No abstract

Branched‐chain amino acids (BCAA) are essential in the diet and promote several vital cell responses which may have benefits for health and athletic performance, as well as disease prevention. While BCAA are well‐known for their ability to stimulate muscle protein synthesis, their effects on cell energetics are also becoming well‐documented, but these receive less attention. In this review, much of the current evidence demonstrating BCAA ability (as individual amino acids or as part of dietary mixtures) to alter regulators of cellular energetics with an emphasis on mitochondrial biogenesis and related signaling is highlighted. Several studies have shown, both in vitro and in vivo, that BCAA (either individual or as a mixture) may promote signaling associated with increased mitochondrial biogenesis including the upregulation of master regulator of mitochondrial biogenesis peroxisome proliferator‐activated receptor gamma coactivator 1‐alpha (PGC‐1α), as well as numerous downstream targets and related function. However, sparse data in humans and the difficulty of controlling variables associated with feeding studies leave the physiological relevance of these findings unclear. Future well‐controlled diet studies will be needed to assess if BCAA consumption is associated with increased mitochondrial biogenesis and improved metabolic outcomes in healthy and/or diseased human populations.

Background. Type 2 diabetes is characterized by reduced insulin sensitivity, elevated blood metabolites, and reduced mitochondrial metabolism with reduced expression of genes governing metabolism such as peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). PGC-1α regulates the expression of branched-chain amino acid (BCAA) metabolism, and thus, increased circulating BCAA in diabetics may be partially explained by reduced PGC-1α expression. PGC-1α functions in-part through interactions with peroxisome proliferator-activated receptor β/δ (PPARβ/δ). The present report examined the effects of the PPARβ/δ agonism on cell metabolism and related gene/protein expression of cultured myotubes, with a primary emphasis on determining the effects of GW on BCAA disposal and catabolic enzyme expression. Methods. C2C12 myotubes were treated with GW501516 (GW) for up to 24 hours. Mitochondrial and glycolytic metabolism were measured via oxygen consumption and extracellular acidification rate, respectively. Metabolic gene and protein expression were assessed via quantitative real-time polymerase chain reaction (qRT-PCR) and western blot, respectively. Media BCAA content was assessed via liquid chromatography–mass spectrometry (LC/MS). Results. GW significantly increased PGC-1α protein expression, mitochondrial content, and mitochondrial function. GW also significantly reduced BCAA content within culture media following 24-hour treatment; however, expression of BCAA catabolic enzymes/transporter was unchanged. Conclusion. These data confirm the ability of GW to increase muscle PGC-1α content and decrease BCAA media content without affecting BCAA catabolic enzymes/transporter. These findings suggest heightened BCAA uptake (and possibly metabolism) may occur without substantial changes in the protein levels of related cell machinery.

and finish phases of the stroke. PURPOSE: To compare joint angles and peak angular velocities of the knee and lumbar spine during the feet-out drill, as well as peak lumbar extension timing within the stroke, on a static (SRE) versus dynamic (DRE) rowing ergometer, as well as between sexes. METHODS: 15 experienced rowers (8 females, 22.73 ± 5.51 years) participated in this study. Using a within-subjects, repeated measures design, subjects completed 750 meters of the feet-out drill on both the SRE and DRE at 20 ± 1 strokes per minute. Seven inertial measurement units were placed on the subjects' 7th cervical spinal process, sacrum, 12th thoracic spinal process, and bilateral thigh and leg segments. Peak lumbar extension timing for ten consecutive strokes was identified as a percentage of stroke. The beginning and end of each stroke was defined by maximum knee flexion. A mixed between-within ANOVA was run to compare males and females and between ergometers. Paired t-tests were run for kinematic variables between ergometers. Pearson correlations were used for weight and height with kinematic data. RESULTS: Peak lumbar extension occurred later on the SRE (38.08 ± 5.18%) when compared to the DRE (34.60 ± 3.93%, p = .01). Likewise, females had an earlier peak lumbar extension (n = 7, DRE 32.43 ± 3.05%, SRE 35.23 ± 4.12%) compared to males (n = 6, DRE 37.13 ± 3.40%, SRE 41.40 ± 4.41%, p =.01). SRE lumbar ROM and weight had a strong correlation (r = .86, p < .01) which was not seen with the DRE. CONCLUSIONS:The ratio of the phases of the drive and finish of the rowing stroke appears to be affected during the feet-out drill on a SRE vs DRE. The DRE appears to be the more ideal choice for a stroke with less emphasis on the second half of the drive and finish phases and for limiting lumbar spine ROM in heavier athletes. Coaches and athletes should proceed with awareness of such differences when choosing to complete the drill on a dynamic or static rowing ergometer.

The temporal order of movements in the joints and body segments have been described for various athletic movements. In baseball pitching, the proximal-to-distal kinematic sequence (KS) in the upper body is important for maximizing ball velocity and efficient energy transfer. Baseball batting is one of the most difficult skills in sports; however, few studies have investigated the temporal characteristics of baseball batting, particularly between players of different ages and skill levels. PURPOSE: To describe and compare the KS patterns of the pivot hip, the pelvis, and the lumbar and thoracic spine during baseball batting between young and adult players and to investigate the relationship between the KS patterns and batting velocity. METHODS: Twenty-nine high school (13 ± 0.7 yrs) and 30 collegiate (20 ± 1.4 yrs) baseball players underwent the biomechanical analyses of baseball batting. A three-dimensional motion analysis system and two force platforms were utilized for data collection. Each participant completed three baseball swinging trials off a tee. The best trial was used for data analysis. Thirteen KS patterns were identified and assigned into three categories based on the first joint/segment that achieved the peak angular velocity: 1) the pivot hip initiated, 2) the pelvis initiated, 3) the lumbar spine initiated. The chi-square test and one-way ANOVA were used for statistical analyses. RESULTS: Only 3 (10.3%) young players and 2 (6.7%) adult players demonstrated the ideal proximal-to-distal KS pattern. Although a higher percentage of adult players demonstrated the pelvis-initiated KS pattern, there was no significant difference in the KS patterns between groups (χ 2 = 3.221, p = 0.200). The batting velocity between three KS patterns also did not show any significant difference (pivot hip initiated: 68.54 ± 12.01 m/s; pelvis initiated: 75.23 ± 11.19 m/s; lumbar initiated: 71.89 ± 15.30 m/s; F = 1.579, p = 0.215). CONCLUSION: Young and adult baseball players demonstrated similar hip-pelvis-trunk KS patterns during baseball batting, and their KS patterns were not significantly associated with batting velocity. The KS patterns identified in this study can provide reference for analyzing baseball batting.