S160 mt. mt.J.J.Sports Sports Med. Med. 13(1992)
national Biochemistry of Exercise Conference. Abstract E3 13, 1991
Hampson N. B., Piantadosi C. A.: Near infrared monitoring of human skeletal muscle oxygenation during forearm ischemia. J 6
8
________________________________________
K. Sahlin
It) Wilson J. R., Mancini D. M., McCully K., Ferraro N., Lanoce V., Chance B.: Noninvasive detection of skeletal muscle under perfusion with near-infrared spectroscopy in patients with heart failure. Circulation 80: 1668—1674,1989.
ApplPhysiol64: 2449—2457,1988. Henriksson J., Katz A., Sahlin K.: Redox state changes in human
skeletal muscle after isometric contraction. J Physiol 380: 441— 451,1986. Millikan G. A.: ProcRoy Soc London B 129:218, 1937. Sahlin K.: NADH and NADPH in human skeletal muscle at rest and during ischaemia. C/in Physiol3: 477—485, 1983. Wang Z., Noyszewski E. A., Leigh Jr.: In vivo MRS measurement
of deoxymyoglobin in human forearms. Magn Reson Med 14:
Kent Sahlin, Dr. Sci.
Department of Clinical Physiology Huddinge University Hospital S-141 86 Huddinge Sweden
Injury to Skeletal Muscle during Altitude Training: Training: Induction and Prevention J. A. Faulkner, J. A. Opiteck, S. V. Brooks MI,48109-0622, 48109-0622,U. U.S. S.A. A. University of of Michigan, Michigan, Ann Ann Arbor, Arbor,MI, University
Abstract Faulkner, J.J. A. A. Opiteck Opiteckand andS. S.V. V.Brooks, Brooks, J. A. Faulkner, Injury to Skeletal Skeleta' Muscle during Altitude Training: Induction and Prevention. mt j Sports Suppl 1, 1, pp pp Med, Vol 13, Suppl Sports Med, S160—S162, 1992. S160—Sl62,1992.
A contracting skeletal muscle musck will shorten, remain isometric, or lengthen depending on the interaction
load and the force developed by the between external toad muscle. Most physical activities involve shortening, isometric and lengthening contractions. The fluctuations in terrain encountered at altitude, increase both the likelihood that lengthening contractions will occur and the severity of the stretches. When performing a given amount of work, muscles lengthened during contractions expend less energy
Introduction
When aa skeletal skeletal muscle muscle is is activated, activated, the the fibers fibers tend to shorten (4). The type of contraction that does occur depends on the interaction between the external load toad and the force developed by the muscle. muscle. If If the the load load on on the the muscle musck is less than, equivalent to, or greater than the force developed, the
and fatigue less rapidly than muscles that shorten. ConCon. versely, with equal activation, displacement, and velocity,
the work done on a muscle during lengthening contractions
is greater than the work performed by a muscle during shortening contractions, but force decreases more rapidly during lengthening. Furthermore, muscles are more likely to be injured during lengthening contractions than during shortening or isometric contractions. The occurrence of
contraction-induced injury can be eliminated, or minimized, by prior training specific for the performance of lengthening contractions. lengthening Key words Key
Altitude, muscle, training, training, skeletal skektal muscle in-
jury
muscle will shorten, remain isometric, or lengthen respectively. Each type of contraction contraction contributes contributes to to everyday everydayphysiphysical activities. When these activities are performed on uneven terrain such as that encountered encountered routinely routinely at at altitude, altitude, the thework work done on the muscle during lengthening and that done by the muscle during shortening shortening vary vary to to a much greater extent than musck during on level ground (7). At the turn of the century, innovative ex-
periments demonstrated that if shortening (concentric) and Int.J.SportsMed. 13(l992)Sl60—S162 Int.J.SportsMed. 13(1992)S160—S162 GeorgThieme Verlag StuttgartNew York
lengthening (eccentric) contractions involve equivalent equivalent amounts of work, more energy is expended and fatigue occurs
Downloaded by: University of Pennsylvania Libraries. Copyrighted material.
562— 567, 1990.
mt. J. i Sports Sports Med. Med. 13(1992) S161 S161
Injury to Skeletal Muscle duringAltitude Training
contraction-induced injury (3, 8).
Contraction-induced injury involves an initial, mechanical event (3) and a secondary, chemical event (10) with the most severe injury observed at 3 days. The purpose of the present investigation was to develop: 1. a lengthening contraction protocol for the dorsiflexor muscle group of the ankle that injures a sufficient number of muscle fibers to decrease the maximum force by 40% to 50% at 3 days, and 2. a training program of lengthening contractions that would prevent the occurrence of contraction-induced injury of this magnitude. Our working hypothesis was that a training program that induces injury must allow sufficient time for recovery, recovery, but but not not time for the training stimulus to be lost.
Materials and Methods Experiments were performed on twenty-three young (2 to 3 month old) male white mice. All experiments were conducted in accordance with the American Physiologi-
cal Society policy statement outlining the care and use of laboratory animals. Mice were anesthetized with pentobarbital sodium, 80 mg/kg, and placed on a plexiglass platform of a "shoe" apparatus (1). The knee was secured to the platform and the foot was attached to the shoe which was mounted on the shaft of a servomotor. A microcomputer controlled the servomotor and rotated the ankle joint through a given displacement at a constant velocity. Strain gauges mounted on
the shoe monitored the force produced by the dorsiflexor muscle group. Needle electrodes were placed adjacent to the peroneal nerve and the dorsiflexors were stimulated maximally at optimum length for force development. The maximum isometric tetanic force (P0) was determined from the frequency-force curve.
For each lengthening contraction protocol, a stimulation frequency of of 100 100 Hz Hz was was used used resulting resulting in inaaforce force 85%ofPo. 85 %ofP0. Contractions Contractions were were 720 720 ms ms in duration. Lengthening ing was was initiated initiated after after 120 120 ms, ms, at at the the plateau plateau of of isometric isometric force. force.
Lengthening contractions were through 40 degrees of ankle extension at 67 degrees per sec, see, which was equivalent to a displacement through — 20% of average fiber length at a velocity
of 0.5 Lf/sec. The peak force developed during the first lengthening contraction was 194 5% of Po. P0. Lengthening contractions occurred once every 4 sec.
Muscles were stimulated for three five minute periods, each separated by five minutes of rest. During the lengthening contractions, the peak force decreased steadily, and the isometric force was nearly abolished. Following the lengthening contraction protocol, the muscle was returned to L0 and P0 was measured at 0 and 10 mm. The mouse was removed moved from from the the apparatus apparatus and and allowed allowed to to recover. recover. The The P0 Po was was measured at 3 and 7 days following the lengthening lengthening contraccontraction protocol.
Three training programs were tested on separate groups of mice. The lengthening contraction protocol was
100
80
0 60
0 C) 0)
U 0 I-
0
U-
40 20 0
LCPO
+.. +., +.. +,, -I+1 -H-I3 37
10 Mm
1
Hr
30
Days
Time Fig. 1 The relationship of the force deficit (for definition see text) and time after the lengthening contraction protocol.
repeated every 3 days, every 7 days, or every 30 days, based on
the time of maximum injury, partial recovery, and full recovery, respectively. For each program, the lengthening con-
traction protocol was repeated until full recovery occurred and then the protocol was repeated to test for the magnitude of the injury 3 days later. Following these experiments, muscles were weighed. The total fiber cross-sectional area of experimental and control muscles was estimated by dividing muscle mass by the product of Lr Lf and 1.06 g/cm3, the density of mam-
malian skeletal muscle (3). Following the removal of the muscles, the anesthetized mice were killed with an overdose of the anesthetic. Force deficit was calculated for each data set as
(1-{P0 (1 -{P0of of an an injured injured muscle/P0 muscle/P0 of of the the contralateral contralateral control
muscle]) x 100. Data are expressed as the mean 1 SE. Differences between the two groups were assessed by onesided Student's t-tests (p 0.05). 0.05). Results The force deficit of 80% immediately after the lengthening contraction protocol recovered to 40% by 10 mm (Fig. 1). In a longitudinal study, data at 3 hr and 1 day could not be obtained, but from previous recovery curves (3, 8) each force deficit was estimated to be 20%. A secondary decrease to
a force deficit of 40% occurred at 3 days. Full recovery was achieved by 30 days. achieved
The 3 day-repeat training program produced a force deficit of 50% to 60% with no evidence of recovery after
6 repetitions. With the 30 day lapse between exposures to lengthening contraction protocols, the force deficit at 3 days was of the same mgnitude each time and no evidence of a training response was observed. observed. In In contrast, contrast, the the 77 day day repeats repeatsof ofthe the protocol resulted in a force deficit of 10% to 25% for each of 5
repetitions, but no force deficit was observed after the sixth repetition (Fig. 2). Three days after the last repeat of the lengthening contraction protocol no force deficit was observed. The mass of of the the trained traineddorsiflexors dorsiflexorswas was92.1 92.1 6.7 6.7 mg mg compared compared
mgfor forthe the untrained untrained contralateral control with 76.1 6.8 mg control with 76.1 muscle group and the total fiber cross-sectional areas were 7.6 0.4 mm2 and 6.2 0.2 mm2, respectively.
Downloaded by: University of Pennsylvania Libraries. Copyrighted material.
more rapidly with shortening contractions (2). In contrast, compared with shortening contractions, lengthening contractions with equal activation, displacement, and velocity, are characterized by: larger average and peak forces (3, 8), more rapid fatigue (6), and a greater likelihood and magnitude of
S162 mt. J. Sports Med. 13(1992)
J. A. Faulkner, J. A. Opiteck and S. V. Brooks Deficit at Onset onset of of LcP o Deficit at end of LCP • Deficit 10 mm. after LCP
80
muscles increased with the increase in muscle mass and cross-
sectional area, the specific P0 Po (N/cm2) decreased 15%. Decreases in specific P0 have been noted with the hypertrophy associated with ablation of synergistic muscles (5). The mech-
60
40
anism responsible for prevention of contraction-induced injury to skeletal muscle fibers remains unknown.
C,
20
Acknowledgements This research was supported by the National Insti0
7
14
21
28
35
38
tute on Aging, NIH grant AG-06 157.
Time (Days) Fig. 2 The force deficit (for definition see text) during each session of the the 77 day day repeat repeat training training program programand ard time after the initial lengthening contraction protocol and the force deficit 3 days after the final lengthening contraction protocol (U). Note: The force deficit of 0% after the fourth lengthening ng contraction protocol was attributed to a measure-
References Ashton-Miller J. A., He Y., Kadhiresan V. A., McCubbrey D.,
2
Faulkner J. A.: An apparatus to measure in vivo biomechanical behavior of dorsi- and plantarfiexors of the mouse ankle. JAppiPhysioll2: 1205—1211,1992. Chauveau S.: La dépense énergétique de l'entraInement respec-
tive le travail moteur et le travail resistant de l'homme qui s'éléve ou descend sur Ia la roue de Him. Comptes Comptes rendus rendus hebdomadaires hebdomadaires
ment error. One value was excessively high and the rest were in keeping with previous values.
des sénces de l'Académie des sciences 132: 132: 194—202, 1901. Faulkner J. A.,Jones D. A., Round J. M.: Injury to skeletal muscles
of mice by forced lengthening during contractions. Quart J Exp Physiol74: 661—670,1989.
Faulkner J. A., White T. P.: Adaptations of skeletal muscle to
Discussion
physical activity, in Bouchard C., Shephard R. J., Stephens T., Sut-
ton J. R., McPherson B. D. (eds): Exercise, Fitness and Health. Toronto, Human Kinetics Publishers, 1990, Chapter 22, pp 265—
The force force deficit deficit immediately immediately after after the the lengthlength-
ening contraction protocol protocol represents represents both both fatigue fatigue and and injury injury (3). With the the estimate estimate of of aaforce forcedeficit deficitofof20 20% % at at both both 33hr hrand and I day, 1 day, the the recovery recovery from from fatigue fatigue appears appears to to be be complete complete by by 33 hr. The The implication implication is is that that the the initial, initial, predominantly predominantly mechanimechanihr. cal, injury was of this magnitude. The secondary injury, which occurs occurs between between day day 11 and and day day 3, 3, doubles doubles the the magnitude magnitude of of the the initial initial injury. The secondary injury involves oxygen oxygen free free radiradical damage, since this injury can be blocked completely by the free radical scavenger superoxide dismutase (10). The second-
ary injury appears to be responsible for the late onset muscle soreness reported by human beings after contraction-induced injury (9). The results are consistent with the working hy-
pothesis since the training program with 3 day repeats provided insufficient time for recovery from injury, whereas the
279.
Kandarin S. K., White T. P.: Mechanical deficit persists during 6
long-term muscle hypertrophy. hypertrophy. JAppiPhysiol 69: 861—867, 1990. longterm muscle 69:861—867, Lieber R. L., Woodburn T. M., Friden J.: Muscle damage induced Appi Physiol 70: 2498— by eccentric contractions contractions of of 24% 24% strain. strain. JJAppi 2507, 1991. 2507,1991.
Margaria R.: Positive and negative work performances and their efficiencies in human locomotion. locomotion. In! mt Z angew Physiol Physiol einschl Arbeilsphysiol25:33—351, 1968. beiisphysiol25: 33—351,1968.
McCully K. K., Faulkner J. A.: Injury to skeletal muscle fibres of mice following lengthening contractions. JAppl JAppi Physiol 59: 119— 126 1985. 126, 1985. Newham D. J., Jones D. A., Ghosh G., Aurora P.: Muscle fatigue and pain after eccentric contractions at long and short length. C/in Clin Sci74: 553—557,1988. Sci74:553—557, 1988. 10 ZerbaE., '° Zerba E.,Komorowski KomorowskiT. T.E., F., Faulkner Faulkner J. A.: Free radical injury injury to to skeletal muscles of young, adult and old mice. Am J Physiol 258 (Cell Physiol 27): C429—C435, 1990.
program of 30 day repeats failed to initiate a training stimulus.
In contrast, six repetitions with 7 days of recovery between lengthening contraction protocols produced trained muscles that were not injured by a protocol which had previously produced a force deficit of 40% at 3 days. The first myotubes are observed in regenerating fibers 5 days after injury (8), consequently recovery was not complete by 7 days, but apparently recovery was adequate for fibers to undergo an adaptive response that prevented injury. Although the P0 of the trained
John John A. Faulkner, Ph. D. Department of Physiology University of Michigan 7775 Medical Science Bldg. II Ann Arbor, MI 48109-0622
U.S.A.
Downloaded by: University of Pennsylvania Libraries. Copyrighted material.
-2fl -20
national Biochemistry of Exercise Conference. Abstract E3 13, 1991
Hampson N. B., Piantadosi C. A.: Near infrared monitoring of human skeletal muscle oxygenation during forearm ischemia. J 6
8
________________________________________
K. Sahlin
It) Wilson J. R., Mancini D. M., McCully K., Ferraro N., Lanoce V., Chance B.: Noninvasive detection of skeletal muscle under perfusion with near-infrared spectroscopy in patients with heart failure. Circulation 80: 1668—1674,1989.
ApplPhysiol64: 2449—2457,1988. Henriksson J., Katz A., Sahlin K.: Redox state changes in human
skeletal muscle after isometric contraction. J Physiol 380: 441— 451,1986. Millikan G. A.: ProcRoy Soc London B 129:218, 1937. Sahlin K.: NADH and NADPH in human skeletal muscle at rest and during ischaemia. C/in Physiol3: 477—485, 1983. Wang Z., Noyszewski E. A., Leigh Jr.: In vivo MRS measurement
of deoxymyoglobin in human forearms. Magn Reson Med 14:
Kent Sahlin, Dr. Sci.
Department of Clinical Physiology Huddinge University Hospital S-141 86 Huddinge Sweden
Injury to Skeletal Muscle during Altitude Training: Training: Induction and Prevention J. A. Faulkner, J. A. Opiteck, S. V. Brooks MI,48109-0622, 48109-0622,U. U.S. S.A. A. University of of Michigan, Michigan, Ann Ann Arbor, Arbor,MI, University
Abstract Faulkner, J.J. A. A. Opiteck Opiteckand andS. S.V. V.Brooks, Brooks, J. A. Faulkner, Injury to Skeletal Skeleta' Muscle during Altitude Training: Induction and Prevention. mt j Sports Suppl 1, 1, pp pp Med, Vol 13, Suppl Sports Med, S160—S162, 1992. S160—Sl62,1992.
A contracting skeletal muscle musck will shorten, remain isometric, or lengthen depending on the interaction
load and the force developed by the between external toad muscle. Most physical activities involve shortening, isometric and lengthening contractions. The fluctuations in terrain encountered at altitude, increase both the likelihood that lengthening contractions will occur and the severity of the stretches. When performing a given amount of work, muscles lengthened during contractions expend less energy
Introduction
When aa skeletal skeletal muscle muscle is is activated, activated, the the fibers fibers tend to shorten (4). The type of contraction that does occur depends on the interaction between the external load toad and the force developed by the muscle. muscle. If If the the load load on on the the muscle musck is less than, equivalent to, or greater than the force developed, the
and fatigue less rapidly than muscles that shorten. ConCon. versely, with equal activation, displacement, and velocity,
the work done on a muscle during lengthening contractions
is greater than the work performed by a muscle during shortening contractions, but force decreases more rapidly during lengthening. Furthermore, muscles are more likely to be injured during lengthening contractions than during shortening or isometric contractions. The occurrence of
contraction-induced injury can be eliminated, or minimized, by prior training specific for the performance of lengthening contractions. lengthening Key words Key
Altitude, muscle, training, training, skeletal skektal muscle in-
jury
muscle will shorten, remain isometric, or lengthen respectively. Each type of contraction contraction contributes contributes to to everyday everydayphysiphysical activities. When these activities are performed on uneven terrain such as that encountered encountered routinely routinely at at altitude, altitude, the thework work done on the muscle during lengthening and that done by the muscle during shortening shortening vary vary to to a much greater extent than musck during on level ground (7). At the turn of the century, innovative ex-
periments demonstrated that if shortening (concentric) and Int.J.SportsMed. 13(l992)Sl60—S162 Int.J.SportsMed. 13(1992)S160—S162 GeorgThieme Verlag StuttgartNew York
lengthening (eccentric) contractions involve equivalent equivalent amounts of work, more energy is expended and fatigue occurs
Downloaded by: University of Pennsylvania Libraries. Copyrighted material.
562— 567, 1990.
mt. J. i Sports Sports Med. Med. 13(1992) S161 S161
Injury to Skeletal Muscle duringAltitude Training
contraction-induced injury (3, 8).
Contraction-induced injury involves an initial, mechanical event (3) and a secondary, chemical event (10) with the most severe injury observed at 3 days. The purpose of the present investigation was to develop: 1. a lengthening contraction protocol for the dorsiflexor muscle group of the ankle that injures a sufficient number of muscle fibers to decrease the maximum force by 40% to 50% at 3 days, and 2. a training program of lengthening contractions that would prevent the occurrence of contraction-induced injury of this magnitude. Our working hypothesis was that a training program that induces injury must allow sufficient time for recovery, recovery, but but not not time for the training stimulus to be lost.
Materials and Methods Experiments were performed on twenty-three young (2 to 3 month old) male white mice. All experiments were conducted in accordance with the American Physiologi-
cal Society policy statement outlining the care and use of laboratory animals. Mice were anesthetized with pentobarbital sodium, 80 mg/kg, and placed on a plexiglass platform of a "shoe" apparatus (1). The knee was secured to the platform and the foot was attached to the shoe which was mounted on the shaft of a servomotor. A microcomputer controlled the servomotor and rotated the ankle joint through a given displacement at a constant velocity. Strain gauges mounted on
the shoe monitored the force produced by the dorsiflexor muscle group. Needle electrodes were placed adjacent to the peroneal nerve and the dorsiflexors were stimulated maximally at optimum length for force development. The maximum isometric tetanic force (P0) was determined from the frequency-force curve.
For each lengthening contraction protocol, a stimulation frequency of of 100 100 Hz Hz was was used used resulting resulting in inaaforce force 85%ofPo. 85 %ofP0. Contractions Contractions were were 720 720 ms ms in duration. Lengthening ing was was initiated initiated after after 120 120 ms, ms, at at the the plateau plateau of of isometric isometric force. force.
Lengthening contractions were through 40 degrees of ankle extension at 67 degrees per sec, see, which was equivalent to a displacement through — 20% of average fiber length at a velocity
of 0.5 Lf/sec. The peak force developed during the first lengthening contraction was 194 5% of Po. P0. Lengthening contractions occurred once every 4 sec.
Muscles were stimulated for three five minute periods, each separated by five minutes of rest. During the lengthening contractions, the peak force decreased steadily, and the isometric force was nearly abolished. Following the lengthening contraction protocol, the muscle was returned to L0 and P0 was measured at 0 and 10 mm. The mouse was removed moved from from the the apparatus apparatus and and allowed allowed to to recover. recover. The The P0 Po was was measured at 3 and 7 days following the lengthening lengthening contraccontraction protocol.
Three training programs were tested on separate groups of mice. The lengthening contraction protocol was
100
80
0 60
0 C) 0)
U 0 I-
0
U-
40 20 0
LCPO
+.. +., +.. +,, -I+1 -H-I3 37
10 Mm
1
Hr
30
Days
Time Fig. 1 The relationship of the force deficit (for definition see text) and time after the lengthening contraction protocol.
repeated every 3 days, every 7 days, or every 30 days, based on
the time of maximum injury, partial recovery, and full recovery, respectively. For each program, the lengthening con-
traction protocol was repeated until full recovery occurred and then the protocol was repeated to test for the magnitude of the injury 3 days later. Following these experiments, muscles were weighed. The total fiber cross-sectional area of experimental and control muscles was estimated by dividing muscle mass by the product of Lr Lf and 1.06 g/cm3, the density of mam-
malian skeletal muscle (3). Following the removal of the muscles, the anesthetized mice were killed with an overdose of the anesthetic. Force deficit was calculated for each data set as
(1-{P0 (1 -{P0of of an an injured injured muscle/P0 muscle/P0 of of the the contralateral contralateral control
muscle]) x 100. Data are expressed as the mean 1 SE. Differences between the two groups were assessed by onesided Student's t-tests (p 0.05). 0.05). Results The force deficit of 80% immediately after the lengthening contraction protocol recovered to 40% by 10 mm (Fig. 1). In a longitudinal study, data at 3 hr and 1 day could not be obtained, but from previous recovery curves (3, 8) each force deficit was estimated to be 20%. A secondary decrease to
a force deficit of 40% occurred at 3 days. Full recovery was achieved by 30 days. achieved
The 3 day-repeat training program produced a force deficit of 50% to 60% with no evidence of recovery after
6 repetitions. With the 30 day lapse between exposures to lengthening contraction protocols, the force deficit at 3 days was of the same mgnitude each time and no evidence of a training response was observed. observed. In In contrast, contrast, the the 77 day day repeats repeatsof ofthe the protocol resulted in a force deficit of 10% to 25% for each of 5
repetitions, but no force deficit was observed after the sixth repetition (Fig. 2). Three days after the last repeat of the lengthening contraction protocol no force deficit was observed. The mass of of the the trained traineddorsiflexors dorsiflexorswas was92.1 92.1 6.7 6.7 mg mg compared compared
mgfor forthe the untrained untrained contralateral control with 76.1 6.8 mg control with 76.1 muscle group and the total fiber cross-sectional areas were 7.6 0.4 mm2 and 6.2 0.2 mm2, respectively.
Downloaded by: University of Pennsylvania Libraries. Copyrighted material.
more rapidly with shortening contractions (2). In contrast, compared with shortening contractions, lengthening contractions with equal activation, displacement, and velocity, are characterized by: larger average and peak forces (3, 8), more rapid fatigue (6), and a greater likelihood and magnitude of
S162 mt. J. Sports Med. 13(1992)
J. A. Faulkner, J. A. Opiteck and S. V. Brooks Deficit at Onset onset of of LcP o Deficit at end of LCP • Deficit 10 mm. after LCP
80
muscles increased with the increase in muscle mass and cross-
sectional area, the specific P0 Po (N/cm2) decreased 15%. Decreases in specific P0 have been noted with the hypertrophy associated with ablation of synergistic muscles (5). The mech-
60
40
anism responsible for prevention of contraction-induced injury to skeletal muscle fibers remains unknown.
C,
20
Acknowledgements This research was supported by the National Insti0
7
14
21
28
35
38
tute on Aging, NIH grant AG-06 157.
Time (Days) Fig. 2 The force deficit (for definition see text) during each session of the the 77 day day repeat repeat training training program programand ard time after the initial lengthening contraction protocol and the force deficit 3 days after the final lengthening contraction protocol (U). Note: The force deficit of 0% after the fourth lengthening ng contraction protocol was attributed to a measure-
References Ashton-Miller J. A., He Y., Kadhiresan V. A., McCubbrey D.,
2
Faulkner J. A.: An apparatus to measure in vivo biomechanical behavior of dorsi- and plantarfiexors of the mouse ankle. JAppiPhysioll2: 1205—1211,1992. Chauveau S.: La dépense énergétique de l'entraInement respec-
tive le travail moteur et le travail resistant de l'homme qui s'éléve ou descend sur Ia la roue de Him. Comptes Comptes rendus rendus hebdomadaires hebdomadaires
ment error. One value was excessively high and the rest were in keeping with previous values.
des sénces de l'Académie des sciences 132: 132: 194—202, 1901. Faulkner J. A.,Jones D. A., Round J. M.: Injury to skeletal muscles
of mice by forced lengthening during contractions. Quart J Exp Physiol74: 661—670,1989.
Faulkner J. A., White T. P.: Adaptations of skeletal muscle to
Discussion
physical activity, in Bouchard C., Shephard R. J., Stephens T., Sut-
ton J. R., McPherson B. D. (eds): Exercise, Fitness and Health. Toronto, Human Kinetics Publishers, 1990, Chapter 22, pp 265—
The force force deficit deficit immediately immediately after after the the lengthlength-
ening contraction protocol protocol represents represents both both fatigue fatigue and and injury injury (3). With the the estimate estimate of of aaforce forcedeficit deficitofof20 20% % at at both both 33hr hrand and I day, 1 day, the the recovery recovery from from fatigue fatigue appears appears to to be be complete complete by by 33 hr. The The implication implication is is that that the the initial, initial, predominantly predominantly mechanimechanihr. cal, injury was of this magnitude. The secondary injury, which occurs occurs between between day day 11 and and day day 3, 3, doubles doubles the the magnitude magnitude of of the the initial initial injury. The secondary injury involves oxygen oxygen free free radiradical damage, since this injury can be blocked completely by the free radical scavenger superoxide dismutase (10). The second-
ary injury appears to be responsible for the late onset muscle soreness reported by human beings after contraction-induced injury (9). The results are consistent with the working hy-
pothesis since the training program with 3 day repeats provided insufficient time for recovery from injury, whereas the
279.
Kandarin S. K., White T. P.: Mechanical deficit persists during 6
long-term muscle hypertrophy. hypertrophy. JAppiPhysiol 69: 861—867, 1990. longterm muscle 69:861—867, Lieber R. L., Woodburn T. M., Friden J.: Muscle damage induced Appi Physiol 70: 2498— by eccentric contractions contractions of of 24% 24% strain. strain. JJAppi 2507, 1991. 2507,1991.
Margaria R.: Positive and negative work performances and their efficiencies in human locomotion. locomotion. In! mt Z angew Physiol Physiol einschl Arbeilsphysiol25:33—351, 1968. beiisphysiol25: 33—351,1968.
McCully K. K., Faulkner J. A.: Injury to skeletal muscle fibres of mice following lengthening contractions. JAppl JAppi Physiol 59: 119— 126 1985. 126, 1985. Newham D. J., Jones D. A., Ghosh G., Aurora P.: Muscle fatigue and pain after eccentric contractions at long and short length. C/in Clin Sci74: 553—557,1988. Sci74:553—557, 1988. 10 ZerbaE., '° Zerba E.,Komorowski KomorowskiT. T.E., F., Faulkner Faulkner J. A.: Free radical injury injury to to skeletal muscles of young, adult and old mice. Am J Physiol 258 (Cell Physiol 27): C429—C435, 1990.
program of 30 day repeats failed to initiate a training stimulus.
In contrast, six repetitions with 7 days of recovery between lengthening contraction protocols produced trained muscles that were not injured by a protocol which had previously produced a force deficit of 40% at 3 days. The first myotubes are observed in regenerating fibers 5 days after injury (8), consequently recovery was not complete by 7 days, but apparently recovery was adequate for fibers to undergo an adaptive response that prevented injury. Although the P0 of the trained
John John A. Faulkner, Ph. D. Department of Physiology University of Michigan 7775 Medical Science Bldg. II Ann Arbor, MI 48109-0622
U.S.A.
Downloaded by: University of Pennsylvania Libraries. Copyrighted material.
-2fl -20
