Acta Physiol Scand 1979, 107: 33-37
Influence of muscle temperature on maximal muscle strength and power output in human skeletal muscles U. BERGH and B. EKBLOM Department of Physiology 111, Karolinska Institute, Stockholm, Sweden
BERGH, U. & EKBLOM, B.: Influence of muscle temperature on maximal muscle strength and power output in human muscles. Acta Physiol Scand 1979, 107:33-37. Received 15 Dec. 1978. ISSN 0001-6772. Department of Physiology Ill, Karolinska Institute, Stockholm, Sweden. The influence of muscle temperature (T,) on maximal muscle strength, power output, jumping, and sprinting performance was evaluated in four male subjects. In one of the subjects the electromyogram (EMG) was recorded from M. vastus lateralis, M. biceps femoris, and M. semitendinosus. T , ranged from 30.0"C to 39°C. Maximal dynamic strength, power output, jumping, and sprinting performance were positively related to T,. The changes were in the same order of magnitude for all these parameters (4-6%XoC-') Maximal isometric strength decreased by 2%x"C-' with decreasing T,. The force-velocity relationship was shifted to the left at subnormal 7,. Thus in short term exercises, such as jumping and sprinting, performance is reduced at low T, and enhanced at T , above normal, primarily as a result of a variation in maximal dynamic strength. Key words: Muscle temperature, muscle strength, force-velocity, physical performance
An elevated muscle temperature is known to improve performance in exercises such as short term bicycling (Asmussen & Baye 1945) and 100-800 m running (Hogberg & Ljunggren 1947), whereas a subnormal tissue temperature is accompanied by a decrease in performance (Davies et al. 1975). However, in these studies no data were given to illustrate the quantitative aspects of these effects. Therefore, part of the purpose of this investigation was to study the effects of different levels of especially lowered but also enhanced tissue temperatures on short time physical performance. Furthermore, reported data on the effects of different temperatures on muscle strength are conflicting. Thus, Asmussen et al. (1976) found a significant correlation between muscle temperature and maximal isometric strength, whereas Binkhorst et al. (1977) concluded that maximal isometric strength was independent of muscle temperature. Falls (1972), in his review article, stated that maximal isometric strength seemed to be unaffected by temperature. On the other hand, endurance in submaximal isometric exercise was reported by Ed3-795879
wards et al. (1972) to be enhanced at subnormal muscle temperature. Binkhorst et al. (1977) also reported maximal dynamic strength to be higher at elevated muscle temperature, while no data are available about the effects of lowered temperature on maximal dynamic strength. Therefore, the aim of this study was to study the quantitative effects of different muscle and core temperatures on static and dynamic maximal strength with special emphasize on the force-velocity relationship and its consequence on sprinting and vertical jump performance.
METHODS AND PROCEDURE Four male subjects, aged 2 k 3 9 years, participated in the study. They were physically well-trained and familiar with the laboratory preceedings. Muscle fibre composition, expressed as the relative number of type I fibres, ranged from 45 % to 65 %. Temperature may affect the function of the different fibre types differently (Ranatunga, 1977). Therefore it was considered necessary to use subjects with rather similar fibre type distribution. The experimental protocoi is illustrated in Fig. 1. This protocol was repeated at the following levels of core (T,) and vastus lateralis muscle temperature (T,,). Acta Physiol S c a d 107
34
U . Bcrgh trnd B . Ekblorii
1. Sprinting
Resting Cooling Strength
Warming 20min
1 min
?
4 Tm
I
Tm
Tm
Tes measured continuously
3 0 min
Fig. I . The experimental protocol. T,,=esophageal temperature, T,, =muscle temperature.
14r
M a x . speed
Experimental situations
Te,"C T,"C
1
2
3
4
35-36 30-32
35-36 33-35
36-37 36-37
37-38 3%39
Elevated body temperatures were achieved by intermittent bicycle ergometer exercise. Low muscle temperatures (expts. 1 and 2) were produced by immersing the legs (to trochanter major) in cold water. The order of the experimental situations was varied in order to diminish the influence of a possible training effect with testing day at least 2 days apart. Maximal muscle strength of the left knee extensors was recorded as torque during maximal voluntary knee extension with fixed angular velocities. The subjects were sitting in a n experimental chair and the lower leg moved the lever arm of an isokinetic dynamometer (Cybex 11, Lumex Inc., New York). Maximal strength was measured at 3 different angular velocities, 0"(isometric strength), 90", 18O0xs-'. Jumping performance was determined by a vertical jump. The subjects were allowed to start the jump with a countermovement (knee-flexion) and a downward-upward arm swing. The height of the jump was measured by a measuring tape with one end fastened to the subject's waist. The attached tape was sliding through a slit with friction just enough to stop the tape at the peak of the jump. Sprinting performance was evaluated on using a mechanically braked bicycle ergometer. All subjects performed 20 full pedal revolutions (-8.5 kJ) as fast as possible. Time for each revolution was electrically measured with an accuracy of 0.005 s. Time for 2, 5, 10, and 20 revolutions, respectively, was recorded. Speed of the periphery of the fly-wheel was also calculated at all of the above particular revolutions. Peak power output during knee extensions was calculated according to P = M x o , where P=power (W), M=peak torque ( N x m ) , and w=angular velocity (rad x s-1). Average power output during the first two revolutions of bicycling was determined according to P = ( w , + w , ) X r-I, where P=power, w,=force necessary to overcome the frictions between the fly-wheel and the friction belt A (,I( I Phy.c iol Suoi(I I0 7
6L 0.6
r
:eight
of jump ..
.ts ~
Fig. 2. Individual data for peak torque during knee exten-
sions, maximal speed obtained during bicycling, and the height of the vertical jump at different vastus lateralis temperatures ( T,n).
times the distance covered by a point on the periphery of the fly-wheel and w 2 =work transferred to the fly-wheel when its mass is accelerated [ ( M J ~ = ~J x d , where J = moment of inertia (0.435xm2), and o=speed of the flywheel (rad x s-l)]. Body temperatures were measured by thermocouples: T , in the esophagus at the level of the heart. Muscle temperatures were recorded in M. vastus lateralis of the left leg at various depths of 30 to 50 mm and peak value was used (Saldn et al. 1968). T,, was monitored, continuously during the experiments. T , was measured immediately before the strength measurements, after the jumping test and after the sprinting test (cf. Fig. 1). T , values given in the Results in relation to the different tests are means of values obtained before and after the test. Muscle samples from M. vastus lateralis were obtained using percutaneous needle biopsy technique (Bergstrom 1962). The myofibrillar ATP-ase method (Padykula & Herman 1955), as modified by Guth & Samaha (1969), was used for muscle fibre classification. The reaction was car-
Muscle temperature and strength
Power output. During knee extensions the peak power output was positively related to T,. The rates of the changes were 28.5 Wx'C-' (5.6%xoC-') and 15.8 Wx"C-' (4.9%xnC-') at the angular velocities 90" and 180"x s-', respectively. For the first two revolutions of bicycling average power output increased with increasing temperature at a rate of 45.7 Wx'C-' (5.1 %X"C-'). EMG. The EMG-activity pattern (defined as in "Methods") of the M. vastus lateralis, M. semitendinosus, and M. biceps femoris were similar regardless of muscle temperature.
PEAK TORQUE Nm
*0°
100
t 1
\ .
0
90 ANGULAR VELOCITY,
*
30.4
180 degrees
35
s-'
Fig. 3. Peak torque as a function of angular velocity of the knee joint at different levels of T,. Average values, n =4.
ried out at pH 9.4 following alkaline preincubation at pH 103. In one of the subjects an electromyogram (EMG) from M. vastus lateralis, M . semitendinosus, and M. biceps femoris was recorded using skin surface electrodes. The EMG was evaluated only in regard to the timing of onset and termination of activity of these muscles, relative to one another.
RESULTS The number of subjects was small. Therefore, statistical analyses would be of limited value. Instead, individual data for maximal dynamic strength (90"x s-'), sprinting, and jumping performance are shown in Fig. 2. Average values are presented in Fig. 3 and 4, and in Table 1. Maximal muscle strength. Peak torque was positively related to T,. The changes were 6.5 N x m x " C 1 (2.1 %x"C-'), 9.8 NxmxaC-l (4.7%X0C-'), and 8.3 Nxmx'C-' (4.9%XnC-') at the angular velocities of O", 90°, and 1 8 0 " ~ s - re~, spectively. Thus, the effect of temperature was greater in dynamic than in isometric exercise. Vertical jump. The height of the jump decreased with decreasing T , at a rate of 2.1 cm x"C-' (4.2%X0C-'). Sprinting performance. The shortest time in which 20 revolutions could be performed was inversely releated to T,. The work time increased from 10.72 s at T,=38.3 to 15.27 s at Tm=31.4"C. The increment in the average speed of the periphery of the flywheel was 0.5 mxs-' (4.7%x0C-'). Peak velocity was also positively related to T , and changed by 0.51 mxs-'x"C-l (4.4%x0C-I).
DISCUSSION In this study the effect of temperature on jumping and sprinting performance was of the same order of magnitude as indicated by the data reported by Asmussen et al. (1945, 1976). According to the latter studies the changes were 4.4%xoC-' for jumping (T,n range 27-4VC), and 5.3%xoC-' for sprinting ( T , range 3640°C) performance compared to 4.2%x°C-' and 5.1 %x"C-', respectively, in the present study. Sprinting and jumping performances were affected in direct proportion to the change in peak torque. This implies that temperature changes had little, if any effect on coordination in these rather uncomplicated movements. This is also supported by the fact that the EMG-activity patterns were unaffected by temperature. Falls (1972), in his review article, stated that maximal isometric strength is unaffected by temperature. This is in agreement with the data reported by Binkhorst et al. (1977). Asmussen et al. (1976)
1 5 r SPEED,
Fig. 4 . Speed of the pheriphery of the fly-wheel as a function of time at 4 different levels of T,. Average values, n=4. Actn Physiol Scand 107
U . Bergli mnd B . Ekblorn
36
Table 1. Average values and range for the data obtained ut the four different experimental situations ( n =4) Experimental situation
Knee extensions T,,, "C
.
T , "C 0% s-l, peak torque (N x m)
9O0xs-', peak torque (Nx m) 9O0xs-', peak power, W 18O0Xs-', peak torque (Nxm) 180"xs-', peak power, W
Verticuljump T,,, "C
1
2
3
4
35.8 35.3-36.4 30.4 30.0-3 1.2
35.6 35.2-36.3 33.6 32 .8-33.8
37.0 36.8-37.5 36.1 35.2-36.5
37.9 36.6-38.4 38.5 37.7-39.0
262 19G302 148 115-163 233 181-256
282 26G3 10 177 158-205
301 275-325 211 181-262
312 289-360 216 197-237
277 248-3 2 1
333 309-372
111 84-137 348 2-30
136 126-163
33 1 284-41 1 I69 139-201
428 366-5 12
510 436-63 1
540 526593
36.9 36.7-37.1 36.2 35.4-36.9
37.8 37.6-38.3
35.8 35.3-36.4
174 167-189
T , . "C
30.6 30.0-31.2
35.6 35.2-36.4 33.9 32.3-34.4
Height, m
0.375 0.3254.4 10
0.435 0.395-0.450
0.493 0.45041.500
38.4 37.6-39.0 0.540 0.510-0.590
35.7 35.2-36.2
35.6 35.2-36.3
37.0 36.6-37.3
37.8 37.6-38.3
31.4 30.2-32.3
34.3 33.8-34.9
36.4 36.1-36.6
38.3 37.3-3 8.8
Time for 20 rev., s
15.27 13.19-20.14
12.63 11.61-13.65
11.32 10.51-12.23
10.37 9.95- 10.72
Max. speed, mxs-l
8.96 7.40-10.15 683 594-789
10.33 10.00-1 1.45
11.54 10.70-1 2.15 921 834-934
12.42 12.25-12.95 999 956-1 113
Bicycfing T,, "C
Power, W , 2 first rev.
found only a minor effect of temperature on maximal isometric strength, and in the present study the changes in muscle temperature had only a small and probably insignificant influence in this respect. Thus, it may be concluded that maximal isometric strength is affected little by changes in muscle temperature. In contrast, maximal dynamic strength was markedly dependent on T,. This difference in temperature response may arise from the fact that peak torque can be attained only in a limited part of the range of movement (Thorstensson et al. 1976). Acfa Plivsiol Srcind 107
797 752-845
Thus, the time available to attain peak torque is shorter in dynamic than in isometric exercise; in the present study the values were only 0.1-0.2 s during dynamic, but 2 4 s in isometric contractions. At a low temperature it might be more difficult to activate the motor units during a short time interval, possibly as a result of a lower nerve impulse frequency (Vangaard 1975). Furthermore, the speed of chemical reactions is decreased at low temperatures. Thus, the breaking and formation of the cross-bridges may be considerably delayed at low temperatures, resulting in a slower rate of tension
Miiscle temperature and strength
development, even though the maximal tension is little affected by temperature. However, this seems to be contradicted by the fact that the temperature effect was 4-6%x°C-', independent of contraction velocity over a wide range of movement (9060Orxs-'). The reason for this remarkable independence of speed of contraction is so far obscure. From the present results it is evident that T , has a considerable effect on performance in short term dynamic exercise. In contrast, changes in T , have little if any importance during maximal isometric contractions, while dynamic muscle strength will be influenced considerably by T,. Finally, the effect of temperature on jumping and sprinting performance was primarily a result of a variation in maximal dynamic strength. This study was supported by the Research Council of the Swedish Sports Federation (grant 29/77).
REFERENCES ASMUSSEN, E. & B@JE, 0. 1945. Body temperature and capacity for work. Acta Physiol Scand 10: 1-22. ASMUSSEN, E., BONDE-PETERSEN, F. & JORGENSEN, K. 1976. Mechano-elastic properties of human muscles at different temperatures. Acta Physiol Scand 96:83-93. BERGSTROM, J . 1%2. Muscle electrolytes in man. Scand J Clin Lab Invest, Suppl. 68. BINKHORST, R. A., HOOFD, L. & VISSERS, A. C. A. 1977. Temperature and force-velocity relationship of human muscles. J Appl Physiol: Respirat Environ . Exercise Physiol42: 471475.
37
DAVIES, M., EKBLOM, B., BERGH, U. & KANSTRUP, I.-L. 1975. The effects of hypothermia on submaximal and maximal work performance. Acta Physiol Scand 95: 201-202. EDWARDS, R. T. H., HARRIS, R. C., HULTMAN, E., KAIJSER, L., KOH, D. & NORDENSJO, L.-0. 1972. Effect of temperature on muscle energy metabolism and endurance during successive isometric contractions sustained to fatigue, of the quadriceps muscle in man. J Physiol (Lond.) 220: 335-352. FALLS, H. B. 1972. Heat and cold applications. In: Ergogenic aids and muscular performance (ed. W. P. Morgan), pp. 11S158. Academic Press, New York. GUTH, L . & SAMAHA, F . I. 1969. Qualitative differences between actomyosin ATPase of slow and fast mammalian muscles. Exp Neurol 25: 138-152. HOGBERG, P. & LJUNGGREN, 0. 1947. Uppvarmningens inverkan pB Iopprestationerna. (The influence of warm-up on running performance.) Svensk ldrott 40: 668-671. PADYKULA, H . A. & HERMAN, E . 1955. The specificity of the histochemical method of adenosine triphosphatase. J Histochem Cytochem 3: 170-195. RANATUNGA, U. W. 1977. Changes produced by chronic denervation in the temperature dependent isometric contractile characteristics of rat fast and slow twitch skeletal muscles. J Physiol (Lond.) 273: 255-262. SALTIN, B., GAGGE, A. P. & STOLWIJK, J. A. J. 1968. Muscle temperature during submaximal exercise in man. J Appl Physiol25:679488. THORSTENSSON, A., GRIMBY, G. & KARLSSON, J. 1976. Force-velocity relations and fiber composition in human kneeextensor muscles. J Appl Physiol40: 1216. VANGAARD, L. 1975. Physiological reactions to wetcold. Arrat Space Environ Med 46: 33-36.
' Measured during bicycling.
Actn Plrysiol Scand 107
Influence of muscle temperature on maximal muscle strength and power output in human skeletal muscles U. BERGH and B. EKBLOM Department of Physiology 111, Karolinska Institute, Stockholm, Sweden
BERGH, U. & EKBLOM, B.: Influence of muscle temperature on maximal muscle strength and power output in human muscles. Acta Physiol Scand 1979, 107:33-37. Received 15 Dec. 1978. ISSN 0001-6772. Department of Physiology Ill, Karolinska Institute, Stockholm, Sweden. The influence of muscle temperature (T,) on maximal muscle strength, power output, jumping, and sprinting performance was evaluated in four male subjects. In one of the subjects the electromyogram (EMG) was recorded from M. vastus lateralis, M. biceps femoris, and M. semitendinosus. T , ranged from 30.0"C to 39°C. Maximal dynamic strength, power output, jumping, and sprinting performance were positively related to T,. The changes were in the same order of magnitude for all these parameters (4-6%XoC-') Maximal isometric strength decreased by 2%x"C-' with decreasing T,. The force-velocity relationship was shifted to the left at subnormal 7,. Thus in short term exercises, such as jumping and sprinting, performance is reduced at low T, and enhanced at T , above normal, primarily as a result of a variation in maximal dynamic strength. Key words: Muscle temperature, muscle strength, force-velocity, physical performance
An elevated muscle temperature is known to improve performance in exercises such as short term bicycling (Asmussen & Baye 1945) and 100-800 m running (Hogberg & Ljunggren 1947), whereas a subnormal tissue temperature is accompanied by a decrease in performance (Davies et al. 1975). However, in these studies no data were given to illustrate the quantitative aspects of these effects. Therefore, part of the purpose of this investigation was to study the effects of different levels of especially lowered but also enhanced tissue temperatures on short time physical performance. Furthermore, reported data on the effects of different temperatures on muscle strength are conflicting. Thus, Asmussen et al. (1976) found a significant correlation between muscle temperature and maximal isometric strength, whereas Binkhorst et al. (1977) concluded that maximal isometric strength was independent of muscle temperature. Falls (1972), in his review article, stated that maximal isometric strength seemed to be unaffected by temperature. On the other hand, endurance in submaximal isometric exercise was reported by Ed3-795879
wards et al. (1972) to be enhanced at subnormal muscle temperature. Binkhorst et al. (1977) also reported maximal dynamic strength to be higher at elevated muscle temperature, while no data are available about the effects of lowered temperature on maximal dynamic strength. Therefore, the aim of this study was to study the quantitative effects of different muscle and core temperatures on static and dynamic maximal strength with special emphasize on the force-velocity relationship and its consequence on sprinting and vertical jump performance.
METHODS AND PROCEDURE Four male subjects, aged 2 k 3 9 years, participated in the study. They were physically well-trained and familiar with the laboratory preceedings. Muscle fibre composition, expressed as the relative number of type I fibres, ranged from 45 % to 65 %. Temperature may affect the function of the different fibre types differently (Ranatunga, 1977). Therefore it was considered necessary to use subjects with rather similar fibre type distribution. The experimental protocoi is illustrated in Fig. 1. This protocol was repeated at the following levels of core (T,) and vastus lateralis muscle temperature (T,,). Acta Physiol S c a d 107
34
U . Bcrgh trnd B . Ekblorii
1. Sprinting
Resting Cooling Strength
Warming 20min
1 min
?
4 Tm
I
Tm
Tm
Tes measured continuously
3 0 min
Fig. I . The experimental protocol. T,,=esophageal temperature, T,, =muscle temperature.
14r
M a x . speed
Experimental situations
Te,"C T,"C
1
2
3
4
35-36 30-32
35-36 33-35
36-37 36-37
37-38 3%39
Elevated body temperatures were achieved by intermittent bicycle ergometer exercise. Low muscle temperatures (expts. 1 and 2) were produced by immersing the legs (to trochanter major) in cold water. The order of the experimental situations was varied in order to diminish the influence of a possible training effect with testing day at least 2 days apart. Maximal muscle strength of the left knee extensors was recorded as torque during maximal voluntary knee extension with fixed angular velocities. The subjects were sitting in a n experimental chair and the lower leg moved the lever arm of an isokinetic dynamometer (Cybex 11, Lumex Inc., New York). Maximal strength was measured at 3 different angular velocities, 0"(isometric strength), 90", 18O0xs-'. Jumping performance was determined by a vertical jump. The subjects were allowed to start the jump with a countermovement (knee-flexion) and a downward-upward arm swing. The height of the jump was measured by a measuring tape with one end fastened to the subject's waist. The attached tape was sliding through a slit with friction just enough to stop the tape at the peak of the jump. Sprinting performance was evaluated on using a mechanically braked bicycle ergometer. All subjects performed 20 full pedal revolutions (-8.5 kJ) as fast as possible. Time for each revolution was electrically measured with an accuracy of 0.005 s. Time for 2, 5, 10, and 20 revolutions, respectively, was recorded. Speed of the periphery of the fly-wheel was also calculated at all of the above particular revolutions. Peak power output during knee extensions was calculated according to P = M x o , where P=power (W), M=peak torque ( N x m ) , and w=angular velocity (rad x s-1). Average power output during the first two revolutions of bicycling was determined according to P = ( w , + w , ) X r-I, where P=power, w,=force necessary to overcome the frictions between the fly-wheel and the friction belt A (,I( I Phy.c iol Suoi(I I0 7
6L 0.6
r
:eight
of jump ..
.ts ~
Fig. 2. Individual data for peak torque during knee exten-
sions, maximal speed obtained during bicycling, and the height of the vertical jump at different vastus lateralis temperatures ( T,n).
times the distance covered by a point on the periphery of the fly-wheel and w 2 =work transferred to the fly-wheel when its mass is accelerated [ ( M J ~ = ~J x d , where J = moment of inertia (0.435xm2), and o=speed of the flywheel (rad x s-l)]. Body temperatures were measured by thermocouples: T , in the esophagus at the level of the heart. Muscle temperatures were recorded in M. vastus lateralis of the left leg at various depths of 30 to 50 mm and peak value was used (Saldn et al. 1968). T,, was monitored, continuously during the experiments. T , was measured immediately before the strength measurements, after the jumping test and after the sprinting test (cf. Fig. 1). T , values given in the Results in relation to the different tests are means of values obtained before and after the test. Muscle samples from M. vastus lateralis were obtained using percutaneous needle biopsy technique (Bergstrom 1962). The myofibrillar ATP-ase method (Padykula & Herman 1955), as modified by Guth & Samaha (1969), was used for muscle fibre classification. The reaction was car-
Muscle temperature and strength
Power output. During knee extensions the peak power output was positively related to T,. The rates of the changes were 28.5 Wx'C-' (5.6%xoC-') and 15.8 Wx"C-' (4.9%xnC-') at the angular velocities 90" and 180"x s-', respectively. For the first two revolutions of bicycling average power output increased with increasing temperature at a rate of 45.7 Wx'C-' (5.1 %X"C-'). EMG. The EMG-activity pattern (defined as in "Methods") of the M. vastus lateralis, M. semitendinosus, and M. biceps femoris were similar regardless of muscle temperature.
PEAK TORQUE Nm
*0°
100
t 1
\ .
0
90 ANGULAR VELOCITY,
*
30.4
180 degrees
35
s-'
Fig. 3. Peak torque as a function of angular velocity of the knee joint at different levels of T,. Average values, n =4.
ried out at pH 9.4 following alkaline preincubation at pH 103. In one of the subjects an electromyogram (EMG) from M. vastus lateralis, M . semitendinosus, and M. biceps femoris was recorded using skin surface electrodes. The EMG was evaluated only in regard to the timing of onset and termination of activity of these muscles, relative to one another.
RESULTS The number of subjects was small. Therefore, statistical analyses would be of limited value. Instead, individual data for maximal dynamic strength (90"x s-'), sprinting, and jumping performance are shown in Fig. 2. Average values are presented in Fig. 3 and 4, and in Table 1. Maximal muscle strength. Peak torque was positively related to T,. The changes were 6.5 N x m x " C 1 (2.1 %x"C-'), 9.8 NxmxaC-l (4.7%X0C-'), and 8.3 Nxmx'C-' (4.9%XnC-') at the angular velocities of O", 90°, and 1 8 0 " ~ s - re~, spectively. Thus, the effect of temperature was greater in dynamic than in isometric exercise. Vertical jump. The height of the jump decreased with decreasing T , at a rate of 2.1 cm x"C-' (4.2%X0C-'). Sprinting performance. The shortest time in which 20 revolutions could be performed was inversely releated to T,. The work time increased from 10.72 s at T,=38.3 to 15.27 s at Tm=31.4"C. The increment in the average speed of the periphery of the flywheel was 0.5 mxs-' (4.7%x0C-'). Peak velocity was also positively related to T , and changed by 0.51 mxs-'x"C-l (4.4%x0C-I).
DISCUSSION In this study the effect of temperature on jumping and sprinting performance was of the same order of magnitude as indicated by the data reported by Asmussen et al. (1945, 1976). According to the latter studies the changes were 4.4%xoC-' for jumping (T,n range 27-4VC), and 5.3%xoC-' for sprinting ( T , range 3640°C) performance compared to 4.2%x°C-' and 5.1 %x"C-', respectively, in the present study. Sprinting and jumping performances were affected in direct proportion to the change in peak torque. This implies that temperature changes had little, if any effect on coordination in these rather uncomplicated movements. This is also supported by the fact that the EMG-activity patterns were unaffected by temperature. Falls (1972), in his review article, stated that maximal isometric strength is unaffected by temperature. This is in agreement with the data reported by Binkhorst et al. (1977). Asmussen et al. (1976)
1 5 r SPEED,
Fig. 4 . Speed of the pheriphery of the fly-wheel as a function of time at 4 different levels of T,. Average values, n=4. Actn Physiol Scand 107
U . Bergli mnd B . Ekblorn
36
Table 1. Average values and range for the data obtained ut the four different experimental situations ( n =4) Experimental situation
Knee extensions T,,, "C
.
T , "C 0% s-l, peak torque (N x m)
9O0xs-', peak torque (Nx m) 9O0xs-', peak power, W 18O0Xs-', peak torque (Nxm) 180"xs-', peak power, W
Verticuljump T,,, "C
1
2
3
4
35.8 35.3-36.4 30.4 30.0-3 1.2
35.6 35.2-36.3 33.6 32 .8-33.8
37.0 36.8-37.5 36.1 35.2-36.5
37.9 36.6-38.4 38.5 37.7-39.0
262 19G302 148 115-163 233 181-256
282 26G3 10 177 158-205
301 275-325 211 181-262
312 289-360 216 197-237
277 248-3 2 1
333 309-372
111 84-137 348 2-30
136 126-163
33 1 284-41 1 I69 139-201
428 366-5 12
510 436-63 1
540 526593
36.9 36.7-37.1 36.2 35.4-36.9
37.8 37.6-38.3
35.8 35.3-36.4
174 167-189
T , . "C
30.6 30.0-31.2
35.6 35.2-36.4 33.9 32.3-34.4
Height, m
0.375 0.3254.4 10
0.435 0.395-0.450
0.493 0.45041.500
38.4 37.6-39.0 0.540 0.510-0.590
35.7 35.2-36.2
35.6 35.2-36.3
37.0 36.6-37.3
37.8 37.6-38.3
31.4 30.2-32.3
34.3 33.8-34.9
36.4 36.1-36.6
38.3 37.3-3 8.8
Time for 20 rev., s
15.27 13.19-20.14
12.63 11.61-13.65
11.32 10.51-12.23
10.37 9.95- 10.72
Max. speed, mxs-l
8.96 7.40-10.15 683 594-789
10.33 10.00-1 1.45
11.54 10.70-1 2.15 921 834-934
12.42 12.25-12.95 999 956-1 113
Bicycfing T,, "C
Power, W , 2 first rev.
found only a minor effect of temperature on maximal isometric strength, and in the present study the changes in muscle temperature had only a small and probably insignificant influence in this respect. Thus, it may be concluded that maximal isometric strength is affected little by changes in muscle temperature. In contrast, maximal dynamic strength was markedly dependent on T,. This difference in temperature response may arise from the fact that peak torque can be attained only in a limited part of the range of movement (Thorstensson et al. 1976). Acfa Plivsiol Srcind 107
797 752-845
Thus, the time available to attain peak torque is shorter in dynamic than in isometric exercise; in the present study the values were only 0.1-0.2 s during dynamic, but 2 4 s in isometric contractions. At a low temperature it might be more difficult to activate the motor units during a short time interval, possibly as a result of a lower nerve impulse frequency (Vangaard 1975). Furthermore, the speed of chemical reactions is decreased at low temperatures. Thus, the breaking and formation of the cross-bridges may be considerably delayed at low temperatures, resulting in a slower rate of tension
Miiscle temperature and strength
development, even though the maximal tension is little affected by temperature. However, this seems to be contradicted by the fact that the temperature effect was 4-6%x°C-', independent of contraction velocity over a wide range of movement (9060Orxs-'). The reason for this remarkable independence of speed of contraction is so far obscure. From the present results it is evident that T , has a considerable effect on performance in short term dynamic exercise. In contrast, changes in T , have little if any importance during maximal isometric contractions, while dynamic muscle strength will be influenced considerably by T,. Finally, the effect of temperature on jumping and sprinting performance was primarily a result of a variation in maximal dynamic strength. This study was supported by the Research Council of the Swedish Sports Federation (grant 29/77).
REFERENCES ASMUSSEN, E. & B@JE, 0. 1945. Body temperature and capacity for work. Acta Physiol Scand 10: 1-22. ASMUSSEN, E., BONDE-PETERSEN, F. & JORGENSEN, K. 1976. Mechano-elastic properties of human muscles at different temperatures. Acta Physiol Scand 96:83-93. BERGSTROM, J . 1%2. Muscle electrolytes in man. Scand J Clin Lab Invest, Suppl. 68. BINKHORST, R. A., HOOFD, L. & VISSERS, A. C. A. 1977. Temperature and force-velocity relationship of human muscles. J Appl Physiol: Respirat Environ . Exercise Physiol42: 471475.
37
DAVIES, M., EKBLOM, B., BERGH, U. & KANSTRUP, I.-L. 1975. The effects of hypothermia on submaximal and maximal work performance. Acta Physiol Scand 95: 201-202. EDWARDS, R. T. H., HARRIS, R. C., HULTMAN, E., KAIJSER, L., KOH, D. & NORDENSJO, L.-0. 1972. Effect of temperature on muscle energy metabolism and endurance during successive isometric contractions sustained to fatigue, of the quadriceps muscle in man. J Physiol (Lond.) 220: 335-352. FALLS, H. B. 1972. Heat and cold applications. In: Ergogenic aids and muscular performance (ed. W. P. Morgan), pp. 11S158. Academic Press, New York. GUTH, L . & SAMAHA, F . I. 1969. Qualitative differences between actomyosin ATPase of slow and fast mammalian muscles. Exp Neurol 25: 138-152. HOGBERG, P. & LJUNGGREN, 0. 1947. Uppvarmningens inverkan pB Iopprestationerna. (The influence of warm-up on running performance.) Svensk ldrott 40: 668-671. PADYKULA, H . A. & HERMAN, E . 1955. The specificity of the histochemical method of adenosine triphosphatase. J Histochem Cytochem 3: 170-195. RANATUNGA, U. W. 1977. Changes produced by chronic denervation in the temperature dependent isometric contractile characteristics of rat fast and slow twitch skeletal muscles. J Physiol (Lond.) 273: 255-262. SALTIN, B., GAGGE, A. P. & STOLWIJK, J. A. J. 1968. Muscle temperature during submaximal exercise in man. J Appl Physiol25:679488. THORSTENSSON, A., GRIMBY, G. & KARLSSON, J. 1976. Force-velocity relations and fiber composition in human kneeextensor muscles. J Appl Physiol40: 1216. VANGAARD, L. 1975. Physiological reactions to wetcold. Arrat Space Environ Med 46: 33-36.
' Measured during bicycling.
Actn Plrysiol Scand 107
