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Estimation of the breaking of rigor mortis by myotonometry
Fbnw ic Forensic Science International 79 (1996) 155-161
ELSEVIER
Estimation of the breaking of rigor mortis by myotonometry Arved Vain”, Riitta Kauppilab**, Erkki Vuorib “Institute of Experimental
Physics and Technology, Univruit~ of Tarts, Narva mnt.. 6 EE2400 Tartu. Estonia hDepartment of Forensic Medicine, P.0. Box 40, 00014 University of Helsinki. Helsinki, Finland Received 30 May 1995: revised 21 November
1995; accepted 16 January 1996
Abstract Myotonometry was used to detect breaking of rigor mortis. The myotonometer is a new instrument which measures the decaying oscillations of a muscle after a brief mechanical impact. The method gives two numerical parameters for rigor mortis, namely the period and decrement of the oscillations, both of which depend on the time period elapsed after death. In the case of breaking the rigor mortis by muscle lengthening, both the oscillation period and decrement decreased, whereas, shortening the muscle caused the opposite changes. Fourteen h after breaking the stiffness characteristics of the right and left m. biceps brachii, or oscillation periods, were assimilated. However, the values for decrement of the muscle. reflecting the dissipation of mechanical energy. maintained their differences. Keywords:
Rigor mortis; Rigor mortis break; Myotonometry
1. Introduction A current problem encountered in forensic practice involves ascertaining whether the posture of the deceased has changed after the formation of rigor mortis. Development of rigor mortis of the skeletal muscles may take up to 12 h, and if rigor mortis has been broken before full development is reached, its restoration is possible [l]. Myotonometry can be used to monitor the process of rigor mortis formation [2]. *Corresponding
author.
0379..0738/96/$15.00 @ 1996 Elsevier PII SO379-0738(96)01902-O
Science Ireland Ltd. All rights reserved
156
A. Vain et al. I Forensic Science International
79 (1996) 155-161
The method gives two numerical parameters for rigor mortis which depend on the time period elapsed after death, namely oscillation period and decrement. These parameters refer to the oscillation of the muscle after an initial kick by an electromagnetic pick-up. This study shows that myotonometry can also be employed to establish whether rigor mortis has been broken, which would thus indicate a change in posture after death.
2. Materials and methods Using a myotonometer, both m. biceps brachii of six cadavers were measured during a period of up to 48 h. The measurements were started from 1.5 to 2.5 h after death (Table 1). In four cadavers the initial position of the upper limb was extended, and the angle of the elbow joint was 180”; while in two cadavers the initial elbow joint angle was 90”. In order to break the rigor mortis, the initial angle of the elbow joint at 90” was forced into a post stretch angle of 180”. If the initial position of the elbow joint angle was 180”, the upper limb was bent at the elbow joint to a 90 angle. In both cases,the initial position of the limb was restored after an interval of 5.5 to 24 h (Table 1). The breaking of rigor mortis was performed not earlier than 8.5 h and not later than 21.5 h after death (Table 1). All measurements were performed after the muscle length changes had been carried out, and not while stretching or shortening the muscles. During the entire study period the oscillation period and logarithmic decrement of the decay of the muscles under investigation were measured at half-hour intervals using a myotonometer [2]. The comparative analysis of the means of the right and left side muscle oscillation periods and decrements was carried out using the Statgraphics software package.
Table 1 Time of observation and time intervals after breaking and restoration of rigor mortis Subject
1 2 3 4 5 6
Posture
180” 180 180” 90” 180” 90”
Duration of
Time interval elapsed (h) From death to measurement
From death to breaking
From breaking to restoration
measurement
2.5 1.5 2.5 2.5 2.5 1.5
21.0 19.0 13.0 15.0 21.5 8.5
24.0 23.3 14.0 9.0 5.5 12.0
48.0 46.5 31.0 28.0 31.0 26.5
A. Vain et al. I Forensic
Scienw
International
79 (1996)
1.57
15.5-161
3. Results
Fig. 1 and Fig. 2 show that the oscillation period and decrement of m. biceps brachii during the first 13 h after death correlated well with the elapsed time interval. The oscillation period decreased nearly twofold, and the decrement decreased more than 20%. After breaking the rigor mortis. from 11 to 21 measurements were carried out at 30-min intervals (Table 2). A comparison of the means of the left and right side
_____..... --......... .-.. 60..
x
. I:;;::;::::;I~;;::;:I::;:::;;::::l:::,
A31
16:03
l&32
20:53 23:29 TIME in hours left right
8:04
10:28
12:59
1001
g0.. ,/2,, 80-I..” -L__._.__,,
50.40.. 30.. 20.. 10 so,35
. lo:54
14~26
19:24 22:28 16:57 TIME in hours left ...--- right
x 7:35
9:53
12::
Fig. 1. Changes in the oscillation period of m. biceps brachii after breaking rigor mortis (m) and after restoring the initial position (x). (a) Initial elbow angle of 90”, and (b) initial elbow angle of 180”.
A. Vain et al. I Forensic Science International
79 (1996) 155-161
1.8
,““--“~ ../‘“‘. ..,,___,__....,_,.” ..,,
1.0.. 0.8..
':. :: ,'l,.l...A.~ ,,,.
‘:. , ‘..J
0.6.. 0.4.. 0.2..
. 0.01 f : : : : I : : : : f ) : I I : : 13:31 16:03 l&32 20:53 TIME ...... right
x f I : : I : : : : : : : : : : : : : : f 23:29 8:04 10:28 i2:59 in hours left
1.4. ,( ',..__._,._ 1,'i
0.6.. 0.4.. 0.2.. .
x
0.01 : : : I : : I : : : I i i : : : f I : : : : : i : I I f : : I f I : : : i : I I 8:35 lo:54 14:26 16:57 19:24 22:28 7:35 9:53 12:23 TIME in hours left I....- right
Fig. 2. Changes in the oscillation decrement of m. biceps brachii after breaking rigor mortis (M) and after restoring the initial position (x). (a) Initial elbow angle of 90”, and (b) initial elbow angle of 180”.
oscillation periods and decrements revealed the difference to be statistically significant (P < 0.02).
4. Discussion
In muscle preparations alteration in muscle length has been shown to cause reorientation of the intramuscular collagen fibre network and changes in the mechanical properties of the entire muscle [3,4]. Corresponding changes in the oscillation period and decrement have been observed in living subjects [5]. Similarly, in the present study on cadavers, muscle lengthening, i.e. the breaking
A. Vain et al. I Forensic Science International
159
79 (1996) 15% 161
Table 2 Results of measurements of broken (right) and control (left) m. biceps hrachii. The difference between right and left side was significant in all cases (P < 0.02) Subject
1
2
3
4
s
6
n
21
16
13
1’)
Ii
11
62.1 (2.7) 52.4
53.5, (2.9) 4x.0 (1.2)
56.3
(2.1)
73.0 (4.4) 66.3 (2.3)
(3.1) 60.7 (2.5)
61.0 (2.9) 57.6 (1.4)
57.6 (1.X) 63.0 (2.9)
1.827 (0.184) 1.036 (0.194)
2.011 (0.199) 1.738 (0.137)
1.160 (0.098) 0.739 (0.052)
1.200 (0.103) 1.132 (0.063)
1.262 (0.103) 0.888 (0.0.54)
0.X01 (0.122) 1.137 ( 0.084)
Period (ms) Right, mean (SD.) Left, mean (S.D.) Decrement Right, mean (S.D.) Left, mean (S.D.)
of rigor mortis, caused the oscillation period and decrement to decrease. Muscle shortening, in turn, caused changes to the opposite direction. In the process of muscle length change the mechanical properties of the muscle vary extensively. Zink [6] concluded that the increase in the ratio of applied mechanical strain maximum to the corresponding muscle length is the same in both living and rigor mortis-state tissue. and furthermore, that rigor mortis is brought about by changes in muscular fibres and is not related to the state of muscle envelopes. Our results, obtained after muscle length changes had been carried out, show that the properties of muscle envelopes also are transformed in the rigor mortis state, when changes in muscle length have occurred. This phenomenon can be explained by the findings of Maughan and Godt [7] who reported that, in the rigor mortis formation process, the radial force evoked in the muscle fibre by myofilament cross-bridges surpassed the longitudinal force by an order of magnitude. The breaking of rigor mortis causes the radial force of the crossbridges to break off and a simultaneous weakening of the muscle envelopes. If the rigor mortis of m. biceps brachii had formed in the stretched position, with the elbow joint angle at 180”. and the arm was later bent at the elbow joint to 90”, then the muscle envelopes were released from the strain. Correspondingly. Fig. lb shows the oscillation period of the muscle increased after the muscle length was shortened (right), and the decrease for the period was stronger after the shortening procedure than that found for the control (left). It is possible that the myofilament cross-bridges of the shortened muscle move off radially when the strain on the muscle envelopes decreases. This notion is in agreement with the conclusion of Zink [6], suggesting that when rigor mortis has formed changes can only occur in the myofilaments and not in the muscle envelopes. If the breaking of rigor mortis has taken place the change in muscle properties persists for a long period, up to 9 h, and after the initial length has been restored, the differences in the oscillation periods and decrement are statistically significant again (Fig. la and Fig. 2a).
160
A. Vain et al. I Forensic Science International
79 (1996) 155-161
Fig. la shows that the difference between the left and right m. biceps brachii oscillation periods decreased after rigor mortis had been broken, the elbow angle changed from 90” to 180”. The situation was different if the arm had originally been stretched when no actual breaking of rigor mortis in the measured muscle had occurred, and the elbow angle changed from 180” to 90”. After restoring the initial position no differences were observed between the right and left sides in the latter group (Fig. lb and Fig. 2b). The presently described changes in the mechanical properties of m. biceps brachii can be explained by means of the new biomechanical model of skeletal muscle [5,8,9], according to which an increase of intramuscular pressure (increase in stiffness) evokes the radial pressure of myosin filament cross-bridges [8]. As a result of this process the helixes of collagen fibres situated in the endo-, peri- and epimyseum become strained. Through the latter, the mechanical strain of the skeletal muscles is transmitted to the tendons. In the case of rigor mortis break the elasticity capacity of the myosin filament cross-bridge is surpassed and when the influence of the external force ceases, the mechanical strain of the collagen helixes will, in turn, decrease due to the plastic deformation of the cross-bridges. This explanation is in agreement with the results of Forster [lo]. It is noteworthy that after the breaking of rigor mortis the stiffness of a muscle is restored but the characteristics reflecting the dissipation of mechanical energy, dempherity, behave differently (Fig. 2). This is understandable if it is supposed that the muscle stiffness is more or less determined by intramuscular pressure [ll], but dempherity characteristics depend on the rheological properties of the epimyseum of the muscle [8]. This conclusion is further supported by the decrease in the oscillation decrement values, measured immediately after the breaking of rigor mortis. Thus, the oscillation decrement apparently is more informative than the oscillation period when estimating the breaking of rigor mortis. The use of myotonometry enables the detection of changes in the posture of a cadaver. In the case that the position of only one arm or leg has been changed it can be detected by comparing the oscillation decrements of the corresponding muscles on the other side. If the positions of both extremities have been changed, then the results must be compared with corresponding norm values.
References [l] B. Knight, Forensic Pathology, Edward Arnold, London 1991, pp. 54-57. [2] A. Vain, R. Kauppila and E. Vuori, Grading rigor mortis with myotonometry: a new possibility to estimate time of death. Forensic Sci. Inc., 56 (1992) 147-150. [3] P.P. Purslow, Strain-induced reorientation of an intramuscular connective tissue network: implications for passive muscle elasticity. J. Biomech., 22 (1989) 21-32. [4] P.P Purslow and VC. Duance, Structure and function of intramuscular connective tissue. In D.W.L. Hukins (ed.), Connective Tissue Matrix, Part 2, CRC Press, Boca Raton, FL, 1991, pp. 127-166. [5] A. Vain, On the Phenomenon of Mechanical Stress Transmission in Skeletal Muscle. Tartu University Press, Tartu, 1990.
A. Vain et al. I Forensic Science International
79 (1996) 15Slhl
161
[6] P. Zink, Mechanische Eigenshaften lebenfrischer und totenstarrer menchlicher Skeletmuskelfasern und ganzer Muskeln. 2. Rechtsmed.. 70 (1972) 163-177. [7] D.W. Maughan and E.E. Godt. Radial forces within muscle fibers in rigor. J. Gen. Ph,wiol.. 77 (1980) 49-64. [S] A. Vain, The Phenomenon of Mechanical Stress Transmission in Skeletal ML&es. Dissertation. University of Tartu, 1993 (in Russian). [9] A. Vain, A New Biomechanical Model o,f the Skeletal Muscle. Abstracts of the Second World Congress of Biomechanics, Vol. I. Amsterdam, 1994. p. X7. [lo] B. Forster. The plastic and elastic deformation of skeletal muscle in rigor mortis. J. Forensic Med., 10 (1963) 91-110. [ll] C.J. Polson, D.J. Gee and B. Knight (eds.). The Essentials of’ Forensic Medicine. 4th Edn.. Pergamon Press, Oxford 1985. p. 17.
ELSEVIER
Estimation of the breaking of rigor mortis by myotonometry Arved Vain”, Riitta Kauppilab**, Erkki Vuorib “Institute of Experimental
Physics and Technology, Univruit~ of Tarts, Narva mnt.. 6 EE2400 Tartu. Estonia hDepartment of Forensic Medicine, P.0. Box 40, 00014 University of Helsinki. Helsinki, Finland Received 30 May 1995: revised 21 November
1995; accepted 16 January 1996
Abstract Myotonometry was used to detect breaking of rigor mortis. The myotonometer is a new instrument which measures the decaying oscillations of a muscle after a brief mechanical impact. The method gives two numerical parameters for rigor mortis, namely the period and decrement of the oscillations, both of which depend on the time period elapsed after death. In the case of breaking the rigor mortis by muscle lengthening, both the oscillation period and decrement decreased, whereas, shortening the muscle caused the opposite changes. Fourteen h after breaking the stiffness characteristics of the right and left m. biceps brachii, or oscillation periods, were assimilated. However, the values for decrement of the muscle. reflecting the dissipation of mechanical energy. maintained their differences. Keywords:
Rigor mortis; Rigor mortis break; Myotonometry
1. Introduction A current problem encountered in forensic practice involves ascertaining whether the posture of the deceased has changed after the formation of rigor mortis. Development of rigor mortis of the skeletal muscles may take up to 12 h, and if rigor mortis has been broken before full development is reached, its restoration is possible [l]. Myotonometry can be used to monitor the process of rigor mortis formation [2]. *Corresponding
author.
0379..0738/96/$15.00 @ 1996 Elsevier PII SO379-0738(96)01902-O
Science Ireland Ltd. All rights reserved
156
A. Vain et al. I Forensic Science International
79 (1996) 155-161
The method gives two numerical parameters for rigor mortis which depend on the time period elapsed after death, namely oscillation period and decrement. These parameters refer to the oscillation of the muscle after an initial kick by an electromagnetic pick-up. This study shows that myotonometry can also be employed to establish whether rigor mortis has been broken, which would thus indicate a change in posture after death.
2. Materials and methods Using a myotonometer, both m. biceps brachii of six cadavers were measured during a period of up to 48 h. The measurements were started from 1.5 to 2.5 h after death (Table 1). In four cadavers the initial position of the upper limb was extended, and the angle of the elbow joint was 180”; while in two cadavers the initial elbow joint angle was 90”. In order to break the rigor mortis, the initial angle of the elbow joint at 90” was forced into a post stretch angle of 180”. If the initial position of the elbow joint angle was 180”, the upper limb was bent at the elbow joint to a 90 angle. In both cases,the initial position of the limb was restored after an interval of 5.5 to 24 h (Table 1). The breaking of rigor mortis was performed not earlier than 8.5 h and not later than 21.5 h after death (Table 1). All measurements were performed after the muscle length changes had been carried out, and not while stretching or shortening the muscles. During the entire study period the oscillation period and logarithmic decrement of the decay of the muscles under investigation were measured at half-hour intervals using a myotonometer [2]. The comparative analysis of the means of the right and left side muscle oscillation periods and decrements was carried out using the Statgraphics software package.
Table 1 Time of observation and time intervals after breaking and restoration of rigor mortis Subject
1 2 3 4 5 6
Posture
180” 180 180” 90” 180” 90”
Duration of
Time interval elapsed (h) From death to measurement
From death to breaking
From breaking to restoration
measurement
2.5 1.5 2.5 2.5 2.5 1.5
21.0 19.0 13.0 15.0 21.5 8.5
24.0 23.3 14.0 9.0 5.5 12.0
48.0 46.5 31.0 28.0 31.0 26.5
A. Vain et al. I Forensic
Scienw
International
79 (1996)
1.57
15.5-161
3. Results
Fig. 1 and Fig. 2 show that the oscillation period and decrement of m. biceps brachii during the first 13 h after death correlated well with the elapsed time interval. The oscillation period decreased nearly twofold, and the decrement decreased more than 20%. After breaking the rigor mortis. from 11 to 21 measurements were carried out at 30-min intervals (Table 2). A comparison of the means of the left and right side
_____..... --......... .-.. 60..
x
. I:;;::;::::;I~;;::;:I::;:::;;::::l:::,
A31
16:03
l&32
20:53 23:29 TIME in hours left right
8:04
10:28
12:59
1001
g0.. ,/2,, 80-I..” -L__._.__,,
50.40.. 30.. 20.. 10 so,35
. lo:54
14~26
19:24 22:28 16:57 TIME in hours left ...--- right
x 7:35
9:53
12::
Fig. 1. Changes in the oscillation period of m. biceps brachii after breaking rigor mortis (m) and after restoring the initial position (x). (a) Initial elbow angle of 90”, and (b) initial elbow angle of 180”.
A. Vain et al. I Forensic Science International
79 (1996) 155-161
1.8
,““--“~ ../‘“‘. ..,,___,__....,_,.” ..,,
1.0.. 0.8..
':. :: ,'l,.l...A.~ ,,,.
‘:. , ‘..J
0.6.. 0.4.. 0.2..
. 0.01 f : : : : I : : : : f ) : I I : : 13:31 16:03 l&32 20:53 TIME ...... right
x f I : : I : : : : : : : : : : : : : : f 23:29 8:04 10:28 i2:59 in hours left
1.4. ,( ',..__._,._ 1,'i
0.6.. 0.4.. 0.2.. .
x
0.01 : : : I : : I : : : I i i : : : f I : : : : : i : I I f : : I f I : : : i : I I 8:35 lo:54 14:26 16:57 19:24 22:28 7:35 9:53 12:23 TIME in hours left I....- right
Fig. 2. Changes in the oscillation decrement of m. biceps brachii after breaking rigor mortis (M) and after restoring the initial position (x). (a) Initial elbow angle of 90”, and (b) initial elbow angle of 180”.
oscillation periods and decrements revealed the difference to be statistically significant (P < 0.02).
4. Discussion
In muscle preparations alteration in muscle length has been shown to cause reorientation of the intramuscular collagen fibre network and changes in the mechanical properties of the entire muscle [3,4]. Corresponding changes in the oscillation period and decrement have been observed in living subjects [5]. Similarly, in the present study on cadavers, muscle lengthening, i.e. the breaking
A. Vain et al. I Forensic Science International
159
79 (1996) 15% 161
Table 2 Results of measurements of broken (right) and control (left) m. biceps hrachii. The difference between right and left side was significant in all cases (P < 0.02) Subject
1
2
3
4
s
6
n
21
16
13
1’)
Ii
11
62.1 (2.7) 52.4
53.5, (2.9) 4x.0 (1.2)
56.3
(2.1)
73.0 (4.4) 66.3 (2.3)
(3.1) 60.7 (2.5)
61.0 (2.9) 57.6 (1.4)
57.6 (1.X) 63.0 (2.9)
1.827 (0.184) 1.036 (0.194)
2.011 (0.199) 1.738 (0.137)
1.160 (0.098) 0.739 (0.052)
1.200 (0.103) 1.132 (0.063)
1.262 (0.103) 0.888 (0.0.54)
0.X01 (0.122) 1.137 ( 0.084)
Period (ms) Right, mean (SD.) Left, mean (S.D.) Decrement Right, mean (S.D.) Left, mean (S.D.)
of rigor mortis, caused the oscillation period and decrement to decrease. Muscle shortening, in turn, caused changes to the opposite direction. In the process of muscle length change the mechanical properties of the muscle vary extensively. Zink [6] concluded that the increase in the ratio of applied mechanical strain maximum to the corresponding muscle length is the same in both living and rigor mortis-state tissue. and furthermore, that rigor mortis is brought about by changes in muscular fibres and is not related to the state of muscle envelopes. Our results, obtained after muscle length changes had been carried out, show that the properties of muscle envelopes also are transformed in the rigor mortis state, when changes in muscle length have occurred. This phenomenon can be explained by the findings of Maughan and Godt [7] who reported that, in the rigor mortis formation process, the radial force evoked in the muscle fibre by myofilament cross-bridges surpassed the longitudinal force by an order of magnitude. The breaking of rigor mortis causes the radial force of the crossbridges to break off and a simultaneous weakening of the muscle envelopes. If the rigor mortis of m. biceps brachii had formed in the stretched position, with the elbow joint angle at 180”. and the arm was later bent at the elbow joint to 90”, then the muscle envelopes were released from the strain. Correspondingly. Fig. lb shows the oscillation period of the muscle increased after the muscle length was shortened (right), and the decrease for the period was stronger after the shortening procedure than that found for the control (left). It is possible that the myofilament cross-bridges of the shortened muscle move off radially when the strain on the muscle envelopes decreases. This notion is in agreement with the conclusion of Zink [6], suggesting that when rigor mortis has formed changes can only occur in the myofilaments and not in the muscle envelopes. If the breaking of rigor mortis has taken place the change in muscle properties persists for a long period, up to 9 h, and after the initial length has been restored, the differences in the oscillation periods and decrement are statistically significant again (Fig. la and Fig. 2a).
160
A. Vain et al. I Forensic Science International
79 (1996) 155-161
Fig. la shows that the difference between the left and right m. biceps brachii oscillation periods decreased after rigor mortis had been broken, the elbow angle changed from 90” to 180”. The situation was different if the arm had originally been stretched when no actual breaking of rigor mortis in the measured muscle had occurred, and the elbow angle changed from 180” to 90”. After restoring the initial position no differences were observed between the right and left sides in the latter group (Fig. lb and Fig. 2b). The presently described changes in the mechanical properties of m. biceps brachii can be explained by means of the new biomechanical model of skeletal muscle [5,8,9], according to which an increase of intramuscular pressure (increase in stiffness) evokes the radial pressure of myosin filament cross-bridges [8]. As a result of this process the helixes of collagen fibres situated in the endo-, peri- and epimyseum become strained. Through the latter, the mechanical strain of the skeletal muscles is transmitted to the tendons. In the case of rigor mortis break the elasticity capacity of the myosin filament cross-bridge is surpassed and when the influence of the external force ceases, the mechanical strain of the collagen helixes will, in turn, decrease due to the plastic deformation of the cross-bridges. This explanation is in agreement with the results of Forster [lo]. It is noteworthy that after the breaking of rigor mortis the stiffness of a muscle is restored but the characteristics reflecting the dissipation of mechanical energy, dempherity, behave differently (Fig. 2). This is understandable if it is supposed that the muscle stiffness is more or less determined by intramuscular pressure [ll], but dempherity characteristics depend on the rheological properties of the epimyseum of the muscle [8]. This conclusion is further supported by the decrease in the oscillation decrement values, measured immediately after the breaking of rigor mortis. Thus, the oscillation decrement apparently is more informative than the oscillation period when estimating the breaking of rigor mortis. The use of myotonometry enables the detection of changes in the posture of a cadaver. In the case that the position of only one arm or leg has been changed it can be detected by comparing the oscillation decrements of the corresponding muscles on the other side. If the positions of both extremities have been changed, then the results must be compared with corresponding norm values.
References [l] B. Knight, Forensic Pathology, Edward Arnold, London 1991, pp. 54-57. [2] A. Vain, R. Kauppila and E. Vuori, Grading rigor mortis with myotonometry: a new possibility to estimate time of death. Forensic Sci. Inc., 56 (1992) 147-150. [3] P.P. Purslow, Strain-induced reorientation of an intramuscular connective tissue network: implications for passive muscle elasticity. J. Biomech., 22 (1989) 21-32. [4] P.P Purslow and VC. Duance, Structure and function of intramuscular connective tissue. In D.W.L. Hukins (ed.), Connective Tissue Matrix, Part 2, CRC Press, Boca Raton, FL, 1991, pp. 127-166. [5] A. Vain, On the Phenomenon of Mechanical Stress Transmission in Skeletal Muscle. Tartu University Press, Tartu, 1990.
A. Vain et al. I Forensic Science International
79 (1996) 15Slhl
161
[6] P. Zink, Mechanische Eigenshaften lebenfrischer und totenstarrer menchlicher Skeletmuskelfasern und ganzer Muskeln. 2. Rechtsmed.. 70 (1972) 163-177. [7] D.W. Maughan and E.E. Godt. Radial forces within muscle fibers in rigor. J. Gen. Ph,wiol.. 77 (1980) 49-64. [S] A. Vain, The Phenomenon of Mechanical Stress Transmission in Skeletal ML&es. Dissertation. University of Tartu, 1993 (in Russian). [9] A. Vain, A New Biomechanical Model o,f the Skeletal Muscle. Abstracts of the Second World Congress of Biomechanics, Vol. I. Amsterdam, 1994. p. X7. [lo] B. Forster. The plastic and elastic deformation of skeletal muscle in rigor mortis. J. Forensic Med., 10 (1963) 91-110. [ll] C.J. Polson, D.J. Gee and B. Knight (eds.). The Essentials of’ Forensic Medicine. 4th Edn.. Pergamon Press, Oxford 1985. p. 17.