Studies are typically relatively short (weeks to months). However, we often want to know what happens with longer-term adherence to interventions such as a training protocol or a diet.
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Therefore, data from studies needs to be extrapolated; make assumptions what would happen if the interventions would be continued.
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Extrapolation requires assumptions. Essentially, weβre trying to make an educated guess what would happen. This guess should be based on the available data and logic.
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For example, if a study observes 5 kg fat loss after 12 weeks on a diet, that does not necessarily mean you can expect an additional 5 kg fat loss in the next 12 weeks.
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It is important to realize that extrapolation is heavily influenced by personal bias.
For example, if you are a proponent of a certain training style or diet, it is more likely that your extrapolation is (too) optimistic.
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It has been shown that a ketogenic diet decreases exercise performance, while a high carbohydrate diet increases exercise performance during a 3-week training program.
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A common critique is that this study gives a misleading picture, because the ketogenic diet is claimed to require a longer adaptation phase. Once the athlete is fully keto-adapted, the superiority of the ketogenic diet would become apparent (scenario 4).
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But scenario 4 is a drastic change compared to the observed data, requires several assumptions, and therefore the burden of proof would be on those would claim this scenario is most likely.
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An assumption of this scenario is that keto-adaptation requires >3 weeks, but there is no convincing supporting evidence.
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The second assumption of this scenario is that further keto-adaptation would drastically improve exercise performance. However, it could also be argued that further keto-adaptation would only further decreases exercise efficiency and performance (scenario 1).
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It is up to each individual to extrapolate how they see fit. The more an extrapolation diverges from the observed data, the more assumptions are involved. If no strong evidence for these can be provided, it may be a sign that the extrapolation is mostly wishful thinking.
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Creatine is an organic compound which is naturally present in our bodies. Creatine supplementation increases muscle creatine levels, strength and muscle mass gains during resistance training.
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Nitrate-rich beetroot juice has been shown to increase endurance performance because. Beetroot juice supplementation can also improve repeated sprint performance compared to nitrate-depleted beetroot juice.
The ketogenic diet is a very low carb, high fat diet, that claims to improve exercise performance by increasing the use of fat (fat oxidation) during exercise.
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This study investigated the effect of 3 different diets during an intensive training period on training adaptations in elite race walkers.
Protein ingestion after exercise stimulates muscle protein synthesis (the main process regulating muscle recovery, adaptation and growth). It has been well established that protein intake improves resistance training adaptations.
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However, little is known about the impact of protein on muscle adaptations following endurance exercise.
The gut absorption of the carbohydrate glucose is the limiting factor in using glucose drinks for energy during exercise (carbohydrate oxidation). Fructose is a carbohydrate that is absorbed differently in the gut than glucose. Sucrose consists out of glucose and fructose.
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Therefore, a combined ingestion of glucose and fructose allows a higher total carbohydrate absorption rate, oxidation rate, and exercise performance. But does this combination also improve the recovery of the muscle carbohydrate stores (i.e. muscle glycogen) after exercise?
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It is often suggested that coffee causes dehydration. This is because coffee contains caffeine, which has a dehydrating effect. However, coffee also contains fluid which has a hydrating effect. Therefore, it can be questioned if coffee intake really causes dehydration.
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This study investigated the effect of coffee intake on hydration levels in habitual coffee consumers (3-6 cups a day). Each subject participated in two 3-day experiment periods: one coffee period and one water period.
Poor sleep is associated with susceptibility to acute infectious illness. In addition, sleep deprivation has been shown to negatively affect immune system functioning. Does this mean that you have a higher chance of getting sick when getting insufficient sleep?
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This study investigated whether sleep duration affects the development of the common cold. Sleep duration was objectively measured for 7 days/nights with a sleep watch.