“The more you sweat in practice/training, the less you bleed in battle” is a popular sports and fitness adage, often printed on T-shirts. “The more you sweat in peace, the less you bleed in war” was said in 1939 by Chinese Generalissimo Chiang Kai-shek (1887-1975).
 
The popular military saying (using the words “peace” an “war”) eventually became the sports and fitness saying (using the words “practice/training” and “battle”). “The more you sweat in training, the less you will bleed in battle” has been cited in print since at least 1970. “The more you sweat in practice, the less you bleed in battle” has been cited in print since at least 1999.
 
   
Google Books
Port Moresby, yesterday and today
By Ian Stuart
Sydney: Pacific Publications
1970
Pg. 154:
... slogan: The more you sweat in training, the less you will bleed in battle.
 
Google Books
Gods of War
By John Toland
Garden City, NY: Doubleday
1985
Pg. 167:
Some wise man said, and it’s been proven, “The more you sweat in training, the less you’ll bleed in war.’
 
23 October 1992, Seguin (TX) Gazette-Enterprise, “Congressional candidates speak here” by Bob Thaxton, pg. 1, col. 4:
“The more you sweat in practice, the less you bleed in war,” Tejeda said was one of the lessons he learned after enlisting in the U. S. Marine Corps.
 
Google Books
Marine:
A Guided Tour of a Marine Expeditionary Unit
By Tom Clancy
New York, NY: Berkley Books
1996
Pg. ?:
Still, the old saying goes, “The more you sweat in training, the less you bleed in war.” It is true. The training and examination during this period are incredibly intense.
 
Google Books
Rogue Warrior—Designation Gold
By Richard Marcinko and John Weisman
New York, NY: Pocket Books
1997
Pg. 111:
It read, THE MORE YOU SWEAT IN TRAINING, THE LESS YOU’LL BLEED IN BATTLE. That sign, as you can probably guess, was the source for one of the Ten Commandments of SpecWar.
 
Google Books
Battle Born
By Dale Brown
New York, NY: Bantam
1999
Pg. 2:
As someone once said, “The more you sweat in practice, the less you bleed in battle.”
     
Firefighters Forum
heywood
02-16-2001, 01:16 AM
(...)
TRAIN TRAIN TRAIN.
The more we sweat in practice the less we bleed in battle.
     
6 September 2001, Courier-News (Bridgewater, NJ), “Warren to review emergency plan” by Richard Quinn, pg. B1:
“The more you sweat in practice, the less you bleed in battle,” Ceccato said.
 
Google Books
Beyond Selling Value:
A proven process to avoid the vendor trap
By Mark Shonka and Dan Kosch
Chicago, IL: Dearborn Trade Pub.
2002
Pg. ?:
“Better to sweat in practice than bleed in battle. ” — Unknown
 
Richmond (KY) Register
October 27, 2011
Safety ‘drilled’ home during mock disaster
By Kelly McKinney Register News Writer
(...)
“There was a saying I learned in the Navy,” Horwitz said. “‘The more you sweat in practice, the less you bleed in battle.’ I think that applies here.”
 
Lichfield People (UK) 
What a difference a week makes after two victories
By Lichfield Mercury | Friday, October 28, 2011, 09:00
(...) 
I’ve got a T-shirt which says on the back ‘the more you sweat in practice the less you bleed in battle’.
 
I know that’s kind of cheesy but the idea of training is to prepare you for the matches, the better you train the better you will perform.
 
Good habits carry over from training to matches.