see subject...
see subject...
I think they are beneficial even if you do them everyday as long as you aren't doing more than 8x100 everyday and you give yourself full rest every time. To switch it up a bit you could sometimes do them barefoot in grass.
...Also, I'm not saying you should do 8x100 everyday, I'm just saying that's the max. Realistically you should vary it between 5-8 reps of 70-100m.
...oh, and also, I'm saying these are strides so of course you can do a sprint workout that is more than that but we are just talking strides here.