Pain, 50 (1992) 317-321 © 1992 Elsevier Science Publishers B.V. All rights reserved 0304-3959/92/$05.00
317
PAIN 02123
An effect of ascorbic acid on delayed-onset muscle soreness Mark Kaminski and Robert Boal Dicision of Basic Sciences, Western States Chiropractic College, 2900 NE 132nd, Portland, OR 97230 (USA) (Received 4 November 1991, revision received 24 April 1992, accepted 4 May 1992)
Summary Delayed-onset muscle soreness following strenuous use of the posterior calf muscles was studied to determine if ascorbic acid might have an effect on the appearance of this familiar pain. A double-blind, randomized, crossover study compared the soreness in subjects taking ascorbic acid against those taking a lactose placebo. Visual analog scales were used in conjunction with a variety of pain-challenging methods, and the results indicated a significant difference between experimental and placebo groups at the height of soreness. Typical soreness abatement scores of 25-44% were observed. A sample size of 19, lack of an untreated control group as well as the singular nature of the exercise and its intensity were considered limitations of the study. Key words: Skeletal muscle; Soreness; Ascorbic acid; Exertion; Pain
Introduction The delayed appearance of pain and stiffness following muscular exertion is a common experience. Often termed delayed-onset muscle soreness (DOMS) or postexercise muscle soreness, the phenomenon was first studied by Hough (1902). The soreness represents a type of pain which follows the strenuous use of skeletal muscle not accustomed to such activity. DOMS typically appears within 24 h, reaches a peak at about 48 h, and gradually declines over an additional 2--5 days (Talag 1973; Abraham 1977; Armstrong 1984; Bobbert et al. 1986). Experiments have demonstrated that the eccentric component of exercise is primarily responsible for DOMS (Armstrong et al. 1983; Jones et al. 1987; Newham et al. 1987). The pain associated with this condition is currently thought to be a consequence of microtraumatization of endo- and perimysial connective tissues and/or myofibers; however, a precise understanding of its chemical and physical basis is largely unknown (Armstrong 1984; Frid6n 1984; Howell et al. 1985; Ebbeling and Clarkson 1989; Armstrong et al. 1991).
Correspondence to: Mark Kaminski, Division of Basic Sciences, Western States Chiropractic College, 2900 NE 132nd, Portland, OR 97230, USA.
While the characterization of DOMS has been an area of active research, the prevention or attenuation of this phenomenon has largely gone unstudied. As a protective measure, eccentric training of muscle has been shown to prevent DOMS in subsequent bouts of similiar activity (Hough 1902; A,~'mstrong 1984; Newham et al. 1987). Additionally, it is known that in cases in which DOMS is initiated, there is transient relief of soreness during the muscle's r~.-use (Hough 1902; Armstrong 1984). Other methods of eliminating the delayed pain of exercise are currently not well established (Armstrong 1984); however, electrotherapy has shown some benefit (Denegar et al. 1989; Kulig et al. 1990) and anti-inflammatory medications have provided mixed results (Janssen et al. 1983; Francis and Hoobler 1987; Headley et al. 1987). For the past 40 years there have been sporadic reports of a possible effect of ascorbic acid on exercise-induced pain and stiffness in muscles. Staton, in 1952, observed that ascorbic acid reduced postexercise soreness as evidenced by extending the ability of young men to perform sit-ups several days after a previous bout of the same activity. Syed, in 1966, briefly reported a reduction in delayed onset muscle stiffness in his patients taking ascorbic acid supplements. Not surprisingly, given its popularity as a nutritional supplement, there have been claims of potent protective effects of ascorbic acid on DOMS in the lay press (Mueller 1986; Monroe 1990).
318 T h i s p r e s e n t s t u d y a t t e m p t s to o b s e r v e a n e f f e c t of a s c o r b i c acid o n t h e d e g r e e o f p a i n in D O M S . T h e e x p e r i m e n t c o m p a r e s t h e s o r e n e s s e x p e r i e n c e d bet w e e n subjects t a k i n g 3 g o f ascorbic acid daily a n d t h o s e t a k i n g a lactose p l a c e b o a f t e r c h a l l e n g i n g t h e p l a n t a r flexors o f t h e p o s t e r i o r c o m p a r t m e n t o f t h e c a l f ( p r i m a r i l y the t r i c e p s s u r a e ) w i t h b o u t s o f e c c e n t r i c c o n t r a c t i o n s . A d d i t i o n a l l y , v a r i o u s m e t h o d s for rout i n e l y assessing D O M S a r e e x p l o r e d .
Methods
any worse" at the other. Experimental and control legs where assessed in 4 ways: (1) sitting at rest, (2) during self-palpation with the thumb over the midpoint of the posterior calf (into the triceps surae) while seated, (3) during a calf stretch by forced dorsiflexion of the foot to a 45° ankle angle, (4) during a 5-sec repeat bout of the soreness-producing exercise. In all cases, the experimental leg was compared to the non-exercised leg (under the same assessment) and a difference score was taken as the indication of muscle soreness. Muscle soreness was measured at noon immediately prior to the exercise (0 hour) and then at 10, 24, 34, 48, 58, 72, and 96 h after exercise. Subjects were also directed to complete a general log which asked for the following: integrity of supplement capsules, illness, gastrointestinal complaints, consumption of supplements, completion of VAS for the 4 assessments, exercise activities, and general compliance with the experimental protocol. These forms were reviewed for any indicators which might exclude a given subject from the study.
Sllbjects Twenty-five healthy subjects were recruited for the study. All individuals were students or employees of Western States Chiropractic College (WSCC) or members of their families. Subjects were excluded from the study if they were older than 50 years, had a sensitivity to lactose, took analgesic or anti-inflammatory agents during the trials, participated in rigorous athletic training, had a current musculoskeletal ailment in the legs, or took ascorbic acid or riboflavin supplements within 3 weeks of the study. Participants were generally aware of the nature of the study and, following the guidelines of the American College of Sports Medicine, informed consent was received from each. Procedures used in this study were approved by the WSCC Protection of Human Subjects Committee.
Experimental design Designed as a doulfle-blind, randomized, crossover study, subjects w~re challenged with 2 separate bouts of exercise consisting of subs, mtial eccentric work of the plantar flexors of the calf to create soreness in the lower leg. The 2 trials were separated by 3 weeks and ,.,,ere perfl~rmcd using different legs to minimize any carry-(wer effects between trials. Three weeks was c~nsitlered sufficient time to eliminate the chance of residual ascol'bic acid in the body from the previous treatment (Melethil !t)87), and using separate legs for the 2 triat~ removed the potential threat of any training effect or residual muscle impairment from the first exercise session. Given the extremely limited body of knowledge on leg dominance, it was not considered important fl)r randomization. Subjects were randomly selected to receive placebo (lactose) or ascorbic acid for the first trial. In the second trial, all subjects were switched to the other supplement. Participants were told that they were randomly assigned to placebo or ascorbic acid groups in both trials. The investigators were blind to all supplementations until after the second trial.
Supplem en ts For each trial, the supplements were taken 3 times/day as l-g capsules and consisted of either reagent-grade lactose or food-grade ascorbic acid. The ascorbic acid was pulverized to render it indistinguishable from lactose. Supplementation began 3 days prior to the leg exercise and continued for seven days (including the 96 h postexercise evaluation period).
Data analysis All VAS records were measured to the nearest millimeter, and the levels of soreness were analyzed as difference scores (experimental leg minus contro! leg). Due to the iarge number of comparisons made, multivariate tests of significance with post hoc univariate tests were performed. Multivariate analysis of variance (MANOVA) was used to test for any ordering effect as well as for significant differences between the treatment and phtcebo groups at baseline and at each of the 8 follow-up soreness evalution times for each of the 4 different assessment methods. Because of concerns about sample size and distribution, nonpat'ametric tests of significance were also performed (Rosner 1986). To test h)r treatment effects at the 8 soreness assessment times, Friedman's non-pararnetric analysis of variance (ANOVA) was used with a Wilcoxon sign rank test as the post hoc significance test. A Wilcoxon rank sum test was used as a univariate test of significance for any ordering effect. All analyses were performed using SPCC/PC+ software (Norusis 1990a,b), and statistical significance was set at the 0.1)5 level for all tests.
Results
Pt'uccd¢~ t ~3
Muscle soreness was created in the subjects' plantar flexors following the method of Bobbert et al. (1986). The c~lf was strenuously exercised by compleiir~g a series of body liftings ,no2 Iowerings by plantar- and dorsiflexion of the foot ,~f one leg. With the anterior half ol the foot of the experimental leg on a 1.5-in board (posterior half of the foot suspended) and the knee in an extended position, individuals were asked to complete alternating cycles of 15 sec of the exercise followed by 15 sec of rest for a total of 15 rain. Subjects v,ere free to choose their own exercise intensity as long as they maintained a minimum of 1() raises/drops during a 15-see exercise cycle. All participants exercised their right leg in the first trial and t!,eir left leg dr:ring the second trial 3 weeks later. Muscle soreness was monitored by self-reporting using a 10-cm continuous, unmarked line as a ~,isual analog scale (VAS) anchored with "'I have no soreness" at one end and "my soreness could not be
O f t h e 25 o r i g i n a l s u b j e c t s , 2 d r o p p e d o u t o f t h e e x p e r i m e n t , 3 w e r e e x c l u d e d for a v a r i e t y o f r e a s o n s (loss o f c a p s u l e i n t e g r i t y , faiittre to p r o p e r l y m a i n t a i n records, and non-compliance with experimental protocol), a n d 1 w a s r e m o v e d for f a i l u r e to d e v e l o p D O M S in e i t h e r trial. T h e r e m a i n i n g 19 s u b j e c t s c o n s i s t e d o f 6 w o m e n a n d 13 m e n w h o ( r a n g e : 2 4 - 4 8 years).
a v e r a g e d 35 y e a r s o f a g e
T h e o u t c o m e s f r o m all 4 a s s e s s m e n t m e t h o d s w e r e u s e d to d e t e r m i n e if a n y o r d e r i n g (i.e., c a r r y - o v e r ) e f f e c t wa~ at w o r k b e t w e e n t h e 2 trials. B o t h m u l t i v a r i a t e a n d u n i v a r i a t e p a r a m e t r i c t e s t s as well as n o n - p a r a metric analyses yielded no significant ordering effects
319
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POST E~ERCiSE TIME COURSE (h0t,,,:nl)
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Fig. 1. Average soreness observed over postexercise period while the
Fig. 2. Average soreness observed over postexercise period while the subject stretched his/her posterior calf by forced dorsiflexion of their foot to a 45 ° ankle angle. Note: time scaling alternates belween l0 and 14 h except for a 24-h period at the end of the observation
subject was sitting at rest. Note: time scaling alternates between 10 and 14 h except for a 24-h period at the end of the observation interval.
period.
at any of the 8 soreness assessment times for the exercise, stretch and resting methods ( P > 0.05). An analysis of the palpation assessment method indicated an ordering effect at one measurement point (34 h) and, therefore, this data was not used further, despite a significant difference between treatment and placebo groups. Comparisons were then made between subjects given ascorbic acid or lactose placebo, and the average VAS soreness scores across the 4-day postexercise period are displayed in Figs. 1-3. The divergence of treatment and placebo groups began at approximately 34 h postexercise, reached a maximum at approximately 58 h, and ended at approximately 96 h. Multivariate analysis indicated that there was a significant difference between the groups for the exercise and ,,;tretch assessments; univariate tests showed significance at the 48-, 58- and 72-h measurements for the stretch assessment, and at the 58- and 72-h measurements for the exercise assessment. The average VAS scores for each assessment method at 58 h and at maximum are presented in Tables I and It. The 58-h observation was selected since it represented the time o f g r e a t e s t average pain and the great-
est statistical significance. The maximum score for each subject allowed an evaluation independent of time. Review of the pain scores for individual subjects demonstrated a variation in soreness relief, Using data
EXERCISE ASSESSMENT
,
,
,'
,
,
,
0
10
24
34
48
56
I-m- ASCOR"IC ACID ~
,,
PLACEBO
M E A N 58-h S O R E N E S S S C O R E S *
Resting Stretch Exercise
Treatment
Placebo
Difference
% Reduction
iT)
(P)
(P - T)
((P - T ) / P ) I O 0
1.0 4.0 3.5
1.7 5.8 6.3
0.7 1.8 2.8
41 31 44
* = Difference scores between experimental and control legs. += Significance from non-parametric Wilcoxon sign rank test. NS = Not significant.
,
96
,,
I
Fig. 3. Average soreness observed over postexercise period while the subject performed a 5-sec bout of the original soreness-producing activity. Note: time scaling alternates between l0 and 14 h except for a 24-h period at the end of the observation interval.
TABLE 1
Assessment
,
72
P + NS < 0.05 < 0.0 !
32O
TABLE I! IVlEAN MAXIMUM SORENESS SCORES Assessment
Resting Stretch Exercise
Treatment
Placebo
Difference
(P)
~P - T)
% Reduction (((P - T)/P)100)
P +
(T) 1.6 5.0 4.6
2.3 6.7 6.8
0.7 1.7 2.2
30 25 32
< 0.05 < 0.01 < 0.01
* = Difference scores between experimental and control legs. + = Significance from non-parametric Wilcoxon sign rank test.
T A B L E 111 % Reduction
N
58-h soreness relief * > 33 0-33 33 0-33 < 0
8 7 4
* = The exercise assessment method.
from 58-h and maximum scores, subjects are grouped into arbitrary soreness relief categories, and these results are tabulated in Table i!!.
D~scassion
For the purposes of this study, DOMS rcduction was defined as a difference in average soreness between ,'l placebo group and an ascorbic acid treatment group. The largest reduction was observed at the height of DOMS. For approximately one-half of the subjects, there was substantial soreness relief ( > 33% reduction in soreness from placebo); however, several subjects showed no remarkable difference between the ascorbic acid and placebo trials. Whether these non-responders are unique test subjects or simply represent experimental errors is unknown. All 4 assessment methods appeared to show the ascorbic acid effect on DOMS. The palpation method demonstated a limited ordering effect and was excluded from a presentation of findings; furthermore, interpretation of the palpation assessment would have been complicated by the likely variability in subject self-assessment of tenderness (i.e., the location and force used to monitor pain was not controlled). Not surprisingly the resting assessment showed the least effect since DOMS produces a relatively low level of background pain. The stretch assessment may be of limited value because the 45° ankle angle used to stretch the calf was probably excessive in that some subjects reported pain even in their control leg. The
exercise assessment seemed to be the most realistic in approximating the normal use of the leg; furthermore, the amount of force used to elicit pain with this assessment is crodely metered out by the weight of the subject, and the procedure can easily be duplicated between experimental and control legs. There are important limitations of this study that warrant further analysis and consideration. First, the relatively small subject pool requires caution in the interpretation of these results. A substantial increase in sample size within both experimental and placebo groups is necessary to strengthen any claims of soreness reduction by ascorbic acid. Second, the lack of an untreated control group raises the question of what role any placebo effect may play in these results. Third, leg dominance, although there are no indications in the literature that it is important, may be a confounding factor since it was not randomized in this trial. Finally, the strenuous eccentric use of the plantar flexors employed in this investigation may not easily generalize to large muscle groups elsewhere in the body, and it remains to be seen if the effect can be observed with lesser unaccustomed activities. Further studies of ascorbic acid and DOMS should also address the dosage and time of delivery of the supplement. Since this project used large oral dosages of ascorbic acid, it would be important to learn if ,~ substantially lower dosage (perhaps 500 mg/day) would be equally effective in the abatement of DOMS; establishing a dose-dependent relationship between ascorbic acid and this soreness should be one of the goals of future research in this area. Alternatively, the treatment delivery period might be varied to learn if presaturation with ascorbic acid was necessary to produce the effect (e.g., treatment may be shown to be equally effective if delivered at 24 h after the unaccustomed exercise). Whether ascorbic acid may serve to prevent the injury (i.e., prophylaxis) or simply minimize the painful symptoms (i.e., analgesia), there are important experiments that could be performed that might begin to uncover its mechanism of action on DOMS. For example, it would be interesting to learn if ascorbic acid cannot only lessen the perception of soreness but also reduce any previously studied changes in plasma crea-
321
tine kinase activity (Schwane et al. 1983; Tiidus and lanuzzo 1983; Newham et al. 1986; Triffletti et al. 1988), skeletal muscle tissue morphology (Armstrong et al. 1983; Frid6n 1984; Clarkson and Trembley 1988) or calcium homeostasis (Clarkson and Trembley 1988; Duan et al. 1990). Observing an attenuation of these parameters might suggest a protective role for ascorbic acid in skeletal muscle or associated connective tissue. Furthermore, changing the treatment delivery period may uncover evidence which favors one mechanistic scheme over another. If the body must be saturated with ascorbic acid prior to exercise to observe the effect, then this would suggest a possible mechanism related to collagen synthesis and integrity given ascorbic acid's well known cofactor role for this protein (Englard and Seifter 1986). Whatever model is developed for DOMS, it should encompass the ascorbic acid findings of this study. In summary, this investigation suggests that ascorbic acid may significantly reduce the delayed soreness typically seen following the strenuous use of muscles in an unaccustomed manner. Supplementation appears to blunt the reported soreness, showing the greatest effect when DOMS was at its peak. However, more extensive studies using larger sample sizes will be needed to strengthen this assertion.
,Acknowledgements
The authors wish to acknowledge the vital efforts of Mitchell Haas for statistical assistance. Additionally, the work of Richard Gill,~tte for aid with experimental design, the WSCC Research and Publications Committee for manuscript review, and James Edward Perkins fc,r the original stimulus are greatly appreciated.
References Abraham, W.M., Factors in delayed muscle soreness, Med. Sci. Sports Exerc., 9 (1977) ! 1-20. Ar~astrong, R.B., Mechanisms of exercise-induced delayed onset "nuscular soreness: a brief review, Med. Sci. Sports Exerc., 16 (1984) 529-538. Armstrong, R.B., Ogilvie, R.W. and Schwane, J.A., Eccentric exercise-induced injury to rat skeletal muscle, J. Appl. Physiol., 54 (1983) 80-93. Armstrong, R.B., Warren, G.L. and Warreu, J.A., Mechanisms of exercise-induced muscle fibre injury, Sports Med., 12 (1991) 184207. Bobbert, M.F., Hollander, A.P. and Huijing, P.A., Factors in delayed onset muscular soreness in man, Med. Sci. Sports Exerc., 18 (1986) 75-81. Clarkson, P.M. and Trembley, I., Rapi~ adaptation to exercise to induced muscle damage, J. Appl. Physiol., 65 (1988) 1-6. Dene~;ar, C.R., Perrin, D.H., Rogol, A.D. and Rutt, R., Influence of transcutaneous electrical nerve stimulation on pain, range of
motion, and serum cortisol concentration in females experiencing delayed onset muscle soreness, J. Orthop. Sports Phys. Ther., 11 (1989) 100-103. Duan, C.; Delp, M.D., Hayes, A., Delp, P.D. and Armstrong, R.B., Rat skeletal muscle mitochondrial [Ca +2] and injury from downhill walking, J. Appl. Physiol., 68 (1990) 1241-1251. Ebbeling, C.B. and Clarkson, P.M., Exercise-in~u,.ed muscle damage and adaptation, Sports Med., 7 (1989)207-234. Englard, S. and Seifter, S., The biochemical functions of ascorbic acid, Ann. Rev. Nutr., 6 (1986) 365-406. Francis, K.T. and Hoobler, T., Effects of aspirin on delayed muscle soreness, J. Sports Med., 7 (1987) 333-337. Frid6n, J., Muscle soreness after exercise: implications of morphological changes, Int. J. Sports Med., 5 (1984) 57-66. Headley, S.A.E., Newham, D.J. and Jones, D.A., The effect of prednisolone on exercise induced muscle pain and damage, Clin. Sci., 70, Suppl. 13 (1987) 85P. Hough, T., Ergographic studies of muscular soreness, J. Appl. Physiol., 7 (1902) 76-92. Howell, J.N., Chila, A.G., Ford, G., David, D.D. and Gates, T., An electromyographic study of elbow motion during postexercise muscle soreness, J. Appl. Physiol., 58 (1085) 1713-1718. Janssen, E., Kuipers, H., Verstappen, F. and Costill, D., Influenc.e of an anti-inflammatory drug on muscle soreness, Med. Sci. Sports Exer., 15 (1983) 165. Jones, D.A., Newham, D.J. and Clarkson, P.M., Skeletal muscle stiffness and pain following eccentric exercise of the elbow flexors, Pain, 30 (1987) 233-242. Kulig, K., Isles, S., Rapaski, D. and Smith, J., Comparison of three microcurrent stimulation protocols in reducing delayed onset muscle soreness and edema, Phys. Ther., 70 (Suppl.)(1990) R222. Melethil, S., Subrahmanyam, M.B., Chang, C.J. and Mason, W.D., Megadoses of vitamin C: a pharmacokinetic evaluation, Ann. NY Acad. Sci., 498 (1987) 491-493. Monroe, B., Vitamin C can be of help to hunters, The Oregonian, (November 14, 1990)E8. Mueller, L., C-cret for soreness, Outdoor Life, 178 (1986) 76-78. Newham, D.J., Jones, D.A. and Clarkson, P.M., Repeated high-force eccentric exercise: effects on muscle pain and damage, J. Appl. Physiol., 63 (1987) 1381-1386. Newham, D.J., Jones, D.A. and Edwards, H.T., Plasma creatine kinase changes after eccentric and concentric contractions, Muscle Nerve, 9 (1986) 59-63. Norusis, M.J., SPSS/PC+ Statistics 4.0, SPSS Inc., Chicago, IL, 1990a. Norusis, M.J., SPSS/PC+ Advanced Statistics 4.0, SPSS Inc., Chicago, IL, 1990b. Rosner, B., Fundamentals of Biostatistics, 2nd edn., Duxbury Press, Boston, MA, 1986, pp. 283-293. Schwane, J.A., Johnson, S.R., Vandenakker, C.B. and Armstrong, R.B., Delayed-onset muscular soreness and plasma CPK and LDH activities after downhill running, Med. Sci. Sports Exerc., 15 (1983) 51-56. Staton, W.M., The influence of ascorbic acid in minimizing post-exercise muscle soreness in young men, Res. Quart., 23 (1952) 356 360. Syed, I.H., Muscle stiffness and vitamin C (letter), Br. Med. J., 2 (~966) 304. Talag, T.S., Residual muscular soreness as influenced by concentric, eccentric, and static contractions, Res. Quart., 44 (i973) 458-469. Tiidus, P.M. and hmuzzo, C.D., Effects of intensity and duration of muscular exercise on delayed soreness and serum enzyme activities, Med. Sci. Sports Exerc., 15 (1983) 461-465. Triffletti, P., Litchfield, P.E., Clarkson, P.M. and Byrnes, W.C., Creatine kinase and muscle soreness aider repeated isometric: exercise, Med. Sci. Sports Exerc., 20 (1988)242-248.
317
PAIN 02123
An effect of ascorbic acid on delayed-onset muscle soreness Mark Kaminski and Robert Boal Dicision of Basic Sciences, Western States Chiropractic College, 2900 NE 132nd, Portland, OR 97230 (USA) (Received 4 November 1991, revision received 24 April 1992, accepted 4 May 1992)
Summary Delayed-onset muscle soreness following strenuous use of the posterior calf muscles was studied to determine if ascorbic acid might have an effect on the appearance of this familiar pain. A double-blind, randomized, crossover study compared the soreness in subjects taking ascorbic acid against those taking a lactose placebo. Visual analog scales were used in conjunction with a variety of pain-challenging methods, and the results indicated a significant difference between experimental and placebo groups at the height of soreness. Typical soreness abatement scores of 25-44% were observed. A sample size of 19, lack of an untreated control group as well as the singular nature of the exercise and its intensity were considered limitations of the study. Key words: Skeletal muscle; Soreness; Ascorbic acid; Exertion; Pain
Introduction The delayed appearance of pain and stiffness following muscular exertion is a common experience. Often termed delayed-onset muscle soreness (DOMS) or postexercise muscle soreness, the phenomenon was first studied by Hough (1902). The soreness represents a type of pain which follows the strenuous use of skeletal muscle not accustomed to such activity. DOMS typically appears within 24 h, reaches a peak at about 48 h, and gradually declines over an additional 2--5 days (Talag 1973; Abraham 1977; Armstrong 1984; Bobbert et al. 1986). Experiments have demonstrated that the eccentric component of exercise is primarily responsible for DOMS (Armstrong et al. 1983; Jones et al. 1987; Newham et al. 1987). The pain associated with this condition is currently thought to be a consequence of microtraumatization of endo- and perimysial connective tissues and/or myofibers; however, a precise understanding of its chemical and physical basis is largely unknown (Armstrong 1984; Frid6n 1984; Howell et al. 1985; Ebbeling and Clarkson 1989; Armstrong et al. 1991).
Correspondence to: Mark Kaminski, Division of Basic Sciences, Western States Chiropractic College, 2900 NE 132nd, Portland, OR 97230, USA.
While the characterization of DOMS has been an area of active research, the prevention or attenuation of this phenomenon has largely gone unstudied. As a protective measure, eccentric training of muscle has been shown to prevent DOMS in subsequent bouts of similiar activity (Hough 1902; A,~'mstrong 1984; Newham et al. 1987). Additionally, it is known that in cases in which DOMS is initiated, there is transient relief of soreness during the muscle's r~.-use (Hough 1902; Armstrong 1984). Other methods of eliminating the delayed pain of exercise are currently not well established (Armstrong 1984); however, electrotherapy has shown some benefit (Denegar et al. 1989; Kulig et al. 1990) and anti-inflammatory medications have provided mixed results (Janssen et al. 1983; Francis and Hoobler 1987; Headley et al. 1987). For the past 40 years there have been sporadic reports of a possible effect of ascorbic acid on exercise-induced pain and stiffness in muscles. Staton, in 1952, observed that ascorbic acid reduced postexercise soreness as evidenced by extending the ability of young men to perform sit-ups several days after a previous bout of the same activity. Syed, in 1966, briefly reported a reduction in delayed onset muscle stiffness in his patients taking ascorbic acid supplements. Not surprisingly, given its popularity as a nutritional supplement, there have been claims of potent protective effects of ascorbic acid on DOMS in the lay press (Mueller 1986; Monroe 1990).
318 T h i s p r e s e n t s t u d y a t t e m p t s to o b s e r v e a n e f f e c t of a s c o r b i c acid o n t h e d e g r e e o f p a i n in D O M S . T h e e x p e r i m e n t c o m p a r e s t h e s o r e n e s s e x p e r i e n c e d bet w e e n subjects t a k i n g 3 g o f ascorbic acid daily a n d t h o s e t a k i n g a lactose p l a c e b o a f t e r c h a l l e n g i n g t h e p l a n t a r flexors o f t h e p o s t e r i o r c o m p a r t m e n t o f t h e c a l f ( p r i m a r i l y the t r i c e p s s u r a e ) w i t h b o u t s o f e c c e n t r i c c o n t r a c t i o n s . A d d i t i o n a l l y , v a r i o u s m e t h o d s for rout i n e l y assessing D O M S a r e e x p l o r e d .
Methods
any worse" at the other. Experimental and control legs where assessed in 4 ways: (1) sitting at rest, (2) during self-palpation with the thumb over the midpoint of the posterior calf (into the triceps surae) while seated, (3) during a calf stretch by forced dorsiflexion of the foot to a 45° ankle angle, (4) during a 5-sec repeat bout of the soreness-producing exercise. In all cases, the experimental leg was compared to the non-exercised leg (under the same assessment) and a difference score was taken as the indication of muscle soreness. Muscle soreness was measured at noon immediately prior to the exercise (0 hour) and then at 10, 24, 34, 48, 58, 72, and 96 h after exercise. Subjects were also directed to complete a general log which asked for the following: integrity of supplement capsules, illness, gastrointestinal complaints, consumption of supplements, completion of VAS for the 4 assessments, exercise activities, and general compliance with the experimental protocol. These forms were reviewed for any indicators which might exclude a given subject from the study.
Sllbjects Twenty-five healthy subjects were recruited for the study. All individuals were students or employees of Western States Chiropractic College (WSCC) or members of their families. Subjects were excluded from the study if they were older than 50 years, had a sensitivity to lactose, took analgesic or anti-inflammatory agents during the trials, participated in rigorous athletic training, had a current musculoskeletal ailment in the legs, or took ascorbic acid or riboflavin supplements within 3 weeks of the study. Participants were generally aware of the nature of the study and, following the guidelines of the American College of Sports Medicine, informed consent was received from each. Procedures used in this study were approved by the WSCC Protection of Human Subjects Committee.
Experimental design Designed as a doulfle-blind, randomized, crossover study, subjects w~re challenged with 2 separate bouts of exercise consisting of subs, mtial eccentric work of the plantar flexors of the calf to create soreness in the lower leg. The 2 trials were separated by 3 weeks and ,.,,ere perfl~rmcd using different legs to minimize any carry-(wer effects between trials. Three weeks was c~nsitlered sufficient time to eliminate the chance of residual ascol'bic acid in the body from the previous treatment (Melethil !t)87), and using separate legs for the 2 triat~ removed the potential threat of any training effect or residual muscle impairment from the first exercise session. Given the extremely limited body of knowledge on leg dominance, it was not considered important fl)r randomization. Subjects were randomly selected to receive placebo (lactose) or ascorbic acid for the first trial. In the second trial, all subjects were switched to the other supplement. Participants were told that they were randomly assigned to placebo or ascorbic acid groups in both trials. The investigators were blind to all supplementations until after the second trial.
Supplem en ts For each trial, the supplements were taken 3 times/day as l-g capsules and consisted of either reagent-grade lactose or food-grade ascorbic acid. The ascorbic acid was pulverized to render it indistinguishable from lactose. Supplementation began 3 days prior to the leg exercise and continued for seven days (including the 96 h postexercise evaluation period).
Data analysis All VAS records were measured to the nearest millimeter, and the levels of soreness were analyzed as difference scores (experimental leg minus contro! leg). Due to the iarge number of comparisons made, multivariate tests of significance with post hoc univariate tests were performed. Multivariate analysis of variance (MANOVA) was used to test for any ordering effect as well as for significant differences between the treatment and phtcebo groups at baseline and at each of the 8 follow-up soreness evalution times for each of the 4 different assessment methods. Because of concerns about sample size and distribution, nonpat'ametric tests of significance were also performed (Rosner 1986). To test h)r treatment effects at the 8 soreness assessment times, Friedman's non-pararnetric analysis of variance (ANOVA) was used with a Wilcoxon sign rank test as the post hoc significance test. A Wilcoxon rank sum test was used as a univariate test of significance for any ordering effect. All analyses were performed using SPCC/PC+ software (Norusis 1990a,b), and statistical significance was set at the 0.1)5 level for all tests.
Results
Pt'uccd¢~ t ~3
Muscle soreness was created in the subjects' plantar flexors following the method of Bobbert et al. (1986). The c~lf was strenuously exercised by compleiir~g a series of body liftings ,no2 Iowerings by plantar- and dorsiflexion of the foot ,~f one leg. With the anterior half ol the foot of the experimental leg on a 1.5-in board (posterior half of the foot suspended) and the knee in an extended position, individuals were asked to complete alternating cycles of 15 sec of the exercise followed by 15 sec of rest for a total of 15 rain. Subjects v,ere free to choose their own exercise intensity as long as they maintained a minimum of 1() raises/drops during a 15-see exercise cycle. All participants exercised their right leg in the first trial and t!,eir left leg dr:ring the second trial 3 weeks later. Muscle soreness was monitored by self-reporting using a 10-cm continuous, unmarked line as a ~,isual analog scale (VAS) anchored with "'I have no soreness" at one end and "my soreness could not be
O f t h e 25 o r i g i n a l s u b j e c t s , 2 d r o p p e d o u t o f t h e e x p e r i m e n t , 3 w e r e e x c l u d e d for a v a r i e t y o f r e a s o n s (loss o f c a p s u l e i n t e g r i t y , faiittre to p r o p e r l y m a i n t a i n records, and non-compliance with experimental protocol), a n d 1 w a s r e m o v e d for f a i l u r e to d e v e l o p D O M S in e i t h e r trial. T h e r e m a i n i n g 19 s u b j e c t s c o n s i s t e d o f 6 w o m e n a n d 13 m e n w h o ( r a n g e : 2 4 - 4 8 years).
a v e r a g e d 35 y e a r s o f a g e
T h e o u t c o m e s f r o m all 4 a s s e s s m e n t m e t h o d s w e r e u s e d to d e t e r m i n e if a n y o r d e r i n g (i.e., c a r r y - o v e r ) e f f e c t wa~ at w o r k b e t w e e n t h e 2 trials. B o t h m u l t i v a r i a t e a n d u n i v a r i a t e p a r a m e t r i c t e s t s as well as n o n - p a r a metric analyses yielded no significant ordering effects
319
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Fig. 1. Average soreness observed over postexercise period while the
Fig. 2. Average soreness observed over postexercise period while the subject stretched his/her posterior calf by forced dorsiflexion of their foot to a 45 ° ankle angle. Note: time scaling alternates belween l0 and 14 h except for a 24-h period at the end of the observation
subject was sitting at rest. Note: time scaling alternates between 10 and 14 h except for a 24-h period at the end of the observation interval.
period.
at any of the 8 soreness assessment times for the exercise, stretch and resting methods ( P > 0.05). An analysis of the palpation assessment method indicated an ordering effect at one measurement point (34 h) and, therefore, this data was not used further, despite a significant difference between treatment and placebo groups. Comparisons were then made between subjects given ascorbic acid or lactose placebo, and the average VAS soreness scores across the 4-day postexercise period are displayed in Figs. 1-3. The divergence of treatment and placebo groups began at approximately 34 h postexercise, reached a maximum at approximately 58 h, and ended at approximately 96 h. Multivariate analysis indicated that there was a significant difference between the groups for the exercise and ,,;tretch assessments; univariate tests showed significance at the 48-, 58- and 72-h measurements for the stretch assessment, and at the 58- and 72-h measurements for the exercise assessment. The average VAS scores for each assessment method at 58 h and at maximum are presented in Tables I and It. The 58-h observation was selected since it represented the time o f g r e a t e s t average pain and the great-
est statistical significance. The maximum score for each subject allowed an evaluation independent of time. Review of the pain scores for individual subjects demonstrated a variation in soreness relief, Using data
EXERCISE ASSESSMENT
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Fig. 3. Average soreness observed over postexercise period while the subject performed a 5-sec bout of the original soreness-producing activity. Note: time scaling alternates between l0 and 14 h except for a 24-h period at the end of the observation interval.
TABLE 1
Assessment
,
72
P + NS < 0.05 < 0.0 !
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TABLE I! IVlEAN MAXIMUM SORENESS SCORES Assessment
Resting Stretch Exercise
Treatment
Placebo
Difference
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T A B L E 111 % Reduction
N
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8 7 4
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from 58-h and maximum scores, subjects are grouped into arbitrary soreness relief categories, and these results are tabulated in Table i!!.
D~scassion
For the purposes of this study, DOMS rcduction was defined as a difference in average soreness between ,'l placebo group and an ascorbic acid treatment group. The largest reduction was observed at the height of DOMS. For approximately one-half of the subjects, there was substantial soreness relief ( > 33% reduction in soreness from placebo); however, several subjects showed no remarkable difference between the ascorbic acid and placebo trials. Whether these non-responders are unique test subjects or simply represent experimental errors is unknown. All 4 assessment methods appeared to show the ascorbic acid effect on DOMS. The palpation method demonstated a limited ordering effect and was excluded from a presentation of findings; furthermore, interpretation of the palpation assessment would have been complicated by the likely variability in subject self-assessment of tenderness (i.e., the location and force used to monitor pain was not controlled). Not surprisingly the resting assessment showed the least effect since DOMS produces a relatively low level of background pain. The stretch assessment may be of limited value because the 45° ankle angle used to stretch the calf was probably excessive in that some subjects reported pain even in their control leg. The
exercise assessment seemed to be the most realistic in approximating the normal use of the leg; furthermore, the amount of force used to elicit pain with this assessment is crodely metered out by the weight of the subject, and the procedure can easily be duplicated between experimental and control legs. There are important limitations of this study that warrant further analysis and consideration. First, the relatively small subject pool requires caution in the interpretation of these results. A substantial increase in sample size within both experimental and placebo groups is necessary to strengthen any claims of soreness reduction by ascorbic acid. Second, the lack of an untreated control group raises the question of what role any placebo effect may play in these results. Third, leg dominance, although there are no indications in the literature that it is important, may be a confounding factor since it was not randomized in this trial. Finally, the strenuous eccentric use of the plantar flexors employed in this investigation may not easily generalize to large muscle groups elsewhere in the body, and it remains to be seen if the effect can be observed with lesser unaccustomed activities. Further studies of ascorbic acid and DOMS should also address the dosage and time of delivery of the supplement. Since this project used large oral dosages of ascorbic acid, it would be important to learn if ,~ substantially lower dosage (perhaps 500 mg/day) would be equally effective in the abatement of DOMS; establishing a dose-dependent relationship between ascorbic acid and this soreness should be one of the goals of future research in this area. Alternatively, the treatment delivery period might be varied to learn if presaturation with ascorbic acid was necessary to produce the effect (e.g., treatment may be shown to be equally effective if delivered at 24 h after the unaccustomed exercise). Whether ascorbic acid may serve to prevent the injury (i.e., prophylaxis) or simply minimize the painful symptoms (i.e., analgesia), there are important experiments that could be performed that might begin to uncover its mechanism of action on DOMS. For example, it would be interesting to learn if ascorbic acid cannot only lessen the perception of soreness but also reduce any previously studied changes in plasma crea-
321
tine kinase activity (Schwane et al. 1983; Tiidus and lanuzzo 1983; Newham et al. 1986; Triffletti et al. 1988), skeletal muscle tissue morphology (Armstrong et al. 1983; Frid6n 1984; Clarkson and Trembley 1988) or calcium homeostasis (Clarkson and Trembley 1988; Duan et al. 1990). Observing an attenuation of these parameters might suggest a protective role for ascorbic acid in skeletal muscle or associated connective tissue. Furthermore, changing the treatment delivery period may uncover evidence which favors one mechanistic scheme over another. If the body must be saturated with ascorbic acid prior to exercise to observe the effect, then this would suggest a possible mechanism related to collagen synthesis and integrity given ascorbic acid's well known cofactor role for this protein (Englard and Seifter 1986). Whatever model is developed for DOMS, it should encompass the ascorbic acid findings of this study. In summary, this investigation suggests that ascorbic acid may significantly reduce the delayed soreness typically seen following the strenuous use of muscles in an unaccustomed manner. Supplementation appears to blunt the reported soreness, showing the greatest effect when DOMS was at its peak. However, more extensive studies using larger sample sizes will be needed to strengthen this assertion.
,Acknowledgements
The authors wish to acknowledge the vital efforts of Mitchell Haas for statistical assistance. Additionally, the work of Richard Gill,~tte for aid with experimental design, the WSCC Research and Publications Committee for manuscript review, and James Edward Perkins fc,r the original stimulus are greatly appreciated.
References Abraham, W.M., Factors in delayed muscle soreness, Med. Sci. Sports Exerc., 9 (1977) ! 1-20. Ar~astrong, R.B., Mechanisms of exercise-induced delayed onset "nuscular soreness: a brief review, Med. Sci. Sports Exerc., 16 (1984) 529-538. Armstrong, R.B., Ogilvie, R.W. and Schwane, J.A., Eccentric exercise-induced injury to rat skeletal muscle, J. Appl. Physiol., 54 (1983) 80-93. Armstrong, R.B., Warren, G.L. and Warreu, J.A., Mechanisms of exercise-induced muscle fibre injury, Sports Med., 12 (1991) 184207. Bobbert, M.F., Hollander, A.P. and Huijing, P.A., Factors in delayed onset muscular soreness in man, Med. Sci. Sports Exerc., 18 (1986) 75-81. Clarkson, P.M. and Trembley, I., Rapi~ adaptation to exercise to induced muscle damage, J. Appl. Physiol., 65 (1988) 1-6. Dene~;ar, C.R., Perrin, D.H., Rogol, A.D. and Rutt, R., Influence of transcutaneous electrical nerve stimulation on pain, range of
motion, and serum cortisol concentration in females experiencing delayed onset muscle soreness, J. Orthop. Sports Phys. Ther., 11 (1989) 100-103. Duan, C.; Delp, M.D., Hayes, A., Delp, P.D. and Armstrong, R.B., Rat skeletal muscle mitochondrial [Ca +2] and injury from downhill walking, J. Appl. Physiol., 68 (1990) 1241-1251. Ebbeling, C.B. and Clarkson, P.M., Exercise-in~u,.ed muscle damage and adaptation, Sports Med., 7 (1989)207-234. Englard, S. and Seifter, S., The biochemical functions of ascorbic acid, Ann. Rev. Nutr., 6 (1986) 365-406. Francis, K.T. and Hoobler, T., Effects of aspirin on delayed muscle soreness, J. Sports Med., 7 (1987) 333-337. Frid6n, J., Muscle soreness after exercise: implications of morphological changes, Int. J. Sports Med., 5 (1984) 57-66. Headley, S.A.E., Newham, D.J. and Jones, D.A., The effect of prednisolone on exercise induced muscle pain and damage, Clin. Sci., 70, Suppl. 13 (1987) 85P. Hough, T., Ergographic studies of muscular soreness, J. Appl. Physiol., 7 (1902) 76-92. Howell, J.N., Chila, A.G., Ford, G., David, D.D. and Gates, T., An electromyographic study of elbow motion during postexercise muscle soreness, J. Appl. Physiol., 58 (1085) 1713-1718. Janssen, E., Kuipers, H., Verstappen, F. and Costill, D., Influenc.e of an anti-inflammatory drug on muscle soreness, Med. Sci. Sports Exer., 15 (1983) 165. Jones, D.A., Newham, D.J. and Clarkson, P.M., Skeletal muscle stiffness and pain following eccentric exercise of the elbow flexors, Pain, 30 (1987) 233-242. Kulig, K., Isles, S., Rapaski, D. and Smith, J., Comparison of three microcurrent stimulation protocols in reducing delayed onset muscle soreness and edema, Phys. Ther., 70 (Suppl.)(1990) R222. Melethil, S., Subrahmanyam, M.B., Chang, C.J. and Mason, W.D., Megadoses of vitamin C: a pharmacokinetic evaluation, Ann. NY Acad. Sci., 498 (1987) 491-493. Monroe, B., Vitamin C can be of help to hunters, The Oregonian, (November 14, 1990)E8. Mueller, L., C-cret for soreness, Outdoor Life, 178 (1986) 76-78. Newham, D.J., Jones, D.A. and Clarkson, P.M., Repeated high-force eccentric exercise: effects on muscle pain and damage, J. Appl. Physiol., 63 (1987) 1381-1386. Newham, D.J., Jones, D.A. and Edwards, H.T., Plasma creatine kinase changes after eccentric and concentric contractions, Muscle Nerve, 9 (1986) 59-63. Norusis, M.J., SPSS/PC+ Statistics 4.0, SPSS Inc., Chicago, IL, 1990a. Norusis, M.J., SPSS/PC+ Advanced Statistics 4.0, SPSS Inc., Chicago, IL, 1990b. Rosner, B., Fundamentals of Biostatistics, 2nd edn., Duxbury Press, Boston, MA, 1986, pp. 283-293. Schwane, J.A., Johnson, S.R., Vandenakker, C.B. and Armstrong, R.B., Delayed-onset muscular soreness and plasma CPK and LDH activities after downhill running, Med. Sci. Sports Exerc., 15 (1983) 51-56. Staton, W.M., The influence of ascorbic acid in minimizing post-exercise muscle soreness in young men, Res. Quart., 23 (1952) 356 360. Syed, I.H., Muscle stiffness and vitamin C (letter), Br. Med. J., 2 (~966) 304. Talag, T.S., Residual muscular soreness as influenced by concentric, eccentric, and static contractions, Res. Quart., 44 (i973) 458-469. Tiidus, P.M. and hmuzzo, C.D., Effects of intensity and duration of muscular exercise on delayed soreness and serum enzyme activities, Med. Sci. Sports Exerc., 15 (1983) 461-465. Triffletti, P., Litchfield, P.E., Clarkson, P.M. and Byrnes, W.C., Creatine kinase and muscle soreness aider repeated isometric: exercise, Med. Sci. Sports Exerc., 20 (1988)242-248.
