European Journalo f
Europ. J. appl. Physiol. 36, 231--238 (1977)
Applied
Physiology
and Occupational Physiology c by Springer-Verlag 1977
Blood Biochemical Alterations during Recovery from Competitive Marathon Running* Michael B. Maron, Steven M. Horvath, and James E. Wilkerson 1 Institute of Environmental Stress, University of California, Santa Barbara, Santa Barbara, California 93106, USA
Summary. The occurrence of possible prolonged alterations in plasma levels of cortisol, epinephrine, norepinephrine, selected energy metabolites, and water and electrolyte balance was assessed in six highly trained male marathon runners by measuring blood biochemical constituents on the 10th day before and for the three days following the running of a marathon. Post-race changes in hemoglobin, hematocrit, and protein levels indicated that a hemodilution had occurred, possibly as a result of elevated sodium levels. Epinephrine remained elevated until the second day. Cortisol was depressed on the first and third post-race days while variable levels were observed on the second day. No prolonged alterations were noted in norepinephrine, FFA, glycerol, triglycerides, glucose, lactate, and pyruvate. Key words: Marathon -- Catecholamines - Cortisol - Fluid balance - Intermediary metabolites.
Introduction Previous studies investigating the blood biochemical responses to marathon (26.2 mi, 42.2 km) running have generally only been concerned with alterations observed immediately post-race. However, in view of the prolonged recovery period many runners stated was necessary after such an effort, the question arises whether any of these previously observed biochemical alterations persist for prolonged periods following the run. Recently, Riley et al. [13] reported sustained elevations in the serum levels of uric acid, phosphate, and various blood enzymes which were still apparent up to 30 h after a marathon race. However, only one of their five runners was able to complete the run. We were fortunate in being able to further investigate * This work was supported in part by the Air Force Office of Scientific Research, Air Force Systems Command, Grant AFOSR 73-2455 1 The present address of Dr. J. E. Wilkerson is the Department of Physical Education, Indiana University, Bloomington, Indiana 47401, USA
232
M.B. Maron et al.
this q u e s t i o n in a g r o u p o f r u n n e r s ( w h o h a d r u n similar t i m e s for t h e m a r a t h o n : 2 : 3 7 : 3 7 - - 2 : 4 8 : 4 6 ) b y s t u d y i n g t h e m for a p e r i o d o f t h r e e d a y s f o l l o w i n g t h e race. I m m e d i a t e p o s t - r a c e d a t a for t h e s e r u n n e r s h a v e b e e n r e p o r t e d p r e v i o u s l y [7].
Methods Selected blood biochemical constituents were measured in six highly trained male marathon runners 2 10 days prior to the running of the marathon, on the day of the race, and for the following three days. The runners' physical characteristics and pre- and post-race alterations in blood biochemistry have been previously described [7]. Since the runners' pre-race meals could not be dictated, prior to each blood sampling the runners were asked to eat an identical breakfast to that which they would have on the day of the marathon and at the same time. Breakfasts were consumed approximately 11/2h prior to blood sampling and generally consisted of a bowl of hot cereal or several slices of toast. All blood samples were drawn at 8 a.m. At each blood sampling, the supine subjects had 24 ml of venous blood withdrawn without stasis from an antecubital vein into two plastic syringes. The dead space of one syringe was filled with sodium metabisulfite [3, 12] dissolved in heparin (5000 USP units/ml). The other syringe was untreated to obtain serum. The runners did not run before blood sampling - the control blood sample being drawn at least 16 h following the runner's last training run. No other restrictions were placed on diet or activity, but the runners were asked to keep a dietary and training log for the duration of the study. Between control and race days the runners pursued their normal activities but reduced their mileage run in training by approximately one half and increased their carbohydrate intake in preparation for the marathon. During the three days following the race the runners consumed their usual meals and did little or no running. Hematocrit was determined by the microhematocrit method with a 5% correction being made for trapped plasma 3, hemoglobin by the cyanmethemoglobin technique, serum sodium by flame photometry, and total plasma blood proteins by use of a Goldberg refractometer. Lactate was assayed by the modified Str6m [15] method, cortisol by radioimmunoassay [2], epinephrine and norepinephrine by fluorometry [3, 12] and plasma hemoglobin by a modification of the benzidine technique [4]. Free fatty acids and glucose were determined within 24 h of sampling by the Novak [11] and Hyeel methods (Hycel Inc., Houston, Texas), respectively. Triglycerides, free glycerol, and pyruvate were analyzed utilizing kits purchased from the Boehringer-Mannheim Company. In addition a single control blood volume measurement was made on each runner using the carbon monoxide rebreathing technique of Myhre et al. [9]. Biochemical data were expressed both in concentration and as a function of the hemoglobin concentration to correct for possible fluid shifts and analyzed utilizing a single-factor analysis of variance with repeated measures across treatment conditions. Where significant interaction effects were found a further analysis was made of the simple main effects followed by a Newman-Keuls test of ordered means at the 0.05 level of significance [17].
Results S i n c e p r e - r a c e b l o o d s a m p l e s m i g h t n o t b e r e p r e s e n t a t i v e o f a t r u e r e s t i n g state, a d d i t i o n a l c o n t r o l v e n o u s s a m p l e s w e r e d r a w n in t h e l a b o r a t o r y 10 d a y s p r i o r t o t h e race. N o r e p i n e p h r i n e , glucose, a n d in s o m e c a s e s e p i n e p h r i n e w e r e e l e v a t e d o n t h e 2 The nature and purpose of the study and the risks involved were explained verbally and given on a written form to each subject prior to their voluntary consent to participate. The protocol and procedures for this study have been approved by the Committee on Activities Involving Human Subjects, of the University of California, Santa Barbara, USA 3 Based on data obtained in our laboratories using 51Cr-labelled RBC's with ~25RISA used as a plasma marker
4.84 1.40 0.158 0.45 0.9 56.8
Glucose(mM) Lactate(raM) Pyruvate (raM) FFA(mEq/I) Glycerol (mg%) Triglycerides (mg%)
0.23 0.19 0.016 0.07 0.1 8.4
5.49 1.08 0.113 0.30 1.0 77.1
• 0.16 • 0.06 _+ 0.008 +_ 0.06 • 0.1 _+ 13.4
• • • • • •
0.20 0.27 0.020 0.29 0.6 8.7
6.03 1.92 0.175 1.74 5.2 60.6
4.69 1.33 0.158 0.42 1.0 44.7
a Race day b p < 0.05, P < 0.05, P < 0.05,
9.3 45.3 7.0 143 0.795 0.968 16.84
Hemoglobin (mM) Hematoerit (%) Plasma proteins (g%) Serum sodium (mEq/1) Epinephrine (ng/ml) Norepinephrine (ng/ml) Cortisol (~g%)
mean data (Maron et al., 1975) compared to control compared to post day one compared to post day three
• 0.2 • 0.6 _+ 0.1 • 1 • 0.204 k 0.092 • 0.81
Control
Parameter
• • • • • + •
8.8 42.8 6.8 139 1.583 1.005 10.38
• 0.2 • 0.7 • 0.2 • i • 0.217 +_ 0.344 • 0.75
9,6 46.9 8.3 141 1,814 2.715 27.95
• 0.1 • 0.4 • 0.1 + 1 +_ 0.365 +_ 0.242 • 0.49
Day 1
Post
Pre 9.2 46.6 7.2 141 1.121 1.608 17.56
Post-race
Race day a
• • • • • •
Day 1
Pre
Post
Post-race
Race day ~
Table 2. Mean biochemical data • SEM for sample periods: control, and days 1, 2, and 3 post-race
Race day mean data (Maron et al., 1975)
• • • • • •
Control
Parameter
Table 1. Mean energy substrate levels • SEM for control, race, and post-race days
Day 2
4.60 1.46 0.155 0.43 1.2 73.6
0.2 8.6 0.7 t' 40.4 0.I 6.4 0b 146 0.336 bd 0.920 0.152 1.044 0.90 b 12.66
0.1 3.5
0.17 0.17 0.015
Day 2
• 0.1 bd • 0.9 bc'~ _+ 0.1 t'r +_ 2t'r _+ 0.165 c +_ 0.154 • 1.59bd
• 0.22 • 0.17 • 0.018 +_0.05 • 0.1 + 8.1
8.8 42.7 6.9 140 0,879 0.913 8.14
Day 3
4.87 1.47 0.133 0.37 1.1 78.9
Day 3
• • • • • + •
0.2 0.4 t' 0.1 1b 0.121 e 0.240 0,46 b
• 0.31 • 0.14 • 0.006 • 0.06 • 0.1 • 16.0
O
o
o
7~
5"
t~
234
M.B. Maron et al.
morning of the race, probably as a reflection of anxiety [7]. In spite of the runners' change in dietary and training patterns between the control and race days, no alterations were observed in any of the other measured resting blood constituent levels (Tables 1 and 2). Therefore, the values for resting blood biochemistry obtained on the control day were considered to be representative of the runners' true resting state prior to the race and were used for comparison of post-race data. Mean data for the four measurement days are presented in Tables 1 and 2. Hemoglobin, hematocrit, and plasma protein showed a similar pattern for the three post-race days. On the first day after the marathon, hemoglobin, hematocrit, and plasma protein concentrations were respectively 5.4% (N.S.), 5.5% (P < 0.05), and 2.9% (N.S.) lower than control values. By ,the second day, these values were further depressed, being respectively, 7.5% (P < 0.05), 10.8% (P < 0.05), and 8.6% (P < 0.05) lower than control. On the third day after the race, both hemoglobin and hematocrit had essentially returned to values observed on post day one but were still below control while plasma protein levels had returned to control. Correction of plasma protein concentration for possible plasma volume changes indicated that plasma protein content was not significantly different from control on any of the three post-race days. Both plasma hemoglobin and the mean corpuscular hemoglobin concentration remained constant on all days of the study. Plasma volume changes as calculated by the method of Dill and Costill [5], and utilizing control blood volume measurements to estimate absolute changes indicated that plasma volume increased for the first two days after the race. Serum sodium concentration was significantly lower than control on post days one and three (P < 0.05). On the second day after the race however, sodium concentrations were significantly higher than control, day one, and day three (P < 0.05). Correction for hemodilution indicated that the absolute sodium content of the blood on days one, two, and three was respectively 3.2, 9.9, and 3.8% higher than control, but the only relationship of statistical significance was Na/Hb on day two being greater than control (P < 0.05). Mean cortisol levels on all three days after the marathon were significantly lower than control (P < 0.05), but a clearer picture of cortisol alterations was observed when the individual data were considered. On post day one, every runner had depressed eortisol levels, but on days two and three, variable patterns were observed (Fig. 1). Correction of cortisol levels for hemodilution did not alter these patterns. Epinephrine concentrations on day one were significantly greater than control, daytwo, and day-three values, relationships which did not change upon correction for hemodilution. Glucose, lactate, pyruvate, free fatty acid, glycerol, triglyceride, and norepinephrine levels on the three days were not significantly different from control values expressed either as concentrations or corrected for hemodilution.
Discussion
The possibility that strenuous protracted exertion (e.g. marathon running) might evoke prolonged metabolic alterations has heretofore received little attention. The perturbations in blood chemistry observed to occur in our runners during the three days following a marathon run however indicated that some forms of exertion may
Blood BiochemicalAlterations during Recovery from Marathon Running
235
well indeed result in disturbances which remain apparent long after the original stress has ceased. While indications of prolonged alterations at the hormonal level were provided by the patterns of epinephrine and cortisol levels observed in the runners during the post-race days, the significance of such changes is not clear. Inasmuch as the persistence of elevated epinephrine levels until the second day following the race suggested that there might be accompanying alterations in energy metabolism occurring during this period, any elevations observed immediately post race [7] in the concentrations of the blood substrates measured in this study (Table 1) were no longer apparent by the next morning. This does not negate the possibility of epinephrine induced metabolic effects, as the substrates measured in this investigation represent only selected indices of a limited number of processes epinephrine is known to modulate. In addition it must also be considered that blood concentrations may not necessarily reflect changes in turnover rates. Cortisol levels for the three days following the race were generally depressed with the mean values more closely approximating normal levels observed both in these runners (1t.93 vg%) [7], and in normal controls [2] at 11 a.m. rather than at 8 a.m. However there was considerable variation in individual levels on post day two (Fig. 1). In contrast to the elevated levels [7] exhibited immediately post race by these runners, Viru and Ktrge [16] reported immediate (5 min) post-race decrements in plasma cortisol of approximately one-half the magnitude of those reported here for the post-race days. In the absence of any evidence for increased hemolysis the decline in hemoglobin and hematocrit for the first two days probably reflected the occurrence of a progressive hemodilution. Similar changes in plasma protein concentration on these days further strengthened this interpretation. Hemoglobins and hematocrits on the third day were identical to those observed on day one and probably reflected a trend towards control values. One runner, who we were able to study for a longer period, required six post-race days (Fig. 2) before his control hematocrit value was reattained supporting the concept of prolonged recovery. It was estimated that these hemoglobin and hematocrit values reflected increments in plasma volume of 364 ml or 10.1% on days one and three and 597 ml or 16.5% on day two. Although a causal relationship cannot be demonstrated from these data a possible explanation for the observed sequence of plasma volume shifts may lie in the pattern of elevated total sodium content of the blood calculated to have occurred in the three days following the race. Such an increase in sodium would be expected to exert an osmotic influence causing an increase in plasma volume. This interpretation is consistent with the results of previous studies implicating alterations in renal salt conserving activity during and after prolonged work. In an investigation conducted during the 1902 Boston Marathon, Connolly, under the direction of Blake and Larrabee [1] observed a reduction in the post-marathon 24-h urinary chloride output in three runners studied before and after the race. Calculations utilizing their data indicated that the magnitude of the observed renal chloride retention could not be accounted for by a decreased chloride output occurring solely during the period of the race, i.e. chloride output remained diminished during the remainder of the 24 h period. One runner restudied one week after the race however, exhibited a significant water and chloride diuresis and an enhanced urea excretion as
236
M.B. Maron et al.
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Alterations in cortisol levels in the three days following a marathon. Arrows point to control-day levels. Numerical figures are the runners' race times in minutes F i g . 1.
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Europ. J. appl. Physiol. 36, 231--238 (1977)
Applied
Physiology
and Occupational Physiology c by Springer-Verlag 1977
Blood Biochemical Alterations during Recovery from Competitive Marathon Running* Michael B. Maron, Steven M. Horvath, and James E. Wilkerson 1 Institute of Environmental Stress, University of California, Santa Barbara, Santa Barbara, California 93106, USA
Summary. The occurrence of possible prolonged alterations in plasma levels of cortisol, epinephrine, norepinephrine, selected energy metabolites, and water and electrolyte balance was assessed in six highly trained male marathon runners by measuring blood biochemical constituents on the 10th day before and for the three days following the running of a marathon. Post-race changes in hemoglobin, hematocrit, and protein levels indicated that a hemodilution had occurred, possibly as a result of elevated sodium levels. Epinephrine remained elevated until the second day. Cortisol was depressed on the first and third post-race days while variable levels were observed on the second day. No prolonged alterations were noted in norepinephrine, FFA, glycerol, triglycerides, glucose, lactate, and pyruvate. Key words: Marathon -- Catecholamines - Cortisol - Fluid balance - Intermediary metabolites.
Introduction Previous studies investigating the blood biochemical responses to marathon (26.2 mi, 42.2 km) running have generally only been concerned with alterations observed immediately post-race. However, in view of the prolonged recovery period many runners stated was necessary after such an effort, the question arises whether any of these previously observed biochemical alterations persist for prolonged periods following the run. Recently, Riley et al. [13] reported sustained elevations in the serum levels of uric acid, phosphate, and various blood enzymes which were still apparent up to 30 h after a marathon race. However, only one of their five runners was able to complete the run. We were fortunate in being able to further investigate * This work was supported in part by the Air Force Office of Scientific Research, Air Force Systems Command, Grant AFOSR 73-2455 1 The present address of Dr. J. E. Wilkerson is the Department of Physical Education, Indiana University, Bloomington, Indiana 47401, USA
232
M.B. Maron et al.
this q u e s t i o n in a g r o u p o f r u n n e r s ( w h o h a d r u n similar t i m e s for t h e m a r a t h o n : 2 : 3 7 : 3 7 - - 2 : 4 8 : 4 6 ) b y s t u d y i n g t h e m for a p e r i o d o f t h r e e d a y s f o l l o w i n g t h e race. I m m e d i a t e p o s t - r a c e d a t a for t h e s e r u n n e r s h a v e b e e n r e p o r t e d p r e v i o u s l y [7].
Methods Selected blood biochemical constituents were measured in six highly trained male marathon runners 2 10 days prior to the running of the marathon, on the day of the race, and for the following three days. The runners' physical characteristics and pre- and post-race alterations in blood biochemistry have been previously described [7]. Since the runners' pre-race meals could not be dictated, prior to each blood sampling the runners were asked to eat an identical breakfast to that which they would have on the day of the marathon and at the same time. Breakfasts were consumed approximately 11/2h prior to blood sampling and generally consisted of a bowl of hot cereal or several slices of toast. All blood samples were drawn at 8 a.m. At each blood sampling, the supine subjects had 24 ml of venous blood withdrawn without stasis from an antecubital vein into two plastic syringes. The dead space of one syringe was filled with sodium metabisulfite [3, 12] dissolved in heparin (5000 USP units/ml). The other syringe was untreated to obtain serum. The runners did not run before blood sampling - the control blood sample being drawn at least 16 h following the runner's last training run. No other restrictions were placed on diet or activity, but the runners were asked to keep a dietary and training log for the duration of the study. Between control and race days the runners pursued their normal activities but reduced their mileage run in training by approximately one half and increased their carbohydrate intake in preparation for the marathon. During the three days following the race the runners consumed their usual meals and did little or no running. Hematocrit was determined by the microhematocrit method with a 5% correction being made for trapped plasma 3, hemoglobin by the cyanmethemoglobin technique, serum sodium by flame photometry, and total plasma blood proteins by use of a Goldberg refractometer. Lactate was assayed by the modified Str6m [15] method, cortisol by radioimmunoassay [2], epinephrine and norepinephrine by fluorometry [3, 12] and plasma hemoglobin by a modification of the benzidine technique [4]. Free fatty acids and glucose were determined within 24 h of sampling by the Novak [11] and Hyeel methods (Hycel Inc., Houston, Texas), respectively. Triglycerides, free glycerol, and pyruvate were analyzed utilizing kits purchased from the Boehringer-Mannheim Company. In addition a single control blood volume measurement was made on each runner using the carbon monoxide rebreathing technique of Myhre et al. [9]. Biochemical data were expressed both in concentration and as a function of the hemoglobin concentration to correct for possible fluid shifts and analyzed utilizing a single-factor analysis of variance with repeated measures across treatment conditions. Where significant interaction effects were found a further analysis was made of the simple main effects followed by a Newman-Keuls test of ordered means at the 0.05 level of significance [17].
Results S i n c e p r e - r a c e b l o o d s a m p l e s m i g h t n o t b e r e p r e s e n t a t i v e o f a t r u e r e s t i n g state, a d d i t i o n a l c o n t r o l v e n o u s s a m p l e s w e r e d r a w n in t h e l a b o r a t o r y 10 d a y s p r i o r t o t h e race. N o r e p i n e p h r i n e , glucose, a n d in s o m e c a s e s e p i n e p h r i n e w e r e e l e v a t e d o n t h e 2 The nature and purpose of the study and the risks involved were explained verbally and given on a written form to each subject prior to their voluntary consent to participate. The protocol and procedures for this study have been approved by the Committee on Activities Involving Human Subjects, of the University of California, Santa Barbara, USA 3 Based on data obtained in our laboratories using 51Cr-labelled RBC's with ~25RISA used as a plasma marker
4.84 1.40 0.158 0.45 0.9 56.8
Glucose(mM) Lactate(raM) Pyruvate (raM) FFA(mEq/I) Glycerol (mg%) Triglycerides (mg%)
0.23 0.19 0.016 0.07 0.1 8.4
5.49 1.08 0.113 0.30 1.0 77.1
• 0.16 • 0.06 _+ 0.008 +_ 0.06 • 0.1 _+ 13.4
• • • • • •
0.20 0.27 0.020 0.29 0.6 8.7
6.03 1.92 0.175 1.74 5.2 60.6
4.69 1.33 0.158 0.42 1.0 44.7
a Race day b p < 0.05, P < 0.05, P < 0.05,
9.3 45.3 7.0 143 0.795 0.968 16.84
Hemoglobin (mM) Hematoerit (%) Plasma proteins (g%) Serum sodium (mEq/1) Epinephrine (ng/ml) Norepinephrine (ng/ml) Cortisol (~g%)
mean data (Maron et al., 1975) compared to control compared to post day one compared to post day three
• 0.2 • 0.6 _+ 0.1 • 1 • 0.204 k 0.092 • 0.81
Control
Parameter
• • • • • + •
8.8 42.8 6.8 139 1.583 1.005 10.38
• 0.2 • 0.7 • 0.2 • i • 0.217 +_ 0.344 • 0.75
9,6 46.9 8.3 141 1,814 2.715 27.95
• 0.1 • 0.4 • 0.1 + 1 +_ 0.365 +_ 0.242 • 0.49
Day 1
Post
Pre 9.2 46.6 7.2 141 1.121 1.608 17.56
Post-race
Race day a
• • • • • •
Day 1
Pre
Post
Post-race
Race day ~
Table 2. Mean biochemical data • SEM for sample periods: control, and days 1, 2, and 3 post-race
Race day mean data (Maron et al., 1975)
• • • • • •
Control
Parameter
Table 1. Mean energy substrate levels • SEM for control, race, and post-race days
Day 2
4.60 1.46 0.155 0.43 1.2 73.6
0.2 8.6 0.7 t' 40.4 0.I 6.4 0b 146 0.336 bd 0.920 0.152 1.044 0.90 b 12.66
0.1 3.5
0.17 0.17 0.015
Day 2
• 0.1 bd • 0.9 bc'~ _+ 0.1 t'r +_ 2t'r _+ 0.165 c +_ 0.154 • 1.59bd
• 0.22 • 0.17 • 0.018 +_0.05 • 0.1 + 8.1
8.8 42.7 6.9 140 0,879 0.913 8.14
Day 3
4.87 1.47 0.133 0.37 1.1 78.9
Day 3
• • • • • + •
0.2 0.4 t' 0.1 1b 0.121 e 0.240 0,46 b
• 0.31 • 0.14 • 0.006 • 0.06 • 0.1 • 16.0
O
o
o
7~
5"
t~
234
M.B. Maron et al.
morning of the race, probably as a reflection of anxiety [7]. In spite of the runners' change in dietary and training patterns between the control and race days, no alterations were observed in any of the other measured resting blood constituent levels (Tables 1 and 2). Therefore, the values for resting blood biochemistry obtained on the control day were considered to be representative of the runners' true resting state prior to the race and were used for comparison of post-race data. Mean data for the four measurement days are presented in Tables 1 and 2. Hemoglobin, hematocrit, and plasma protein showed a similar pattern for the three post-race days. On the first day after the marathon, hemoglobin, hematocrit, and plasma protein concentrations were respectively 5.4% (N.S.), 5.5% (P < 0.05), and 2.9% (N.S.) lower than control values. By ,the second day, these values were further depressed, being respectively, 7.5% (P < 0.05), 10.8% (P < 0.05), and 8.6% (P < 0.05) lower than control. On the third day after the race, both hemoglobin and hematocrit had essentially returned to values observed on post day one but were still below control while plasma protein levels had returned to control. Correction of plasma protein concentration for possible plasma volume changes indicated that plasma protein content was not significantly different from control on any of the three post-race days. Both plasma hemoglobin and the mean corpuscular hemoglobin concentration remained constant on all days of the study. Plasma volume changes as calculated by the method of Dill and Costill [5], and utilizing control blood volume measurements to estimate absolute changes indicated that plasma volume increased for the first two days after the race. Serum sodium concentration was significantly lower than control on post days one and three (P < 0.05). On the second day after the race however, sodium concentrations were significantly higher than control, day one, and day three (P < 0.05). Correction for hemodilution indicated that the absolute sodium content of the blood on days one, two, and three was respectively 3.2, 9.9, and 3.8% higher than control, but the only relationship of statistical significance was Na/Hb on day two being greater than control (P < 0.05). Mean cortisol levels on all three days after the marathon were significantly lower than control (P < 0.05), but a clearer picture of cortisol alterations was observed when the individual data were considered. On post day one, every runner had depressed eortisol levels, but on days two and three, variable patterns were observed (Fig. 1). Correction of cortisol levels for hemodilution did not alter these patterns. Epinephrine concentrations on day one were significantly greater than control, daytwo, and day-three values, relationships which did not change upon correction for hemodilution. Glucose, lactate, pyruvate, free fatty acid, glycerol, triglyceride, and norepinephrine levels on the three days were not significantly different from control values expressed either as concentrations or corrected for hemodilution.
Discussion
The possibility that strenuous protracted exertion (e.g. marathon running) might evoke prolonged metabolic alterations has heretofore received little attention. The perturbations in blood chemistry observed to occur in our runners during the three days following a marathon run however indicated that some forms of exertion may
Blood BiochemicalAlterations during Recovery from Marathon Running
235
well indeed result in disturbances which remain apparent long after the original stress has ceased. While indications of prolonged alterations at the hormonal level were provided by the patterns of epinephrine and cortisol levels observed in the runners during the post-race days, the significance of such changes is not clear. Inasmuch as the persistence of elevated epinephrine levels until the second day following the race suggested that there might be accompanying alterations in energy metabolism occurring during this period, any elevations observed immediately post race [7] in the concentrations of the blood substrates measured in this study (Table 1) were no longer apparent by the next morning. This does not negate the possibility of epinephrine induced metabolic effects, as the substrates measured in this investigation represent only selected indices of a limited number of processes epinephrine is known to modulate. In addition it must also be considered that blood concentrations may not necessarily reflect changes in turnover rates. Cortisol levels for the three days following the race were generally depressed with the mean values more closely approximating normal levels observed both in these runners (1t.93 vg%) [7], and in normal controls [2] at 11 a.m. rather than at 8 a.m. However there was considerable variation in individual levels on post day two (Fig. 1). In contrast to the elevated levels [7] exhibited immediately post race by these runners, Viru and Ktrge [16] reported immediate (5 min) post-race decrements in plasma cortisol of approximately one-half the magnitude of those reported here for the post-race days. In the absence of any evidence for increased hemolysis the decline in hemoglobin and hematocrit for the first two days probably reflected the occurrence of a progressive hemodilution. Similar changes in plasma protein concentration on these days further strengthened this interpretation. Hemoglobins and hematocrits on the third day were identical to those observed on day one and probably reflected a trend towards control values. One runner, who we were able to study for a longer period, required six post-race days (Fig. 2) before his control hematocrit value was reattained supporting the concept of prolonged recovery. It was estimated that these hemoglobin and hematocrit values reflected increments in plasma volume of 364 ml or 10.1% on days one and three and 597 ml or 16.5% on day two. Although a causal relationship cannot be demonstrated from these data a possible explanation for the observed sequence of plasma volume shifts may lie in the pattern of elevated total sodium content of the blood calculated to have occurred in the three days following the race. Such an increase in sodium would be expected to exert an osmotic influence causing an increase in plasma volume. This interpretation is consistent with the results of previous studies implicating alterations in renal salt conserving activity during and after prolonged work. In an investigation conducted during the 1902 Boston Marathon, Connolly, under the direction of Blake and Larrabee [1] observed a reduction in the post-marathon 24-h urinary chloride output in three runners studied before and after the race. Calculations utilizing their data indicated that the magnitude of the observed renal chloride retention could not be accounted for by a decreased chloride output occurring solely during the period of the race, i.e. chloride output remained diminished during the remainder of the 24 h period. One runner restudied one week after the race however, exhibited a significant water and chloride diuresis and an enhanced urea excretion as
236
M.B. Maron et al.
~~ 20
iii
:::: o
o
i!i e
Q o~15 d~
A~L6
::::
~
~715
6.2
163.4
::::
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Alterations in cortisol levels in the three days following a marathon. Arrows point to control-day levels. Numerical figures are the runners' race times in minutes F i g . 1.
%~ ,~ %~176
48 ! @
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46 44
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