There are so many flaws in the accurate measurement of training load (Training status) with Garmin watches / wearables, here are some of them that I have found... there are more. If you use your watch purely for endurance steady state sports, then they are great, but when it comes to calculating training load for just about any other sport (including general fitness) then they are way off the mark. Garmin own and use FirstBeat Technologies' who have created algorithms to calculate training stress that has been placed on the body, but this is based on HR. i.e. if you work hard, then your HR spikes and therefore more stress is placed on the body.
But it measures VO2 Max on speed as well, there are 'norms' for your age and speed and HR, and it takes these into account to measure a comparison of your VO2 Max to others. So if you train on a concept 2 rower, then it can't measure your speed but perhaps you are way above the 'Norms' on a rower and you are extremely fit, but it won't recognise that. So unless you are getting measured by GPS, then it can't measure your VO2 Max properly.
Then strength training - it has no way of measuring how hard you worked in a strength session. This is a huge part of an athletes training diary and the load / stress needs to be factored in. In fact they don't even offer "self-evaluation" for 'Strength'. Your HR may not spike much, especially when you are lifting >80% max, but your neural fatigue or muscle soreness could be huge, which could acutely affect your run performance and subsequently your training status.
Speed work - useless! 20m, 40m, 60m sprints are non accurate in terms of time. The GPS can not catch up or accurately measure the speed (important for field athletes). The HR data won't be able to accurately record the training load or stress.
I was ecstatic when I was able to add in a "self-evaluation" post a running training session because this was what I thought was Garmin's solution for gaps in their training load measures. But in fact it doesn't (to my knowledge) give an arbitrary number that could be used to measure internal training load. For example, I have tried to find my accumulative workload totals (Chronic workloads) but couldn't find them.
I'm sure they will get there, but at this stage, they are a long way off being able to measure training load for accuracy and quantification.
