Sinusoidal variation of cadence in cycle ergometry and the implications for exercise testing in patients. A pilot project.

Jessica Caterini. Supervisors: Dr. James Duffin and Dr. Greg Wells, PhD.University of Toronto & The Hospital for Sick Children

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Introduction Results Results

Methods

Conclusions

Lode cycle ergometer VO2max

test30

minsrest

ProtocolConstant 50% peak

workload (W)

5 minutes to achieve steady-

state

12 minutes data collection: 6

cycles on portable breath-

by-breath system

(CosMed)

Sine waves fitted in Labview

using least-squares method

Objective

Cadence: sine wave 50-100 rpm- 2 minute

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 Mean ± SD

Age (n=5)Height (cm)

Weight (kg)

Vo2max (ml/kg/min

)Workload Max (W)

21.2± 1.7 175±5.5 74.6±11.7 43.6±2.9 255±20.9Table 1. Participant statistics following VO2max test on a cycle ergometer.

 Ve

(L/min) fH (b/min)PetO2

(mmhg)

PetCO2(mmHg)

VO2

(mL/min)VCO2

(mL/min)

Mean 57.9 148.1 98.6 37.9 2317.9 1737.7

SD 6.5 16.2 5.2 2.2 192.4 131.3

Table 2. Mean participant (n=5) metabolic variables through 5 recorded sinusoidal cadence cycles.

A B

C D

E F

Aspects of disease affecting respiratory performance are easily observed during exercise testing. Exercise tests are commonly used by clinicians when monitoring disease progression1.Oxygen consumption (VO2) is the typical dependent variable in these tests, and thought to be affected by workload. However, recent research using treadmill exercise has shown that respiratory variables can be affected by factors independent of workload2.

Electrically-braked cycle ergometers are a reliable method of testing the effects of limb movement frequency on respiration, as workload can be kept constant and is independent of cadence.

Figure 1. An electrically-braked cycle ergometer can maintain a consistent work rate as cadence increases or decreases.

A preliminary study testing the effects of a sinusoidally varying cadence using a cycle ergometer with a consistent work rate on participants’ ventilation and oxygen uptake.

Figure 2. A typical participant’s’ response to sinusoidal changes in pedalling cadence. Response of VO2(A), VCO2 (B), Ve (C), PetCO2 (D), and fH (F) to cadence (E).

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Ventilation vs. Cadence

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VO2 vs. Cadence

Figure 3. Relationship of sine wave cadence amplitude (rpm) against ventilation amplitude (A) and oxygen consumption (B) for all participants (n=5).

Table 3. R correlates of mean sine amplitudes of metabolic variables and cadence. Correlations estimated using restricted maximum likelihood method, n=5.

• Factors other than work rate influence oxygen consumption during exercise since VO2 followed a sinusoidal change in cadence, although work rate by the participants was consistent and determined by the cycle ergometer.

•An increase in VO2 with higher cadences and constant work rates has been observed3 although these studies compared participants’ VO2 from differing cadences at timed intervals (i.e. 65rpm for 10 minutes versus 90 rpm for ten minutes).

•VO2 is negatively correlated with peak power4. Therefore, the elevated VO2 observed with increased cadence during sinusoidal pedaling suggests that individuals may have confounding values and inaccurate results in their exercise tests if they cannot maintain a consistent speed.

References1. Wells GD, Norris SR. (2009). Assessment of physiological capacities of elite athletes & respiratory limitations to

exercise performance. Paed Resp Reviews 10: 91-98.

2. Wells GD, Diep T, Duffin J. (2007). The ventilatory response to sine wave variation in exercise loads and limb movement frequency. Resp. physiol & Neurobio. 158:45-50.

.3. Tokui M, Hirakoba K. (2008). Estimation of oxygen cost of internal power during cycling exercise with changing pedal

rate. J. Physiol Anthropol 27(3):133-138.

4. Cannon DT, White AC, Andriano MF, Kolkhorst FW, Rossiter HB. (2011). Skeletal muscle fatigue precedes the slow component of oxygen uptake kinetics during exercise in humans. J Physiol 589(3):727-739.