|If Yap et al. were right and only continuous and not accumulative physical activity mattered, activity trackers like the this would be useless. No one needs a device to remind him of the 30 min of brisk walking he did / skipped today.|
- Dietary nitrate improves sprint performance and cognitive function during prolonged intermittent exercise - While anyone of you should know that nitrate from beetroots can have significant physiological effects, the observations Thompson et al. made in their recent double-blind randomised crossover study are probably real news and above all practically relevant for some of you and/or your clients from various athletic domains (Thompson. 2015).
To investigate the effects of dietary NO3(-) supplementation on exercise performance and cognitive function, the scientists had 16 male team-sport players consume NO3(-)-rich (BR; 140 mL/day; 12.8 mmol of NO3(-)), and NO3(-)-depleted (PL; 140 mL day/1; 0.08 mmol NO3(-)) beetroot juice for 7 days (these are the regular shots you can buy at supplement stores | if you want to drink regular beetroot juice, you need 3-4x the amount). With the nitrate supplement being consumed over a one week period we are thus not talking about the effects of acute, but about the effects of chronic supplementation. Keep that in mind, if you buy one shot and don't feel the results immediately.
On the test day the subjects completed a prolonged intermittent sprint test (IST) protocol (two 40-min "halves" of repeated 2-min blocks consisting of a 6-s "all-out" sprint, 100-s active recovery and 20 s of rest) on a cycle ergometer during which cognitive tasks were simultaneously performed.
Figure 1: Comparison of total work during the sprints and reaction times during cognitive decision making tasks designed to emulate the cognitive tasks during team sports (Thompson. 2015).
Even though, the scientists didn't find a difference in response accuracy, the findings are highly relevant for any athlete who has to (a) perform at high intensities, while (b) maintaining optimal cognitive performance and decision-making reaction times. Who is that? Well, I'd say almost every team sport athlete of whom previous studies have shown that his / her cognitive acuity suffers during prolonged intermittent exercise.
- Extra water is not necessary for optimal glycogen replenishment after workouts - In fact, bodybuilders may want to avoid it... Avoid water? No, I am not saying you should not drink water at all, but if you look at the results of Valentín E. Fernández-Elías' recent "analysis of the relationship between muscle water and glycogen recovery after prolonged exercise in the heat in humans" you will see that too much water in the post-workout window may actually give you the 'watery' look some physique athletes like bodybuilders are trying to avoid.
It is usually stated that glycogen is stored in human muscle bound to water in a proportion of 1:3 to 1:4 g. In their latest study, the scientists from the University of Castilla-La Mancha investigated this proportion in biopsy samples that were taken when their trained subjects recovered from prolonged exercise in the heat:
"On two occasions, nine aerobically trained subjects (VO2max = 54.4 ± 1.05 mL/kg/min; mean ± SD) dehydrated 4.6 ± 0.2 % by cycling 150 min at 65 % VO2max in a hot-dry environment (33 ± 4 °C). One hour after exercise subjects ingested 250 g of carbohydrates in 400 mL of water (REHLOW) or the same syrup plus water to match fluid losses (i.e., 3170 ± 190 mL; REHFULL). Muscle biopsies were obtained before, 1 and 4 h after exercise" (Fernández-Elías. 2015).In contrast to what you may have expected, the muscle glycogen replenishment was not impaired by the lack of water in the REHLOW group. Ok, if you look at the data in Figure 2 right, there is a minimal advantage for the adequate water group, but this advantage is not statistically and almost certainly not practically relevant (79 ± 15 and 87 ± 18 g/kg dry muscle; P = 0.20).
SuppVersity Suggested: "Hydrated or Dumb: Dehydration Affects Brain, Muscle and Other Vital Organs - Plus: 15+ Causes of Dehydration + Can the Color of Your Urine Tell You if You Drink Enough?" After reading this SV Classic and my recent article about the link between dehydration and type II diabetes you will probably stop thinking about using dehydration more than just occasionally.
- Study says: Only continuous, not accumulated 30 min of walking will improve your glucose sensitivity - While step counters suggest that all you have to do to improve your health is to take "X" steps per day, the conclusion of a recent study from the DSO National Laboratories in Singapore refutes the simple and beautiful idea that you can distribute the X number of steps you would usually take during 30 minutes of brisk walking over three or more small "exercise servings" and see the same benefits as you'd see with 30 minutes of continuous brisk walking:
"These findings demonstrate that 30 min of brisk walking is sufficient to improve insulin sensitivity in healthy, young Asians but only continuous and not accumulated walking provides this benefit. " (Yap. 2015).In said study, twenty-five healthy participants (12 males) participated in an oral glucose tolerance test (OGTT) the morning after: (i) accumulating three 10 min bouts of walking the previous evening; (ii) walking continuously for 30 min the previous evening or; (iii) resting the previous evening. Blood samples were taken in the fasted state and for 2 h post-OGTT. The subjects' insulin sensitivity was estimated from fasting blood glucose and insulin using the quantitative insulin sensitivity check index (QUICKI) and in response to the OGTT using an insulin sensitivity index (ISI-Matsuda).
Figure 3: Changes in fasting glucose, insulin and insulin sensitivity (QUICKI) the morning after accumulated walking, continuous walking or a rest day; values expressed rel. to sedentary control (Yap. 2015).
re-read the SV article.
- Ahtiainen, Juha P., et al. "Exercise type and volume alter signaling pathways regulating skeletal muscle glucose uptake and protein synthesis." European journal of applied physiology (2015): 1-11.
- Fernández-Elías, Valentín E., et al. "Relationship between muscle water and glycogen recovery after prolonged exercise in the heat in humans." European journal of applied physiology (2015): 1-8.
- Op‘t Eijnde, B., et al. "Effect of creatine supplementation on creatine and glycogen content in rat skeletal muscle." Acta physiologica Scandinavica 171.2 (2001): 169-176.
- Thompson, Christopher, et al. "Dietary nitrate improves sprint performance and cognitive function during prolonged intermittent exercise." European journal of applied physiology (2015): 1-10.
- Yap, Mei Chan, Govindasamy Balasekaran, and Stephen F. Burns. "Acute effect of 30 min of accumulated versus continuous brisk walking on insulin sensitivity in young Asian adults." European journal of applied physiology (2015): 1-9.