Recovery from Run Training: Efficacy of a Carbohydrate-Protein Beverage?

Abstract

Post-exercise nutrition is critical to facilitate recovery from training. To determine if added protein (P) or increased carbohydrate (CHO) differentially improves recovery, eight runners ingested: 6% CHO (CHO6), 8% CHO + 2% protein (CHO-P), and isocaloric 10% CHO (CHO10) following a 21-km run plus treadmill run to fatigue (RTF) at 90% VO2max. RTF was repeated after 2 h recovery. After 24 h, a 5 km time trial was performed. Insulin and blood glucose were higher (P < 0.05) following CHO10 compared to CHO-P and CHO6, but did not affect improvement from the first to second RTF (29.6% +/- 6, 40.5% +/- 8.8, 40.5% +/- 14.5) or 5 km time (1100 +/- 36.3, 1110 +/- 37.3, 1118 +/- 36.5 s). CK was not different, but perceived soreness with CHO-P (2.1 +/- 0.5) was lower than CHO10 (5.2 +/- 0.7). Additional calories from CHO or P above that provided in sports drinks does not improve subsequent performance after recovery; but less soreness suggests benefits with CHO-P.

Full text

610
Millard-Stafford is with the Exercise Physiology Laboratory, School of Applied Physiology, Georgia
Institute of Technology, Atlanta, GA 30332-0356. Warren is with the Dept of Physical Therapy and
Applied Physiology Laboratory, Georgia State University, Atlanta, GA 30302. Thomas and Doyle are
with the Dept of Kinesiology and Health, Georgia State University, Atlanta, GA 30302. Snow and
Hitchcock are with the School of Applied Physiology, Georgia Institute of Technology, Atlanta, GA
30332-0356.
International Journal of Sport Nutrition and Exercise Metabolism, 2005, 15, 610-624
© 2005 Human Kinetics, Inc.
Recovery from Run Training:
Effi cacy of a Carbohydrate-Protein
Beverage?
Mindy Millard-Stafford, Gordon L. Warren,
Leah Moore Thomas, J. Andrew Doyle,
Teresa Snow, and Kristen Hitchcock
Post-exercise nutrition is critical to facilitate recovery from training. To determine
if added protein (P) or increased carbohydrate (CHO) differentially improves
recovery, eight runners ingested: 6% CHO (CHO6), 8% CHO + 2% protein (CHO-
P), and isocaloric 10% CHO (CHO10) following a 21-km run plus treadmill run
to fatigue (RTF) at 90% VO2max. RTF was repeated after 2 h recovery. After 24 h, a
5 km time trial was performed. Insulin and blood glucose were higher (P < 0.05)
following CHO10 compared to CHO-P and CHO6, but did not affect improvement
from the fi rst to second RTF (29.6% ± 6, 40.5% ± 8.8, 40.5% ± 14.5) or 5 km time
(1100 ± 36.3, 1110 ± 37.3, 1118 ± 36.5 s). CK was not different, but perceived
soreness with CHO-P (2.1 ± 0.5) was lower than CHO10 (5.2 ± 0.7). Additional
calories from CHO or P above that provided in sports drinks does not improve
subsequent performance after recovery; but less soreness suggests benefi ts with
CHO-P.
Key Words: sports drinks, muscle damage, whey protein
Exercise training is performed with the goal of adaptation so that subsequent exer-
cise capacity is improved. Optimal nutrition is an important aid to facilitate this
recovery from training. For example, prolonged, strenuous training performed over
consecutive days without suffi cient dietary carbohydrate (CHO) can deplete muscle
glycogen (6) and adversely affect exercise performance (17). Muscle glycogen
resynthesis is optimized when suffi cient calories are ingested soon after exercise,
particularly when CHO is ingested immediately after exercise compared to a delay
of 2 h (16). CHO sports drinks consumed within 30 min after running improve
performance 4 h later compared to placebo (10) but not necessarily with additional
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Effi cacy of Protein with Carbohydrate 611
consumption after 1 h of recovery (41). Thus, it is clear that both the provision and
timing of CHO supplementation following exercise is crucial for optimal recovery
of performance. Consequently, athletes have traditionally ingested CHO in the form
of sports drinks or higher-concentrated CHO products (e.g., gels, beverages, bars,
food) when recovering from exercise. Yet, the most optimal CHO product that
promotes training adaptations and enhances subsequent exercise capacity (within
hours or next day) is not well-defi ned (17).
Recently, the co-ingestion of protein and CHO has been considered advanta-
geous when consumed immediately after exercise compared to CHO alone (14, 16,
31). One purported mechanism indicates muscle glycogen re-synthesis is enhanced
when protein is added to a CHO recovery formula (14, 42). Insulinemic responses
are elevated with CHO-protein (CHO-P) feedings after exercise compared to CHO
alone (18, 35, 36) which, in turn, might lead to greater storage of CHO in muscle.
Muscle glycogen replenishment is not necessarily improved, however, when CHO
content is similar to CHO-P and ingested at rates ≥ 1 g/kg of body weight/h (5,
18, 19, 35, 37). Collectively, these studies have been diffi cult to interpret due to
differences in feeding frequency, CHO dosage, caloric content, and protein source
(wheat, whey, casein hydrosylates, or individual amino acids) of the recovery
supplement. In addition, these studies failed to evaluate potential effi cacy related
to exercise performance. Two studies (31, 40) have compared performance fol-
lowing prolonged cycling when either a CHO-P or CHO beverage was consumed
throughout a recovery period. The CHO treatments were not matched for caloric
content with the CHO-P condition, however.
Therefore, the purpose of the present study was to investigate if added calories
(via CHO-P of 3.5:1 ratio or eucaloric CHO) provide ergogenic benefi ts over tra-
ditional CHO sports drink when ingested immediately following training. Sports
drinks are considered a standard treatment to be consumed before, during, and after
training or competition (12). Thus, a moderately concentrated (6%) CHO sports
drink was used as the “control” treatment condition. We sought to further defi ne if
recovery of run performance (within the same day and following day) is enhanced
with additional calories in the form of CHO or CHO-P. Our working hypothesis was
that performance would not be affected over the short-term in trained runners, but
that performance 24 h later would be enhanced due to improved recovery with the
additional calories provided in both CHO and CHO-P versus a lower calorie CHO
sports drink. We felt the advantage observed with CHO-P in previous studies (31,
40) was related primarily to the provision of energy intake (calories).
Methods
Subjects
Nine subjects originally volunteered to participate in the study, but due to an injury
sustained (non-study related) by one male subject, complete data was only obtained
on eight runners (fi ve female and three male). All subjects gave informed consent
approved by the institutional review board. Mean physical characteristics for the
entire group are presented in Table 1. Runners were highly trained as evidenced by
their weekly training distance and 5 km run times. Due to the small subject pool,
no analyses by gender were performed.
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612 Millard-Stafford et al.
Beverage Treatments
Subjects completed a double-blind, cross-over study to examine the effects of three
beverage treatments during recovery from strenuous running. Subjects served as
their own control by completing three test run trials while consuming three dif-
ferent beverages: 1) CHO-P (8% sucrose, 2.3% whey protein isolate containing
branched-chain amino acids, glutamine, and vitamins E and C); 2) isocaloric 10%
CHO or CHO10 (8% sucrose and 2.3% maltodextrin); and 3) commercially-avail-
able sports drink or CHO6 [6% sucrose/glucose drink (Gatorade, The Quaker
Oats Co., Chicago, IL)], all of which used similar fruit punch fl avoring and color.
Osmolality of test beverages was measured via freeze-point depression at the time
of testing and observed to be similar for CHO6, CHO10, and CHO-P (392, 395,
and 404 mosmol/kg, respectively). A minimum of 7 d separated each of the three
experimental run trials. Subjects completed a food record for 2 d prior and the day
of each recovery test session. Runners were instructed to follow a standard normal-
mixed diet (55% carbohydrate, 15% protein, 30% fat) and to replicate this diet prior
to each experimental session. Training records were also obtained for 3 d before
each experimental session (and training replicated on subsequent sessions).
During the fi rst test session, all subjects completed a graded incremental tread-
mill run test to determine peak heart rate, maximal oxygen uptake (VO2max), and
peak workload/run velocity. The run velocity that elicited 90% of VO2max was used
in the subsequent testing sessions to assess short term (2 h) recovery following the
endurance run. Near maximal exercise intensity was selected due to rapid CHO
loading (within 2 h) demonstrated previously (9). There was an average of 7 d (range
of 4 to 15 d) between the initial session and the fi rst recovery test session.
Recovery Test Protocol
Several days following the initial session, subjects reported to the lab in a fasted state
at 0800 h. After providing a urine specimen and obtaining body weight, subjects
completed a 21 km training run at a heart rate estimated to elicit 70% VO2max on a
designated outdoor course. This exercise duration and intensity has been demon-
strated to signifi cantly reduce muscle glycogen concentrations (2). Immediately
Table 1 Physical Characteristics of the Subjects Completing
All Beverage Treatments
Mean (SD) Minimum–maximum
Age (y) 28.6 (6.6) 19 – 38
Height (cm) 169.4 (10.2) 157 – 191
Weight (kg) 59.3 (8.1) 49 – 77
% body fat 11.3 (4.9) 5.2 – 17.3
VO2max (mL–1 · kg–1 · min–1) 56.5 (5.9) 47.5 – 65.7
Best 5 km run (s) 1006.1 (108) 869 – 1110
Training (km/wk) 98.3 (19.8) 72.9 – 137.7
Note. n = 8 (5 women, 3 men).
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Effi cacy of Protein with Carbohydrate 613
upon returning to the lab, subjects ran on a treadmill to volitional fatigue (RTF) at
a workload consistent with 90% VO2max. Subjectsʼ rating of perceived exertion (3)
and heart rate were measured each minute during the run to exhaustion. RTF tests
were performed in thermoneutral lab conditions (21 oC, 40% RH).
The period of interest was the recovery period following the 21 km and initial
RTF (Figure 1). Subjects were fed 1.0 g/kg body weight per hour of the CHO-P
and isocaloric CHO10 during the 2 h recovery. CHO6 was consumed in the same
volume but resulted in a CHO dosage of 0.6 g-1 · kg-1 · h-1. Subjects were given an
additional 700 mL of the test beverage after the fi nal RTF to ingest later that day.
Blood samples were obtained by venipuncture at 1 h recovery and by fi ngerstick
at 0, 30, 45, 90, and 120 min. Blood glucose and lactate were measured at all time
points using a YSI model 2300 StatPlus analyzer (Yellow Springs Instruments,
Inc., Yellow Springs, OH). Insulin was measured at 1 h recovery via ELISA (Linco
Research, Inc., St. Charles, MO).
Following the second beverage ingestion and ~ 90 min following the exhaus-
tive running, subjects completed a 10 cm visual analog scale (VAS) for beverage
palatability. After 2 h of recovery, subjects repeated the run to exhaustion at 90%
VO2max after a brief 5 min warm-up period. The recovery of time to fatigue via a
two bout maximal exercise test (but separated by 4 h) has been used previously to
diagnose training status and the inability to fully recover (i.e., overtraining) (23).
Thus, a similar two bout exercise approach has been used previously to evaluate
recovery of performance but modifi ed by a shorter (2 h) recovery period.
Time Trial Protocol
At 24 h following the recovery test protocol, subjects reported to the track for a 5
km time trial. Subjects repeated the VAS scale for beverage palatability prior to
Figure 1 — Schematic of testing protocol.
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614 Millard-Stafford et al.
running 5 km. A 10 cm VAS for muscle soreness was also completed at this time.
Following active movement (walking across the lab), subjects marked the rating
of “How sore are your legs?” from 0 (not sore at all) to 10 (very, very sore). Spe-
cifi c muscle groups were not palpated prior to obtaining the response. Blood was
obtained via venipuncture from an antecubital vein prior to running. Blood was
collected into 3 mL heparinized Vacutainer tubes. Plasma was obtained after 10
min of centrifugation at 5000 g and 4 oC. Plasma samples were stored at –80 oC
until the time the samples were assayed in duplicate using a CK assay kit (Pointe
Scientifi c 7512-400; Lincoln Park, MI). Enzyme activities were measured at room
temperature but corrected to 30 oC.
Study B
In addition to conducting the main study described above, 24 collegiate cross-
country runners (9 women, 15 men) were assigned to one of the three beverage
treatments (CHO-P, CHO6, and CHO10) and groups were matched by gender and
career best 5 km run time (Table 2). Subjects were involved in the same intercol-
legiate training program and tested within 2 wk following their competitive
season. The test protocol was identical to that described above except plasma
CK was not measured. One advantage of this design was that subjects complet-
ing a single trial would not be affected by the repeated bout effect known to
infl uence muscle soreness.
Statistical Analysis
For the main study, a two factor (beverage by time) ANOVA with repeated measures
was used to compare means from the three beverage treatments. Differences in
5 km time trial performance, plasma insulin, CK, and dietary intake prior to test-
ing were analyzed via one-way ANOVA. A Bonferroni post hoc test was used to
determine differences among means. An alpha level of 0.05 was used to indicate
statistical signifi cance.
Results
Mean calories consumed per trial were similar across the treatments and were 2300
kcal/d. The percent calories from macronutrients (CHO, fat, and protein) prior to
each trial were within ± 5% of target values, averaging 54%, 30%, and 16% of
energy intake, respectively. Training distance was also similar for 3 d prior to each
test session. The 21 km run was completed in 90.0 ± 8.7, 87.9 ± 9.2, and 88.9 ± 5.7
min for CHO6, CHO10, and CHO-P trials, respectively. The mean environmental
conditions were mild for the 21 km run and similar among CHO6, CHO10, and
CHO-P (18.0 oC, 77% RH, 17.0 oC, 68% RH, and 18.7 oC, 68% RH).
Blood Parameters
Blood glucose was signifi cantly elevated at 45 min of recovery with CHO10 com-
pared to CHO-P and CHO6, but no signifi cant differences occurred following the
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Effi cacy of Protein with Carbohydrate 615
second beverage bolus (Figure 2). Blood lactate was elevated following RTF and
fell signifi cantly over time but was unaffected by beverage. Blood lactate remained
elevated above 1 mmol/L throughout recovery. Mean blood insulin levels at 1 h
recovery (Figure 3) were signifi cantly higher (P < 0.05) for CHO10 compared to
CHO6 and CHO-P.
Figure 2 — Blood lactate (top panel) and glucose (bottom panel) over 2 h following 90
min training run and treadmill run to fatigue at 90% VO2max for within-subjects design (n =
8). Arrows indicate times of beverage ingestion during recovery. * indicates signifi cantly
higher (P < 0.05) for 10% carbohydrate drink (CHO10) compared to 6% carbohydrate
drink (CHO6).
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616 Millard-Stafford et al.
Recovery of Run Performance
The improvement in performance of RTF following recovery did not differ sig-
nifi cantly among beverage treatments. When RTF at 90% VO2max was repeated
after 2 h recovery, there was no difference when expressed as increase in absolute
run time (Run 2 in Figure 4) or relative improvement in RTF for each individual.
Subjects ran 40.5% longer with CHO-P and CHO6 and 29.6% longer with CHO10
(P > 0.05). As subjects ran different lengths of time during RTF, therefore, the
minimum duration of 2 min was selected to compare HR and RPE. The percent of
maximum HR used during RTF before and after 2 h recovery was similar among
beverages (~ 97% of HRmax). There was a trend (P = 0.2) for subjects to rate their
effort higher during RTF after ingesting CHO-P during recovery.
Exercise performance 24 h later, assessed by a 5 km time trial on a track, showed
a similar pattern to RTF. Subjects ran 5 km in a similar time following CHO-P
CHO6, and CHO10 beverages (Figure 4, bottom panel). These times were ~ 12%
slower than subjectsʼ career best 5 km run times.
Beverage Acceptability
During 2 h recovery, subjects rated the beverages signifi cantly different in several
aspects of taste and acceptability as illustrated in Figure 5. CHO-P was rated as
signifi cantly lower for overall taste, sweetness versus CHO10, and lower for thirst-
quenching, desire to drink again, and desire to use after training compared to CHO6
and the CHO10. CHO-P was rated signifi cantly higher for bitterness compared to
CHO10 (and a strong trend compared to CHO6 at P = 0.07). There were no sig-
nifi cant differences in ratings of stomach upset, bloating, or nausea.
Figure 3 — Plasma insulin at 1 h following beverage ingestion using the within-sub-
jects design. * indicates signifi cantly higher (P < 0.05) value for 10% carbohydrate drink
(CHO10) compared to 6% carbohydrate (CHO6) and isocaloric carbohydrate-protein
(CHO-P) drink.
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Effi cacy of Protein with Carbohydrate 617
Other 24 h Markers
Ratings of muscle soreness were signifi cantly lower (half as much) when runners
ingested CHO-P during recovery compared to CHO10 (Figure 6). There was no
signifi cant difference in muscle soreness between the CHO treatments, but CHO-P
also tended to elicit lower ratings versus CHO6. Markers of muscle damage might
be expected to be greatest following the fi rst trial compared to the second and third
trials due to a protective effect following bouts of repeated intense exercise (26).
Muscle soreness based on trial order, however, was not signifi cantly different (P =
0.86). Plasma CK was also not signifi cantly affected by trial order. Mean plasma
Figure 4 — (Top panel) Treadmill runs to fatigue at 90% VO2max immediately following the
90 min training run (RUN 1) and repeated after a 2 h recovery period of beverage ingestion
(RUN 2). (Bottom panel) Time trial track run 24 h following the recovery test protocol.
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618 Millard-Stafford et al.
CK was not signifi cantly different among treatments at 24 h, i.e., just prior to the
5 km time trial. Elevations in CK although “mild” were above the normal range
of the enzymatic kit for females (< 75 U/L) and males (< 90 U/L) during all treat-
ments.
Study B
In this additional data set, to verify the fi ndings of reduced muscle soreness, male
and female runners (n = 24) performed one experimental run recovery trial and
beverage treatments were matched according to runnersʼ best 5 km time. The 5
km track time performed 24 h after the recovery protocol was similar relative to
subjectsʼ personal best (percent) among CHO-P (97.3 ± 1.6%), CHO6 (97.1 ± 1%),
and CHO10 (96.4 ± 1.8%). Mean (± standard deviation) 5 km times were also not
different (1068 ± 48, 1030 ± 37, and 1087 ± 55 s for CHO-P, CHO6, and CHO10,
respectively). The 30 to 40 s differential in 5 km time among groups remained
consistent with their previous best time described in Table 2. In addition, in a mag-
nitude strikingly similar to our main study (using within-subjects design), muscle
soreness rating (Figure 6, top) with CHO-P was signifi cantly reduced (again by
about one-half) compared to isocaloric CHO (CHO10), and a non-signifi cant trend
(P = 0.2) compared to CHO6.
Figure 5 — Beverage taste and acceptability ratings for 10% carbohydrate (CHO10),
6% carbohydrate (CHO6) and isocaloric carbohydrate-protein (CHO-P) drinks.* indicates
signifi cantly different rating for CHO-P compared to CHO6 and CHO10. ● indicates sig-
nifi cantly different rating for CHO-P compared to CHO10.
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Effi cacy of Protein with Carbohydrate 619
Discussion
The optimal macronutrient composition and dosage to facilitate recovery from
endurance exercise has been of research interest for several decades (1, 2). Recent
studies suggest a CHO-P mixture might be advantageous over CHO alone, although
several investigations did not control for total energy intake (29, 38, 40, 42). Those
studies, which have included an isocaloric treatment to quantify the value of CHO-P
for muscle glycogen replenishment, have not examined the impact on subsequent
exercise performance (5, 18, 35, 36, 37). Two studies (31, 40) demonstrated
Figure 6 — (Top panel) Muscle soreness ratings 24 h following recovery test protocol
for Study A (within-subjects design; n = 8) and Study B (between-subjects design; n =
24). (Bottom panel) Plasma creatine kinase (CK) values at 24 h for within-subjects design
(n = 8). *indicates signifi cantly lower for carbohydrate-protein drink (CHO-P) compared
to CHO10.
03Mil-Staf(610) 619 1/10/06, 5:27:12 PM

620 Millard-Stafford et al.
markedly improved (40% and 55%) cycle time to fatigue at 85%VO2max following
ingestion of CHO-P versus CHO during recovery. But, to our knowledge, no peer-
reviewed study has compared the impact of CHO-P recovery treatment to isocaloric
CHO on subsequent exercise performance. Using a unique combination of labora-
tory and fi eld-based performance measures, we assessed whether runners would
differentially benefi t within the same day or next-dayʼs recovery from hard training
by ingesting either 6% sports drink, higher calorie (10%) CHO, or energy-matched
blend of CHO-P. Since most top athletes may train and even compete multiple times
within the same day and on consecutive days (e.g., tournaments), these results have
real-world relevance for multi-sport endurance athletes and team players alike.
Contrary to our hypothesis and the aforementioned studies (31, 40), however, we
observed no benefi t in performance 2 or 24 h later when additional calories (in the
form of CHO or protein) were ingested in the preceding recovery.
To date, relatively few running-based studies have investigated the ergogenic
benefi t of nutritional interventions immediately following exercise. It is clear CHO
ingestion (vs. placebo) immediately after running improves performance 4 h later
(10). However, 50 g of CHO taken within 30 min of recovery, was just as effective
in restoring run performance 4 h later compared to three-fold higher CHO ingestion
throughout 3 h of recovery (similar dosage as our CHO6 trial)(41). Thus, initial
nutrient ingestion during recovery may be the most important in short-term (2 to
4 h) performance restoration. It is stated that CHO intake needs to be high (≥ 1 g ·
kg · h) to facilitate recovery in the immediate post-exercise period (19). Although
our dosage of 1 g · kg · h is at the low end of this range, we observed no advantage
in subsequent run performance with the addition of protein (or CHO) above 0.6 g ·
kg · h. This is inconsistent with reports of improved glycogen re-synthesis follow-
ing cycling when CHO is increased from 0.8 to 1.2 g · kg · h (19, 37); suggesting,
improved glycogen synthesis post-exercise may not translate into meaningful run
performance improvements soon after (2 h) or the following day.
Greater glycogen repletion that is often, but not always (5, 35), demonstrated
in the recovery from exercise with CHO-P versus CHO (14, 30, 42) is believed to
be the result of greater insulin release via protein. Yet, higher insulin is not always
observed with CHO-P (14) and, furthermore, might not infl uence glycogen synthesis
(18, 37). There was no evidence of increased glycemic/insulinemic response with
Table 2 Physical Characteristics of Matched Subjects in Study B
CHO-P
(
n
= 9)
CHO6
(
n
= 8)
CHO10
(
n
= 7)
Age (y) 19.9 (1.6) 19.4 (1.4) 19.4 (1.1)
Height (cm) 170.3 (9.0) 173.5 (8.7)0 173.6 (10.4)
Weight (kg) 61.5 (4.5) 60.9 (9.3) 63.4 (6.9)
% body fat 10.5 (7.4) 10.2 (3.4) 9.3 (3.6)
VO2max (mL–1 · kg–1 · min–1) 61.2 (7.9) 61.2 (7.6) 61.9 (10.4)
Best 5 km run (s) 1035.9 (37.7) 999.5 (33.0)01046.3 (53.4)
Training (km/wk) 89.7 (15.8) 97.4 (17.4) 86.3 (14.5)
Note: Values are means ± standard deviation; n = 24 (9 women, 15 men).
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Effi cacy of Protein with Carbohydrate 621
our CHO-P contrary to previous studies (38, 39). It is possible additional sampling
points (for insulin) might have yielded additional insight, but our insulin and gly-
cemic data are consistent with at least one other study using an energy-matched
comparison (14).
Although greater energy intake did not translate into improved recovery of run
performance at 2 or 24 h after training, we acknowledge these time points might
not provide the best sensitivity to detect performance changes related to differen-
tial muscle glycogen levels. The earliest time point investigated in most recovery
studies (10, 40, 41) has been 4 h post-exercise to allow for signifi cant glycogen
repletion. Differences in the rapid phase (fi rst 30 min) of glycogen resynthesis have
been demonstrated, however, within 2 h (19) of running-based exercise protocols
(43) and were infl uenced by various CHO formulas (28). Ingestion of energy
equivalent CHO solutions, either markedly hypotonic (84 mosmol/kg) or slightly
hypertonic (350 mosmol/kg), resulted in faster glycogen resynthesis after 2 h with
the hypotonic solution (28). Thus, intestinal glucose absorption of the recovery
drink could be a rate-limiting factor for muscle glycogen synthesis (19). Since our
drink osmolalities differed by < 12 mosmol/kg among all three trials, this should
not have been a mitigating factor.
There is limited indirect evidence of reduced muscle damage following exhaus-
tive endurance exercise with CHO-P ingestion versus CHO (20, 31). Eccentric
(downhill) exercise impairs glycogen re-synthesis over the subsequent 24 to 48
h (7, 8) and might not restore muscle glycogen even after a 2 h recovery of CHO
ingestion (43). Although our protocol was not specifi cally designed to elicit muscle
damage, it is possible that increased running distance (21 km) on a hilly course
followed by a race-like effort (RTF at 90% VO2max) presented an unaccustomed
stress and resulting muscle damage to these well-trained runners (27). Our data
(using both within- and between-subject comparisons) indicate CHO-P during
the recovery from run training attenuated muscle soreness compared to isocaloric
CHO. The effi cacy of CHO-P is consistent with a report (25) that muscle soreness
(and other functional markers of muscle damage such as plasma CK and reduc-
tion in isometric force) in the days following 15 min of downhill running was not
ameliorated with high CHO intake compared to no CHO. Likewise, protein (10
g) added to CHO signifi cantly attenuated muscle soreness in Marine recruits at 34
and 54 d of basic training compared to placebo (0 g) and CHO (8 g) supplemented
groups (11), although there was no eucaloric comparison to CHO-P.
Although soreness ratings were lower in the present study, plasma CK was not
signifi cantly attenuated with CHO-P. While CK in the present study was mildly
elevated across beverage treatments, muscular adaptation (due to the repeated bout
effect, 26) could explain attenuated CK over the course of 3 trials. Saunders (31)
compared a 7.3% CHO-1.8% whey protein isolate (Accelerade, Pacifi c Health,
Inc., Matawan, NJ) to sports drink, but reconstituted it to provide higher CHO
(from 6% to 7.3%), to match CHO content. Plasma CK was lower by 83% with
CHO-P compared to CHO 12 to 15 h after prolonged cycling, but since there
was no isocaloric treatment, it is diffi cult to ascertain if added protein or calories
provided the benefi t.
A potential mechanism underlying attenuated muscle soreness from CHO-P
(compared to CHO) could be enhanced protein synthesis and/or reduced catabolism
(31). A negative nitrogen balance in the fi rst few days after eccentric contraction-
induced injury plays an important role in limiting the rate of recovery (13, 22, 39).
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622 Millard-Stafford et al.
Muscle protein synthesis is depressed for several hours after injury (22), as well
as following “non-injurious” exercise (29). This, coupled with increased protein
degradation rate in the days after injury (i.e., 2 to 5 d), leads to a net loss of total
protein content (13, 22) which limits the functional restoration rate (13). Thus, it is
logical to hypothesize a drink with protein could attenuate functional losses and/or
accelerate recovery by counteracting the negative nitrogen balance occurring after
injury. This parallels observations of improved muscle protein anabolism with oral
protein-CHO consumed either during recovery from (4, 24, 34) or prior to weight
training (33). A mixture of whey protein, amino acids, and CHO stimulated protein
synthesis to a greater extent than isoenergetic CHO (4). Interestingly, the amount
of protein observed to increase synthesis immediately post-exercise is quite modest
(6 g or 24 kcal) (21, 32, 33).
There were few adverse effects related to CHO-P ingestion compared to CHO
over a short-term (2 h) recovery. A trend for higher ratings of perceived effort when
performing high intensity running after 2 h of CHO-P ingestion was noted. This
might be related to less acceptable overall taste and palatability or assimilation,
although perceived stomach upset and bloating was not signifi cantly different.
In summary, post-exercise ingestion of a traditional sports drink versus higher
calorie CHO-P or CHO following exhaustive running had no effect on subsequent
run performance either 2 or 24 h later. Elevated blood glucose and insulin response
elicited by higher calorie CHO did not translate into an ergogenic advantage. One
day after exhaustive running, perceived muscle soreness was lower with CHO-P
compared to isocaloric CHO, suggesting a potential benefi t for athletes, during
heavy training or tournament play, that merits additional investigation.
Acknowledgments
This study was supported by a grant from the Coca-Cola Co., Atlanta, GA. The primary
investigator serves as a consultant to the Beverage Institute for Health and Wellness
for the Minute Maid Co., Houston, TX. We acknowledge technical assistance from
Charles Arnold at Georgia State University and David Fritz. The results of the present
study do not constitute endorsement of products by the authors.
References
1. Bergstrom, J., and E. Hultman. Muscle glycogen synthesis after exercise. An enhancing
factor localized to the muscle cells in man. Nature. 210:309-310, 1966.
2. Bergstrom, J., L. Hermansen, E. Hultman, and B. Saltin. Diet, muscle glycogen and
physical performance. Acta Physiol. Scand. 71:140-150, 1967.
3. Borg, G. Perceived exertion: A note on “history” and methods. Med. Sci. Sports Exerc.
19:398-403, 1987.
4. Borsheim, E., A. Aarsland, and R.R Wolfe. Effect of an amino acid, protein, and car-
bohydrate mixture on net muscle protein balance after resistance exercise. Int. J. Sport
Nutr. Exerc. Metab.14:255-271, 2004.
5. Carrithers, J.A., D.L. Williamson, P.M. Gallagher, M.P. Godard, K.E. Schulze, and
S.W. Trappe. Effects of postexercise carbohydrate-protein feedings on muscle glycogen
restoration. J. Appl. Physiol. 88:1976-1982, 2000.
6. Costill, D.L., W.M. Sherman, W.J. Fink, C. Maresh, M. Witten, and J.M. Miller. The
role of dietary carbohydrate in muscle glycogen resynthesis after strenuous running.
Am. J. Clin. Nutr. 34:1831-1836, 1981.
03Mil-Staf(610) 622 1/10/06, 5:27:17 PM

Effi cacy of Protein with Carbohydrate 623
7. Costill, D.L., D.D. Pascoe, W.J. Fink, R.A. Robergs, S.I. Barr, and D. Pearson. Impaired
muscle glycogen resynthesis after eccentric exercise. J. Appl. Physiol. 69(1):46-50, 1990.
8. Doyle, J.A., W.M. Sherman, and R.L. Strauss. Effects of eccentric and concentric exer-
cise on muscle glycogen replenishment. J. Appl. Physiol. 74(4):1848-1855, 1993.
9. Fairchild, T.J., S. Fletcher, P. Steele, C. Goodman, B. Dawson, and P.A. Fournier. Rapid
carbohydrate loading after a short bout of near maximal-intensity exercise. Med. Sci.
Sports Exerc. 34:980-986, 2002.
10. Fallowfi eld, J.L., C. Williams, and R. Singh. The infl uence of ingesting a carbohydrate-
electrolyte beverage during 4 hours of recovery on subsequent endurance capacity. Int.
J. Sports Nutr. 5:285-299, 1995.
11. Flakoll, P.J., T. Judy, K. Flinn, C. Carr, and S. Flinn. Postexercise protein supplemen-
tation improves health and muscle soreness during basic military training in Marine
recruits. J. Appl. Physiol. 96:951-956, 2004.
12. Gisolfi , C.V. and S.M. Duchman. Guidelines for optimal replacement beverages for
different athletic events. Med. Sci. Sports Exerc. 24:679-687, 1992.
13. Ingalls, C.P., G.L. Warren, and R.B. Armstrong. Dissociation of force production from
MHC and actin contents in muscles injured by eccentric contractions. J. Mus. Res. Cell
Motil. 19:215-224, 1998.
14. Ivy, J.L., H.W. Goforth, B.M. Damon, T.R. McCauley, E.C. Parsons, and T.B. Price.
Early post-exercise muscle glycogen recovery is enhanced with a carbohydrate-protein
supplement. J. Appl. Physiol. 93:1337-1344, 2002.
15. Ivy, J.L., A.L. Katz, C.L. Cutler, W.M. Sherman, and E.F. Coyle. Muscle glycogen
synthesis after exercise: effect of time of carbohydrate ingestion. J Appl. Physiol. 64:
1480-1485, 1988.
16. Ivy, J.L., P.T. Res, R.C. Sprague, and M.O. Widzer. Effect of a carbohydrate-protein
supplement on endurance performance during exercise of varying intensity. Int. J. Sport
Nutr. Exerc. Metab. 13:382-395, 2003.
17. Jacobs, K.A., and W.M. Sherman. The effi cacy of carbohydrate supplementation and
chronic high-carbohydrate diets for improving endurance performance. Int. J. Sport.
Nutr. 9(1):92-115, 1999.
18. Jentjens, R.L.P.G., L.J.C. VanLoon, C.H. Mann, A.J.M. Wagenmakers, and A.E.
Jeukendrup. Addition of protein and amino acids to carbohydrates does not enhance
postexercise muscle glycogen synthesis. J. Appl. Physiol. 91:839-846, 2001.
19. Jentjens, R.L.P.G., and A.E. Jeukendrup. Determinants of post-exercise glycogen
synthesis during short-term recovery. Sports Med. 33:117-144, 2003.
20. Koopman, R., D.L.E. Pannemans, A.E. Jeukendrup, A.P. Gijsen, J.M.G. Senden, D.
Halliday, W.H.M. Saris, L.J.C. van Loon, and A.J.M. Wagenmakers. Combined ingestion
of protein and carbohydrate improves protein balance during ultra-endurance exercise.
Am. J. Physiol. 287:E712-E720, 2004.
21. Levenhagen, D.K., C. Carr, M.G. Carlson, D.J. Maron, M.J. Borel, and P.J. Flakoll.
Post-exercise protein intake enhances whole-body and leg protein accretion in humans.
Med. Sci. Sports Exerc. 34:828-837, 2002.
22. Lowe, D.A., G.L. Warren, C.P. Ingalls, D.B. Boorstein, and R.B. Armstrong. Muscle
function and protein metabolism following initiation of eccentric contraction-induced
injury. J. Appl. Physiol. 79:1260-1270, 1995.
23. Meeusen, R., M.F. Piacentini, B. Busschaert, L. Buyse, G. DeSchutter, J. Stray-Gunder-
sen. Hormonal responses in athletes: the use of a two bout exercise protocol to detect
subtle differences in (over)training status. Eur. J. Appl. Physiol. 91:140-146, 2004.
24. Miller, S.L., K.D. Tipton, D.L. Chinkes, S.E. Wolf, and R.R. Wolfe. Independent and
combined effects of amino acids and glucose after resistance exercise. Med. Sci. Sports
Exerc. 35(3):449-455, 2003.
25. Nelson, M.R., R.K. Conlee, and A.C. Parcell. Inadequate carbohydrate intake following
prolonged exercise does not increase muscle soreness after 15 min of downhill running.
Int. J. Sport Nutr. Exerc. Metab. 14(2):171-184, 2004.
03Mil-Staf(610) 623 1/10/06, 5:27:19 PM

624 Millard-Stafford et al.
26. Nosaka, K., P.M. Clarkson, M.E. McGuiggin, and J.M. Byrne. Time course of muscle
adaptation after high force eccentric exercise. Eur. J. Appl. Physiol. Occup. Physiol.
63:70-76, 1991.
27. Overgaard, K., A. Fredsted, A. Hyldal, T. Ingemann-Hansen, H. Gissel, and T. Clausen.
Effects of running distance and training on Ca2+ content and damage in human muscle.
Med. Sci. Sports Exerc. 36:821-829, 2004.
28. Piehl Aulin, K., K. Soderlund, and E. Hultman. Muscle glycogen resynthesis rate in
humans after supplementation of drinks containing carbohydrates with low and high
molecular masses. Eur. J. Appl. Physiol. 81:346-351, 2000.
29. Rennie, M.J., and K.D. Tipton. Protein and amino acid metabolism during and after
exercise and the effects of nutrition. Ann. Rev. Nutr. 20:457-483, 2000.
30. Roy, B.D., and M.A. Tarnopolsky. Infl uence of differing macronutrient intakes on muscle
glycogen resynthesis after resistance exercise. J. Appl. Physiol. 84:890-896, 1998.
31. Saunders, M.J., M.D. Kane, and M.K. Todd. Effects of a carbohydrate-protein beverage on
cycling endurance and muscle damage. Med. Sci. Sports Exerc. 36:1233-1238, 2004.
32. Tipton, K.D., A.A. Ferrando, S.M. Phillips, D. Doyle, and R.R. Wolfe. Postexercise
net protein synthesis in human muscle from orally administered amino acids. Am. J.
Physiol. 276:E628-E634, 1999.
33. Tipton, K.D., B.B Rasmussen, S.L. Miller, S.E Wolf, S.K. Owens-Stovall, B.E. Petrini,
and R.R. Wolfe. Timing of amino acid-carbohydrate ingestion alters anabolic response
of muscle. Am. J. Physiol. Endocrinol. Metab. 281(2):E197-E206, 2001.
34. Tipton, K.D., T.A. Elliott, M.G. Cree, S.E Wolf, A.P. Sanford, and R.R. Wolfe. Inges-
tion of casein and whey proteins result in muscle anabolism after resistance exercise.
Med. Sci. Sports Exerc. 36(12):2073-2081, 2004.
35. Van Hall, G., S.M. Shirreffs, and J.A.L. Calbet. Muscle glycogen resynthesis during
recovery from cycle exercise: no effect of additional protein ingestion. J. Appl. Physiol.
88:1631-1636, 2000.
36. Van Loon, L. J.C., W.H.M. Saris, H. Verhagen, and A.J.M. Wagenmakers. Plasma insulin
responses after ingestion of different amino acid or protein mixtures with carbohydrate.
Am. J. Clin. Nutr. 72:96-105, 2000.
37. Van Loon, L.J.C., W.H.M. Saris, M. Kruijshoop, and A.J.M. Wagenmakers. Maximizing
postexercise muscle glycogen synthesis: carbohydrate supplementation and the application
of amino acid or protein hydrolysate mixtures. Am. J. Clin. Nutr. 72:106-111, 2000.
38. Yaspelkis, B.B., and J.L. Ivy. The effect of a carbohydrate-arginine supplement on
postexercise carbohydrate metabolism. Int. J. Sport Nutr. 9:241-250, 1999.
39. Warren, G.L., C.P. Ingalls, D.A. Lowe, and R.B. Armstrong. What mechanisms con-
tribute to the strength loss that occurs during and in the recovery from skeletal muscle
injury? J. Orthop. Sports Phys. Ther. 32:58-64, 2002.
40. Williams, M.B., P.B. Raven, D.L. Fogt, and J.L. Ivy. Effects of recovery beverages
on glycogen restoration and endurance exercise performance. J. Strength Cond. Res.
17(1):12-19, 2003.
41. Wong, S.H., C. Williams, and N. Adams. Effects of ingesting a large volume of carbo-
hydrate-electrolyte solution on rehydration during recovery and subsequent exercise
capacity. Int. J. Sport Nutr. Exerc. Metab. 10:375-393, 2000.
42. Zawadzki, K.M., B.B. Yaspelkis, and J.L. Ivy. Carbohydrate-protein supplement
increases the rate of muscle glycogen storage post exercise. J. Appl. Physiol. 72:
1854-1859, 1992.
43. Zehnder, M., M. Muelli, R. Buchli, G. Kuehne, and U. Boutellier. Further glycogen
decrease during early recovery after eccentric exercise despite a high carbohydrate
intake. Eur. J. Nutr. 43(3):148-159, 2004.
03Mil-Staf(610) 624 1/10/06, 5:27:22 PM