Found an interesting article (half way down page) on Mike Mahlers site recommending a carnitine product called Quadracarn containing four carnitine analogues that looks to be pretty good at improving androgen, insulin and leptin receptor activity. Never one to take things for granted, I tracked down some studies on the analogues used and the stuff does actually look pretty promising:
Androgenic Responses to Resistance Exercise: Effects of Feeding and L-Carnitine
KRAEMER, WILLIAM J.; SPIERING, BARRY A.; VOLEK, JEFF S.; RATAMESS, NICHOLAS A.; SHARMAN, MATTHEW J.; RUBIN, MARTYN R.; FRENCH, DUNCAN N.; SILVESTRE, RICARDO; HATFIELD, DISA L.; VAN HEEST, JACI L.; VINGREN, JAKOB L.; JUDELSON, DANIEL A.; DESCHENES, MICHAEL R.; MARESH, CARL M.
Purpose: The purpose of this investigation was to determine the effects of 3 wk of L-carnitine L-tartrate (LCLT) supplementation and post-resistance-exercise (RE) feeding on hormonal and androgen receptor (AR) responses.
Methods: Ten resistance-trained men (mean ± SD: age, 22 ± 1 yr; mass, 86.3 ± 15.3 kg; height, 181 ± 11 cm) supplemented with LCLT (equivalent to 2 g of L-carnitine per day) or placebo (PL) for 21 d, provided muscle biopsies for AR determinations, then performed two RE protocols: one followed by water intake, and one followed by feeding (8 kcal·kg-1 body mass, consisting of 56% carbohydrate, 16% protein, and 28% fat). RE protocols were randomized and included serial blood draws and a 1-h post-RE biopsy. After a 7-d washout period, subjects crossed over, and all experimental procedures were repeated.
Results: LCLT supplementation upregulated (P < 0.05) preexercise AR content compared with PL (12.9 ± 5.9 vs 11.2 ± 4.0 au, respectively). RE increased (P < 0.05) AR content compared with pre-RE values in the PL trial only. Post-RE feeding significantly increased AR content compared with baseline and water trials for both LCLT and PL. Serum total testosterone concentrations were suppressed (P < 0.05) during feeding trials with respect to corresponding water and pre-RE values. Luteinizing hormone demonstrated subtle, yet significant changes in response to feeding and LCLT.
Conclusion: In summary, these data demonstrated that: 1) feeding after RE increased AR content, which may result in increased testosterone uptake, and thus enhanced luteinizing hormone secretion via feedback mechanisms; and 2) LCLT supplementation upregulated AR content, which may promote recovery from RE.
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Effects of L-carnitine L-tartrate supplementation on muscle oxygenation responses to resistance exercise.
Spiering BA, Kraemer WJ, Hatfield DL, Vingren JL, Fragala MS, Ho JY, Thomas GA, Häkkinen K, Volek JS.
Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, Connecticut, USA.
Previous research has shown that L-carnitine L-tartrate (LCLT) supplementation beneficially affects markers of hypoxic stress following resistance exercise. However, the mechanism of this response is unclear. Therefore, the primary purpose of this study was to determine the effects of LCLT supplementation on muscle tissue oxygenation during and after multiple sets of squat exercise. Nine healthy, previously resistance-trained men (25.2 +/- 6.years, 91.2 +/- 10.2 kg, 180.2 +/- 6.3 cm) ingested 2 g.d of LCLT or an identical placebo for 23 days in a randomized, balanced, crossover, double-blind, placebo-controlled, repeated-measures study design. On day 21, forearm muscle oxygenation was measured during and after an upper arm occlusion protocol using near infrared spectroscopy (NIRS), which measures the balance of oxygen delivery in relation to oxygen consumption. On day 22, subjects performed 5 sets of 15 to 20 repetitions of squat exercise with corresponding measures of thigh muscle oxygenation, via NIRS, and serial blood draws. Compared to the placebo trial, muscle oxygenation was reduced in the LCLT trial during upper arm occlusion and following each set of resistance exercise. Despite reduced oxygenation, plasma malondealdehyde, a marker of membrane damage, was attenuated during the LCLT trial. There were no differences between trials in the vasoactive substance prostacyclin. In conclusion, because oxygen delivery was occluded during the forearm protocol, it is proposed that enhanced oxygen consumption mediated the reduced muscle oxygenation during the LCLT trial. Enhanced oxygen consumption would explain why hypoxic stress was attenuated with LCLT supplementation.
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Glycine propionyl-L-carnitine produces enhanced anaerobic work capacity with reduced lactate accumulation in resistance trained males.
Jacobs PL, Goldstein ER, Blackburn W, Orem I, Hughes JJ.
Department of Exercise Science and Health Promotion, Florida Atlantic University, Davie, FL 33314, USA. pjacobs4@fau.edu.
ABSTRACT: BACKGROUND: Recent research has indicated that short term administration of glycine propionyl-L-carnitine (GPLC) significantly elevates levels of nitric oxide metabolites at rest and in response to reactive hyperaemia. However, no scientific evidence exists that suggests such supplementation enhances exercise performance in healthy, trained individuals. The purpose of this study was to examine the effects of GPLC on the performance of repeated high intensity stationary cycle sprints with limited recovery periods in resistance trained male subjects. METHODS: In a double-blind, placebo-controlled, cross-over design, twenty-four male resistance trained subjects (25.2 +/- 3.6 years) participated in two test sessions separated by one week. Testing was performed 90 minutes following oral ingestion of either 4.5 grams GPLC or 4.5 grams cellulose (PL), in randomized order. The exercise testing protocol consisted of five 10-second Wingate cycle sprints separated by 1-minute active recovery periods. Peak (PP) and mean values (MP) of sprint power output and percent decrement of power (DEC) were determined per bout and standardized relative to body masss. Heart rate (HR) and blood lactate (LAC) were measured prior to, during and following the five sprint bouts. RESULTS: Significant main effects (p < 0.001) were observed for sprint bout order in values of PP, MP, DEC, and HR. There were significant main effects detected for condition in PP and MP (p < 0.05), with values across the five sprint bouts 2.6 - 15% greater with GPLC. Significant statistical interactions were detected between bout order and condition for both PP and MP (p < 0.05). There was a significant main effect of condition for LAC, LAC values 15.7% lower 4 min post-exercise with GPLC (p = 0.09) and with GPLC resulting in 16.2% less LAC at 14 min post-exercise (p < 0.05). CONCLUSION: These findings indicate that short-term oral supplementation of GPLC can enhance peak power production in resistance trained males with significantly less LAC accumulation.
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