Core muscles thickness is not associated with knee frontal plane projection angle during single-leg squat in healthy people.

BACKGROUND: Core muscles play an important role in lower limb stability and alignment, with their weakness being associated with poor alignment and, consequently, with injuries. Despite muscle structure being critical to muscle strength production, we did not find studies associating the morphology of the core muscles and lower limb alignment during functional tasks. RESEARCH QUESTION: Is there association between thickness of core muscles (external oblique - EO, internal oblique - IO, transversus abdominis - TrA and gluteus medius - GMed) and lower limb alignment during the single-leg squat in healthy subjects? METHODS: Forty-six healthy participants (27 male and 19 female) performed the following evaluations: (i) measurements of muscle thickness of the EO, IO, TrA and GMed using ultrasound and (ii) measurements of lower limb alignment using the knee frontal plane projection angle (FPPA) during the single-leg squat. A Spearman rank correlation coefficient (rs) was performed between the thickness of selected core muscles (OE, OI, TrA and GMed) and the knee FPPA. In addition, a partial correlation (r) was performed, using sex, physical activity level and body mass index as control variables. RESULTS: We did not observe significant correlations between the knee FPPA and the thickness of the EO (rs = 0.194; p = 0.197), IO (rs = 0.182; p = 0.225), TrA (rs = 0.073; p = 0.627) and GMed (rs = -0.092; p = 0.542). When controlling for sex, physical activity level and body mass index, similar results were observed [EO (r = 0.157; p = 0.316), IO (r = 0.261; p = 0.092), TrA (r = 0.030; p = 0.850) and GMed (r = -0.144; p = 0.356)] SIGNIFICANCE: Our results demonstrated that core muscles' thickness is not associated with lower limb alignment during the single-leg squat in healthy people.

Stability of functionalized corannulene cations [R-C20 H10 ](+) : An influence of the nature of R-Group.

The first comprehensive theoretical study of stability of hub-functionalized corannulene cations [R-C20 H10 ](+) as the function of the nature of R-group was accomplished. The initial set of linear alkyl R-group of different length (R=(CH2 )n CH3 , n = 0-9) was augmented by groups which form stable organic cations, such as tert-butyl, isopropyl, allyl, and phenyl. Investigation of relative stability (with bonding energy as the measure) was accompanied by detailed study of changes in aromaticity using a large set of descriptors, as well as by the evaluation of energetics of possible migration of R-group from the hub-site to the spoke-position. Decrease in stability of functionalized corannulene cations with lengthening of R-group and/or replacing it with branched alkyl group was found to be the general trend. At the same time, π-conjugated groups such as allyl or phenyl ones, stabilize the system. All methods/approaches applied unambiguously indicated that the actual stability of the hub-functionalized corannulene cations is indeed a multi faceted phenomenon. Important contributions come from different interplay between attractive (ΔEorb vs. ΔEelstat ) and repulsive (ΔEPauli ) components of the bonding, from changes in aromatic behavior of rings in polyaromatic fragment, and from activation barrier for the process of migration of R-group. © 2016 Wiley Periodicals, Inc.