First Workouts with Hammerhead’s new Heart Rate Monitor

Hammerhead’s new chest strap HRM is one of several accessories for the Hammerhead Karoo 2 performance bikenav, reviewed here last year. AFAIK, it’s made in Taiwan by a UK-based OEM company called Cardiosport and it’s slightly unusual in its design and that warrants a few comments which I’ll make below.

In a nutshell: Hammerhead’s new Heart Rate Strap appears to be a sufficiently accurate BLE/ANT+ Heart Rate Monitor that’s comfortable to wear.

Point Of Interest

Hammerhead’s strap has an unusual construction where silver is interwoven in fabric to make the sensor.

As you can see in the image below, the Hammerhead’s sensor is approximately the same size as the Garmin HRM-TRI but both are notably smaller than the Polar H10. The larger sensor doesn’t make it any more accurate per se, it’s just that the chance of the sensor missing a few beats is reduced by the larger surface area in the Polar sensor. The Polar strap also has a mechanism that helps it stay in place better and that has a similar effect to minimise the likelihood of data loss.

HOWEVER! Hammerhead suggests that their silver sensor area is less likely to fail. I’ve no data to dispute or agree with that, I would tend to err towards them being correct though. In my experience, it is the strap sensor area that usually fails rather than the pod.

Accuracy

This is NOT a detailed accuracy test.

Let’s look briefly at a ride and a run, each was hill reps of various lengths. The Hammerhead HRM reported the correct levels during the effort periods. However, you can see on the run that there were unexpected spikes (green) towards the start but note that I was wearing two chest straps and so there is quite a good chance that caused a problem. 

Ride Comparison – vs HRM-PRO and Apple Watch SE

8 mini hill reps on the Richmond Hill Octopus.

Run Comparison – vs Polar H10 and Apple Watch

6 Hill reps in Richmond Park

Hammerhead Heart Rate Monitor Specifications

These are the official specs that have so far been released. The HRM may have additional capabilities but…probably not.

Of specific interest here is the two BLE channels, ANT+ compatibility and the ability to produce RR-intervals ie to work for HRV.

Compared to the Garmin HRM-PRO, the Hammerhead HRM has a 900-hour life whereas Garmin claims 1 hour of use per day for a year…ie 365 hours. Garmin also claims 50m waterproofing which gives me more confidence than the 30m that Hammerhead claims…don’t go swimming with that.

Hammerhead Heart Rate Monitor Price & Availability

You can buy this initially from Hammerhead’s site. Most likely you’ll buy it bundled into the Karoo 2. Retailers like Wiggle and Power Meter City will stock the HRM later in 2021

Buy UK: £55

Buy USA: $64

Buy EU: Eu64

The new Hammerhead HRM ticks the basic boxes for connectivity, battery life and comfort. If its novel silver sensor really does last longer then this would justify its price tag. Nevertheless, it’s a nice-looking strap and I’d wear it for that reason alone…plus it’s probably accurate enough.