Within- and between-session reliability of a pedal force system for power output and pedal force effectiveness measurements

Abstract

Purpose. The study assessed within-and between-session reliability of power output (PO) and pedal force effectiveness and compared PO from the pedals with the Lode Excalibur cycle ergometer. Methods. Seventeen male cyclists performed 10 trials at 3 levels of PO (1.5, 2.5, and 3.5 W/kg) and 3 cadences (60, 80, and 100 rpm) in 2 sessions. Instrumented pedals and a portable motion tracking system were synchronized to collect pedal forces and 3D full body motion, respectively. PO and the index of effectiveness (IE) were compared within and between sessions for the pedals while PO was compared with the Lode Excalibur. Results. Good agreement was observed for PO within sessions whilst right and left pedal IEs were moderate. Betweensession reliability ranged from poor to good for PO measured from the pedals, and reliability for IE ranged from poor to good. Significant differences in PO were observed between the pedals and the Lode Excalibur ergometer (17-50 W). Conclusions. The customized system to measure pedal forces was reliable within a given session for measuring IE and PO but variability in data increased in the second session, potentially because of the repositioning of the motion tracking sensors. Validity in measuring PO from the pedals without the use of the crank encoder is questionable.

A literature overview of modern biomechanical-based technologies for bike-fitting professionals and coaches

“…10 Two-dimensional (Powerforce) or three-dimensional (JA: Ped3; I-crank system, Sensix, Poitiers, France; Forped, Cycling Science, d.o.o., Ljubljana, Slovenia) dynamometric pedals have been used in the literature to measure pedal forces. [50][51][52][53][54] Authors have shown that the I-crank system provides accurate measurements of crank torque, power output and mechanical work output. 53 However, Bini and Hume have observed that this system is reliable to measure power output and IE within a given session, but variability in data increased between two sessions, probably due to the repositioning of the motion tracking sensors.…”

“…53 However, Bini and Hume have observed that this system is reliable to measure power output and IE within a given session, but variability in data increased between two sessions, probably due to the repositioning of the motion tracking sensors. 54 In addition, instrumented bicycle crank systems, which can be used for laboratory and field tests (Axis Cranks, Swift Performance, Australia), allow accurate measurements of 2D pedal forces on both the left and right crank arms independently. 55 As mentioned previously, these systems are often used in scientific studies to measure IE (Eq.…”