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Reprint requests to Mark S. Nash, PhD, Dept of Neurological Surgery, University of Miami, Miller School of Medicine, 1095 NW 14th Ter, R-48, Miami, FL 33136.
Department of Neurological Surgery, Miller School of Medicine, University of Miami, Miami, FLDepartment of Rehabilitation Medicine, Miller School of Medicine, University of Miami, Miami, FLDepartment of Physical Therapy, Miller School of Medicine, University of Miami, Miami, FLThe Miami Project to Cure Paralysis, Miller School of Medicine, University of Miami, Miami, FL
Department of Neurological Surgery, Miller School of Medicine, University of Miami, Miami, FLDepartment of Physical Therapy, Miller School of Medicine, University of Miami, Miami, FLThe Miami Project to Cure Paralysis, Miller School of Medicine, University of Miami, Miami, FL
Nash MS, Meltzer NM, Martins SC, Burns PA, Lindley SD, Field-Fote EC. Nutrient supplementation post ambulation in persons with incomplete spinal cord injuries: a randomized, double-blinded, placebo-controlled case series.
Objective
To examine effects of protein-carbohydrate intake on ambulation performance in persons with incomplete spinal cord injury (SCI).
Design
Double-blinded treatment with washout and placebo crossover.
Setting
Academic medical center.
Participants
Three subjects aged 34 to 43 years with incomplete SCI at C5-T4.
Interventions
Subjects walked to fatigue on 5 consecutive days. On fatigue, participants consumed 48g of vanilla-flavored whey and 1g/kg of body weight of carbohydrate (CH2O). Weekend rest followed, and the process was repeated. A 2-week washout was interposed and the process repeated using 48g of vanilla-flavored soy.
Main Outcome Measures
Oxygen consumed (V̇o2; in L/min), carbon dioxide evolved (V̇co2), respiratory exchange ratio (RER: V̇co2/V̇o2), time (in minutes), and distance walked (in meters) were recorded. Caloric expenditure was computed as V̇o2 by time by 21kJ/L (5kcal/L) of oxygen consumed. Data were averaged across the final 2 ambulation sessions for each testing condition.
Results
Despite slow ambulation velocities (range, .11–.34m/s), RERs near or above unity reflected reliance on CH2O fuel substrates. Average ambulation time to fatigue was 17.8% longer; distance walked 37.9% longer, and energy expenditure 12.2% greater with the whey and CH2O supplement than with the soy drink.
Conclusions
Whey and CH2O ingestion after fatiguing ambulation enhanced ensuing ambulation by increasing ambulation distance, time, and caloric expenditure in persons with incomplete SCI.
Combined use of body weight support, functional electric stimulation, and treadmill training to improve walking ability in individuals with chronic incomplete spinal cord injury.
mirroring exercise benefits attained by those without disability. Unfortunately, altered contractile properties of muscle after SCI often limit the ability of weakened muscle to undergo aggressive exercise and satisfy vigorous functional performance needs.
These muscle alterations include transformation to fibers having fast contractile properties and favored use of glycolytic energy substrates. In such cases the relative intensity of muscle actions increases to the point of early fatigue while still performing relatively little physical work.
The mixture of muscle fuels can be examined during exercise by monitoring the respiratory exchange ratio (RER), an index of fuel use derived from the quotient of carbon dioxide evolved (V̇co2) to oxygen consumed (V̇o2), which increases as proportional use of muscle fuel shifts from low-intensity use of fatty fuels to high-intensity use of carbohydrates. Unity of the RER (ie, 1.0), and values above this level, indicate an increasing reliance on carbohydrate substrates (ie, muscle glycogen and blood glucose), and generally forecasts impending fatigue.
Considerable research and clinical effort has focused on locomotor rehabilitation of persons with incomplete SCI as a pathway to improved function and enhanced health.
To date, however, dietary, pharmacologic, and nutrient modification that optimize physical performance for those with SCI have met with limited scrutiny, compared with the extensive research base and well-established benefits of immediate postexercise nutrient supplementation in persons without disability. In many cases of intense exercise the combined intake of carbohydrate (CH2O) and protein immediately after muscle fatigue hastens recovery from intense physical activity, and improves performance during ensuing exercise bouts.
which serves as the basis for testing of potential benefits in persons with SCI. The purpose of this case series was to examine whether postexercise nutrient supplementation with whey protein and CH2O administered immediately after fatiguing ambulation enhances locomotor performance over a 2-week period.
Methods
Participants
Study participants were 3 people aged 34 to 43 years with incomplete SCI (American Spinal Injury Association [ASIA] grades C and D) at the C5-T4 levels. The International Guidelines for Classification of Neurological Injury (revised 2000) served as the standard for participant classification. Participants were in good health and free of infection or illness at the time of testing. They refrained from ingestion of food and caffeine for 4 hours before and 3 hours after testing sessions. Participants consented to undergo study with the approval of the Medical Sciences Committee for the Protection of Human Subjects. Descriptive characteristics of the study participants are shown in table 1.
Table 1Descriptive Characteristics of the Study Participants
Participant
Age (y)
Duration of Injury (y)
Level of Injury/ASIA Grade
Sex
Assistive Device(s)
1
43
21.8
C4-5 ASIA C
F
Bilateral AFO
2
39
5.6
C5-6 ASIA C
M
None
3
34
6.5
T4 ASIA D
M
Left AFO
Mean
38.7
11.3
Abbreviations: AFO, ankle-foot orthosis; F, female; M, male.
Study participants were experienced in overground locomotion through participation in an earlier research study, but were not actively ambulating when studied. More than 3 months had passed since they had participated in these studies. They were not enrolled in concurrent studies, undergoing structured therapy, or independently exercising in a home-based program. They wore a safety harness and used a rolling walker during testing, but were not provided additional body weight support. Assistive devices used during ambulation are shown in table 1 and were kept constant throughout all testing.
Ambulation was performed to fatigue over a 24-m (80-ft) long indoor oval track on 5 consecutive days. Fatigue was determined by the inability of participants to take additional steps. Weekend rest followed, and the process was repeated for another 5 days. Within 5 minutes of experiencing fatigue participants consumed a blended drink containing 48g of vanilla-flavored whey
Now Foods, 395 S Glen Ellyn Rd, Bloomingdale, IL 60108.
). This combination drink, given immediately after fatiguing exercise, is known to rapidly replete muscle glycogen. A 2-week washout period was interposed and the process repeated using 48g of vanilla-flavored soy protein
McNeil Nutritionals, 501 George St, New Brunswick, NJ 08903.
) were added. By contrast, soy protein is slowly absorbed by the body and is not recognized as an aid in recovery from fatiguing exercise. Supplements had similar vanilla flavor, were blended to form similar liquid volumes, and were equally sweetened. There was a slight difference in texture that alerted participants to their difference, but not their identity. The order of supplementation was determined by chance, and the drink composition was unidentified for participants and investigators involved in data collection.
Hans-Rudolph Inc, 7200 Wyandotte, Kansas City, MO 64114.
over their nose and mouth during each session. Oxygen consumed (V̇o2; in L/min), carbon dioxide evolved (V̇co2), and RER (V̇co2/V̇o2) were assessed by open-circuit spirometry using a portable metabolic analyzer carried on body harness (fig 1) and set to average responses over a 1-minute time interval. After preparation for metabolic monitoring participants sat quietly for 5 minutes while baseline data were collected. They then walked to fatigue, accompanied by an investigator. Time (in minutes) and distance walked (in meters) were recorded. Caloric expenditure was computed as the product of V̇o2, time, and a constant reflecting 21kJ (5kcal) burned per liter oxygen consumed.
Fig 1A test participant wearing a metabolic monitor while walking on an indoor oval track. The participant is wearing a harness for safety, but is not being assisted with body weight support.
Data for each test condition were averaged across the final 2 days of ambulation and expressed both as individual participant responses and pooled data. The use of an average expressed over the last 2 days decreased the likelihood of bias imposed by factors that might enhance or limit performance on a single day. Differences between test conditions (whey and CH2O vs soy) were computed as percentage differences.
Results
Participants consumed the study drinks without stomach upset or changes in bowel habits. They noted a slight taste difference between drinks, but were unable to identify the composition.
Responses to walking for individual participants are shown in table 2. Despite slow ambulation velocities (range, .11–.34m/s), RERs near or above unity (RER=1) reflected reliance on CH2O fuel substrates (fig 2). Irrespective of testing order, average ambulation time was 17.8% longer (32.0min vs 27.1min); distance walked 37.9% longer (470m vs 341m), and energy expenditure to fatigue 12.2% greater (731kJ [174kcal] vs 651kJ [155kcal]) with the whey and CH2O supplement than soy (fig 3).
Table 2Individual Performances of Participants Under the 2 Test Conditions
Fig 2RERs (V̇co2/V̇o2) reflecting reliance on glycolytic substrates during locomotion. Increasing RER identifies an increasing proportional use of carbohydrate as a substrate to fuel muscle metabolism.
The key observation of this study is that 3 persons with incomplete injuries walked longer distances and at greater caloric expenditure before sustaining fatigue after 2 weeks of whey and CH2O supplementation, whereas a blinded control condition failed to bring about this change. Although the specific benefit to muscle was not studied, the short duration of testing would argue against muscle strengthening known to accompany longer-term supplementation with whey protein,
Myosin heavy chain isoform transformation in single fibres from m. vastus lateralis in spinal cord injured individuals: effects of long-term functional electrical stimulation (FES).
This reliance was seen in study participants who walked at slow speeds but had RERs that rapidly approached or exceeded unity (1.0), indicating that despite slow walking the work is challenging.
Muscle glycogen is an obligate fuel normally used to support moderate to high intensity contraction of innervated muscle,
Myosin heavy chain isoform transformation in single fibres from m. vastus lateralis in spinal cord injured individuals: effects of long-term functional electrical stimulation (FES).
When glycogen is depleted from innervated or paralyzed muscle the capacity to perform additional voluntary or involuntary activity at moderate and higher work intensities is either completely lost or severely limited.
Enhanced recovery from glycogen-depleting exercise in persons without disability is readily achieved by immediate CH2O administration, which is superior to both no supplementation and supplementation with electrolytes in water.
This generally rules out ingestion of bulk food to achieve the same benefit, because the immediacy of muscle CH2O uptake is stalled by time required for nutrient digestion, intestinal transit, and blood-borne transport. Addition of protein to the supplement mix increases the glycogen resynthetic capacity of ingested carbohydrates by stimulating an insulin response considered permissive for rapid glycogen repletion.
Whey protein generally satisfies this need, because it is easily digested, contains high concentrations of branch-chain amino acids used for muscle repair, and rapidly crosses from the intestinal tract into the circulation. By contrast, soy is slowly ingested, and its uptake exceeds the critical timing need for protein uptake, which explains its selection as a control condition for this study.
The incorporation of locomotor training in rehabilitation of persons with incomplete SCI has received widespread research attention and has achieved diverse performance outcomes.
Combined use of body weight support, functional electric stimulation, and treadmill training to improve walking ability in individuals with chronic incomplete spinal cord injury.
Not all persons who undergo the process become functional ambulators, because walking requires greater muscle forces and more prolonged endurance than many persons can achieve before experiencing fatigue.
Surprisingly, no studies have mentioned dietary enhancements or nutrient supplementation as tools to improve performance outcomes, even though enhanced strength, endurance, ambulation time and speed, and motor efficiency have been primary experimental goals of treatment.
Combined use of body weight support, functional electric stimulation, and treadmill training to improve walking ability in individuals with chronic incomplete spinal cord injury.
By contrast, considerable success has been achieved in enhancing exercise performance of healthy persons without disability, the frail elderly, and people with chronic infections through use of postexercise nutrient supplementation.
The performance-enhancing effects of these supplements underpin a joint position of the American Dietetic Association, Dietitians of Canada, and American College of Sports Medicine that “… physical activity, athletic performance, and recovery from exercise are enhanced by optimal nutrition …, ”
Joint Position Statement: Nutrition and athletic performance. American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada.
(p2130) and who jointly “… recommend appropriate selection of food and fluids, timing of intake, and supplement choices for optimal health and exercise performance.”
(p1543) To our knowledge none of these recommendations have been incorporated or examined for efficacy in persons with SCI undergoing locomotor training. Several studies on persons with SCI have examined pharmacologic approaches to increasing ambulation time and efficiencies, with most efforts focusing on antispasmodic medications having adrenergic, serotonergic, and γ-aminobutyric acid agonist properties,
although responses to these drugs have been mixed and their universal use limited. Benefits on muscle strengthening have been reported for the β2-selective adrenergic agonist metaproterenol.
The nutritional food supplement creatine monohydrate has been used for short periods of time to increase motor function of weakened upper muscles in persons with tetraplegia, but with mixed outcomes
; however, no evidence suggests that activity-induced creatine deficiency is a cause of muscle weakness or premature fatigue in persons with SCI. The α1 sympathomimetic agent midodrine reportedly enhances exercise performance in persons with tetraplegia,
although the benefits of treatment have been attributed to enhanced pressor responses in persons having cardiovascular autonomic dysfunction from injuries above the T1 level. Again, no evidence suggests that ambulation deficiencies in those with SCI are caused by circulatory dysregulation or are corrected by use of α1 selective adrenergic agonists.
Study Limitations
We note a number of study limitations. The study population is a small case-series and therefore subject to selection bias. In this first study examining this topic, we did not control for dietary intake, but instructed participants to maintain their habitual food choices. A treatment group for CH2O alone was not included, and thus, the extent to which whey enhanced the postulated effect of CH2O ingestion cannot be determined. Instead, we elected to examine whether the combination of whey and CH2O appeared beneficial, and then backtrack through its nutritional elements. Whereas protein content was matched in the two study supplements, the CH2O was not, which makes room for the possibility that CH2O alone was responsible for the case observations. No muscle biopsies were taken to confirm glycogen depletion after fatiguing exercise, or greater glycogen storage after treatment. Participants were studied without body weight support, which differs from the partially unloaded state commonly used to train persons with incomplete SCI. We note that postural hypotension and other circulatory dysfunction accompanying SCI may have contributed to the fatigue patterns.
Despite these limitations, the magnitude of change observed under blinded placebo-controlled conditions is encouraging; it exceeds in magnitude and speed of change the benefits provided by other ergogenic aids tested for those with SCI and provides a basis for more systematic study in a larger test population.
Conclusions
Intake of whey and CH2O after fatiguing ambulation enhanced ensuing ambulation by persons with incomplete SCI. Apparent reliance on CH2O substrates, and known benefits of whey and CH2O in postactivity CH2O repletion, suggest a mechanism of action. Ease of digestion and minimal adverse effects were noted. Future research directions could reasonably include studies examining mechanisms of total or subtotal fatigue during locomotory training, as well as investigations of anticatabolic effects of protein supplementation during exhaustive exercise. Confirmation of this benefit requires investigation in a larger study population.
Suppliers
aSolgar Vitamin and Herb, 500 Willow Tree Rd, Leonia, NJ 07605.
bNow Foods, 395 S Glen Ellyn Rd, Bloomingdale, IL 60108.
dMcNeil Nutritionals, 501 George St, New Brunswick, NJ 08903.
eHans-Rudolph Inc, 7200 Wyandotte, Kansas City, MO 64114.
References
Field-Fote E.C.
Combined use of body weight support, functional electric stimulation, and treadmill training to improve walking ability in individuals with chronic incomplete spinal cord injury.
Myosin heavy chain isoform transformation in single fibres from m. vastus lateralis in spinal cord injured individuals: effects of long-term functional electrical stimulation (FES).
Joint Position Statement: Nutrition and athletic performance. American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada.
No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/ are associated.
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