296
NEUROMUSCULAR FATIGUE OF ATHLETES, ENGAGED IN ENDURANCE AND EXPLOSWE CONTRACTION TYPE SPORTS
G. Hering1, E. Hennig2, H. Riehle1
1
Sports
Science,University of Konstnnz, Germnny;
2BiomeclmnicsLnborntory, University of Essell,
Ger111nnyNumerous animal studies reported about the relationship between uu;ervation frequency and the muscle fibre properties (for review ee Pette and Staron 1 97; Gundersen 1998). However, there js little information in the literature about the relationship between electromyographical parameters and different muscle types in athletes. Kupa et al. (1995) and Gerdle et al.
(1997) reported lose links between U1e medi- an
I
m ·an power frequency (MPF) of the EMG-signal and muscle morphology. The aim of this study was to compare the EMG pattern during muscular contraction in four different groups of athletes.EMG and force measurements were taken from three heads of theM. quadriceps femoris of 12 volleyball players (VG), 12 sprinters (SG), 12 marathon rUJmers (MG), and 12 control subje ts (CG, not specifically tramed physical ducation students) in isometric contractions from 10'Yo of the maximum voluntary contraction (MVC) to 90% MVC. All subjects performed at each force level 10 trails (5 seconds of contraction) with a rest of 5 se onds in between until the required force could not be achieved any more.
- The number of contractions of the sprint group (SG) was significantly reduced in
compari~on to the remaining three groups.
The m, thon group (MG) and the control group (CG) were significantly different to SG and to each other.
-The averaged mean power frequency (MPF) from the three heads of the quadriceps did not sho ignificant d;iffer nc s between the group . But for the vastus lateralis EMG, measured with the 2-channel electrode assembly, differences were found, especially betwe n MG and CG and MG and SG (Table 1).
-The MPF-values at 10 to 40% MVC within
140
MPF (Hz(
60
--%-V L
40
-<>--V M
20
__,._ R F
i i r ' t a 88 o ~ i i • 1 ~ ~ Y .. '
' ' '
~
' ' ' ' t t ' ' '~
'~
I ' ' 'Fig.1. MPF oftlw vnstuslntemli. (VL), vt'lstus 111erlinlis (vm) nnd reclu femoris (f{F). VL wns 1/tertsured with tltc 2-chnmzc/
clectro,Je (rigltt side). VM n11d RF tuete measrrred with tzon11nl EMG-electrodes (left side).
N ~IC[Hz) N Clo(Hzj IN SCjHz) N V(.(Hz) MPf_VI._lO.,.J_FT ~u.:;cc· 11 S'!,l9;i 12 101,(\l;i 12 Jllt\2S5 11 Y2,Yl15 1'-.1 PF _ VL_20'f,_FT MCCG" MGsc· 12 8•1,2~6 12 l(l!J,..JJ9 11 W2,3b~ 11 92,':'92 MPF _ VL_31);;,_,_Fr ~lCSG' 12 i''~,050
"
9'i,"t·2 12 J(lJ,-!73 11 91,3:;6MPF _ VL_-IO' •. ,_FT MCCG'
12 S7,3-~5 12 lllt1,2.J-" 12 W2,00·5 11 9(),.j71l
~\CSG' 1-.\GCG'
MPF _ VL_50 ~-IT ccvc· 12 ~G,o33 12 llltl,473 12 ~7.676 11 f'7,-l3o SCVC."
~1Pr: _ Vl_6lF<,_FT CGVG' ;;eve·· 12 ~o.G-l8 12 97,2.2-l 7 "2.~ 11 S:i,o:-:>5 MPF _ VL_7U"-_Ff 11 S:>,lll a 0~528 4 Q:J,<¥.10 8~.160
MPF _ Vl_~O--r.-_FT y 83,22~
"
91/;~s 137.'?·75~IPF_ VL_ av•>_Ff s 77,S21 .::.~.l\\1 6.~.&-11
Tab.l. MPF-Data mzd sig11ijicmzt difji'l'cltces betwce11 groups nt tlze M. vnstus Intern lis lttcasurcd with n specinl
2-c!Willlel electrode
the sprint group (p<0.01) as well as over all subjects (p<0.05) were inversely correlated to the sprint time.
-An inverse correlation (p<0.05) existed also between the number of achieved contractions and the sprint time over all subjects .
The results indicate a strong relationship between the ability t ustain fatigue and the MPF because MG and VG had the highest number of contractions as well as tl1e I >West MPF-values. These results fit well into the concept that low innervatjon frequencies transform muscle fibre properties towards slower contrnction characteristics.
REFERENCES
Gerdlc B, Karlsso11 S, Crws/111w AG, Fridc11 f Acta Pilysiol Sca11d 160:341-51. 1997.
Glllldersc/1 K Acta Pilysiol Scmtrl162:333-41. 1998.
Pcttc 0, Slaro11 RS I11t Rev Cytol 170:143-223, 1997.
K11pa E]. Roy SH, Ka11darirm SC. De Lllca C] f Appl Pilysio/ 79:23-32, 1995.
Konstanzer Online-Publikations-System (KOPS) URL: http://nbn-resolving.de/urn:nbn:de:bsz:352-0-425313
Erschienen in: Perspectives and profiles : 6th Annual Congress of the European College of Sport Science ; 15th Congress of the German Society of Sport Science ; book of abstracts / Mester, Joachim et al. (Hrsg.). - Cologne : Strauss, 2001. - S. 296. - ISBN 978-3-89001-235-3
