A training table is a table where athletes in training are provided meals. The term was popularly used in competitive rowing (especially between Harvard and Yale) in the 1870s and 1880s and is cited in print from at least 1866.
 
   
The Free Dictionary
training table
n.
A table, as in a mess hall, providing planned meals for athletes in training.
   
Merriam-Webster Dictionary
Main Entry: training table
Function: noun
Date: 1893
: a table where athletes under a training regimen eat meals planned to help in their conditioning
       
Google Books
The Arts of Rowing and Training
By “Argonaut” (Edwin Dampier Brickwood)
London: Horace Cox
1866
Pg. 121:   
Porridge need not be discontinued if it has been the custom to take it, but it is not an article that should be specially introduced upon the training table.
 
Google BOoks
Exercise and Training:
their effects upon health
By R. J. Lee
London: Smith, Elder & Co.
1873
Pg. 37:
At dinnertime I would recommend that small eaters should be allowed a light wine, such as hock or claret, instead of beer. The training table will be much improved by attention to such details, and the monotony of training, which produces in some men a dislike of food, will be greatly relieved.
 
Google Books
August 1873, Harper’s New Monthly Magazine, “Ten Years Among the Rowing Men” by WIlliam Blaikie, pg. 408, col. 2:
In a tramp we once took from Boston to New York, covering the distance in five days, with three hours to spare, doing fifty-seven miles the first day and averaging forty-five throughout, only four pounds were lost, and reasonably good fare, such as would be found on any well-ordered training-table, would probably have saved us a couple of these.
   
Google Books
Training, in Theory and Priactice
By Archibald MacLaren
Second and enlarged edition
London: MacMillan and Co.
1874
Pg. 128:
The exclusion of coffee from the training table is an unmeaning crotchet.
 
19 March 1876, New York (NY) Times, “Next Summer’s Boating,” pg. 7:
The men have not yet settled down to a regular training diet, but about the 1st of May they will have a training table, and from that time until after the race at Saratoga many, if not all, delicacies will be forbidden.
       
21 March 1876, Boston (MA) Journal, “Boating at Harvard,” pg. 3:
The men have not yet settled down to a regular training diet, but about the 1st of May they will have a training table.
 
17 March 1882, New York (NY) Times, “The Harvard Oarsmen,” pg. 2:
The length of the rows will, of course, be increased later, and about the middle of May the crew will go to a training table, where, however, their diet will not be changed from that now followed, which is chiefly plenty of meat and vegetables, fruit, and light puddings.
 
3 May 1883, New York (NY) Times, “The Oarsmen of Harvard,” pg. 1:
...although during the Spring recess, when the crew went to a training table, they were out twice daily.
 
22 December 1883, New York (NY) Times, “Yale’s Boating Interests,” pg. 2:
The short sliding seats will be introduced into the boat, the long, heavy oars put into use, and the candidates put to board at a “training table,” where only such food will be given to them as is best calculated to develop bone and muscle.