Validity and Reliability of the Polar® S710 Mobile Cycling Powermeter

Abstract

The purpose of this study was to determine the validity and reliability of a new mobile bike-powermeter, Polar® S710, in laboratory and field conditions, against the SRM crankset. Eight trained subjects performed in a random order six uphill cycling trials of 6-min duration at three different intensities (60 %, 75 % and 90 % of peak power output [PPO]). In addition, 44 other cyclists performed in the laboratory three cycling bouts each of 5-min duration at three different pedal cadences (60, 90 and 110 rpm) at the same absolute intensity (~150 W). Bias between the two devices was correlated (r = 0.79) with the mean power in field conditions; with the S710 reading higher (p < 0.001) by 7.4 ± 5.1 % than the SRM in the range of power studied. In other words, the mean differences between the two devices increased as the exercise intensity increased. The mean power output obtained with S710 was significantly higher (p < 0.001) by 6.8 ± 7.9 W (bias x ÷ random error = 1.042 x ÷ 1.049) than the power obtained with SRM in laboratory conditions. Ninety-five percent of the differences of power measured with the S710 ranged between 21.4 W above to 8.3 W below the SRM in laboratory conditions. Mean differences between the two devices increased as the pedalling cadence increased (0.6 ± 3.8 %, 4.4 ± 3.7 % and 7.8 ± 4.4 % at cadence of 60, 90 and 110 rpm respectively). Coefficients of variation in mean power across the four field-based trials at 75 % PPO was 2.2 % and 1.9 % for S710 and SRM, respectively. In conclusion, the S710 recorded power outputs higher than the SRM system in both field and laboratory conditions. Pedalling cadence and exercise intensity influenced differences in mean power. These characteristics make S710 a useful device for recreational cyclists but not for elite cyclists or scientists who require a greater accuracy and validity. However, the limits of the present study (short-term duration testing; single tested variables as intensity, posture, pedalling cadence) require further investigation for generalizing the present results to extensive use in “real world” cycling.

Key words

Power output - field-testing - performance - accuracy

References

• 1 Balmer J, Davison R C, Bird S R. Peak power predicts performance power during an outdoor 16.1-km cycling time trial.  Med Sci Sports Exerc. 2000;  32 1485-1490
• 2 Balmer J, Davison R C, Bird S R. Reliability of an air-braked ergometer to record peak power during a maximal cycling test.  Med Sci Sports Exerc. 2000;  32 1790-1793
• 3 Balmer J, Davison R C, Coleman D A, Bird S R. The validity of power output recorded during exercise performance tests using a Kingcycle air-braked cycle ergometer when compared with an SRM powermeter.  Int J Sports Med. 2000;  21 195-199
• 4 Bland J M, Altman D G. Statistical methods for assessing agreement between two methods of clinical measurement.  Lancet. 1986;  1 307-310
• 5 Foster C, Green M A, Snyder A C, Thompson N N. Physiological responses during simulated competition.  Med Sci Sports Exerc. 1993;  25 877-882
• 6 Grappe F, Candau R, Belli A, Rouillon J D. Aerodynamic drag in-field cycling with special reference to the Obrees Position.  Ergonomics. 1997;  40 1299-1311
• 7 Hopkins W G. Measures of reliability in sports medicine and science.  Sports Med. 2000;  30 1-15
• 8 Hopkins W G, Schabort E J, Hawley J A. Reliability of power in physical performance tests.  Sports Med. 2001;  31 211-234
• 9 Jeukendrup A, Vandiemen A. Heart-rate monitoring during training and competition in cyclists.  J Sports Sci. 1998;  16 S91-S99
• 10 Jones S M, Passfield L. The dynamic calibration of bicycle power measuring cranks. In: S. J. Haake (Ed). The Engineering of Sport. Oxford; Blackwell Science 1998: 265-274
• 11 Kenny G P, Reardon F D, Marion A, Thoden J S. A comparative analysis of physiological responses at submaximal workloads during different laboratory simulations of field cycling.  Eur J Appl Physiol. 1995;  71 409-415
• 12 Li L, Caldwell G E. Muscle coordination in cycling: effect of surface incline and posture.  J Appl Physiol. 1998;  85 927-934
• 13 Lucia A, Hoyos J, Chicharro J L. Preferred pedalling cadence in professional cycling.  Med Sci Sports Exerc. 2001;  33 1361-1366
• 14 Martin J C, Milliken D L, Cobb J E, Mcfadden K L, Coggan A R. Validation of a mathematical-model for road cycling power.  J Appl Biomech. 1998;  14 276-291
• 15 Paton C D, Hopkins W G. Tests of cycling performance.  Sports Med. 2001;  31 489-496
• 16 Smith M F, Davison R C, Balmer J, Bird S R. Reliability of mean power recorded during indoor and outdoor self-paced 40 km cycling time-trials.  Int J Sports Med. 2001;  22 270-274
• 17 Telford R D, Hooper L, Chennells M HD. Calibration and comparison of air-braked and mechanically-braked bicycle ergometer.  Aust J Sports Med. 1980;  12 40-46
• 18 Wilmore J H, Constable S H, Stanforth P R, Buono M J, Tsao Y W, Roby F B, Lowden B J, Ratliff R A. Mechanical and physiological calibration of four cycle ergometers.  Med Sci Sports Exerc. 1982;  14 322-325