A Resistance Profile (RP) is the graphic representation of the changes in torque as they occur throughout a range of motion, i.e. where in the range it’s “heavier” and where it’s “lighter”.
The RP is based upon two things:
- Changes in force (magnitude)
- Cams, elastomers, inertia (acceleration, deceleration), linkage systems, manual (assistance, resistance), etc.
- Changes in moment
- The relationship between the line of resistance and the involved joints as affected by change in direction of force, change in position, change in placement, etc.
RP is one of the most important factors in exercise response, adaptation, sensation, and experience.
Importance in Exercise
The RP can and often should be strategically created or modified to match the associated Strength Profile (SP) for a given exercise and manipulated appropriately for the individual client as well as other factors such as fatigue, pathology, the effects of deconditioning, etc.
The Relationship between Resistance Profile and Strength Profile
- An RP can be created or modified to match the SP for a given exercise with virtually any tool if the user knows how to manipulate the physics of the related factors.
- Free weights and cables often create compromises for multiple joint activities. Use of these tools can be configured most accurately for single joint challenges.
- For the most part machines only manipulate the magnitude portion of the RP. Quality machines can be optimal for either the early set or the latter set, but due to inherent changes in the SP from fresh to fatigue, most machines still require trainer intervention to create an entirely optimal experience.
- Poorly designed machines will present the biggest obstacle to matching any individual’s mechanics and many of these are completely unusable regardless of the most creative attempts at simple modification. There are very few companies (maybe four) that offer appropriate designs in greater than 50% of their individual pieces.
- Additionally, the vast majority of exercise professional (trainers, therapists, coaches, etc. regardless of their level of formal education) are completely ignorant of the objective design specifics of machines, how mechanics and motor recruitment are directly and indirectly influenced, and how to use them.
- Any movement in the joints that are supposed to be held static will obliterate an appropriate RP. In lay terms: “Cheating blows a good RP.”
- An RP that does not somewhat closely match the SP will make it very difficult to maintain static positions unless the user is willing to stop when necessary or is highly skilled and knows how to adjust optimally (if possible). In lay terms: “A crummy RP encourages cheating!!”
The shorter the range utilized in a given exercise, the less dramatic the RP becomes. In other words, because RP’s change throughout the range, the smaller the range that is performed the less change occurs in SP or RP.
Conversely, the greater the range of motion for a given exercise the greater the change Moment Arms of the Resistance to each joint incorporated resulting in dramatic RP variations.
Furthermore, with larger ranges often come faster movements. The more abrupt the starting and stopping of the load the greater the magnitude of resistance, but of equal concern is the complete loss of resistance through the rest of the actual range of motion due to inertia.
Although a well-engineered (machine) or well-strategized (linear resistance) RP is often desired, no single profile is truly optimal from first rep to last due to fatigue, etc.
consequently, there are at least two options: “Optimum + Manipulation” and “Complementary Ranges/Loads”
“Optimum” + Manipulation
- First rep optimum minus = a near optimum profile for the first rep that is modified on successive reps as needed via manual assistance or the use of mid-set machine manipulation, etc.
- Last rep optimum plus = a near optimum profile for the final rep that is modified on initial reps as needed via manual resistance.
Complementary Ranges with Appropriate Loads: Completing the Challenge
- Due to the limitations in equipment (free weights, body weight, most machines) multiple exercises/loads will typically have to be employed in order to generate appropriate challenges across a full contractile range!
- Performing full range with complementary range-specific loads
- Performing partial ranges limited to the appropriateness of the load.
- Examples: short range top squats with heavy load complemented by bottom/low squats with lighter load OR with full range squats (bottom and top) with the lighter load (normal squats)
Methods of Altering the Resistance Profile
- Manipulate Direction
- Manipulate Magnitude
- Manual manipulate of the MP
- Additional resistance
- Addition of an elastomer to mass based device
- Only works on “pressing” exercises.
- Can increase magnitude
- Can unload or decrease
- “Intertial Dampening”
- Cam manipulation
- Inertial augmentation or reduction
- A free weight squat is virtually zero resistance at the top and maximal resistance (for the chosen load) at the bottom
- Any tubing exercise in which the tube is fully stretched but is lying against the body (extended arm) is virtually zero resistance.
- Swinging a kettlebell can produce a huge increase in resistance at the “launch” (initiation of concentric) and the “catch” (end of eccentric) but is virtually zero resistance throughout the majority of the range due to inertial effects.
- If the RP doesn’t match it’s a “bad” exercise
- The RP doesn’t matter
- Free weights and cables are constant resistance
- The magnitude profile of a machine is the RP for the exercise
- Tubing is increasing resistance (Reality: must understand magnitude vs. torque)
- The RP is not affected by “speed”, i.e. acceleration, deceleration
- Every exercise has one ideal profile
- The belief that one device or tool is inherently better than another without knowing the specifics of the individual and goal for which it is to be used
Intention: precision, control
4 Step Rep