Abhishek Balapur

Blood flow restriction reduces time to muscular failure

Abstract Exercise to failure results in similar muscle protein synthesis responses, independent of intensity. However, low-intensity exercise likely requires more repetitions and individuals with injuries may be incapable of sustaining the mechanical stress to reach failure. The aim of this study was to determine if knee wraps provide a stimulus to decrease time to failure. Twenty healthy individuals participated in a randomized crossover study consisting of three trials. The first trial was used to determine one-repetition maximum (1-RM) on leg extension. Participants were then assigned to a blood flow restriction or control group. After trial 2, participants crossed over to the opposite trial. Knee wraps were placed around the upper thigh of each leg during blood flow restriction. Leg extensions were completed at 30% 1-RM until failure. A rating of perceived exertion was taken after exercise and whole blood samples were taken before, after, and 3 min after exercise for the determination of lactate. Repetitions until failure and total work were significantly lower with practical blood flow restriction compared with the control trial. Metabolic stress as measured by whole blood lactate was higher immediately after muscular failure in the control compared with the blood flow restriction trial, but not so 3 min after exercise. There were no differences in ratings of perceived exertion. In conclusion, knee wraps provide a stimulus for blood flow restriction allowing failure to occur sooner with similar metabolic stress after reperfusion. However, similar perceptual responses despite the lower workload with blood flow restriction may limit its application to the highly motivated.

Blood flow-restricted walking does not result in an accumulation of metabolites.

The American College of Sports Medicine recommends lifting a weight of at least 70% of one’s concentric one repetition maximum to achieve muscular hypertrophy as it is believed that anything below this intensity does not produce significant muscle growth. Recent studies have found muscle hypertrophy to occur with low‐intensity ‘aerobic–like’ exercise with the application of blood flow restriction (BFR) to the limbs. Previous research with low load resistance training has shown that elastic knee wraps provide a practical means to induce elevations in whole blood lactate (WBL), which has been hypothesized to result in many of the adaptations observed with this type of exercise. However, this has yet to be investigated with low‐intensity walking. Thus, the purpose of this paper was to determine the degree to which WBL increases with practical BFR walking. Exercise consisted of five 2‐min bouts of walking at 75 m per min on a motor‐driven treadmill with a 1‐min rest period following each exercise bout. Participants completed the walking with (BFR) and without [control (CON)] restriction to the upper thigh in a randomized order. Practical BFR with elastic knee wraps did statistically increase WBL compared with CON; however, this was not considered a real change because the minimal difference between conditions was not exceeded. In conclusion, metabolic stress is not increased following practical BFR walking exercise. This study may provide an explanation for the lower hormone response observed with BFR walking and provide further evidence that mechanisms other than metabolic accumulation exist with BFR.

Time under tension decreased with blood flow–restricted exercise

Objectives: Exercise to failure results in similar muscle protein synthesis responses, independent of intensity. However, low‐intensity exercise likely requires more time under tension and those with injuries may be incapable of sustaining the mechanical stress to reach failure. Design: The purpose was to determine whether elastic knee wraps (KW) provide a stimulus to decrease time under tension and overall volume of work while maintaining a similar level of metabolic stress. Methods: Thirteen healthy subjects participated in a randomized crossover study consisting of three trials. The first determined 1 repetition maximum (1RM) on the bilateral leg extension. Subjects were then assigned to a blood flow restriction (BFR) or control (CON) group. After trial 2, subjects crossed over to the opposite trial. KW were placed around the thigh of each leg during BFR. Leg extensions were completed at 30% 1RM until failure. Whole blood lactate (WBL) was taken pre‐, post‐, and 3 and 5 min postexercise. Heart rate (HR) was measured before, following the first and second sets, and 3 and 5 min postexercise. Results: This study found KW provide a BFR stimulus allowing failure to occur sooner with similar metabolic stress postreperfusion. There were no differences in HR at any time point. Conclusions: These results may benefit populations that cannot sustain the mechanical stress of high‐intensity exercise or low‐intensity exercise that requires a longer sustained time under tension.

Short Report: Relationship between Quality Protein, Lean Mass and Bone Health

Background: Quality protein intake, and distribution of that protein, could play an important role with lean mass (LM), bone mineral density (BMD) and bone mineral content (BMC). Research has demonstrated that muscle protein synthesis is maximally stimulated at approximately 10 g of essential amino acids (EAA)/meal. This study sought to determine the relationship between the amount of quality protein consumed and the amount of times the approximately 10 g EAA threshold was reached at a meal, with respect to LM, BMD and BMC. Methods: Twenty-seven subjects participated in this study. EAA intake was determined from a 3-day food record, and amino acid profiling was determined using a computer program (USDA Database, release 22). LM, BMD and BMC were measured using dual-energy X-ray absorptiometry. Quality protein was defined as the ratio of EAA to total dietary protein. Data were analyzed using Pearson partial coefficient correlations, controlling for body mass, with an α-level of 0.05. Results: Quality protein consumed in a 24-hour period and the amount of times reaching the EAA threshold per day was positively associated with LM, BMD and BMC, and had an inverse relationship with body fat percentage. Conclusion: Both quality protein intake and frequency are positively associated with favorable body composition and bone health.

The relationship between quality protein, lean mass, and bone health

Background The amount of quality protein (Essential Amino Acids (EAA): Protein) intake, and distribution of that protein to a meal, could play an important role with regard to lean mass (LM), bone mineral density (BMD), and bone mineral content (BMC). Research has demonstrated that muscle protein synthesis (MPS) is maximally stimulated at ~10g of EAA per meal (Cuthbertson, et al. 2005). A cross sectional study sought to determine the relationship between the amount of quality protein consumed in 24 hours and the amount of times the ~10g EAA threshold was reached at a meal, with respect to LM, BMD, and BMC.

Contents Vol. 57, 2010

F. Azizi, Tehran A. Berg, Freiburg F. Branca, Rome R. Brigelius-Flohé, Nuthetal P.C. Calder, Southampton N. Chang, Seoul T. Decsi, Pécs K. Eder, Halle/Saale A. El-Sohemy, Toronto, Ont. H. Goldenberg, Vienna R. Hakkak, Little Rock, Ark. H. Hauner, Munich S. Hercberg, Paris H. Heseker, Paderborn N. Houalla, Beirut A. Kafatos, Heraklion M.-H. Kang, Daejeon E.T. Kennedy, Boston, Mass. M. Krawinkel, Giessen G. Krejs, Graz A.V. Kurpad, Bangalore W. Langhans, Zurich M. Lawrence, Burwood, Vic. D. Li, Hangzhou X. Lin, Shanghai J. Linseisen, Heidelberg J.A. Martinez, Pamplona Y. Naito, Kyoto H.Y. Paik, Seoul M. Panagiotidis, Reno, Nev. J.M. Pettifor, Johannesburg L.A. Réthy, Budapest G. Rimbach, Kiel J. Sabaté, Loma Linda, Calif. W.H.M. Saris, Maastricht L. Serra-Majem, Las Palmas de Gran Canaria A.P. Simopoulos, Washington, D.C. P. Stehle, Bonn J.J. Strain, Coleraine I. Th orsdottir, Reykjavik K. Tontisirin, Nakhon Pathom R. Uauy, Santiago H. Vannucchi, Ribeirão Preto A. von Rücker, Bonn M. Wahlqvist, Clayton W. Waldhäusl, Vienna E. Wasantwisut, Salaya B. Watzl, Karlsruhe W.M. Windisch, Vienna T. Yoshikawa, Kyoto J. Zempleni, Lincoln, Nebr. A. Zittermann, Bad Oeynhausen Journal of Nutrition, Metabolic Diseases and Dietetics