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“Fatigue makes cowards of us all!” When Vince Lombardi uttered this quote many years ago, he couldn’t have been more on the money. There is no worse physical feeling for a healthy athlete than to train or play to the point of exhaustion. Many athletes attempt, but few really push their bodies to their physical limits. The sport of hockey demands an all-out effort on each shift during the course of a game. In the National Hockey League, this effort must be repeated 82 times, provided the player remains healthy throughout the year. Even for the few who can mentally take their bodies “to the wall” each time out, some may not be able to due to a lack of physical energy.
It is far harder to be successful in the sport of hockey, especially at the Junior levels and on up, when you are constantly fighting tired legs or experiencing a power outage due to a lack of get-up-and-go. Playing a multitude of games with few breaks in the schedule will tax players’ energy systems to there fullest. Those in the minor leagues, IHL or AHL, who have played 7 games in 10 nights, can certainly attest to that! One sign of a particular type of fatigue is a player’s inability to generate repeated high speed movements which can result in a reduced lactic acid build up in one’s legs when playing or practicing. If that characteristic burn associated with repeated high intense skating cannot be generated, then one may be the victim a lack of muscle fuel or muscle glycogen.
Muscle glycogen refers to the stored fuel within muscles that is burned when performing highly intense, intermittent activity, i.e. shifts during a game (Robergs, 1991). Glycogen is stored in the body through the ingestion of carbohydrates. When the level of glycogen within the muscles is low, then the opportunity to produce powerfully intense muscular contractions over an extended period of time is greatly reduced. Such a power output can result in lower lactic acid accumulation in the blood. Soon into the game, feelings of overall fatigue invade the body, and a key aspect of this game, speed endurance, is tremendously compromised.
When conditioning one of our players back into playing shape after he incurred a serious injury at the end of the 1998-99 season, I discovered this same type of fatigue at a certain point in his conditioning program, albeit with the help of science. On game days, the player was training two times per day, weight training and conditioning on the ice in the morning and riding the bike or running on the treadmill in the evening. At an early point in his conditioning program I conducted blood lactate testing with him on one of our cycle ergometers (SensorMedics 800S), correlating his power output (to the nearest 5 watts) with his lactate accumulation at anaerobic threshold (4.0 mmols/l). The player’s blood lactate accumulation after five-3 minute intervals interspersed with 3-minute recovery periods was also evaluated as was his lactate clearance after 10 minutes of active recovery following the 3:00 interval protocol.
Follow up testing with him conducted 3 weeks post initial testing revealed what appeared to be a drop in his conditioning. However, the lactate information I obtained provided additional information that told a different story. The same 3:00 interval program (at the same wattage) was subjectively rated just as hard, if not harder, as the 3:00 interval program performed 3 weeks prior. In fact, the wattage had to be dropped on the last 2 intervals in order for the workout to be completed. The lactate reading after completion of the fifth interval, however, was over 3 mmols less than the one recorded 3 weeks prior. Immediately this told me that this player was low in his muscle glycogen stores and not in a de-conditioned shape. This was further confirmed by his improved ability, over the previous 3-week training span, to clear the lactate after 10 minutes of active recovery. As a result of this player’s lactate scores, we intervened immediately with a higher carbohydrate diet. With testing conducted two days later, his lactate reading at anaerobic threshold correlated with a significantly greater power output on the cycle ergometer in comparison to his lactate and power readings recorded two days prior.
As one can attest, the need for proper diet and thus muscle fuel is of utmost importance for success in any sport, not just professional hockey. The factors surrounding how to go about optimizing your capability of enhancing muscle glycogen stores and thus potential for disposable energy will be the focus of this article.
FACTORS THAT AFFECT GYCOGEN SYNTHESIS
1. Insulin:
Insulin is a hormone released by the pancreas and chiefly responsible for transporting glucose (component of carbohydrate) into muscle and liver tissues where it is stored as glycogen (Burke, 1999). Blood insulin concentration therefore plays a major role in determining the rate of glycogen storage (synthesis). The greater the secretion of insulin, the greater the speed in transporting glucose into the muscles cells, thus, the rate of muscle glycogen storage is enhanced (Burke, 1999). Therefore, the key to enhancing glycogen synthesis is to enhance the insulin response or insulin secretion during recovery.
2. Degree of Glycogen Depletion:
The more ice time players receive the greater the depletion of glycogen stores within their muscles. What has been found with research is that the greater the breakdown of glycogen during exercise, the greater the muscles are primed for taking glycogen back up through one’s diet (Bergstrom & Hultman, 1967, as cited in, Ivy, 1998). As a result, if one player plays 28 minutes in a game verses another only playing 10 minutes, then obviously the player who played more minutes would have a higher potential rate of glycogen resynthesis. His need for proper carbohydrate following the game would therefore be of greater significance.
3. Timing of Carbohydrate Ingestion Following a Game:
During the first 2 hours following exhaustive exercise, your muscles are most sensitive to insulin (Ivy, 1998). After this period, your muscles become more resistant to this hormone. Couple this with insulin’s key role in muscle glycogen storage and one can see that it is crucial to take in the appropriate amount of carbohydrate within the first 2 hours after a game. Ivy et al. (1988) found that when a carbohydrate supplement was taken either immediately or 2 hours after exercise, during short term recovery, the rate of glycogen synthesis was about two times greater when the supplement was taken immediately following exercise. In addition, by taking carbohydrate immediately following a game, you begin the muscle glycogen recovery process immediately, which means, more opportunity (time) to take in more total carbohydrate calories prior to the next game or practice. Since
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most games at the Junior, Collegiate, and Professional levels don’t start until 7:00 p.m., it wouldn’t be until approximately 9:30 – 10:00 p.m., at the earliest, before a player’s first carbohydrate feeding. It is recommended that a second feeding of carbohydrate be ingested 1 to 2 hours later (Burke, 1999). Therefore, if one’s first carbohydrate feeding is delayed an hour or two following a game, then he may lose the opportunity to take in a second meal before he goes to bed.
4. Amount of Carbohydrate:
How much carbohydrate you ingest has a significant effect on the rate of glycogen synthesis. Ivy (1998) found that 1.0 – 1.5 grams of carbohydrate per kg bodyweight is the ideal amount of carbohydrate to ingest to maximize recovery. In fact, carbohydrate supplementation in excess of 1.0 grams per kg bodyweight has not been found to further enhance glycogen resynthesis rates. Blom et al. (1987 in Ivy, 1998) found that when comparing the ingestion of 1.4, 0.7, and 0.35 grams of glucose/kg bodyweight immediately after and at two hour intervals following exercise, there were no differences in glycogen resynthesis rates between 1.4 and 0.7 gram concentrations. However, the rate of glycogen resysnthesis was reduced by 50% with the use of 0.35 grams of glucose/kg bodyweight. What this means, therefore, is that a 200lb (90kg) player requires approximately 65 – 90 grams of carbohydrate immediately following exercise, and preferably at additional two hour intervals thereafter, in order to maximize glycogen synthesis.
Another benefit to ingesting the proper amount of carbohydrates following strenuous exercise was demonstrated by Roy (1997) who examined carbohydrate supplementation on protein breakdown following resistance training. Even though the amount and intensity of weight lifting varies during a hockey season, as dependent on the schedule, the degree of muscle breakdown during the course of a game or number of games may be significant (Green, 1999). Roy (1997) found that when 1.0g of carbohydrate per kg bodyweight was ingested following a weight lifting session, muscle protein breakdown was significantly less than those ingesting a placebo. As a result, proper carbohydrate supplementation following games and strenuous lifting sessions may result in a more positive protein balance thus owing to more favorable lean body mass throughout the season.
5. Type of Carbohydrate:
Research indicates that the type of carbohydrate may have a significant influence on the rate of glycogen synthesis (Robergs, 1991). Fructose, which is found in fruit and fruit juices, has been found to be a poor source of carbohydrate to ingest following exhaustive exercise in comparison to glucose due to the difference in how each is metabolized (Ivy, 1998). Fructose is great for enhancing liver glycogen synthesis but very poor for muscle glycogen synthesis. Blom et al. (1987) discovered glycogen sysnthesis to be more than doubled when ingesting a high mixed-carbohydrate diet than when compared to a similar diet composed of fructose. The majority of research suggests that the best type of carbohydrate to ingest following exercise is one that has a high Glycemic Index (Keins et al., 1990 and Burke et al., 1993). Glycemic index refers to a carbohydrate’s effect on blood glucose levels (Burke, 1999). A high glycemic-index carbohydrate causes a rapid rise in blood sugar and hence a greater secretion of insulin from the pancreas. As a result, higher glycemic index foods may be the most beneficial for short term (within 24 hours) recovery after a game. Longer term glycogen storage may be independent of the glycemic index of carbohydrates (Keins et al., 1990).
6. The Role of Protein:
Research has educated supplement companies and nutritionists with regards to combining protein with carbohydrate following exercise. One particular study found that combining protein with carbohydrate results in a higher insulin response and a greater rate (38% greater) of glycogen synthesis than when ingesting carbohydrate by itself (Zawadzki et al., 1992). However the amount of protein is of paramount concern. Protein has been found to delay the emptying of fluids from the stomach into the intestines. As a result, if the amount of protein is too high, then the goals of rehydration and replenishment of very important electrolytes (sodium, potassium, etc.) back into the bloodstream is severely compromised. Burke (1999) explained however, that when the ratio of protein to carbohydrate is 1:4, then two things occur: a) insulin secretion and glycogen synthesis is significantly enhanced in comparison to carbohydrate alone, and b) the rate of gastric emptying and thus fluid absorption is not delayed.
7. Presence of Amino Acids:
Two amino acids have been found to enhance the insulin response following ingestion of a carbohydrate supplement. When arginine was coupled with 1g of carbohydrate per kg bodyweight following exercise, significant increases in glycogen synthesis occurred when compared to just ingesting the same amount of carbohydrate alone (Ivy, 1998). In addition, the ingestion of glutamine with glucose has been shown to enhance the insulin response when compared to just glucose ingestion alone (Bowtell et al., 1999). However, Bowtell et al. (1999) also found that there were no differences in muscle glycogen replenishment between glucose and glucose + glutamine trials. Taking these two amino acids with carbohydrate supplementation may provide a greater opportunity for glycogen synthesis, however, more research needs to be conducted in this area for results to be deemed unequivocal.
8. Type of Exercise:
A vast percentage of the studies involving carbohydrate supplementation have used exhaustive aerobic exercise or a combination of aerobic and anaerobic exercise as the means to deplete glycogen stores. Even though the sport of hockey is unlike exhaustive aerobic exercise, it does not take a master’s graduate or a goalie for that matter, to figure out that the major fuel source for hockey is glycogen. In addition, when hockey players in one particular study completed 10-1 minute bouts (each bout followed by a 5 minute rest) of hard skating (120% of VO2 max), a 45% reduction in muscle glycogen was found after only the 5th bout (Green, 1978). After the 10th bout, muscle glycogen declined to 70% of pre-exercise levels. When a group of hockey players were studied during an actual game, an average of 60% of muscle glycogen depletion occurred when measured after the game (Green et al., 1978). In addition, just as important as these numbers is the influence of eccentric exercise. It is commonly accepted that eccentric or lengthening muscular contractions (e.g. descending down into a squat) is the type of muscular contraction responsible for the majority |
of muscle soreness (Clarkson et al., 1986 in Sherman et al., 1992). What most hockey players do not realize is that during the course of a game, your muscles are subjected to a tremendous amount of eccentric contractions through stop and go play, taking and receiving hits, etc (Green, 1999). This is no more evident then when an injured Black Ace returns to the ice for the first time following an off-ice conditioning program of strictly biking. The next day, the muscle soreness associated with skating is very evident. It has been found that eccentric exercise reduces muscle glycogen synthesis over a longer recovery period (e.g. 48 hrs) in comparison to the effects of concentric exercise (Robergs, 1991 and Doyle et al., 1993). This may be due to a decreased insulin response following eccentric exercise (Sherman et al., 1992). As a result, the need for a high carbohydrate diet immediately following games containing the amino acid supplement, glutamine, may be extremely important in reducing muscle protein breakdown, thus enhancing recovery (Burke, 1999).
Recommendations:
1. Ingest 1.0 grams of carbohydrate per kg bodyweight immediately following games or long, hard practices and weight training sessions.
2. Make sure the type of carbohydrate ingested after each game has a high glycemic index: bagels, baked potatoes, breads, honey, rice, sodas sweetened with sugar (Burke, 1999). Stay away from fruit or fruit juices.
3. Ingest some protein with the carbohydrate. Make sure the quantity of protein does not exceed 25% of the total calories of the carbohydrate supplement.
4. If you are considering taking a powder supplement from a nutrition store, check the label for the aforementioned ingredients and look for the presence of two amino acids, arginine and glutamine.
5. Eat a second, low-fat, high-carbohydrate meal 1 to 2 hours after the first meal.
6. Make sure you are rehydrating properly following a game with the appropriate amounts of water (16oz for every lb lost through sweat) and minerals (potassium, sodium, etc.)
7. Eat a very highly concentrated carbohydrate diet throughout the season, especially when the schedule is very heavy.
8. In order to keep your sanity, treat yourself to higher fat meals after a game when there are a number of days (3 or 4) till the next game.
Conclusions:
Depleted glycogen stores can rid athletes of their energy supplies, especially if the sport being played is hockey. If a player’s speed in practice or in games is not up to par and the associated lactate burn in the legs is difficult to achieve, then that player may be suffering from reduced muscle glycogen stores as the result of insufficient and poor timing of carbohydrate ingestion. Timing the ingestion of carbohydrates immediately after games and very hard practices is crucial, as is the type of carbohydrate to be consumed. Further enhancement of glycogen resynthesis may occur with the addition of the proper amounts of protein and the amino acids arginine and glutamine. Even if Vince Lombardi was correct in his assessment of fatigue and its challenge to manhood, players can all grow a little braver and perform a whole lot better if they just adhere to what science is telling us about recovery.
REFERENCES
Bergstrom, J and Hultman, E. (1967). Muscle glycogen sysnthesis after exercise: an enhancing factor locatlized to the muscle cells in man. Nature, 210, 309-10.
Blom, P.C.S., Hostmark, A.T., Vaage, O., Kadel, K.R., & Maehlum, S. (1987). Effect of different post-exercise sugar diets on the rate of muscle glycogen resynthesis. Medicine and Science in Sports and Exercise, 19, 491-496.
Bowtell, J.L., Gelly, K., Jackman, M.L., Patel, A., Simeoni, M., Rennie, M.J. (1999). Effect of oral glutamine on whole body carbohydrate storage during recovery from exhaustive exercise. Journal of Applied Physiology, 86, 1770-1777.
Burke, L.M., Collier, G.R., & Hargreaves, M. (1993). Muslce glycogen storage after prolonged exercise: effect of the glycemic index of carbohydrate feedings. Journal of Applied Physiology, 75, 1019-1023.
Burke, E.R. (1999). Optimal Muscle Recovery, New York: Avery Publishing Group.
Clarkson, P.M., Byrnes, W.C., McCormick, K.M., Turcotte, L.P., & White, J.S. (1986). Muscle soreness and serum creatine kinase activity following isometric, eccentric and concentric exercise. International Journal of Sports Medicine, 7, 152-156.
Doyle, J.A., Sherman, W.M., & Strauss, R.L. (1993). Effects of eccentric and concentric exercise on muscle glycogen replenishment. Journal of Applied Physiology, 74, 1848-1855.
Green, H.J. (1978). Glycogen depletion patterns during continuous and intermittent ice skating. Medicine and Science in Sports, 10, 183-187.
Green, H.J. (1978). Glycogen depletion patterns during ice hockey performance. Medicine and Science in Sports, 10, 289-293.
Green, H.J. (1999). Fatigue and weakness in ice hockey: mechanisms and management. A paper submitted to the International Ice Hockey Federation.
Ivy, J.L., Katz, A.L., Cutler, C.L., Sherman, W.M., & Coyle, E.F. (1988). Muscle glycogen synthesis after exercise: effect of time of carbohydrate ingestion. Journal of Applied Physiology, 64, 1480-1485.
Ivy, J.L. (1998). Glycogen resynthesis after exercise: effect of carbohydrate intake. International Journal of Sports Medicine, 19, S142-S145.
Keins, B., Raben, A.B., Valeur, A.K., & Richter, E.A. (1990). Benefit of dietary simple carbohydrates on the early postexercise muscle glycogen repletion in male athletes. Medicine and Science in Sports and Exercise, 22 (Abstract 524), S88.
Roy, B.D., Tarnopolsky, M.A., MacDougall, J.D., Fowles, J., & Yarasheski, K.E. (1997). Effect of glucose supplement timing on protein metabolism after resistance training. Journal of Applied Physiology, 82, 1882-1888.
Robergs, R.A. (1991). Nutrition and exercise determinants of postexercise glycogen synthesis. International Journal of Sport Nutrition, 1, 307-337.
Sherman, W.M., Lash, J.M., Simonsen, J.C., & Bloomfield, S.A. (1992). Effects of downhill running on the responses to an oral glucose challenge. International Journal of Sport Nutrition, 2, 251-259.
Zawadzki, K.M, Yaspelkis, B.B., & Ivy, J.L. (1992). Carbohydrate-protein complex increases the rate of muscle glycogen storage after exercise. Journal of Applied Physiology, 72, 1854-1859.
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