal-Mart lady-toning bands for something like leg presses.
And if you're a beginner, none of this is going to benefit you. Beginners will progress just fine using traditional methods with dumbbells, barbells, and machines. There's no need to get fancy in your training to achieve results, because your newbie gains should be coming easily.