Interesting, so it is up to the individuals then....
Well, for me increasing the cadence works better, I feel a strain in my groin when increasing my stride
....I go from around 180 to almost 200 steps per minutes when doing my intervals.
Also my lower legs do not go up higher behind me, they stay pretty close to the ground all the time, it would feel like there is some lost energy from lifting them too high
Mr. Spider Web, I've looked into this a bit, and, for what it's worth, this is what I've concluded:
1.) Speed is a function of stride rate and stride length.
2.) Both rate and length are effects, not causes. Stride rate is an effect of greater muscle activation; stride length is an effect of greater force application.
3.) Most runners increase both muscle activation and force application to achieve greater speed, and have a natural ability to adjust (or 'gear') the ratio of rate (activation) to length (force/torque) for optimal metabolic efficiency.
4.) If, however, you hold speed constant, and increase either muscle activation or force application, then the other variable must decrease.
5.) Both muscle activation and force application involve energy costs, so there is no inherent advantage in increasing one while holding the other constant (thus increasing speed) or decreasing it (maintaining speed constant). You are merely displacing the work of one by increasing the work of the other. If the ratio becomes sub-optimal as a result of these manipulations, you will tire more quickly.
6.) Nonetheless, different runners may favor one or the other side of the rate-length ratio, so that there exist rate-dominant runners, and length-dominant runners.
7.) For a rate-dominant runner, it may be useful to increase stride length/force application when fatigue sets in, in order to relieve muscle activation. For stride-dominant runners, it may be useful to increase stride rate/muscle activation when fatigue sets in, in order to relieve force application.
8.) For over-striders, typically those coming from a shod running background, it may be useful to consciously increase stride rate in order to decrease stride length, holding speed constant.
9.) For those with a good foot landing and posture, it is probably pointless to consciously manipulate stride rate (muscle activation) or stride length (force application).