Tommy - TRX exercises include: press-ups, row, bicep curl, mountain climber & squat-thrust, back extension with arms overhead and also to the side, one and two handed trunk rotation, single leg squats with raised leg in front and behind, hamstring curl.
Excessive exercise is a rather subjective concept. The list of high risk sports is interesting though; quite a variety with no obvious characteristic factor.
DT - Depends which park they use. Welcombe Hills Park is far from flat. I think I'll nip over to Cov Memorial Park in the near future and have a go at that one.
Charlie - I find the 'dead zone' concept quite hard to understand. It's often explained as if there is no benefit to be gained from running in this zone, which I find hard to believe. I think the point is that there is no greater benefit than if the run was slower and the disadvantage is that it results in increased fatigue.
A minor point that I've never managed to comprehend is whether this applies to distance or time. One apparent advantage of running faster is that it takes less time to cover the same distance. So does a 1 hour run which I cover eight miles have no greater training affect then a 1 hour run covering only 7 miles?