Effect Of Rapid Body Mass Loss On Metabolism And Muscle Performance In Combat Sports Athletes

Introduction
Body mass reduction for competitions is widely used by athletes in sports where competitions are held in certain weight
categories. However, the data on the effect of this practice on physical performance are controversial. Some studies
have revealed the negative impact of body mass reduction on performance [1,2] whereas others have reported no
significant changes [3,4] or even improvement [5]. Apparently this divergence is conditioned by the differences in body
mass reduction protocols and in tests applied for assessing performance. The aim of the present study was to examine
the effects of rapid body mass reduction on metabolism and muscle performance in 3-min variable intensity exercise in
combat sports athletes.

Methods
Eighteen well-trained male combat sports athletes [age 20.8+ 1.0 years] reduced their body mass by an average 4.8
(1.5%) during 3 days. The subjects were tested at the Cybex II device before (T1) and after (T2) body mass loss.
Maximal knee extensions at angular velocities of 1.57, 3.14 and 4.71 rad·s-1 were performed, the isokinetic peak torque
(PT) was measured. The second part of the test consisted of submaximal isokinetic knee extensions at 1.5 rad·s-1 for 45
s at the rate of 30 contractions per min (Wsmax) followed by 15 s maximal effort (Wmax). Total work (Wtot) was
calculated as sum of Wsmax and Wmax. Total duration of the variable intensity test exercise was 3 min. The packed
cell volume as well as concentrations of haemoglobin and that of several metabolites (Table 1) were measured in blood
obtained at rest and after cessation of each test exercise. Paired-samples Student’s t-test was used to determine the
significance of differences.

Results
PT measured in T2 was lower in comparison with T1 at angular velocities of 1.57 and 3.14 rad·s-1 (by 5.8 and 8.7%,
respectively; P=0.03). There was tendency towards lower Wsmax and Wmax performed in T2 in comparison with T1.
Wtot was lower in T2 in comparison with T1 during each minute of the test by 14.4% (P=0,03), 14.7% (P=0,005) and
11.0% (P=0,009), respectively. Wtot performed during the whole 3-min test exercise was decreased by 13.7% at T2
(P=0.005). Rapid body mass reduction caused an average 5.7 (4.4)% decrease in plasma volume. The changes in the
concentrations of different metabolites in plasma are shown in Table 1.

Discussion/Conclusions
Rapid body mass reduction by a 5% induced an increase in plasma urea concentration which most likely reflects
increased rate of tissue protein degradation in the body. The data concerning PT at lower angular velocities and work
performed during 3-min variable intensity exercise shows that quadriceps femoris muscle function is impaired as a
result of rapid body mass loss in well-trained combat sports athletes.

References
[1]. HicknerRC. et al. (1991). Int J Sports Med,12, 557-562.
[2]. Horswill CA. et al. (1990). Med Sci Sports Exerc, 22, 470-476.
[3]. McMurray RG. et al. (1991). 12, 167-172.
[4]. Maffulli N. (1992). Br J Sports Med, 26, 107-110.
[5]. Fogelholm GM. et al. (1993). Med Sci Sports Exerc, 25, 371-377.

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