Shavender, K., Spring, D., Salvo, E., Robinson, C., & Moen, E. (2006, January). STATIC AND DYNAMIC KNEE ANGLE MEASUREMENTS IN COMPETITIVE CYCLISTS. (Abstract). Journal of Orthopaedic & Sports Physical Therapy, 36(1), A75-A75. Retrieved March 13, 2009, from SPORTDiscus database.
Conference:CSM Orthopaedic and Sports Physical Therapy Section. Meeting (2006 : San Diego).Source:Journal of Orthopaedic & Sports Physical Therapy Jan 2006: Vol. 36 Issue 1. p. A75 1p.
Indicates static knee measurements are often used for fit and 25-35 is the range when foot is at dead bottom center. Dymanic also available, but few studies compare the two for similarity.
Used USCF licensed riders 3 years of competitive cycling experience.
Used a heel level and static estimated heel position (heel up).
No significant difference found between static estimated heel and 3 of the 4 dynamic knee angles (90rpm/125load, 120rpm/125 load, 120rmp/250 load). Mean angles were 38, 36, 40.3, and 38.6. Mean for the static estimated heel was 39.6.
Most measurements were outside the 25-35 range.
Bertucci, W., Duc, S., & Grappe, F. (2004, September 2). Validity and reliability of the new Axiom and PowerTap cycle ergometer when compared with an SRM powermeter during maximal intensity exercise. Archives of Physiology & Biochemistry, p41-41.
Presents a study which aimed to compare Axiom and PowerTap cycle ergometers with the speed of relative movement (SRM) reference powermeter during maximal intensity exercise. Use of an ergometer to evaluate the performance of competitive cyclists; Information on the Axiom, a stationary electromagnetically ergometer, and the PowerTap, a mobile cycling powermeter; Description of the SRM system.;
The SRM and PowerTap use stain gauges. PowerTap underestimates SRM power only by 1.8 percent. Bertucci attributes this to the location of the gauge. The PowerTap is located on the rear hub and where mechanical loss can occur due to the chain and drive train system. The SRM measures from the crank arm.
Validation of SRM power cranks using dynamic calibration - abstract. Lawton, E.W.; Martin, D.T.; Lee, H., In, Fifth IOC World Congress on Sport Sciences : book of abstracts, Canberra, Sports Medicine Australia, 1999, p.199.
Lawton, E., Martin, D., & Lee, H. (1999). Validation of SRM power cranks using dynamic calibration - abstract. In, Fifth IOC World Congress on Sport Sciences : book of abstracts, Canberra, Sports Medicine Australia, 1999, p.199 Australia. Retrieved July 16, 2009, from SPORTDiscus with Full Text database.
The SRM (Schoberer Rad Messtechnik) Training Crank (Jülich – Welldorf, Germany) was developed in 1986 to quantify power output in the field using a cyclist’s own bicycle. Torque applied to the crank (detected by 4 strain gauges) is multiplied by angular velocity (cadence) to calculate power. Factory calibration using an eddy current brake has shown that the accuracy of power measurement for the professional road version is ± 2.5%. The purpose of this investigation was to evaluate the accuracy of the professional road version SRM Training Crank (SRM) using a dynamic calibration rig (CALRIG) designed and built by Bio-Med Electronic Services. Nineteen SRM cranks were tested over a one-year period in a laboratory under standardised conditions (19-23° C, 695-710 mm Hg). The SRM cranks were mounted on the bottom bracket of a bicycle attached to a stationary wind trainer. The bicycle was attached to the CALRIG for determination of the true power at 100 rpm. After a warm-up protocol and prior to testing, the zero offset for the SRM was set according to manufacture’s instructions. The CALRIG load cell was calibrated with precision masses (1-10kg) and any dynamic system losses were measured to establish no-load zero condition prior to each testing session. All testing sessions were performed at 100 rpm and involved shifting through the full range of 9 gears in the rear cluster using both the large and small front chain rings. After a 15-30 second stabilisation period in each gear, power and frequency output (Hz) from the SRM and the CALRIG were recorded over the range of 50-900 W. For each of the 18 gears selected a relative error term and a calibration factor (slope) were calculated. These data were used to calculate the average (%ERRMEAN=2.5± 5.0%,), minimum (%ERRMIN= -0.7± 5.0%), and maximum (%ERRMAX=5.6± 5.0%) error terms for each SRM crank. These data fall within the specifications of the manufacturer. However the %ERRMEAN was only <2.5% in 9 and <5.0% in 12 of the 19 SRM cranks tested. In four SRM cranks %ERRMEAN was 9-10%. Calibration data from the CALRIG were used to adjust the slope, resulting in a %ERRMEAN <2.5% for all SRM cranks. In summary, the SRM crank is reliable for quantifying cycling power output but accuracy depends on the particular crank purchased and can range from 0-10% measurement error.