Research provides deeper understanding of how ingesting the right nutrients at the right time can support an active lifestyle.
When it comes to exercise program design, educated fitness professionals know that rest, recovery and regeneration are just as important as training intensity and consistency. Clients get better results and reach their goals more quickly when they learn how to take care of their bodies in a smart, sound manner. Nutrition is also a key component of a complete wellness program. Nutrient timing in particular has been the subject of much discussion and research, especially over the past decade. This article looks at how the proper approach to “nutrition by the clock” can boost recovery and performance.
To better understand nutrition’s role in recovery, it’s essential to look at how exercise affects the body (Bird, Tarpenning & Marino 2006a; Kindermann et al. 1982; Bird, Tarpenning & Marino 2006b; Haff et al. 2003). Physiological changes occur in proportion to exercise duration and intensity. Insulin levels decrease in the blood, and levels of stress hormones (such as cortisol) increase—as they do in response to trauma. Carbohydrate stored in muscles as glycogen gets depleted, and muscle fibers break down (cell integrity is destroyed). Glycogen levels in the liver also drop. In general, there is a decrease in macronutrient availability (carbohydrates, fats, etc.) and in hydration levels. This places the body in a catabolic (or “breakdown”) state.
The noticeable effects of these physiological changes include increased and prolonged muscle soreness, low energy and extended fatigue (Touba & Lees 2010; Proske & Morgan 2001). Remedies include nutrition and rest. In fact, the effects can persist for several days if not addressed with rest and proper nutrition. This is where the postexercise meal can make a huge difference. Its focus is to convert the body from a catabolic state to an anabolic (or “buildup”) state. This is achieved by getting the correct nutrients in the right ratios at the appropriate time.
Certain physiological changes need to occur as a result of the postexercise meal. These changes include a rise in blood insulin levels. Insulin is an anabolic hormone with the ability to transmute “breakdown” to “buildup” (Haff et al. 2003). Insulin directly down-regulates cortisol and up-regulates carbohydrate storage, thereby restoring muscle and liver glycogen levels (Haff et al. 2003). Following exercise, insulin also slows muscle breakdown. The postexercise meal has the potential to maximize energy regeneration; therefore, it should be planned as one of the primary meals for the day. For light exercise, such slow walking or low-intensity weightlifting lasting less than 30 minutes, a postexercise meal is not necessary.
The postexercise meal provides energy replenishment. It ignites muscle glycogen recovery and helps repair and protect muscle. Muscle glycogen is important for endurance training as well as strength training. In fact, glycogen stores can be depleted twice as rapidly during resistance training as they can during an endurance or prolonged exercise event (MacDougall, Ward & Sutton 1977; MacDougall et al. 1999). Maintaining consistent stored glycogen levels over time increases the body’s ability to generate or maintain muscle tissue (for easier recovery, not for hypertrophy). Therefore, exercise adaptation may be easier with adequate glycogen stores, which may allow clients to make consistent progress in their training.
The effectiveness of glycogen storage replenishment after a workout relies on the timing of the postexercise meal. Body composition improves—lean mass increases and fat mass decreases—when the correct blend of calories is ingested immediately after exercise (Ferguson-Stegall et al. 2011a). Thus, if a client believes that taking in calories immediately after burning calories is negative, this thinking may need to be modified.
The concept of nutrient timing has been investigated for 30 years (Fell et al. 1982). However, recent clinical trials have provided fine-tuning on what to eat and when to eat it. Research has found that the best time to ingest a postexercise meal for optimal anabolic effect is within 30–45 minutes after exercise (Ivy & Portman 2004). This time period—when the body is most ready for recovery—is called the metabolic window. Ingesting the post-exercise meal within this window can lead to exercise recovery in a quick 4–10 hours (Ivy & Portman 2004). Beyond 45 minutes postexercise, the potential anabolic effect of the postexercise meal steadily declines until, at 2 hours, there is much less of an effect (recovery of 24–36 hours). This decline is due to the prolonged presence of the catabolic state in the body (Ivy & Portman 2004).
For someone who exercises once a week, these variations in anabolic effect may have limited importance. However, for fitness advocates and individuals who exercise several times a week or even several times a day, optimizing the effect is crucial for ensuring appropriate recovery in the shortest time possible. Also, some people who exercise heavily experience appetite suppression, and with them it may be particularly important to discuss the value of the postexercise meal and its timing. For these clients, it may be appropriate to suggest liquid nutrition or food supplements (protein shakes, carbohydrate beverages, etc.) as a viable alternative.
Historically, research on postexercise meal optimization for endurance exercise has focused on carbohydrates for energy replenishment. When it came to strength training, research focused on protein. As I have studied the scientific literature over the past decade, and especially for the past 3 or 4 years, research has honed in on what is needed for individuals who perform both enduranceand resistance/strength training exercise. For such people—who likely make up a large part of the personal training clientele—both carbohydrates and protein are required in an optimal postexercise meal.
A study led by John Ivy, PhD, professor emeritus in the department of kinesiology and health education at the University of Texas at Austin, showed that carbohydrate ingestion immediately following exercise increased glycogen storage almost twofold compared with carbohydrate ingestion 2 hours following exercise (Ivy et al. 1988). Subsequent research found that during the first 4 hours after exercise, the rate of glycogen synthesis increased with the quantity of carbohydrate intake up to a plateau level of 1.5–2.0 grams per kilogram (0.70–1.0 g per pound) of body weight (Coyle 1991). This target intake, however, results in a high caloric density. A more realistic carbohydrate intake is 0.5–1.0 g/kg of body weight, which balances adequate glycogen replenishment with caloric intake. To calculate the grams of carbohydrate required, divide body weight in pounds by 2.2 and multiply the resulting number by either 0.5 or 1.0, depending on the desired target carbohydrate intake and the person’s weight and goals.
Researchers have also investigated the types of carbohydrate required for the optimal postexercise meal. Clinical studies have demonstrated that for best recovery, both rapidly and slowly digested carbohydrates should be used after exercise (Achten et al. 2007; Holub et al. 2010). Rapidly digested carbohydrates, such as simple sugars (glucose and sucrose), provide an almost immediate large increase in blood glucose levels, which prompts insulin secretion and raises blood insulin levels. As mentioned previously, higher insulin levels help promote the anabolic state. Slowly digested carbohydrates, such as isomaltulose and waxy maize starch, provide a lower but more prolonged increase in blood glucose levels, for a full recovery. Food sources that contain slowly digested or low–glycemic index carbohydrates are fresh fruit, carrots and steel-cut oats. The effect of simple sugars declines within 1 hour after exercise, but the effect of slowly digested carbohydrates can last up to 2–3 hours (Achten et al. 2007; Holub et al. 2010).
When combined with a carbohydrate, protein intake maximizes the body’s ability to recover from exercise (Ivy et al. 2003). The combination of protein and carbohydrate in the postexercise meal boosts glycogen synthesis more than carbohydrate does alone. And with the addition of protein, blood insulin levels may rise more as well. Furthermore, because the presence of protein helps maximize muscle glycogen stores, protein consumption during the metabolic window allows individuals to consume fewer carbohydrate calories. A suggested ratio would be 3–4 g of carbohydrate for every 1 g of protein (Ivy & Portman 2004). However, as noted earlier, this results in a high caloric density. I therefore typically recommend a 2:1 ratio as an acceptable balance between calories and glycogen replenishment.
Protein intake may also reduce postexercise muscle damage by inducing repair. In one study using serum myoglobin (an oxygen-transporting protein found in muscle) as an indicator of muscle damage, the placebo group (who consumed artificially flavored, sweetened water) had the highest levels of blood myoglobin (Valentine et al. 2008). This indicated more muscle damage 6–9 hours after an extensive exercise period. The other groups—who consumed carbohydrate alone, high-carbohydrate alone or carbohydrate plus protein—all had significantly lower blood myoglobin levels (indicating less muscle damage) postexercise compared with the placebo group.
The carbohydrate-plus-protein group had the lowest myoglobin levels—nearly at preexercise levels—indicating that they had the least amount of muscle damage. This meant that the damage had been minimized and the muscle could repair and recover quickly. Similar results were found for other markers of muscle damage, such as creatine kinase (another protein found in muscle), when carbohydrates and protein were combined and consumed in the postexercise meal (Valentine et al. 2008).
Studies in both resistance and endurance exercise have shown that a carbohydrate-plus-protein postexercise meal benefits muscle repair. One study also demonstrated that subsequent exercise performance (after a 4-hour recovery period from the original exercise) improved in the carbohydrate-plus-protein group, compared with the carbohydrate and placebo groups (Ferguson-Stegall et al. 2011b).
Protein can be an expensive addition to the postexercise meal; therefore, the amount of protein necessary for optimal exercise recovery is a consideration. Moore et al. (2009) examined muscle protein synthesis—in the presence of differing amounts of protein, ingested immediately after the workout—for 4 hours following leg-based resistance exercise. These researchers found that optimal muscle protein synthesis occurred with 20 g of postexercise protein in men of average weight (86.1 ± 7.6 kg). However, is this protein intake level optimal for all active individuals?
Women have also been tested—with similar results—in other supporting studies. However, individuals with significantly higher-than-average muscle mass or those who want to build muscle (and have lower body fat) may need additional protein. Older or aging individuals may also need extra protein. As we age, muscle mass is naturally lost in a process known as sarcopenia. Losses can be 8%–10% or greater per decade, starting at around the age of 50 years (Doria et al. 2012). Regular exercise and high protein intake can slow the rate of muscle loss as we age.
The quality of protein we ingest is another factor affecting exercise recovery. Grains tend to be lower-quality proteins, but milk, chicken, fish, soy and vegetable proteins are higher quality (Institute of Medicine 2006). Commonly ingested proteins are whey, casein and soy. Whey protein contains a higher level of important amino acids—branch-chain amino acids—compared with soy and casein. And because whey is also digested and absorbed more rapidly, it produces a higher rate of muscle protein synthesis at rest and after exercise (Tang et al. 2009). Soy is digested faster than casein, so soy protein produces higher rates of muscle protein synthesis at rest and after exercise than casein. As both whey and soy are more rapidly digested than casein, they are better able to quickly stimulate muscle protein synthesis during recovery. Nevertheless, casein is still a high-quality protein; it is just digested more slowly and takes longer to produce results. Currently, other vegetable proteins, like pea protein, are being investigated as good sources of protein. Pea protein has a similar amino acid profile to that of soy and is digested in a similar way and at the same rate. Note that complementary proteins are needed in the diet to achieve a balanced amino acid profile.
The leucine metabolite ß-hydroxy- ß-methylbutyrate was originally investigated in cancer patients to halt disease-associated muscle loss (May et al. 2002). Over the past 16 years, HMB has been examined in healthy individuals for its effects on building and retaining muscle mass and strength. Trace amounts of HMB are found in foods, especially in certain types of fish and alfalfa.
A carefully selected 2,000-calorie diet will garner approximately 1 g of HMB. Leucine, ingested through dietary intake, is metabolized for energy production (90%) or converted to HMB (5%–10%) (Nissen & Abumrad 1997). For an average individual, the typical leucine intake from food is 6.1 g per day; thus, about 0.6 g of HMG is produced each day (Institute of Medicine 2005). In clinical studies, however, the typical HMB dose needed to achieve improvements in muscle strength is 3 g (Nissen & Abumrad 1997). Therefore, dietary supplementation is required to match those levels. Alternatively, an individual would have to consume five times the amount of leucine present in the usual diet!
The initial HMB study was conducted in healthy, untrained adults who consumed a controlled diet and performed 1.5 hours of weight training 3 days a week for 3 weeks (Nissen et al. 1996). After each training session, participants received a postexercise drink containing either nothing (control), 1.5 g of HMB or 3 g of HMB. By the end of the study, the control group had increased their total body strength by 8% (suggesting the strength exercise program was effective); however, the HMB groups had increased their total body strength by 13% and 18.4%, respectively. In addition, muscle breakdown markers were significantly lower in the HMB groups. In subsequent HMB studies involving resistance exercises, increases in lean body mass ranged from 50% to 200% for HMB subjects, with increases in body strength being similar for those who received HMB supplementation and those who did not (Nissen & Abumrad 1997).
Not all clinical HMB studies in humans have shown positive results for body composition and strength. Discrepancies between the positive and no-effect studies may be due to differences in study design and population (athletic level of fitness, supplementation dose and/or time period, and type of training).
Based on animal and human studies, HMB supplementation is considered safe, and there has been no evidence of adverse physical effects or negative blood results. A decrease in low-density lipoprotein cholesterol is the only effect observed on blood chemistry parameters (Nissen et al. 2000).
How do exercise professionals apply the information presented in this article while staying within scope of practice? Research supports the notion that the optimal postexercise meal for exercise recovery contains both carbohydrates and protein, with 20–25 g of whey protein and a 3:1 or 4:1 carbohydrate-to-protein ratio. However, taking calories into account, the 2:1 ratio of carbohydrate to protein is probably where most athletes will be comfortable.
Postexercise meals may consist of whole foods, liquid nutrition supplements, bars or smoothies. If whole foods are preferred over supplementation, individuals need to be aware of the quantities required to meet the recommendations. Examples of foods that contain 25–30 g of carbohydrate include 1 cup of juice or one large piece of fruit; one bagel or two slices of bread; 1 cup of most cereals; one large baked potato; 2 cups of milk; 1 cup of rice, corn or squash; and ⅔ cup of dried beans. Some very active individuals may need double or triple these amounts to meet their postexercise needs.
Examples of foods that contain 20–25 g of protein include three eggs (six egg whites or ¾ cup of egg substitute); 2 cups of milk; 3 cups of soy milk or yogurt; ¾ cup of cottage cheese; 3 ounces of chicken, fish, pork, of beef; 3 ounces of cheese (not cream cheese); and 6 tablespoons of peanut butter. Milk is an adequate but not necessarily optimal protein-carbohydrate drink for exercise recovery. Chocolate milk has been in the news lately as a postexercise food; however, keep in mind that the carbohydrates in most chocolate milk comes from added sugar and high-fructose corn syrup.
When implementing an integrated exercise program for active clients who are goal oriented, it’s important to include nutrition as a crucial factor in the recovery and regeneration discussion. Share information about nutrient timing and the postexercise meal as part of a well-rounded and successful experience.