Curious about how your menstrual cycle may affect your carbohydrate needs?
Estrogen has the effect of increasing glycogen uptake and storage in the muscle and glycogen sparing and increased fat utilization during exercise.
So, when estrogen is low, your body should be able to utilize relatively more endogenous carbohydrate (stored glycogen) to fuel exercise. Practically, this means you really need to pay attention to carbohydrate loading and post-exercise carbohydrate recovery to ensure you have adequate glycogen stores, particularly when you have back-to-back training days.
When estrogen is higher, your body should be able to oxidize relatively more fat compared to endogenous carbohydrate (glycogen) during exercise. Does this mean that you should be on a lower carbohydrate diet during these phases? NO! Not if you are still attempting to complete training sessions that include some intensity. This means you may need to increase the amount of exogenous carbohydrate you are taking in just before and during your training sessions to support higher intensity work. Remember, when carbohydrate intake rates are higher than 60 g/h, you are better off taking in mixed glucose-fructose carbohydrate sources to allow your GI tract to effectively absorb the carbohydrate for oxidation. Taking in high rates of carbohydrate also requires practice!
Final point, not all women are the same so MC and fueling needs can differ between individuals. It’s a great idea to start tracking your menstrual cycle and make notes on how you are feeling during training and recovery, and then start adjusting fuel as needed.
How do I use sports drinks?
We’ve talked about carbohydrate recommendations during training and racing, but sometimes it’s hard to EAT 60+ grams of carbs per hour, especially if you are out for a long/hard ride.
Did you know you can also meet (at least a portion) of your hourly carbohydrate goals with a carb-electrolyte drink (CHO-E)? But, before you go that route, you want to know the contents of what you are drinking, the mixing instructions, and scale the serving size information from the nutrition label to the amount of fluid in the bottle you are using.
If you are also using gels or chews, make sure you are factoring in the total grams of carbohydrate and milligrams of sodium the products are providing you together, with your CHO-E drink. Here are some of the more common drinks and their CHO and sodium content per 24 oz (710 ml).
Skratch Hydration: 31 g CHO, 570 mg sodium
Skratch Superfuel: 120 g CHO, 480 mg sodium
Tailwind Endurance Fuel: 50 g CHO, 600 mg sodium
Gu Roctane: 69 g CHO, 366 mg sodium
SWORD Performance: 45 g CHO, 600 mg sodium
As always, try it first during training, try it at race pace, and over time in multiple environmental conditions before you settle on a race day plan!
What are multi-transportable carbs and why do I need them?
Multiple transportable carbohydrates, aka different types of single carbohydrates (i.e. glucose, fructose, maltodextrin) can be beneficial during endurance activity lasting >2.5 hours in duration. Currently recommended practices for carbohydrate intake during endurance exercise include:
Optional CHO mouth rinsing during exercise 30-75 min
30–60 g/h during 1–2.5 h of endurance exercise
Up to 90 g/h of multi-transportable CHO (e.g. glucose or maltodextrin:fructose blends) for exercise >2.5 h.
Previously it was thought that the body could only utilize 1 g of CHO/min (60 g/h) during exercise. However, this was based on research examining a glucose-only solution. When researchers started adding different single CHOs (ie fructose) to the mix, carbohydrate delivery and oxidation rates increased.
Intestinal absorption of carbohydrate is the limiting factor when it comes to how much exogenous carbohydrate your body can utilize during exercise. Glucose and fructose rely on different transport proteins (SGLT1 and GLUT5) for absorption in the gut. Because the glucose transporter is saturated when glucose ingestion exceeds > ~60 g/h, multiple transportable CHO (e.g. glucose-fructose) solutions are recommended when CHO intake rates are higher than ~60 g/h. The ideal solution is proposed to contain a 2:1 glucose to fructose, or maltodextrin to fructose ratio (ie 60 g of glucose or maltodextrin, and 30 g of fructose). It should be noted that the fructose addition to glucose provides benefit after the glucose transporter is saturated at ~60 g/h.
Finally, research has suggested that multiple transportable CHO vs. single CHO can result in performance improvements. One study in particular found an 8% performance improvement with a glucose:fructose solution (56.1 min) compared to a glucose only solution (60.7 min) during a 40 km bike time trial that followed 2 hours of cycling at 55% of max in trained male cyclists. Evidence also suggests reduced GI discomfort with multiple-transportable CHO mixtures compared to glucose alone. Athletes can choose CHO-based sports nutrition products in the form of liquids, gels, or solids based on personal preference, environmental conditions, and demands of the course and event.
PMID: 26373645; 22468766; 20574242; 18202575
Do we need sex-specific carb intake recommendations during endurance exercise?
Ingestion of ~90 g CHO/h in the form of glucose or maltodextrin-fructose can increase exogenous CHO utilization and improve endurance performance. However, the majority of research in this area has been completed in males, but do women require different CHO intake recommendations during endurance exercise?
In general, women are able to oxidize a greater percentage of fat versus stored CHO (glycogen), compared to men completing endurance exercise at the same relative intensity. However, current research does not suggest a sex-difference in exogenous CHO oxidation during exercise after ingesting a glucose solution. What about the ingestion of multiple-transportable CHO (e.g. glucose-fructose solution) > 60 g/h?
A recent study provided elite male and female cross-country ski athletes an 18% maltodextrin and fructose hydrogel beverage at a rate of 2.2 g/min (132 g/h) during a 2 h roller skiing protocol in cold ambient conditions at 70% max. Neither group experienced GI symptoms and there were no significant differences in glycogen utilization change, peak rate of exogenous CHO oxidation (though females tended to have lower peak oxidation rates than males, 1.2 vs 1.5 g/min), RPE, or performance between males and females in response to CHO ingestion.
Results from other studies measuring exogenous CHO oxidation in females vs. males are mixed. Some indicate that exogenous CHO oxidation is ~2-4% higher in females compared to males while others found the opposite or no difference. More research is needed to answer this question specifically, but at this point there is insufficient evidence to indicate CHO intake recommendations should be different for females and males engaging in endurance exercise. Further, it has been demonstrated that both male and female athletes can tolerate high rates (>90 g/h) of CHO (glucose-fructose) intake without experiencing GI symptoms in cool conditions.
Finally, because hormonal changes throughout the menstrual cycle may iinduce changes in fuel utilization, eating a pre-exercise CHO meal in addition to ingesting ~90 g of multiple transportable CHO per hour during endurance exercise > 2.5 h may help minimize hormonal effects and help support performance.
PMID: 10953068, 12070184, 14750011, 14967866, 16278245, 20019632, 31655603, 34015236
Caffeine
Caffeine is a plant alkaloid substance that primarily works by creating actions in the central nervous system. It’s a very well-researched ergogenic aid that reduces symptoms of both physical and mental fatigue and has both stimulatory and psychological effects.
At normal doses, caffeine’s benefit is most likely due to its action as a nonspecific adenosine antagonist in the nervous system by blocking effects of adenosine and increasing transmission of excitatory neurotransmitters such as dopamine. Effects of caffeine ingestion include increased arousal, perceived energy (mental and physical), reduced sense of effort or fatigue during mental or physical tasks, improved cognition, and increased motor drive from the central nervous system to the muscles. Fat lipolysis, metabolic rate, and 24-hour energy expenditure may also be increased after caffeine ingestion. The half-life of caffeine in the body is approximately 5 to 7 hours. Moderate caffeine intake (~3 mg/kg/d) is generally recognized as safe and doses of up to ~6 mg/kg have been shown to improve physical performance. Some individuals, however, may sense jitteriness or perceive other such negative effects near 3 mg/kg.
Find the caffeine content in popular caffeinated beverages in the table below:
Beverage and Typical Caffeine Content (mg)
8 oz drip coffee: 65–180 mg depending on brew method, beans, and grind
1 oz espresso coffee: 30–50 mg
8 oz energy drink: ~80 mg
8 oz decaffeinated coffee: 2.5 mg
How Does Caffeine Benefit Endurance Performance?
Caffeine’s benefit to endurance performance largely relates to caffeine’s ability to:
decrease perception of effort during exercise
increase motivation and perceived energy
increased motor drive
Caffeine also benefits more powerful, explosive movements, likely by increasing peak force production and the rate of force production in the larger lower body muscles. It’s recommended to ingest caffeine (in coffee or another form) approximately 45 minutes prior to exercise in order to attain maximum benefit from the supplement.
Recovery snack ideas
There doesn’t seem to be a strict time frame on the post-exercise recovery window, but we do know that the sooner you can take in your recovery nutrition, the better. While the training is the important stimulus to improve your performance on the bike, you actually make the gains during recovery. Here are a couple tips to ensure you’re getting in what you need to maximize your training and recovery.
If you didn’t take in any calories during the workout but the workout was shorter than 45 minutes and pretty easy, you don’t need a specific recovery drink or meal. Rehydrate with fluid and electrolytes, and eat your next healthy meal or snack as planned.
If the workout was longer than 60 minutes or a hard one, try to take in a recovery snack or drink within 30-60 minutes. A good rule of thumb is to get about 1 gram of carb per kg of your bodyweight. The addition of 20-25 grams of protein is also beneficial, particularly for women and aging athletes. You can then eat your next regular healthy snack or meal another 60-90 minutes after your recovery snack or drink.
Try some of these great examples of post-ride recovery snacks:
Sandwich with protein
Waffles with fruit and yogurt
Rice with eggs and veggies
Yogurt with fruit and granola
Steel-cut oats with fruit
Toast with eggs
Protein smoothie with whey protein, your favorite milk, a banana, some frozen fruit, and a handful of spinach
Should you be taking beetroot juice?
Beetroot juice (BRJ) is often ingested by athletes for its purported benefits on improving exercise capacity and exercise performance through conversion into nitric oxide (NO). NO is active in physiological mechanisms such as vasodilation, immune function, neurotransmission, mitochondrial respiration and skeletal muscle contraction. Dietary nitrate supplementation has been associated with reduced blood pressure, improved muscular contractile function, improved exercise economy, exercise tolerance and cognitive function (Jones et al. 2021). The reduction pathway of nitrate-nitrite-NO is particularly active under conditions when oxygen is limiting, suggesting it may benefit high intensity exercise and possibly performance in high altitude environments.
When dietary nitrate is ingested, the bacteria present in the mouth begins the process of reducing nitrate to nitrite which then increases circulating levels of nitrite which can ultimately be reduced to NO in the circulation and other tissues. Athletes who maintain a diet rich in leafy green vegetables and beets would ingest some amount of dietary nitrate through these food sources. However, many athletes also choose to supplement with BRJ as it can deliver a higher, measurable concentration of nitrate in an easy-to-ingest supplement that can be timed appropriately prior to training or competition. An individual’s ability to benefit from dietary nitrate is dependent on the health of the oral microbiota; and, use of antibacterial mouthwash can also inhibit the reduction of nitrate to nitrite. The composition of the oral microbiome appears to differ between women and men suggesting women may benefit less from nitrate supplementation (Wickham et al. 2019). Interestingly, compared to a high carbohydrate diet, a low-carbohydrate high fat diet also alters the composition of the oral microbiome (Murtaza et al. 2019), suggesting dietary strategies of athletes can also influence the efficacy of nitrate supplementation.
While it has been suggested that dietary nitrate supplementation may have an ergogenic effect, the mechanisms that may improve markers related to endurance exercise appear to be more prevalent in recreational athletes versus in highly trained (Senefeld et al. 2020) but it is possible that highly trained athletes may observe a benefit of supplementation on high intensity performance (Jones et al. 2018). It is not clear why elite athletes may not benefit from supplementation compared to their less trained counterparts, but possible reasons may include elite athletes already having high baseline concentrations of nitrate and nitrite and diets that are habitually high in dietary nitrate. Likewise, women do not appear to benefit from supplementation compared to males, possibly due to higher baseline nitrite levels and the oral microbiome; however, studies in women are extremely limited in the literature (Wickham and Spriet 2019). However, the ergogenic effects of dietary nitrate appear to be highly individual and complex. Recommended dose of BRJ supplementation is suggested to be >300 mg (5 mmol) or higher up to 25 mmol (Senefeld et al. 2020) for trained athletes, ingested at least 90 minutes up to 3.5 h (Jones et al. 2021, Senefeld et al. 2020) prior to exercise. Both acute and multi-day supplementation protocols may be effective (Senefeld et al. 2020).
Though NO has a very short half life in the body, it remains possible that NO can be oxidized back into nitrate and nitrite. If a high level of nitrate supplementation is regularly ingested, there may be associated health risk factors including the formation of carcinogenic nitrosamides and nitrosamines (Zamani et al. 2020). The risks of BRJ are not well studied in the literature but warrant investigation to ensure the safety as an ergogenic aid. Interestingly, Gallardo and Coggan (2019) investigated the nitrate and nitrite content of 45 commercially available BRJ supplements and found that only five of the supplements contained at least 5 mmol nitrate per serving with a moderate-large variability between samples of the same product and large variability between products. Not only are the supplements unregulated, most products do not indicate nitrate content on the label and very rarely are the supplements independently tested to ensure content accuracy.
Should you be taking BCAAs?
BCAAs (branched chain amino acids), leucine, isoleucine, and valine, are three of the nine essential amino acids (EAAs), meaning our body cannot synthesize them, so we must consume them in our diet. BCAAs are present in complete protein sources such as animal proteins (eggs, dairy, poultry, meat, fish) as well as in soy. Many sports nutrition foods and protein powders have added BCAAs and whey and soy protein powders provide all the EAAs including BCAAs.
BCAAs are unique in that they are the only amino acids that the muscle can directly take up and utilize for energy. As glycogen depletes leucine oxidation increases; however, the amount of BCAA oxidation is still generally small during prolonged endurance exercise (>90 min), compared to carbohydrate and fat. BCAAs are also important for triggering the anabolic process of muscle protein synthesis (MPS), although leucine appears to be the primary driver for this. Finally, BCAAs have been suggested to counteract aspects of “central fatigue”.
Like all amino acids, BCAAs flux in and out of the body’s amino acid pool and are used by the body as needed based on the relative demand. Provided an athlete is ingesting adequate protein in their diet and eating high-quality proteins that provide all EAAs, there should be a sufficient amount of BCAAs available in the AA pool for the body to use when needed. In theory, supplementing with BCAA during endurance efforts could support BCAA oxidation, possibly delaying fatigue and improving performance or exercise capacity. However, there is a lack of evidence to suggest that BCAA supplementation actually improves performance. If an athlete is not able to regularly meet protein needs through the regular diet, it is possible that supplementing with BCAAs or with protein and carbohydrate during exercise could be beneficial, especially if the athlete is not meeting during-exercise carbohydrate needs.
Regarding MPS and recovery, leucine is the primary driver of the anabolic response. Likewise, if an athlete is ingesting sufficient protein in the regular diet with adequate leucine, BCAA supplementation is likely not necessary. Research examining the effect of BCAA supplementation compared to a placebo does indicate elevated markers with respect to MPS response, but when compared to a complete protein like whey, BCAAs do not appear to perform better.
Factors related to central fatigue during prolonged exercise are complex and it has been suggested that exercise-induced increases in serotonin may contribute to sensations of fatigue. In theory, it might be expected that BCAA ingestion can blunt the increase in serotonin, thereby decreasing fatigue factors. However, research has been inconclusive in this area and fatigue remains a complex phenomenon.
If you regularly fall short on your protein intake, it would be worth trying supplementation with a complete protein supplement that is high in EAAs and BCAAs like whey. There may be days when you do very long training sessions (or ultra-distance races) and it’s not possible to ingest all your daily protein in regular meals. In this case, you may consider trying a BCAA supplement during exercise and then ingest a high-quality recovery drink and meal ASAP post-exercise. Again, the response to BCAA supplementation is generally equivocal in the literature but you may find that it works for you.
A BCAA supplement may contain ~1.7-3.5 g leucine per serving. For reference, 20-25 grams of whey protein would also provide the recommended amount of leucine.
Taking current evidence into consideration, it makes sense to
Hit your daily protein target by choosing complete protein sources and complementary plant protein sources as often as possible. Both quantity and quality matter!
Eat a mixed meal (carbohydrates with some protein) prior to training
Take in the recommended amount of carbohydrate per hour (as best you can)
Try adding BCAA or protein+carb if you cannot meet your during-exercise carb needs (e.g. during ultra-endurance activity)
Consider additional strategies to help performance, for example there is strong evidence that caffeine combined with carbohydrate may improve performance and counteract central and peripheral fatigue factors. However, if you feel like BCAAs provide a benefit to you as well, the psychological edge may be worth it.
PMID: 22150425, 33106933, 18577773, 24791922, 30854370
Practical tips for training the gut
Higher carbohydrate intake is associated with improved endurance performance but it’s not always comfortable to take in 60-90 grams (or more!) per hour when you haven’t practiced it. If you have a hard time taking in the recommended amount of hourly carbohydrate intake, you aren’t alone! The most common reasons for not reaching the recommendations seem to be:
- GI issues
- Too full
- Carrying that much fluid/food for several hours
- Low appetite and feeling like you’re “forcing” nutrition intake
- More carbs doesn’t seem necessary if you feel like you are performing well with less
In this post I want to address one of the most common complaints: GI issues. But, GI symptoms don’t have to be a regular occurrence if you work on TRAINING THE GUT...Yes! The gut is trainable just like the rest of your body. If you are barely able to reach the 60 g CHO/h intake recommendation then it’s not likely that you will be able to easily go out and throw back 90 g CHO/h without issues. That’s why we need to be deliberate in how we train our body’s ability to digest, absorb, and utilize that amount of hourly carb intake.
One of the best ways to adapt our GI system to a higher carbohydrate intake during exercise is to eat more carbohydrates in your regular diet. Repeated exposure to carbohydrates, including glucose and fructose, can speed up gastric emptying rates of these monosaccharides and increase the transporter activity to facilitate better absorption and oxidation of the carbohydrate. Benefits may include decreased feelings of “fullness”, less GI distress, and better overall performance. There are several other things you can implement when “training the gut”:
1) Start euhydrated (consume ~2-4 ml/lb fluid with sodium 2-4 h prior to establish euhydration)
2) Hydrate with ~ 400-800 ml/h using fluid with sodium (adjust as needed based on environmental conditions)
3) Gradually increase the hourly rate of carbohydrate intake
4) Practice ingesting carbs during different types of workouts (intermittent high intensity intervals and steady state, short and long duration)
5) Train shortly after a meal
6) Decrease fat/fiber/protein leading in the meal(s) prior to the training session
7) Practice your race nutrition strategy in different conditions well in advance of your goal event
PMID: 28332114, 26891166
