I’ve had a private message asking about the role of weight training in the 400m preparation I advocate.
So here are some thoughts:
I always considered weight lifting (or training) as a supplement not a substitute for effort in the running program.
If the running suffered, the weights were usually reduced in volume and sometimes also lowered in intensity.
I always considered quality strength was developed in the gym, while strength endurance was developed on the hills and track.
So I never advocated more than 6 reps, never more than 6 sets and most of the lifting was in the 85-95 per cent of 1rm.
Lifting was done three sessions a week during the prep phases and pre-season and at various phases during the competition period.
The lifts were pretty basic:
Those without any spinal “issues” would start the routine with power-cleans, then go to the bench-press and then to squats (back), thighs to parallel.
These were the main lifts.
However the 44.3 guy I worked with had a mal-formed lumbar vertebra(?), L3 I think, and was told by our chiropractor not to clean or squat.
So he did leg-press and a lot of work on the Keiser pneumatic machines for rapid leg-extension and hamstring curls.
He also did bench-press, but could lift only a single on about 225 lbs 11 days before setting his 400m PB. He got much stronger much later in his career, but never raced as fast.
We did a few sets of boxing at the end of every weights session and after the squats, we did a few vertical jumps (maybe 3 x 10) with no load, just to excite the cns a bit and try to push for some fast contraction.
Boxing consisted of somethig like 12 x 30sec on, 30sec rest. The routine was usually six sets of straight jabs, then six sets of uppercuts wearing mits and hitting a pad held by me or a training partner.
We added in high volume, low speed sit-ups in sets of 20.
We did every session some straight-leg raises where the heel of the straightened leg was propped onto a small brick or block or step and the only other bodypart contacting the floor was the shoulder-blades and back of head and neck.
In this exercise the free leg was bent and raised to force the pelvis to “engage” thereby approximating a sprint posture (only horizontal). We did 3x10 reps, raising the bum from the floor and holding for about two or three seconds each time before lowering to the floor and relaxing momentarily.
I’m sure this was one of Charlie’s exercises.
Combined with “stiff-leg dolly” drills, the two exercises involved using the hamstrings in “long” positions (rather than strengthening and shortening, as in the hammy curl).
I’ve never had a serious hamstring injury since starting to use these two exercises in 1987. More important, neither has any athlete 
I’ve coached in that time.
kk 
Here’s the inevitable contra clause though: Brit Jon Anderson once told me that he coached David Jenkins to run about 45-flat at a Euro Ch - may have won it, can’t recall - and the staple of his program that season was rep 60m. Then again, I don’t know what else he ran, how often, or what his training history involved.]
maybe an exercise physiologist can shed light on the issue. But in the absence of guidance, I’ll stick with a concurrent model of training and largely avoid the complications.