Benjamin T. Wall et al. 2011. The Journal of Physiology.<\/a><\/em><\/p>\n\n\n\nUp until the 2011 study, everyone was still confused about l-carnitine. Results of previous studies had been inconsistent, and the study designs themselves weren\u2019t always up to par.<\/p>\n\n\n\n
The 2011 study aimed to enhance the study design and build upon findings from the past, which highlighted the effects l-carnitine supplementation can have on muscle and exercise performance.<\/p>\n\n\n\n
From the work that came before their study, the scientists felt it was reasonable\/logical to conclude that by increasing the muscle carnitine reservoir (storage) via supplementation, a person could positively affect their muscle fuel metabolism in a couple of ways.<\/p>\n\n\n\n
The largest dynamic would be largely determined by the intensity level of exercise.<\/p>\n\n\n\n
Together, there was a study objective, followed by three hypotheses:<\/p>\n\n\n\n
Objective:<\/strong> Determine whether chronic L-Carnitine plus carbohydrate feeding (in healthy men) increased muscle carnitine content to the same degree as their previous lab studies.<\/p>\n\n\n\nHypothesis 1:<\/strong> Increased muscle carnitine content would decrease glycogen usage and increase\/sustain fatty acid usage as fuel during low intensity exercise<\/strong>.<\/p>\n\n\n\nHypothesis 2:<\/strong> When carnitine switches to acetylcarnitine during high intensity exercise<\/strong>, increased muscle carnitine content would increase mitochondrial flux, and therefore ATP production, thus reducing anaerobic ATP production and the concomitant lactic acid\/lactic acidosis.<\/p>\n\n\n\nHypothesis 3:<\/strong> Those positive effects of increased muscle carnitine content would improve high intensity exercise performance.<\/strong><\/p>\n\n\n\nThe study lasted 24 weeks, and involved 14 healthy, male recreational athletes in their mid-twenties who engaged in triathlon training (run, bike, swim) 3 to 5 times per week.<\/p>\n\n\n\n
Volunteers were tested before commencing the study\u2019s experimental visits to determine their VO2max (maximum amount of oxygen an individual can use during a maximal output exercise session).<\/p>\n\n\n\n
Their VO2max was tested again after the study to ensure no significant improvement in aerobic capacity had been made (meaning the supplemental protocol would be the cause of any significant change in performance).<\/p>\n\n\n\n
<\/span>The Experiment<\/span><\/h3>\n\n\n\nSubjects visited the lab 3 times over the 24 weeks with 12 weeks between each. They exercised on a cycle ergometer for:<\/p>\n\n\n\n
- 30 minutes at 50% max output, followed by<\/li>
- 30 minutes at 80% max output, followed by<\/li>
- 30 minutes of a work output performance test<\/li><\/ul>\n\n\n\n
The third 30 minute spell there is an \u201call out\u201d performance test but where the cycling cadence is under the subject\u2019s own control rather than a pre-determined percentage of VO2max to exhaustion.<\/p>\n\n\n\n
The scientists had determined from previous studies that \u201cvolitional cycling cadence\u201d for a fixed time was a better measure of endurance exercise performance.<\/p>\n\n\n\n
<\/span>The Study Supplementation Protocol<\/span><\/h3>\n\n\n\nThe fourteen men were split into two groups.<\/p>\n\n\n\n
Important:<\/strong> Insulin stimulates the transport and uptake of carnitine into muscle, which is why a carbohydrate drink was used as the delivery method in this study.<\/p>\n\n\n\n- Group 1: Consumed 80 grams of an orange flavoured carbohydrate drink (~600 calorie) twice per day for 168 days.*<\/li>
- Group 2: Consumed the same drink PLUS 2 grams (2000mg) of l-carnitine twice per day for 168 days.<\/li><\/ol>\n\n\n\n
*the first drink was taken at breakfast time and the second 4 hours later. Again, this was based on previous research which showed this to be a viable way to increase carnitine retention.<\/p>\n\n\n\n
<\/span>Samples and Analysis<\/span><\/h3>\n\n\n\nAt each of the three visits, several samples were taken from the subjects for analysis.<\/p>\n\n\n\n
- Blood samples for blood glucose, insulin and of course carnitine levels.<\/li>
- Muscle biopsies<\/strong> from the vastus lateralis (largest quad) at rest and within 5 seconds of finishing exercise, both at 50% and 80% VO2max (while they were still sat on ergometer) for free carnitine, acetylcarnitine, and long-chain acylcarnitine as well as ATP, phosphocreatine, creatine, lactate and glycogen<\/li><\/ol>\n\n\n\n
Let\u2019s just talk about those muscle biopsies for a second.<\/strong><\/p>\n\n\n\nStudy write-ups discuss muscle biopsies with the usual detached\/objective scientific voice, but they are an intense procedure for the subject.<\/p>\n\n\n\n
A biopsy is the surgical removal of muscle tissue. In this instance, the researchers used the Bergstrom percutaneous needle method. Despite sounding rather mild, it still removes a chunk of muscle a few millimetres in cross section, and has to be taken deep enough to ensure 100% muscle tissue extraction.<\/p>\n\n\n\n
With that in mind, remember that these med were subjected to 3 of these biopsies per visit, and two of them within 5 seconds of peddling on an ergometer. What\u2019s more the second and third bioposies were done on the bike immediately before cycling for 30 minutes at 80% VO2max and 30 minutes at volitional max respectively.<\/p>\n\n\n\n
It\u2019s safe to say that these dudes are pretty incredible, and to do this for the advancement of sports science is honourable.<\/p>\n\n\n\n
What I\u2019m saying here is:<\/strong> if you ever meet anyone who\u2019s been subjected to a muscle biopsy, or 9, then buy them a drink. We all benefit from the data that comes out of these studies, but not all of us get sliced up while doing an intense workout in the process.<\/p><\/blockquote>\n\n\n\n<\/span>Study Results<\/span><\/h4>\n\n\n\nThe results of the 2011 l-carnitine study can be summarized as follows:<\/p>\n\n\n\n
- The Carnitine group has no change in body mass over the 24 weeks, where the control group gained over 5 lbs.<\/li>
- Blood total carnitine concentrations were greater in Carnitine group after 12 and 24 weeks of supplementation.<\/li>
- Perceived exertion after the 24 week visit was lower in the Carnitine group compared to the control group<\/li>
- Muscle total carnitine content was 30% greater in the Carnitine group after 24 weeks compared to control.<\/li>
- Resting Free Carnitine trended to 30% greater in Carnitine group over control<\/li><\/ol>\n\n\n\n
The next sub-section is a continuation of the results, but merits some additional focus\u2026<\/p>\n\n\n\n
<\/span>Significant Differences in Metabolic Response to Exercise Intensity<\/span><\/h4>\n\n\n\nFollowing the low intensity exercise<\/strong> (50% VO2max) muscle glycogen content was 35% greater in the Carnitine group compared to control. This equated to 55% less glycogen being used during the exercise.<\/p>\n\n\n\nAlso, free carnitine was 78% greater in the Carnitine group compared to control.<\/p>\n\n\n\n
After high intensity exercise<\/strong> (80% VO2max) muscle glycogen was 71% greater in the Carnitine group over control. This was due to the reduction in glycogen usage during the low intensity exercise and so there was no difference in glycogen usage between groups after high intensity exercise.<\/p>\n\n\n\nHowever, muscle lactate content was 44% lower in the Carnitine group over control following the 80% VO2max cycling. This means of course that less lactic acid was produced during exercise, which in-turn means less anaerobic ATP production was required.<\/p>\n\n\n\n
There was also a trend towards greater acetylcarnitine and free carnitine in the Carnitine group.<\/p>\n\n\n\n
![\"L-Carnitine](\"https:\/\/www.gghc.org\/wp-content\/uploads\/2018\/08\/L-Carnitine750.jpg\")
<\/figure><\/div>\n\n\n\n![\"L-Carnitine](\"https:\/\/www.gghc.org\/wp-content\/uploads\/2018\/08\/L-Carnitine-3-750.jpg\")
<\/figure><\/div>\n\n\n\n