Research on exercise and Heart rate etc...

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    • Yesterday I was having another read of the article by Stephen D Phinny linked a couple of posts up called Ketogenic Diets and Physical Performance and found his conclusion at the end interesting.

      The reason being is the focus of caution has always been on continious high intensity, say over 70% of your heart rate, for example running. But in his conclusion he is cautioning against anaerobic (aka weight training and sprinting) in fit athletes on ketogenic diets after adaption has taken place. I should add this article is in reference to fit athletes not on a calorie deficit and receiving supplemented amounts of sodium and pottasium and adequate protein.

      The conclusion below:


      Both observational and prospectively designed studies
      support the conclusion that submaximal endurance performance
      can be sustained despite the virtual exclusion of
      carbohydrate from the human diet. Clearly this result
      does not automatically follow the casual implementation
      of dietary carbohydrate restriction, however, as careful
      attention to time for keto-adaptation, mineral nutriture,
      and constraint of the daily protein dose is required. Contradictory
      results in the scientific literature can be
      explained by the lack of attention to these lessons learned
      (and for the most part now forgotten) by the cultures that
      traditionally lived by hunting. Therapeutic use of
      ketogenic diets should not require constraint of most
      forms of physical labor or recreational activity, with the
      one caveat that anaerobic (ie, weight lifting or sprint) performance
      is limited by the low muscle glycogen levels
      induced by a ketogenic diet, and this would strongly discourage
      its use under most conditions of competitive

      Will have to check this out some more... but anyway I thought it was interesting, especially coming from a well known low carb researcher.
      Low Carb in a Nutshell ~ Carb Counts ~ Research ~ Measurements/Conversions ~ Glossary

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    • Anthony Colpo has a new forum now focused on athletes and low carb diets, anyway he has a thread going which I think really goes well with this thread so thought I should add it here: [removed link as unfortunately his forum no longer exists]My own experience, and why I started this forum

      So If your interested in this go check out the discussion in his thread.

      I'm going to quote what he said in his reply to me here just for my reference:

      AnthonyColpo wrote:

      Hi Sherrie,

      The study I was referring to was:

      Helge JW, et al. Interaction of training and diet on metabolism and endurance during exercise in man. J Physiol. 1996 Apr 1; 492 (Pt 1): 293-306.

      You can access the full text for free here:…rtid=1158881&blobtype=pdf

      A few comments on this study: The study extended 8 weeks, during the first 7 weeks one group ate a high-carb diet, the other a low-carb, high fat diet. During the eighth week, both groups ate the high-carb diet. During the first 4 weeks, the subjects trained 3 x a week, during the last 4 weeks they trained 4 x a week on stationary cycles, at a controlled exercise intensity that ranged between 60 and 85%. The workouts lasted 60-75 minutes.

      During the first 7 weeks, the high-carb group ate 546g carbs and 75g fat per day; The low-carb/high fat group ate 177g carbs and 217g fat per day. Both groups ate similar amounts of protein. For those who object that 177g carbs per day does not constitute a low-carb diet, keep in mind that blood ketones rose markedly during the 7 weeks in the LCHF group, and were far higher at 7 weeks than in the HCLF group. Traditional thresholds for ketosis are based on studies conducted with sedentary folks; strenuous exercise can change the picture significantly.

      When time to exhaustion at 81% VO2max was tested at 7 weeks, the HCLF group improved their time by 191%, compared to only 68% in the LCHF group--a hefty 280% difference! After the eighth week, when both groups ate the the high-carb diet, the LCHF group managed to impove their time by another 18%, but their average time to exhaustion was still 26% shorter than in the high-carbers.

      In their paper, the authors speculated that, based on muscle biopsy results, the reduced performance in the LCHF group was due not to muscle glycogen depletion but impaired delivery of glucose in the working muscles, an explanation that I found a little hard to fathom. Indeed, in a later review, Helge writes:

      "Evidence is presented that short term adaptation, < 6 days, to a fat-rich diet is detrimental to exercise performance. When adaptation to a fat-rich diet was performed over longer periods, studies where performance was tested at moderate intensity, 60 to 80% of maximal oxygen uptake, demonstrate either no difference or an attenuated performance after consumption of a fat-rich compared with a carbohydrate-rich diet. When performance was measured at high intensity after a longer period of adaptation, it was at best maintained, but in most cases attenuated, compared with consuming a carbohydrate-rich diet. Furthermore, evidence is presented that adaptation to a fat-rich diet leads to an increased capacity of the fat oxidative system and an enhancement of the fat supply and subsequently the amount of fat oxidised during exercise. However, in most cases muscle glycogen storage is compromised, and although muscle glycogen breakdown is diminished to a certain extent, this is probably part of the explanation for the lack of performance enhancement after adaptation to a fat-rich diet."
      (Helge JW. Adaptation to a fat-rich diet: effects on endurance performance in humans. Sports Med. 2000 Nov; 30 (5): 347-57.)

      The literature in this field seems pretty consistent: straight low-carb diets suck for fuelling high level endurance training. But carb-cycling is a different story, one that may allow us to have our low-carb cake and eat it too.

      My strategy of drinking large amounts of carbs immediately after a ride is aimed at preventing muscle glycogen depletion in the first place by taking advanantage of the well-established fact that muscle glycogen synthesis is really kicking immediately after intense activity. If I was to have 150g of carbs away from a workout, I would be in carb coma land within 30 minutes. After a hard ride, however, the carbs get sucked up like water into a dry sponge.

      Low Carb in a Nutshell ~ Carb Counts ~ Research ~ Measurements/Conversions ~ Glossary

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    • Re: Research on exercise and Heart rate etc...

      "Fat adaptation" for athletic performance: the nail in the coffin?

      Louise M. Burke Department of Sports Nutrition
      Australian Institute of Sport
      Canberra, Australia
      and School of Nutrition and Exercise Science
      Deakin University
      Melbourne, Australia

      Bente Kiens
      Copenhagen Muscle Research Centre (CMRC)
      Institute of Exercise and Sport Science
      Department of Human Physiology
      University of Copenhagen
      Copenhagen, Denmark

      [SIZE=-2]ENDURANCE[/SIZE][SIZE=-2] ATHLETES[/SIZE] have a high capacity for the oxidation of fat during exercise as a legacy of their training. Therefore, it is intriguing that this capacity can be easily upregulated by the chronic consumption of a low-carbohydrate (<2.5 g·kg–1·day–1), high-fat ([Blocked Image:]65–70% of energy) diet. For example, 2–4 wk of exposure to such a diet in trained individuals has been shown to markedly increase fat oxidation and reduce the utilization of muscle glycogen during subsequent submaximal exercise (10, 11). Despite the promise of an enhanced ability to "tap into your body fat," fat loading per se does not seem to lead to a clear enhancement of exercise capacity or performance (for review, see Ref. 8). In fact, there is at least a short-term increase in the perceived effort of training (2, 3) and an impairment of the response to training when the high-fat, low-carbohydrate eating continues for periods longer than 4 wk, based on data from previously untrained individuals (7).

      Several more recent studies reignited the interest in fat loading for athletes. Goedecke and colleagues (5) provided a practical option with their observations that an increased fat utilization during submaximal exercise could be achieved in as little as 5 days of training on a high-fat (69% of energy), low-carbohydrate diet. These adaptations were subsequently shown to be consistent and robust, persisting in the face of protocols to increase carbohydrate availability by subsequent restoration of muscle glycogen content with 1 day of rest and the intake of a high-carbohydrate intake (10 g·kg–1·day–1) (1, 3, 4) or the consumption of carbohydrate before and during a bout of prolonged exercise (3, 4). Such a combination of dietary strategies would seem the perfect competition preparation for an endurance or ultraendurance athlete, simultaneously restoring carbohydrate stores while maximizing the capacity for fat oxidation during submaximal exercise. Interestingly, when carbohydrate loading after dietary fat adaptation is extended beyond 3 days, muscle glycogen stores are supercompensated, and a high-carbohydrate utilization during exercise is achieved (8). Nevertheless, the effect of various "dietary periodization" on exercise performance has remained unclear, with studies reporting benefits (9), no change (1, 3, 4), or impairment (7, 8) to various endurance and ultraendurance protocols. A variety of explanations has been offered to explain the apparent lack of transfer between metabolic changes and performance outcomes (2). They include the failure of scientists to detect small changes in performance that might be worthwhile in real-life sports and the existence of "responders" and "nonresponders" to fat-adaptation strategies (1, 11). In addition, adaptations to a fat-rich diet have been shown to increase plasma norepinephrine concentrations and heart rate during submaximal exercise (7), possibly leading to increased perceived effort of exercise training (2, 3). The paper by Havemann and colleagues (6) in the present issue of Journal of Applied Physiology adds weight to this possibility.

      Previous studies have focused on the metabolic changes occurring with dietary fat adaptation strategies as an indication of the upregulation of fat metabolism. Mechanisms have included increases in putative fatty acid transporters as well as enzymes of lipid metabolism (for reviews, see Refs. 2, 8). However, there is now evidence that what was initially viewed as "glycogen sparing" after adaptations to a fat-rich diet may be, in fact, a downregulation of carbohydrate metabolism or "glycogen impairment." One study (12) has reported that fat adaptation/carbohydrate restoration strategies are associated with a reduction in the activity of pyruvate dehydrogenase; this change would act to impair rates of glycogenolysis at a time when muscle carbohydrate requirements are high. The present study of Havemann et al. (6) furthers our knowledge by applying the fat adaptation/carbohydrate restoration model to an endurance cycling protocol that involves several features of a real-life race: self-pacing and the interspersing of high-intensity bouts of cycling with more moderate-intensity segments. The results show that the dietary strategy has no effect on overall performance of a 100-km time trial but compromises the ability of well-trained cyclists to performance high-intensity sprints.

      It is tempting to classify endurance and ultraendurance sports as submaximal exercise, which might benefit from increased fat utilization and a conservation of limited endogenous carbohydrate stores. However, the strategic activities that occur in such sports, the breakaway, the surge during an uphill stage, or the sprint to the finish line, are all dependent on the athlete's ability to work at high intensities. With growing evidence that this critical ability is impaired by dietary fat adaptation strategies and a failure to find clear evidence of benefits to prolonged exercise involving self-pacing, it seems that we are near to closing the door on one application of this dietary protocol. Scientists may remain interested in the body's response to different dietary stimuli and may hunt for the mechanisms that underpin the observed changes in metabolism and function. However, those at the coal-face of sports nutrition can delete fat loading and high-fat diets from their list of genuine ergogenic aids for conventional endurance and ultra-endurance sports.

      Free Full Text:
      Burke LM, Kiens B. "Fat adaptation" for athletic performance: the nail in the coffin? J Appl Physiol. 2006 Jan;100(1):7-8.

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