As and PS

Many studies to date have demonstrated an acute increase in MPS following AA supplementation in association with exercise.159,297,328 Consequently, the studies reviewed below are those that may address some of the open issues discussed in the introduction to this section (Section 15.7.3). The main question is whether the regular practice of ingesting appropriately formulated mixtures of AAs at proper times in relation to an exercise bout in healthy, normally fed (balanced diet and eating patterns) athletes will improve long-term results beyond those obtainable via dietary practices alone. A secondary question is whether specific types of athletes under specific training circumstances are more likely to benefit from a regular AA supplement program.

It is clear that total protein and EAA requirements increase during periods of prolonged negative energy balance. Consequently, AA supplementation may be logical and useful for athletes who regularly experience negative energy balance to meet various demands of their respective sports. However, assuming that using an AA supplement can positively affect PS, the question remains as to whether the results obtained from consuming the supplement can be incremental to those produced by ingesting adequate daily intact protein from typical foods consumed from a typical eating pattern (i.e., three of four traditional meals spaced throughout the day).

Paddon-Jones et al.329 tested this by having seven subjects drink a beverage containing 15 g of EAAs combined with 30 g of carbohydrate (CHO) between meals consumed at 5-h intervals over a 16-h period, during constant infusion of labeled phenylalanine, to measure net phenylalanine balance and fractional synthetic rate of PS. The control and experimental groups consumed identical balanced meals that met energy needs. The study demonstrated that the EAA supplement produced a greater increase in fractional synthetic rate (FSR) of muscle proteins than did consumption of normal meals alone. Also, the EAA supplement did not interfere with normal metabolic responses to the meals. Based on previous work, the authors believe that acute improvement in FSR observed in this short study might translate into cumulative long-term results.273330

15.7.3.5.2 AA Composition

Borsheim et al.271 demonstrated that NEAAs are not needed to stimulate PS, in a study using an EAA composition that was to mimic the muscle AA profile (Table 15.7), with the objective of increasing the availability of the EAAs in proportion to their requirement for MPS. They also found a dose-dependent effect of EAA ingestion on MPS and a dose limit. No additional increase in MPS was realized by increasing the EAA dose beyond 21 g (under these study conditions). They observed equal MPS in response to intake of 40 g of AAs composed of 18 g of EAA and 22 g of NEAAs, compared to 40 g of all EAAs.262 In addition, the Borsheim271 study neatly demonstrated that AA ingestion following exercise stimulates PS independent of all other mechanisms (calories, insulin, exercise, etc.), and the authors calculated that approximately 26 g of muscle tissue (including muscle water content) was

TABLE 15.7

AA Composition of Drink

AA % of Total AAs Grams in EAA Drink

TABLE 15.7

AA Composition of Drink

AA % of Total AAs Grams in EAA Drink

Histidine

10.9

0.6540

Isoleucine

10.1

0.6060

Leucine

18.6

1.1160

Lysine

15.5

0.9300

Methionine

3.1

0.1860

Phenylalanine

15.5

0.9300

Threonine

14.7

0.8820

Valine

11.5

0.6900

Total

99.9

5.994

Note: AA = amino acid; EAA = essential amino acids. Composition is based on a 70-kg person. Drink was given at 1 and 2 h after completion of exercise.

Note: AA = amino acid; EAA = essential amino acids. Composition is based on a 70-kg person. Drink was given at 1 and 2 h after completion of exercise.

From Borsheim, E. et al., Am. J. Physiol. Endocrinol. Metab., 283, E648-E657, 2002. Reprinted with permission of the American Physiological Society.

synthesized in response to the AA supplementation. Other studies have confirmed that under normal diet conditions, the EAAs are primarily responsible for the AA-induced stimulation of MPS.275273329

These results, and those of other recent related studies, show that the total amount of EAA supplementation that might be required to maximize MPS, at least for the average-sized human, seems to lie between 6 and 18 g, and should be consumed two or three times daily and close to the exercise period.273,275329331

15.7.3.5.3 Timing

AA ingestion and exercise increase net muscle protein balance253,261,262 more acutely than exercise alone. However, it has also been suggested that there may be a diurnal physiological adjustment of the body protein pool such that this AA-induced elevation of net protein may be temporary. It may be counterbalanced at other times throughout the day, so that there is no longer-term net increase.

In a well-controlled study that maintained normal/adequate eating patterns, Tipton et al.273 dosed seven subjects with 15 g of EAAs immediately before and 1 h after resistance exercise. Results of the study demonstrated that an increase in net muscle protein balance, as previously shown to take place within 3 h of AA ingestion and exercise,232 262 was representative of changes in net muscle protein balance for a full 24-h period. Therefore, it was responsible for an incremental contribution to muscle protein.273 In other words, the acute response to exercise and EAA ingestion was not temporary, but did in fact persist to maintain a positive muscle protein balance over the 24-h period, when compared to the resting nonsupplemented state.

15.7.3.5.4 Elderly

Nutritional supplementation with meal replacement formulas (balanced protein, fat, and CHO) used to increase the protein intake of elderly subjects has failed to increase NPS.332-334 However, Volpi et al.,335336 using a balanced mixture of AAs administered by infusion or oral routes, observed a significant increase in PS in healthy elderly subjects.

The authors have subsequently surmised that MPS is resistant to the anabolic qualities of insulin driven by mixed meals in the elderly.337-339 They clearly demonstrated that AA supplementation alone can overcome at least some of the age-related reduced stimulation (e.g., movement) or diminished sensitivity to normal anabolic factors,338339 suggesting a potential justification for long-term use of AA supplementation as a nutritional strategy for sarcopenia.

In contrast to the earlier studies using a mixed-meal supplement,332-334 Esmarck et al.278 used a mixed supplement to produce a dramatic long-term (12-week) outcome (25% increase in mean muscle fiber area with no gain in muscle mass; see Section 15.7.2.5.2). The positive results may have been due to the immediate postexercise timing of ingestion and the formula's higher protein-to-low CHO content ratio (10 g of protein and 7 g of CHO). These data would seem to support the notion that there is a solid application for AA supplementation in elderly athletes.

15.7.3.5.5 Athletes Engaged in High-Intensity or Volume Training

Overreaching is a short-term training phase in which the volume and intensity of training are far above normal. During an overreaching training phase, muscle strength and power generally decrease, due to the inability of the muscles to recover adequately between exercise bouts. Since AA supplementation can improve post-exercise MPS, Ratamess et al.288 investigated the potential of AA supplementation to attenuate the usual strength reduction associated with overreaching. Subjects ingested 0.4 g/kg body weight daily of an AA supplement, divided into three doses consumed between meals. They found that the initial impact of overreaching did decrease muscle strength and power, and that AA supplementation did attenuate the reduction. However, there was no long-term ergogenic effect from continued use of the supplement, which is consistent with previous studies that have tested the effects of prolonged AA supplementation on strength increases340341 in resistance training subjects.

15.7.3.5.6 Hypertrophy and Performance

Andersen et al.331 tested the effects of having healthy untrained young men consume 25 g of whey protein before and after resistance exercise, compared to having them consume 25 g of isoenergetic CHO, all other factors, including diet, remaining equal. The study involved measurement of performance and mass changes after 14 weeks. The principal findings were that resistance training combined with the protein supplement yielded gains in muscle performance similar to those observed with carbohydrate supplementation. However, only the protein-supplemented group demonstrated muscle hypertrophy, as determined through muscle biopsy sampling and analysis. The protein group had an 18% increase in type 1 fibers and a 26% increase in type 2, as opposed to no measurable changes in the carbohydrate group. Although this study provided protein rather than an AA mixture, the amounts provided were adequate to satisfy the EAA amounts (6 to 18 g) that have been shown to promote an acute increase in MPS.

Eccentric training is known to cause increased muscle damage while contributing to strength development,342-346 often resulting in delayed-onset muscle soreness (DOMS). Sugita et al.347 investigated the effects of two doses per day of an AA mixture containing L-glutamine (~14% by weight), L-ARG (~14%/w), BCAAs (~30%/w), L-threonine, L-lysine, L-proline, L-methionine, L-histidine, L-phenyl-alanine, and L-tryptophan, totaling 5.6 g/dose. They used a double-blind crossover design to determine if regular AA ingestion could reduce muscle damage and speed recovery. The AA mixture accelerated the rate of elbow extensor muscle recovery compared to the placebo. Additionally, the mixture produced higher muscle strength throughout the recovery period and subjects reported less DOMS.

In a long-term trial, using the same AA combination, the investigators attempted to identify an effective dose range for reducing muscle damage during sustained exercise for 2 to 3 h/day, 5 days/week, for 6 months.348 Athletes consumed three doses per day of AA mix: 2.2, 4.4, and 6.6 g/dose. Each dose was consumed for a 1-month period, and each period was separated from the next changed dosage period by a 1-month washout period. Blood was drawn at the end of each dosage trial. With the 2.2-g dose, there were no significant effects on blood indices of muscle damage or oxygen-carrying capacity. The 4.4-g dose produced significant increases in serum albumin and reductions in serum iron and blood lactic acid concentrations. The 6.6-g dose produced the greatest improvements in all areas, including noticeable changes in physical condition (self-assessment) and measures of muscle damage and oxygen-carrying capacity (Table 15.8).

In another long-term trial, rugby players ingested the same 6.6-g formula two times daily for 3 months during intense training.349 The investigators compared a variety of blood values following supplementation to presupplementation and 1 year postsupplementation in these continuously training athletes. Blood values following the supplementation period had significantly greater levels of red blood cells, hematocrit, and hemoglobin compared to presupplementation and 1 year postsupplemen-tation, indicating potentially enhanced oxygen-carrying capacity of the blood. In addition, subjective reports of the athletes indicated a favorable effect on their physical performance; however, subject blinding was not possible in this study (Table 15.9).

As with the overreaching study by Ratamess et al.,288 these studies seem to validate the use of AA supplementation during intense training. Many athletes, such as the track runners and rugby players in these studies, may always be close to overreaching or overtraining conditions for undesired or unknown periods. Based on these results, bodybuilders preparing for competition, star players that must play back-to-back games, practices, etc., or chronically overtrained athletes may all benefit from some sort of daily AA or high-quality protein supplementation.

TABLE 15.8

Effect of the 6.6 g/day Dose of the AA Mixture on Physical Parameters, Hematology, and Blood Biochemistry in Runners

Pre-Test Period Post-Test Period

TABLE 15.8

Effect of the 6.6 g/day Dose of the AA Mixture on Physical Parameters, Hematology, and Blood Biochemistry in Runners

Body weight, kg

60.4 ± 0.9

59.4 ±

0.9

Exercise load, % max

80 ± 4

90 ±

3

Physical condition (score range 1-5)

3.0 ± 0.1

3.7 ±

0.2*

Blood glucose, mg/dL

88 ± 1

93 ±

1*

Blood ammonia, |ig/dL

79 ± 3

82 ±

6

Blood lactate, mmol/L

1.2 ± 0.1

1.2 ±

0.1

Hematocrit, %

44.9 ± 0.8

46.8 ±

0.6*

WBC, |iL-1

5300 ± 400

5400 ±

300

RBC, 10>L

508 ± 12

528 ±

9*

Platelets, 10>L

20.3 ± 0.9

20.2 ±

0.8

Hemoglobin, g/dL

15.2 ± 0.2

15.8 ±

0.3*

Serum HDL, mg/dL

65 ± 5

63 ±

4

Serum albumin, g/dL

5.0 ± 0.1

5.2 ±

0.1*

Serum TC, mg/dL

168 ± 7

161 ±

7

BUN, mg/dL

17.2 ± 15

16.6 ±

0.8

Serum iron, |ig/L

114 ± 15

99 ±

12

Serum ferritin, |ig/L

40 ± 6

43 ±

7

Serum CPK, U/L

366 ± 52

198 ±

22*

Serum GOT, U/L

32 ± 2

24 ±

1*

Serum GPT, U/L

28 ± 3

27 ±

5

Serum LDH, U/L

365 ± 19

361 ±

16

Serum y-GTP, U/L

25 ± 4

25 ±

3

Note: Subjects (n = 13) consumed the 6.6 g/day AA mixture for 30 days

; blood

samples were taken just before and after the 30-day period. Data are means 6 SEM.

samples were taken just before and after the 30-day period. Data are means 6 SEM.

WBC = white blood cells; RBC = red blood cells; HDL = high-density lipoproteins; TC, total cholesterol; BUN = blood urea nitrogen; GOT = glutamate-oxaloacetate aminotransferase; GPT = glutamate-pyruvate aminotransferase; LDH = lactate dehydrogenase; y-GTP = y-glutamyltranspeptidase.

Reproduced from Ohtani et al, J. Nutr., 136(2), 538-543, 2006. With permission of American Society for Nutrition.

TABLE 15.9

Effect of Ingesting 6.6 g/d of the AA Mixtue for 90 d on Physical Parameters, Hematology, and Blood Chemistry in Elite Rugby Players

TABLE 15.9

Effect of Ingesting 6.6 g/d of the AA Mixtue for 90 d on Physical Parameters, Hematology, and Blood Chemistry in Elite Rugby Players

Sampling Time

a

Statisticsb

Pre

(A)

Post (B)

1-y Post (C)

A vs. B

B vs.

Body weight, kg

93.6

± 2.8

93.5

± 2.7

93.2 ±

2.6

BUN, mg/dL

16.4

± 0.8

16.1

± 0.6

17.7 ±

0.8

*

Creatine, mg/dL

1.09

± 0.04

1.10

± 0.03

1.14 ±

0.02

*

WBC, mm3

5900

± 200

5400

± 200

6500 ±

300

*

RBC, 10>L

505

± 7

516

± 13

490 ±

6

*

*

Hematocrit, %

44.5

± 0.6

46.2

± 0.5

43.4 ±

0.5

*

*

Hemoglobin, g/dL

15.3

± 0.2

15.6

± 0.2

14.8 ±

0.2

*

*

Serum iron, |ig/L

101

± 6

121

± 7

109 ±

9

Total protein, g/dL

7.1

± 0.1

7.2

± 0.1

7.1 ±

0.1

Total cholesterol, mg/L

169

± 5

191

± 8

178 ±

6

*

*

High density lipoprotein, mg/dL

52

± 2

52

± 2

51 ±

1

Low density lipoprotein, mg/dL

87

± 6

109

± 10

101 ±

8

*

Triglyceride, mg/dL

148

± 18

150

± 12

129 ±

13

GOT, U/L

28

± 4

26

± 2

28 ±

2

GPT, U/L

23

± 2

21

± 2

27 ±

4

Y-GTP, U/L

26

± 2

29

± 4

39 ±

6

*

Alkaline phosphatase, U/L

229

± 16

171

± 10

225 ±

22

*

*

a The 90-d study period occurred from June through August. b An asterisk indicates a significant difference (p < 0.05).

BUN, blood urea nitrogen; WBC, white blood cell count; RBC, red blood cell count; GOT, glutamate-oxalacetate aminotransferase; GPT, glutamate-pyruvate aminotransferase; y-GTP, y-glutamyl transpeptidase.

Reproduced from Ohtani et al., J. Nutr., 136(2), 538-543 , 2006. With permission from the American Society for Nutrition.

15.7.4 Conclusion and Suggestions

Daily exercise-induced changes in human muscle are virtually unnoticeable. Measurable alterations in muscle fiber type and diameter require repeated and progressive stimuli and relatively lengthy training periods (6 to 8 weeks).350-352 Also, it seems clear that it is the post-exercise period when the greatest changes in MPS and tissue structure occur.256257353 MPS can be stimulated in many ways, and as the research presented here describes, the various mechanisms may interact and have additive effects. Other variables are involved besides providing the appropriate amounts and types of AAs to muscle cells at the best times. Examples are type and amount of exercise, hormonal changes, cell volume changes, and vasodilatation. All of these elements may contribute to MPS and related adaptations to training.

Present rationale for a nutritional strategy to avoid training plateaus centers around findings354 that the extent of negative protein balance induced by exercise appears to remain constant throughout a prolonged training regimen. Consequently, repeated exercise sessions continue to provide opportunity or "open the door" for anabolism. When the benefits of training and diet on muscle mass/performance have stabilized, measures like properly timed ingestion of specific AAs may play a role in plateau avoidance and progressive development for some athletes.

The question that remains to be answered for serious athletes is: Given that diet and training are already as optimal as individually possible, can additional strategies incorporating supplementation with AAs further enhance performance and adaptations to training in sports? The following paragraphs summarize the current analysis on the subject.

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