There seems to be no doubt that volume is one of the, if not the most effective variable to evoke hyperotphic changes to skeletal soft tissue. Higher frequency training, longer duration sets and “time-under-tension” are all hot topics when it comes to making effective exercise selection with the goal of packing on slabs of muscle.
Time-under-tension is a term that gets tossed around a lot when it comes to body composition circles, and I think it gets used haphazardly. Time under tension is not just merely how long a set lasts for. Time under tension is a full sale inquisition of correct exercise selection, machine selection, and proper tempo designation.
First off, when considering time under tension we need to realize that tension during an exercise is not a constant, its a continuously variant stimulus based on the resistance profile of the machine and the strength curve of the muscle.
Strength Curve:
Without having this article turn into a full-scale biomechanics lesson, we’ll give a very brief synopsis of what a strength curve is and how it is relevant when talking about loading for an optimal time under tension.
The strength curve is a representation of where our muscle is most (and least) capable of exerting force through its active range. Simply put, each muscle has 3 positions
1. Fully Lengthened
2. Mid-Range
3. Fully Shortened
Whereat fully lengthened and fully shortened, the muscles are less capable of producing force than in the mid-range position. Think of a bicep, when the elbow is fully extended the bicep is weaker than when its halfway through its arch of elbow flexion, but after that halfway point the bicep is approaching its fully shortened position where it becomes weak again.
Resistance Profiles:
Just as every muscle has a strength curve, every machine, dumbbell, and cable has a resistance profile. Which is to say, each machine, dumbbell, and cable has a predetermined point at which it will exert the greatest amount of force on the muscle as it moves through its active range.
The goal of effective exercise programming, at least when it comes to organizing a program based around Hypertrophy principles, is to be able to appraise resistance profiles and superimpose strength curves of muscles effectively with the profile that matches a particular part of the range.
This is the only way we can optimize tension in a muscle, in an exercise. Once we’ve standardized for this variable of tension, we can then begin to quantify how much tension we are actually applying.
Let take for example a lying hamstring curl, now based off the mechanics of the machine, the lying hamstring curl is a great machine from a resistance profile standpoint to overload fully shortened position of the hamstring (as the knee will be in resisted flexion as the hip is in extension). So we know that the intent of this exercise from a tension standpoint will be in the fully shortened position, so if we were to take the muscles strength curve, the resistance profile of the machine and the tempo and try and construct the most optimal repetition from a time under tension standpoint, we would want the majority of the duration of each rep to be spent on the parts of the range which we are attempting to utilize the greatest tension.
So a lying hamstring curl tempo designation would look something like this 2c-2–2e-1
Using this four-digit tempo designation, we would spend 2 seconds in the shortening phase of the muscle, 2 seconds isometrically contracting, 2 seconds in the eccentric phase and only one second in the end range, as we don’t want to waste time during the rep in a position where then tension applied by the resistance profile of the machine isn’t harmonious with particular part of the strength curve we are trying to emphasize in the particular movement.
CONCLUSION
This may seem complicated, especially if this is your first exposure to this kind vein of thought, but I can assure you this is merely the tip of the programming iceberg, there are so many factors that need to coalesce to create the most harmonious and expedient exercise program. Time under tension is an incredible training variable ...If we can get it right, otherwise it can leave our programming arbitrary, redundant and ineffective.
Stay Strong,
Jordan Shallow
