• Indication
• Pros and cons
• Practical considerations
• Resources required
• References
• Examples and links

• Physical activity assessment
• Methods
• Combination heart sensors
• Practical considerations

Practical considerations

Positioning of a combined device
In the initial validation study of the Actiheart device, a tilt away from the longitudinal axis where the motion sensor measured, was predicted to result in an attenuation of the movement signal if the acceleration along the new axis was different (Brage et al, 2005).  The Actiheart should be positioned so that it is reasonably horizontally orientated but without stretching the wire which could add noise to the heart rate readings and also cause discomfort. Belt-based devices (e.g., Acti-Trainer, Ickal) may be bulkier but are more robust to such placement issues.

Another study evaluated the effect of monitor placement on physical activity estimates during treadmill and free-living activities (Brage et al, 2006).  The study found that placement (i.e. above or below the apex of the sternum) had minimal effect on registered movement and estimates of energy expenditure; placement of the monitor below the sternum may be marginally preferable to reduce noise levels of heart-rate data (Brage et al, 2006) and is usually preferred by the volunteer. .
In addition to the practical considerations for using accelerometers and heart rate monitoring the following points should be considered:
1. What level of calibration is required? Will calibration methods used commonly for fitness testing be adequate?
2. Is the individual confident and competent at placing the device i.e. have sufficient explanation and written instructions been given and are they capable of carrying these out or should the individual’s personal carer be involved?
3. Supply individuals with additional pads to replace as required.

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