Calculation of resistive loads for elastic resistive exercises

Context: What is the correct resistive load to start resistive training with elastic resistance to gain strength? This question is typically answered by the clinician's best estimate and patient's level of discomfort without objective evidence. Objective: To determine the average level of resistance to initiate a strengthening routine with elastic resistance following isometric strength testing. Design: Cohort. Setting: Clinical. Participants: 34 subjects (31 ± 13 y, 73 ± 17 kg, 170 ± 12 cm). Interventions: The force produced was measured in Newtons (N) with an isometric dynamometer. The force distance was the distance from center of joint to location of force applied was measured in meters to calculate torque that was called "Test Torque" for the purposes of this report. This torque data was converted to "Exercise Load" in pounds based on the location where the resistance was applied, specifically the distance away from the center of rotation of the exercising limb. The average amount of exercise load as percentage of initial Test Torque for each individual for each exercise was recorded to determine what the average level of resistance that could be used for elastic resistance strengthening program. Main Outcome Measures: The percentage of initial test torque calculated for the exercise was recorded for each exercise and torque produced was normalized to body weight. Results: The average percentage of maximal isometric force that was used to initiate exercises was 30 ± 7% of test torque. Conclusions: This provides clinicians with an objective target load to start elastic resistance training. Individual variations will occur but utilization of a load cell during elastic resistance provides objective documentation of exercise progression.