Komi, P. V., Rusko, H.: Quantitative evaluation of mechanical and electrical changes during fatigue. In ar re 1 , loading of eccentric and concentric work. Scand.
-
-
European Journal of
.H.Norris
Applied
Eur. J. Appl. Physiol.42, 41-50 (1979)
Physiology and OccupationalPhysiology ~ Springer-Verlag 1979 -
. 42, 73-86 age.Copenical material.
EMG Frequency Spectrum,Muscle Structure, and Fatigue
lw-Hill1971
During Dynamic Contractions In Man
td paying the
Paavo V. Komll. and Per Tesch2
06, 689-715
I
KinesiologyLaboratory,Departmentof Biologyof physicalActivity, Universityof Jyvaskyla,
: on creatinine
SF-40 100 Jyvaskyla, Finland 1 Department of Clinical Physiology, Karolinska Hospital,
-163 (1976)
S-10401 Stockholm, Sweden
agedand older ., Hedman, R., cl and maximal .tional reference
d women in the cisePhysiol. 43,
Summary. conditioned
Fatigue
of the vastus lateralis
muscle was studied in healthy
students, who differed considerably
well-
regarding their muscle fibre type
distribution. Muscle force declineduring repeatedmaximumvoluntary knee extensions at a constant angular velocity (180° x S-l or n rad x S-l), using isokinetic equipment,was taken as the criterion for the degreeof fatigue. In an
19itudinal Study.
attempt to study quantitative as well as qualitative changes in the EMG pattern, integrated EMG (IEMG) and the frequency of the mean power (MPF), com-
cularwork.Acta
puted from the power spectraldensity function (PSDF), were analysed.It was found that individuals with musclesmade up of a high proportion of fast twitch (FT) musclefibres demonstratedhigher peak knee extensiontorque, and a greater susceptibilityto fatiguethan did individuals with musclesmainly composedof
J. Appl.Physiol.:
slow twitch (ST) muscle fibres. An IEMG decline (p
< 0.01) was demonstrated
during 100 contractionsin individuals rich in FT fibres. Only a slight, but not significant,reductionin IEMG occurredin individualswith a high percentageof ST fibres. Concomitantly,MPF decreased(p < 0.001)in individualswith a high percentageof FT fibres, while their oppositesdemonstratedonly a slight decrease(non-significant).It is suggestedthat musclecontractionfailure might also be related to qualitativechangesin the motor unit recruitmentpattern, and that thesechangesoccur more rapidly in musclescomposedof a high proportion of FT muscle fibres than in muscles composed of a high proportion of ST fibres. Key words: Electromyography
-
Isokinetic contractions
-
Mean power fre-
quency - Muscle fatigue - Muscle fibre types From animal experimentsit is known that musclescomposedof slow twitch (ST) fibres possessa greaterresistanceto fatigue than musclescontainingpredominantly fast twitch (FT) fibres (e.g.,Edstrom and Kugelberg, 1968;Kugelbergand Edstrom, Offprint requests to: Per Tesch,Laboratory for Human Performance(FOA 57), Karolinska Hospital,
S-l04 01 Stockholm, Sweden
0301-5548/79/0042/0041/$02.00
"
42
P.V.KomiandP.Tesch
f'EMG Changes a
;-LumexInc.,Ne\\
1968;Baldwin and Tipton, 1972).In h~man skeletalmuscle,b.othfib~etypes ex~stin one and the same muscle. Recently, rt was found that subjects wrth a relatively;,; higher proportion of FT fibres in the quadricepsmusclewere more susceptibleto fatiguewhen performing 50 consecutivemaximal kneeextensionsthan subjectsrich
Each subject
t~ joint an~at an ! li~c~ ted °ns twas ,~ contr
.
was
in ST fibres (Thorstenssonand Karlsson, 1976; Nllsson et al., 1977; Tesch et al., 1978a).In addition,large amountsof lactatewerefound to have accumulatedpreferentially in the FT fibres after only 25 contractions (Tesch et al., 1978a, 1978b). Lactate formation and/or associatedpH changeswithin engagedmusclefibres may be responsiblefor muscle contraction failure (cf. Fitts and Holloszy, 1976). .
.'
In experimentsusing electromyographic(EMG) techmques,rt has been suggested
that
the
shift
in
EMG
spectral
density
function
towards
lower
frequency
componentsis associatedwith reductionin muscleaction potentialconductionvelocity
(Mortimer
et al.,
1970).
In
addition,
the
shift
in
EMG
frequency
. . " . d. . h b h t b I t d t h lsometnclatlgue con ltions as een~. own 0 ere a e. 0 tel "'
tion
of
the
muscle
(Larsson,
1978;
Vlltasalo
and
Koffil,
spectrum
fib
1978).
under
The
" r:i ;,~ :1
I
I
present
study
'
t I
Results
-
Eleven
male
ments,
all subjects
~hysical
mental.p~oc~ures.
"",.!
were diVIded
:';1,'
":"' !:'f':,1
ed~cation
students
were Informed After
Into two
muscle
about
volunte.ered the possible
biopsy
groups,
.s~~ling
in.the
histochemical
muscle
study:
and nsks
Prior
associated
~aI~sis.(see
fibre
type
.to theexpe~With the expen-
below),
distribution.
the
Table
I
occupied
subj~cts
area.
The
knee
extensioJ
II)
Nm
1 summanzes
theirphysical characteristics withrespect to age,weight, height, percentdistribution, andrelative area of fast twitch
(FT)
were
fibres in the vastus
biopsies
!j,~
Classificati.on
i "j
based on histochelDlcal
staining
Herman,
1962). Muscle
taken
from
of the, fibres
1955; Engel,
M.
vastus
lateralis
muscle,
lateralis
prior
~n~o slow twitch
for myofibnllar fibre
transverse muscle sections stained for NADH area occupied
fibres
to experiments
ATPase
was calculated
dynamic
according
according
strength.
to Bergstrom
at pH
to Thorstensson
When the I
(1962).
t
and
~
greater
I
experiments
10.3 (Padykula (1976)
and
con
(Tab!,
Muscle
~FT or type II) fibre types was
after preincubation
area was measured
;:
by FT
as well as maximum
(~T or type 1) and fast ~witch
~ 1';1 1 I~;
~o participate discomforts
and
based on indiVIdual
i\-!!
)1
area
averagevalue
I'~~
i~
wa
latedfor the bar
Methods
!'~I
'!T - (ill
'".
d.
Thetwo groul
;\~; : ;t.lf!
-:':;.,
spectral
power (MPF) I
~
n-
The data pr( 2116 C labol
Piersol(1971). T
4~
~
range
of knee extensioJ
power ~
~
~
requency
(PhilipsAnalog 7
~P
.
t
was undertakento investigateEMG spectral changesunder maximal dynamic fatigue conditionswherelactateformation is likely to occur preferentiallyin FT fibres (Tesch et al., 1978a, 1978b).
c,
ficnstaillaca.EM!
I
re ype composl-
0 th
IDl
Electromyog entireexperiment placed overthev; aI~ay~ ~verthet
the knee exten lb.
Both in
gro h
from
diaphorase activity (Novikofif et aI., 1961). The relative' according
to Tesch
et aI. (1978a).
01
..:. :;' \ :.. '. i 1:: ,
"","
..
ili:
TableI. Physical characteristics (mean:t SE)of thetwo subjectgroups.Percentdistribution and relative
'I ii.
':1,:: "" ,:
area of fast twitch
(FT)
fibres were obtained
r---
--.
Group
I
Group
:,.f ,
< 50% FT
I:'\]"' i\: il rl
(n = 5)
I
( ,,/
biopsy
.
...", "c..'
.:\,
muscle
sample
of M. vastus lateralis.
Thepeaktorqueexpresses themaximum torqueof theunilateral kneeextension
-, -»), ",-~.;
from
area
> 50%
1'50 ~
~
-.Difference
II FT
m
area
(n = 6) 50
Age (year) Weight (kg)
27.8:t 74.0:t
2.8 3.4
23.1:t 1.1 69.6 :t 2.0
t 0
, 2.
Height
(cm)
180.4 :t 1.8
;:: ii,'!
%FT % FT
area
41.2:t3.2 43.2:t 1.0
60.3:t3.0 67.0:t 3.4
p
6
40
-1 ()1 15
~
~ ~5 s'o ;!5 '100 ~ s'o ;!5 ~100 a _oIC(Xrtr8Ct;,"," b _",c actionS Fig. 1aandb. Mean(:I: SE)torqueexpressed asNm (a) andpercentof initial value(b), respectively, during 100 repeatedkneeextensionsat an angularvelocity of 1800x S-I. Filled and open dots represent groupsof subjectswith a relativeareaof 67%(n = 6) and41%(n = 5) fast twitch fibres,
respectively
'~
~EMG Changes "'
"'C~
.
~\~ ~ ""
~~!;,
110 '.
GI ~
~> ~ ~ '2 .-
90
"0
~ 0
-
u:
Do
~
I
100
300
400
~
Fig. 2. Power spectrum density function (PSDF) recorded for one subject (65% FT area) initially ("non-fatigued") and at end of exercise("fatigued")
110
I
,;%
L'
" \,\ \ \
'
,
\~"",
-
'f
1
\\ \\\\\
1 .1 1
_-1,
"
'"
---
" Fig. 4. Relatio
(n= II)
T
~
,Ii .~
.5 '0 ~
L~!
*
*
.
tively. If the
*
weig ht
' meal
kg-I, respect lated positivI and lb, the j :!i~tions. EMG t (IEMG) dec, ,,~An increase slightly, but T 0
, 25
, 50
I 75
I 100
.,'"
Numberof contractions Fig. 3. Meanvalues(:t SE)of meanpowerfrequency(MPF)expressed aspercentage of initialvaluefor the two groups studied during 100 contractions. Differences between groups are denoted with
p < 0.05 and
..= p < 0.01.For furtherexplanationseeFig. 1
-~-
.=
!C:..shiP. was est. decline (r = f
1!!loading (Fig, .1.i,12 ::!:4% (n. f;. Differences '" 25-30 cont
45
.
. . . .
u: Q.
.
2 .rea)
.
initially
r = 0.73 P< 0.01
Y = 0.81x
+ 32.77
. . L~---sQ
TORQUE, 6t % of initial ~ value
~
Fig. 4. Relationshipbetweenrelativechangesin peak torque and MPF after 25-30 contractions (n= 11) tively. If the torque decline during the 100 contractions was expressed per kg body weight, mean (::t SE) reductions were 1.1 ::t 0.1 Nm x kg-1 and 1.7 ::t 0.1 Nm x kg-1, respectively, for groupS I and II (p < 0.001). The decline in torque was correlated positively to the % FT area (r = 0.73,p < 0.01). Moreover, as shown in Fig. 1a and 1b, the initial torque decline in group I was delayed until the 7th-10th contracEMG measurements revealed that integrated electromyographic activity tions. (IEMG) declined as follows: group I, 4 ::t 3% (n.s.); group II, 15 ::t 3% (p < 0.01). An increase in IEMG/torque ratio occurred with fatigue (p < 0.01), and it was slightly, but not significantly, more pronounced in group II. Furthermore, a relationship was established between the relative increase in IEMG/torque ratio and torque decline (r = 0.88, p < 0.00 1). PSDF changed considerably in group II during fatigue loading (Fig. 2). For instance, mean power frequency (MPF) declined 13 ::t 4 Hz or 12 ::t 4% (n.s.) (group I) and 26 ::t 3 Hz or 25 ::t 3% (p < 0.001) (group II) (Fig. 3). Differences in the PSDF change between the two groups were observed after only 25-30 contractions (p < 0.01).
-
46
24-48Hz .1%
:' c~:
,
+100 ,,' T
1' 1 """
*
movements. ,,- J(1 ",
",'i'
Y
'
I
Integrated decreas~ng
,"7'
,1
The decrease
:.~ IEMG activity ir The increase in I cles of the fast tv et al. (1977), wh gastrocnemius a
**
*
and Karlsson, IS sessedby the dec FT muscle fibre:
i E
in so
(e.g., NIlsson et
1'
1
b---l> *
6
&---l>o---~-
* -
t
!
-
136-400 Hz .1 %
T .J, ~o-* ""
I
partially explain
I
muscle to anotht
~
muscles)but al! pold (1955), (1976).
an,
) The changes crease in MPF