Spark's exercise tracker assumes continuous activity, and you are smart to wind your 3 hours back to 2 hours to allow for breaks, etc.
Yes, Spark does take into account your own bodyweight (from your most recent weigh-in).
A very rough rule of thumb is that you burn about 100 calories per mile walked on level ground. Hiking tends to burn significantly more than this on a per mile basis. Each vertical foot gained is about equivalent in effort to 8 horizontal feet. Even a sideways tilted path without a climb (eg. going round the side of a hill) involves your muscles working significantly harder to keep you upright and balanced.
Another rough guide is that you burn between 6 and 10 calories per minute while exercising. 6 at the more moderate end, 10 at the higher end. Walking would generally be moderate, and if you were getting winded on the climbs, an overall average of 7 per minute seems pretty reasonable. 400 calories per hour, or 800 for 2 hours of active hiking seems pretty reasonable.
M@L (regular hiker and backpacker)
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.
| current weight: 178.0