range of 60–90% of maximal heart rate and
50–80%V
.
o2max.(Docherty 1982; Elliott et al. 1985;
Garden et al. 1986; Reilly 1990; Bergeron et al.
1991; Therminarias et al. 1991; Christmass et al.
1995; Faccini & Dal Monte 1996). The heart rate
and blood pressure responses tend to be higher
in squash and this has led to some discussion
about the risk of cardiovascular events in suscep-
tible individuals who play squash vigorously.
The metabolic changes during racquet sports
are consistent with the cardiorespiratory
responses. Blood glucose usually increases or
remains at pre-exercise levels during relatively
short periods (45–90 min) of play (Noakes et al.
1982; Garden et al. 1986; Bergeron et al. 1991;
Therminariaset al. 1991; Christmass et al. 1995). It
is possible that, in the absence of carbohydrate
supplementation, blood glucose may fall during
an extended duration match (Burke & Ekblom
1982). Blood lactate levels are generally within
the 1–4 mmol · l–1 range (Noakes et al. 1982;
Garden et al. 1986; Bergeron et al. 1991; Thermi-
nariaset al. 1991), although values as high as
5–6 mmol · l–1have been observed (Reilly 1990;
Christmasset al. 1995). While this may reflect a
period of intense activity just prior to sampling,
it nevertheless suggests the potential for signifi-
cant lactate production during racquet sports.
Although no data on muscle metabolites during
racquet sports exist, there is likely to be a large
reliance on muscle glycogen, particularly during
longer matches. The observed increases in
plasma glycerol and free fatty acids (Noakes et al.
1982; Garden et al. 1986; Christmass et al. 1995),
which correlate with match duration, suggest an
increase in lipolysis. Increases in the plasma
levels of catecholamines, adrenocorticotrophic
hormone, growth hormone, renin and vaso-
pressin, and decreases in insulin, have been
observed during racquet sports (Noakes et al.
1982; Garden et al. 1986; Therminarias et al. 1991).
The intermittent nature of racquet sports
results in a thermal load which is less than that
encountered during continuous exercise of
similar intensity. Environmental heat and
humidity will potentially have a greater impact
on thermoregulation and fluid balance during
racquet sports. For example, it is not uncommon
for the on-court temperature to be as high as
45–50°C on some days of the Australian Open
tennis tournament (held during the summer
month of January) and this creates a major chal-
lenge to the thermal and fluid balance of elite
players. Medical treatment for heat illness (i.v.
fluids and postmatch monitoring) was required
for two players in the 1997 tournament. In addi-
tion, factors such as air-conditioning, ventilation,
humidity, and heat generation from lighting
will influence the environmental conditions
when squash, badminton and tennis are played
indoors. Increases in rectal temperature of
0.8–1.5°C have been observed following tennisracquet sports 633
Fig. 48.1The intermittent nature of sports such as
tennis combines the demands of an endurance event
with those of repeated sprints. Photo © Allsport / G.M.
Prior.