Hello Again Almighty Sprint Gods,
I bought an EMS machine but have found out that it only allows 30 seconds rest between contractions. I know that in CF’s ‘Training for Speed’ it says that for every 10 second contraction you must have 50 seconds rest. But ive tried out using 5 second contractions with 30 seconds rest(ps. I got the shock of my life when i used it for the first time!). My coach seems to think that i can handle 10 second contractions with the 30 seconds rest and maybe i can but is it safe to do that. Furthermore, are there any side effects of using EMS?
Thanks Guys, any help you can give me would be welcomed with open arms. 
Well I’m not an expert in this field, but it just looks like a little math is all you need. A 10 second contraction to every 50 seconds rest is a 1:5 ratio. So with a max of 30 second rest time, a 1:5 ratio would suggest using a 6 second contraction. That’s all I have to say about that though, and maybe someone else could help out with your other queries…
I’ve spoken with a high-level coach who recommended 5-7 second contractions. I imagine you’d be fine with the 5-7second on and 30 second rests.
10 seconds may be superior but 5 seconds will be fine with 30s recovery. I use Compex which has only 3 seconds on and 20 or so seconds off and it works very very well. Now all you have to do is look forward to the pain!
Yes keep the ratio at 1:5 (work to rest) as done with the Compex programs for maximum strength. Otherwise you will find your muscle fatigues quicker and the quality of contractions dissipates towards the latter reps.
From CF’s article: ” Sprinters use the full ten second contraction time, though shot putters and linemen find that six seconds is about the longest they can maintain a maximal contraction. In either case, the same fifty second rest period must be maintained.” (The Truth About EMS)
I guess jumpers and throwers fall into the 5—6s category as well? I talked to a researcher in the field, and he also suggested the 1:5 ratio over any absolute rest time. However, why not be on the safe side and have a longer rest anyhow, it’s probably better that way. Mine is programmed for 40s (max. by the machine I use) between 6s contractions, although I mainly use my EMS/TENS unit for rehab and recovery. Also, there is of course always the option of pausing or shutting it down between contractions.
TENS is really great for sciatic and piriformis problems, makes you sleepy before bedtime too 
One side effect is that you will find your muscles get stronger
Is it wise to use ems for 5 second contractions with 15 second rest intervals. I saw it in a study that Chris put in his modern training book. Since my settings dont go up further than 30 seconds for rest i find it to be a good compromise. Also it seems i can tolerate the highest setting too well so i was thinking about going with 10 sec contractions and 30 sec rest. I was also curious about using it on my upper body as well, any advice?