Peak & Mean Power + Power Capacity Increase (5-8%) in 11 Trained Women W/ OTC Rhodiola Extract in Non-Sponsored Cross-Over Trial ++ Review of Evidence from Other Studies

While there's some evidence that other plants from the genus "Rhodiola" may have similar effects, you want to rely on the std. exctracts from "Rhodiola Rosea" that were used in several studies if you want to try it | for dosage recommendation, see bottom line.

Some of you will probably remember that "Rhodiola" aka"Golden Root" is a putative adaptogen, i.e. a "nontoxic [sic!] substance and especially a plant extract that is held to increase the body's ability to resist the damaging effects of stress and promote or restore normal physiological functioning" (Merriam-Webster Medical Dictionary)...

No? Well, I remembered "Rhodiola Rosea", as I should have written before to avoid confusion with other plants from the same genus, when I saw a recent post by Jason Cholewa on Facebook.

The link to a study that was attached to the post didn't just remind me of this almost forgotten herb (ten years ago it was used in many more 'kitchen-sink supplements' than today); It drew my attention to a recent paper by scientists from the Samford University in Birmingham, USA (Ballmann 2018).
In the conclusion of their abstract, the scientists, ..., write about the standardized Golden Root Extract (#GRE) that they tested in N=11 physically active college-aged females (=accruing at least 150 minutes/week of moderate physical activity) in a within groups counterbalanced placebo-controlled trial that...

"GRE [more specifically, 3x500mg of a std. Rhodiola extract per day for three days and 500mg in the AM on the test day,] may possess ergogenic benefits and findings hold important implications for boosting anaerobic performance in repeated anaerobic bouts of exercise" (Ballmann 2018).

Needless to say that this sounds interesting for all sorts of sports and athletes ranging from sprinters over team sports athletes to the average gymrat. And, if we take the large effect sizes into account, I would speculate that your next question is:

"Where can I buy this stuff?" 

The good news is: While it is a special product that is standardized for 3% total rosavins and 1% salidroside, you can, much in contrast to a dozen other promising herbal supplements, buy it (almost) everywhere - even the exact product that was used in the study at hand, i.e. NOW Food's 500mg caps which go by the simple name "Rhodiola".

This makes the study at hand particularly interesting for you, me, and everyone else who's always on the look-out for safe and still functional performance boosters that are actually available on the market (vs. some exotic extracts you would have to order from a research supplier such as Sigma Aldrich).

In that, it is not clear if a 'loading phase' as the scientists used it in the study at hand is even necessary. Other studies, I am about to cite later in this article seem to suggest that an effect can be seen immediately (~1h) post ingestion and evidence of a cumulative effect is - as of now - not available and warrants further research (see red box on potential anti-hormetic effects, too).

"So, I'll take 500 mg 30-60 minutes before workouts, right? Won't more help more?

If this is not your first visit at suppversity.com, you should know by now that "more helps more" is as invalid for supplements and exercise performance as it has been shown to before money and happinesss (Easterlin 1973).

Figure 1: In Noreen's 2013 study, the provision of R. rosea at a dosage of 3mg/kg  only once, 1 hour before the 6k-cycling trial, yielded significantly improved time-trial times (left) and reduced rates of perceived exertion (RPE | p = 0.04), as well as RPE/power (right | p = 0.007) compared to a carbohydrate placebo (adapted from Noreen 2013).

Moreover, studies like Noreen et al. (2013 | see Figure 1) or Duncan & Clarke (2014) seem to suggest that an even lower dosage of 3mg/kg of the same standardized extract taken 1h before (in those studies albeit aerobic) exercise tests will have significant ergogenic effects, too.

Overall, it has to be said, though that the optimal dosing strategy is still in the open, though, because: (a) we do not have any studies comparing different dosing regimens directly, and (b) we do not even know how Rhodiola Rosea does whatever it is, it does. If we knew (b), we could at least speculate about the optimal timing and potential dosing thresholds, but as of yet, there are only various unconfirmed and often disputed hypotheses as to how Rhodiola works.
These hypotheses include, most prominently, the 'ATP hypotheses'. Unfortunately, researchers from the Air Force Research Laboratory (Walker 2007) found in their 2007 study that the significant increases in ATP-turnover/resynthesis that had been observed in a previous rodent study (Abidov 2003) doesn't seem to occur in humans.

Walker et al. (2007) had used the same dosing scheme as Ballmann, but relied on what I would call a pretty odd performance test: wrist curls. Be that as it may,... their measurement of the ATP kinetics by phosphorus 31 nuclear magnetic resonance spectroscopy, revealed absolutely zero effects of the rhodiola supplement - whether that's simply due to the hardly exhaustive nature of the exercise protocol in this Air Force study, is not clear, but I certainly wouldn't discard the possibility of muscle-physiological/-metabolic effects completely with high(er) intensity exercise, yet.

The actual mechanism is not clear, but it could be of metabolic, muscle-physiologic or neuro-physiologic origin... or, obviously, a combination of all three!

If we look for other potential mechanisms, the previously cited study by Noreen et al (2013) comes to mind. The scientists Gettysburg College found significant performance improvements, in this case, improved 6-km cycle times (Figure 1, left), they ascribe to a reduced perception of effort (Figure 1, right). Similar beneficial effects on RPE were observed by Duncan & Clarke (2014), who tested the effects of 3mg/kg BW in ten young men, who completed two 30-minute cycling trials at an intensity of 70% of VO2Max in a double-blind, crossover design trial. Together these two studies seem to suggest that - at least during endurance exercise - the mechanism of action could, in fact, be of central neurological vs. peripheral muscle-physiological nature.

Figure 3: Mean anaerobic performance variables over all three WAnTs (for individual data see Figure 4). Data are presented as mean ±SD. * indicates significantly different from placebo (p < 0.05 | Ballmann 2018)

Since tests that would be able to confirm this hypothesis were not conducted in the Ballmann study, and the mean fatigue index (Figure 3, bottom right) was non-significantly elevated, not decreased, it does yet seem very unlikely that this is what triggered the beneficial effects Rhodiola had in this most recent study on the effects of Rhodiola on anaerobic exercise performance.

Figure 4: Results from the study under review (Ballmann 2018) - Anaerobic performance outcomes compared from 1st, 2nd, and 3rd 15-second Wingate Anaerobic Tests (WAnT); Data are presented at mean ±SD; * indicates significantly different from 1st WAnT, # indicates significantly different from 2nd WAnT (p < 0.05).

As far as the observed effects are concerned, it is worth mentioning that we're talking about a cumulative effect, which occurred in the absence of significant effects in the individual 15s-bouts of all-out cycling (see Figure 4).

This is in line with the previously hinted at observation that there are more 'Rhodiola studies' using aerobic vs anaerobic outcomes to gauge its efficacy; and, more importantly, that the former are also more likely to report performance increases than studies that used (ultra-)short bouts of high-intensity exercises, such as the 3x15s Wingate tests.

Even if Rhodiola was more of an endurance supplement, though, this would not change the results of the study at hand: There's a statistically significant cumulative effect over "only" 3x15s high-intensity cycling bouts in the study under review, which thus provides convincing evidence that:  Athletes competing in sports that require intermittent all-out sprinting or other forms of intermittent high-intensity exercise may benefit from standardized Rhodiola extracts.

Figure 5: Graphical illustration of the relative improvements in mean and peak power (blue) and anaerobic capacity and power (orange) with Rhodiola vs placebo; all differences that are shown were statistically significant (p < 0.05) in the cumulative analysis (i.e. considering all three bouts) and the individual effect sizes (Cohen's d) are provided in the captions.

In that, it is still not clear, whether the benefits, which I have summarized and plotted once more for you in Figure 5 (figure shows relative differences between Rhodiola and placebo), would occur with the 3mg/kg (for the ladies in the study at hand that would be ~200mg) dosage of the standardized extract that both, Duncan & Clarke (2014) and Noreen et al (2013), administered only once ~1h before the performance tests would be identical.How safe is rhodiola? While Rhodiola Rosea is not just easily available, but also classified as generally recognized as safe (GRAS), it should be mentioned that studies on potential supplement-drug interactions are ambiguous. While there's evidence of competition for CYP2C9 (Thu 2016 & Thu 2017) and other CYP enzymes, and hence potential interactions with NSAIDs, certain diabetes meds, angiotensin II inhibitors (blood pressure), SERMs (tamoxifen) and even sildenafil, Noeldner et al. and Panossian et al. write that the IC50 for interactions with drug metabolizing enzymes is too high to be physiologically relevant for the proprietary dry extracts WS® 1375 and SHR-5, respectively... if you take any meds, though, it makes perfect sense to check with your doctor before you trial any Rhodiola supplement.Another thing we have to keep in mind, though is that in a situation where we have almost no clue about the underlying mechanism of the effects, it is not warranted to blindly generalize the results from one exercise context (aerobic | Noreen 2013) to another (anaerobic | Ballmann 2018).

Sex differences are possible but unlikely in either, exercise-, or psychophysiological contexts.

Speaking of methodological differences, you may have noticed that Ballmann et al. as well as Naureen conducted their studies in healthy, college-aged, recreationally active women, not - as most studies do - in healthy, college-aged recreationally active men. This raises the question: Could the efficacy of Rhodiola be sex-specific? Well, while this cannot be completely ruled out, the previously referenced results from Duncan & Clarke (2014) do at least suggest that it works in males, too.

Figure 6: Illustration of observed benefits (not all unambiguous, though) of Rhodiola Rosea supplementation in exercise (blue) and psycho-physiological contexts (orange); based on a 2011 review by Hung et al.

This, i.e. an absence of significant inter-sex differences, can also be seen in the studies Hung et al. summarized in their 2011 review in Phytomedicine, which lists, on top of the exercise-related benefits that are the topic of the article at hand, additional psycho-physiological effects that range from the reduction of depressive symptoms, over general anti-stress and well-being effects to very practical reductions in work-related fatigue - even after night duty in both male and female subjects.

Other studies, reviewed by Ponassian & Wikman in Pharmaceuticals in 2010 found evidence supporting the benefits I've illustrated in Figure 6 and suggest the following related/additional benefits...

• CNS-stimulating effects and downstream benefits in physical & cognitive performance,
• Neuroprotective, hepatoprotective, and cardioprotective effects,
• general antioxidant, as well as radioprotective effects,
• anti-inflammatory/-allergic and immunotropic effects, as well as
• the previously hinted at antidepressive and anxiolytic.

Unfortunately, the methodology of the pertinent studies in this 2010 review is even more heterogeneous than in the exercise-related studies, I discussed in quite some detail. Hence, it's impossible to use them to refine the previously made statements about different timing and dosing regimen. A pattern that emerges, however, is that the dosages are mostly within a range of 100-500mg of standardized Rhodiola extracts (often identical to the one Ballmann et al. used) and that the supplement was administered, in most cases, only on the day the tests were conducted.
References:

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• Abidov, M., et al. "Extract of Rhodiola rosea radix reduces the level of C-reactive protein and creatinine kinase in the blood." Bulletin of experimental biology and medicine 138.1 (2004): 63-64.
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