Tennis is a sport that demands concentration and steady nerves.
Some can benefit from a little caffeine early in the day or after a long work day - too much and you are jittery and lose focus.
Tennis players should also be aware that caffeine has a diuretic effect, so be sure to hydrate during practice/play with water or a non-caffeinated sports drink.
Tennis players should know that caffeine interferes with heat regulation, so overheating is more common on hot days with caffeine.
Relentless has 160 mg of caffeine in a 16 ounce can.
"Acording to The American Beverage Asscoiation
Coffee, 8oz drip 104-192 mg [depending on the brand]"
From the USTA Recovery in Tennis
Caffeine is a naturally occurring stimulant
that can be found in coffee, tea, caffeinated
soda, and chocolate in dosages typically
between 30-200mg of caffeine. A large
strong coffee could have more than 200mg
of caffeine. Although caffeine has been
studied extensively in many sports, showing
a multitude of physical improvements in
strength, power, speed and endurance, the
data is limited in tennis players. The few
studies that have been conducted have not
shown positive performance improvements in
Recent research on caffeine
and dehydration show limited evidence
of caffeine having a negative response
to thermoregulation or hydration status
in dosages between 300-400mg per day.
However, caffeine is not a supplement that is
recommended for tennis play or competition,
but under appropriate guidance, may have
some positive effects for off-court training
for adult players. Large dosages (>500mg per
day) need to be discouraged, as this could
have detrimental effects on heart rate, fine
motor control, technique, over-arousal and
Not enough data is available
on children and thus caffeine should not be a
supplement used by junior tennis players."
There does not seem to be a huge excess of calories in a can of Relentless:
Original 108 calories (all from sugar)
Apple and Kiwi 113 calories (all from sugar)
Lemon Ice 120 calories (all from sugar)