Tissue Oxygen Recovery Time Difference in Front and Back Squats

Muscle oxygenation (SmO2) has been studied through near-infrared spectrometry (NIRS) to describe the change in oxygen saturation within a muscle. The MOXY sensor is an inexpensive and mobile NIRS device. The purpose of this study is twofold: first to determine if SmO2 recovers faster when comparing individual hamstring or quadricep muscles and second to determine if SmO2 recovers faster when comparing front or back squats at 70% of an individual’s measured 1-repetition maximal (1-RM) weight. Eleven recreationally trained participants completed the study. Each participant performed a 1-RM test and another test at 70% of their 1-RM for both front and back squats. Data was collected during the 70% of 1-RM test by placing MOXY sensors on the vastus lateralis and biceps femoris of the left and right legs. SmO2 recovery rate was reported as the rate constant by performing a linear regression from 10-50 seconds of each resting period. A repeated measures ANOVA was used to determine whether there were significant differences in SmO2 recovery rates. The level of significance was set at p < .05. There was a significant difference of muscle type in each of the three rest periods of both the left and right legs (Right Leg 1st rest period: F(1,9) = 5.708, p = .041, Right Leg 2nd rest period: F(1,9) = 8.781, p = .016, Right Leg 3rd rest period: F(1,9) = 9.609, p = .013) (Left Leg 1st rest period: F(1,10) = 6.466, p = .029, Left Leg 2nd rest period: F(1,10) = 5.952, p = .035, Left Leg 3rd rest period: F(1,10) = 14.754, p = .003). The quadricep muscles had a greater recovery rate mean when compared to the hamstring muscle. With the greater recovery rate in quadricep muscles, this may suggest a faster recovery due to metabolic pathways, greater blood delivery, greater capillarization, or increased muscle activation compared to the hamstring muscles during the lifts

Muscle Oxygen Demands of the Vastus Lateralis in Back and Front Squats

International Journal of Exercise Science 13(6): 734-743, 2020. In resistance training squats are often used to strengthen the muscles of the lower extremities and core muscles. There are two common forms of squats that use a barbell for loading, the back squat and the front squat. The technique and loading of each squat differ markedly. However, the energetic demands on the muscle between the two forms are not well understood. The purpose of this study was to investigate the difference in energy demands between front and back squats by measuring the change in skeletal muscle oxygen saturation (SmO2) through the use of near infrared spectroscopy (NIRS). Methods: Eleven resistance trained individuals, (5 female, 6 male) with an average age of 23.7 ± 1.4, completed 3 sets of 15 repetitions at 70% of their 1-RM weight for both back and front squats. Skeletal muscle oxygen saturation (SmO2) of the vastus lateralis was measured using a wireless NIRS device. Results: The ΔSmO2 was not significantly different between back and front squats but was different between sets 1-3 (44.76 ± 3.24% vs. 55.19 ± 2.75% vs. 56.30 ± 2.63%), main effect p ≤ 0.0001 . The recovery of SmO2 was significantly different between back (42.5 ± 3.4 sec) and front squats (30.9 ± 2.8 sec), main effect p ≤ 0.05. Conclusions: The findings of this study suggest that the energetic demands placed on the vastus lateralis during both front and back squats are similar with a slower recovery of energetics in the back squat

Cooperative interactions among subunits of a voltage-dependent potassium channel. Evidence from expression of concatenated cDNAs

Four copies of the coding sequence for a voltage-dependent potassium channel (RBK1, rat Kv1.1) were ligated contiguously and transcribed in vitro. The resulting RNA encodes four covalently linked subunit domains ([4]RBK1). Injection of this RNA into Xenopus oocytes resulted in the expression of voltage-dependent potassium currents. A single amino acid substitution, Tyr--\u3eVal, located within the outer mouth of the pore, introduced into the equivalent position of any of the four domains, reduced affinity for external tetraethylammonium by approximately the same amount. In constructs containing 0, 1, 2, 3, or 4 Tyr residues the free energy of binding tetraethylammonium was linearly related to the number of Tyr residues. A different amino acid substitution, Leu--\u3eIle, located in the S4 region, was made in the equivalent position of one, two, three, or four domains. The depolarization required for channel activation increased approximately linearly with the number of Ile residues, whereas models of independent gating of each domain predict marked nonlinearity. Expression of this concatenated channel provides direct evidence that voltage-dependent potassium channels have four subunits positioned symmetrically around a central permeation pathway and that these subunits interact cooperatively during channel activation

Characterization of boron carbide thin films fabricated by plasma enhanced chemical vapor deposition from boranes

We have fabricated boron carbide thin films on Si(111) and other substrates by plasma-enhanced chemical-vapor deposition (PECVD). The PECVD of boron carbides from nido-cage boranes, specially nido-pentaborane(9) (B5H9), and methane ( CH4) is demonstrated. The band gap is closely correlated with the boron to carbon ratio and can range from 0.77 to 1.80 eV and is consistent with the thermal activation barrier of 1.25 eV for conductivity. We have made boron carbide by PECVD from pentaborane and methane that is sufficiently isotropic to obtain resistivities as large as 1010 Ω cm at room temperature. This material is also shown to be suitable for photoactive p-n heterojunction diode fabrication in combination with Si( 111)