Heart rate (HR) is commonly taken from a chest strap sensing your heart muscles’ electrical activity. This signal is then transmitted to a monitor on you or your bike. From the mid 80s, amateur and pro athletes have used this digital analysis of activity levels and it remains one of the most reliable methods of performance tracking today.
HR monitors analyse your body like a tachograph on a formula 1 car, alerting you as to how hard various systems are working. It may be disrupted by local electrical signals, cross talk and core temperature rises – so it’s not perfect, but if used in conjunction with perceived exertion its better than relying on factors such as average speed or personal ‘feel’.
To make the most of HR training you need to ideally test yourself to find out your maximum heart rate (HRmax) and then calculate your specific aerobic zones. Zone 1 is 55-80% of your HRmax, Zone 2 is 81-87% (tempo training) and Zone 3, or high-intensity, is 88-100% of your HRmax. It’s wise to assess HR data downloaded after sessions to check you’ve done what you planned to do in the session/race – if you just store the data without understanding it it ceases to be useful.
However your HR spike is not uncommon, and may be due to:
Electrical disturbances in the vicinity of the first 10mins of your run route. To solve this, try a separate starting point and route and see if this still happens.
It could simply be that you’re going too fast out of the blocks, causing a short-term stress response. Your body then naturally slows down to an average pace, and your HR eventually comes back down. To solve this, and to ensure you’re starting in Zone 1, start with a jogged warm-up, then build into your intended pace for the run over a 3-8min period. Close your mouth and try to breathe through your nose for the rest of the run. This will ensure your run is steady.
Your clothing could be affecting static on the chest strap, or your chest strap fitting is too loose before you’ve started sweating. Try wetting the HR sensors before putting the chest strap on, and vary run top materials to see if this makes a difference. You could also borrow a friend’s device to see if this solves the problem.