I regularly use drills and runs with the sprinters and jumpers holding a light bar overhead. In the video below  I explain the purpose and protocols I use for fast running using a bar held at arms' length.
I have used these methods for the last couple of years to great success. The drills and runs improve posture, technique and speed and can potentate performance. So it's a win, win, win and win scenario. Take a look at the video content to get more information. 
The bars we use are readily available - see amazon link below too. 

 If you want to get away from the blocks quickly as well as a fast reaction you will need to make sure you hit the right shapes.
The key elements for successful accel from a technical (and not conditioning) response focus down on:
Torso angle
Shin angle
Use of arms
Foot position

HERE ARE SOME KEY POINTS FOR YOU TO FOCUS ON
Torso and body angle - on leaving the blocks it should be around 40-degrees. Don't fold at the waist
Shin angle - this needs to be negative (knee in front of shin) & this needs to be maintained for 6-10 strides at least. Doing this will keep you low and accelerating. You don't want to "pop up" and go no where!
Use of arms - some sprinters will use a longer (front arm (more advanced). Experiment as this may help your drive and block clearance and first steps. Whatever method used the arm action needs to be explosive and deliberate
Foot position - the toes need to be down but the ankle has to be stiff. It's a right angle as you can see in the image. This will enable the piston like motion of the leg to permit the foot to really hit the track and create forward motion

OTHER CONSIDERATIONS
Toe-drag - some sprinters scrape the track with the rear leg on block clearance as they are trying to minimise back-lift and get the foot to advance low and fast ... some coaches like others don't. If it works for you stick with it
Don't rush - workout your optimum acceleration pattern - keep focussed on that and like a long jump take-off from a run-up, keep working on it over and over again.
Low heel recovery - do not overly cycle (lift) the heels over the first 6-10 steps of accel - keep the heels low as you drive. Too much stride airtime will kill your acceleration.
TAKE-HOME MESSAGE
Don't neglect your acceleration training start working on it now and keep working on it!

WATCH THIS VIDEO WITH TOP SPRINTS COACH JONAS DODOO TO 
FIND OUT MORE ABOUT ACCELERATION AND MAX VELOCITY
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