Int J Sports Med 2011; 32(5): 353-356
DOI: 10.1055/s-0031-1271772
Training & Testing

© Georg Thieme Verlag KG Stuttgart · New York

Reliability/Validity of the Fortius Trainer

J. J. Peiffer1 , B. Losco1
  • 1School of Chiropractic and Sports Science, Murdoch University, Murdoch, Australia
Further Information

Publication History

accepted after revision January 19, 2011

Publication Date:
04 March 2011 (online)


This study examined the reliability/validity of power output measured using the Fortius Virtual Reality cycle trainer. 10 cyclists (age: 28±6 years; V˙O2max: 60.9±7.2 ml · kg−1 · min−1; peak power: 393±82 W) completed three 20 km time trials on a Fortius cycle trainer. During each time trial, power output was measured at 1 Hz using the Fortius internal software and a PowerTap power monitor. Validity calculated for the Fortius trainer; Pearson correlation coefficient (r=0.99; 95% CI: 0.98–0.99; p<0.01) and typical error of estimate (3.5%; 95% CI: 3.2–3.9%), was similar to other established laboratory ergometers. No differences (F2,16=0.32; p=0.73) in mean 20 km power were observed between trial 1 (253±46 W), 2 (258±49 W), or 3 (255±50 W). Test-retest reliability (intraclass correlation coefficient (ICC) and coefficient of variation (CV)) was better between trial 2 and 3 (ICC=1.00 (CI: 0.98–1.00); CV: 1.6% (CI: 1.1–3.3%)) compared with trial 1 and 2 (ICC=0.98 (CI: 0.91–1.00); CV: 3.3% (CI: 2.2–6.4%)). The Fortius cycle trainer is a valid and reliable device for the measurement of power output in cyclists, thus providing an alternative to larger more expensive laboratory ergometers.


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Dr. Jeremiah PeifferPhD 

Murdoch University

School of Chiropractic and

Sports Science

90 South Street

6150 Murdoch


Phone: + 61/08/9360 7603

Fax: + 61/08/9360 7579