Physics

Fleming, N., Donne, B., Fletcher, D., & Mahony, N. (2012). A biomechanical assessment of ergometer task specificity in elite flatwater kayakers. Journal of Sports Science and Medicine, 11(1), 16+. Retrieved from http://sc4.idm.oclc.org/login?url=http://go.galegroup.com/ps/i.do?p=AONE&sw=w&u=lom_stclaircocc&v=2.1&it=r&id=GALE%7CA283261571&sid=summon&asid=1549fa1287050dcd7a4f761bf84a8090

The current study compared EMG, stroke force and 2D kinematics during on-ergometer and on-water kayaking. Male elite flatwater kayakers (n = 10) performed matched exercise protocols consisting of 3 min bouts at heart and stroke rates equivalent to 85% of V[O.sub.2]peak (assessed by prior graded incremental test). EMG data were recorded from Anterior Deltoid (AD), Triceps Brachii (TB), Latissimus Dorsi (LD) and Vastus Lateralis (VL) via wireless telemetry. Video data recorded at 50 Hz with audio triggers pre- and post-exercise facilitated synchronisation of EMG and kinematic variables. Force data were recorded via strain gauge arrays on paddle and ergometer shafts. EMG data were root mean squared (20ms window), temporally and amplitude normalised, and averaged over 10 consecutive cycles. In addition, overall muscle activity was quantified via iEMG and discrete stroke force and kinematic variables computed. Significantly greater TB and LD mean iEMG activity were recorded on-water (239 [+ or -] 15 vs. 179 [+ or -] 10 [micro]V.s, p < 0.01 and 158 [+ or -] 12 vs. 137 [+ or -] 14 [micro]V.s, p < 0.05, respectively), while significantly greater AD activity was recorded on-ergometer (494 [+ or -] 66 vs. 340 [+ or -] 35 [micro]V.s, p < 0.01). Time to vertical shaft position occurred significantly earlier on-ergometer (p < 0.05). Analysis of stroke force data and EMG revealed that increased AD activity was concurrent with increased external forces applied to the paddle shaft at discrete phases of the on-ergometer stroke cycle. These external forces were associated with the ergometer loading mechanism and were not observed on-water. The current results contradict a previous published hypothesis on shoulder muscle recruitment during on-water kayaking.

Pendergast, D., Mollendorf, J., Zamparo, P., Termin,A,,II, & al, e. (2005). The influence of drag on human locomotion in water. Undersea & Hyperbaric Medicine, 32(1), 45-57. Retrieved from https://sc4.idm.oclc.org/login?url=http://search.proquest.com/docview/204932965?accountid=41091

Propulsion in water requires a propulsive force to overcome drag. Male subjects were measured for cycle frequency, energy cost and drag (D) as a function of velocity (V), up to maximal V, for fin and front crawl swimming, kayaking and rowing. The locomotion with the largest propulsive arms and longest hulls traveled the greatest distance per cycle (d/c) and reached higher maximal V. D while locomotoring increased as a function of V, with lower levels for kayaking and rowing at lower Vs. For Vs below 1 m/s, pressure D dominated, while friction D dominated up to 3 m/s, after which wave D dominated total D. Sport training reduced the D, increased d/c, and thus lowered C and increased maximal V. Maximal powers and responses to training were similar in all types of locomotion. To minimize C or maximize V, D has to be minimized by tailoring D type (friction, pressure or wave) to the form of locomotion and velocity.

Vegas, Á., Liebman, J. F. and Jenkins, H. D. B. (2012), Unique thermodynamic relationships for ΔfHo and ΔfGo for crystalline inorganic salts. I. Predicting the possible existence and synthesis of Na2SO2 and Na2SeO2. Acta Crystallographica Section B, 68: 511–527. doi: 10.1107/S0108768112030686

The concept that equates oxidation and pressure has been successfully utilized in explaining the structural changes observed in the M2S subnets of M2SOx (x = 3, 4) compounds (M = Na, K) when compared with the structures (room- and high-pressure phases) of their parent M2S `alloy' [Martínez-Cruz et al. (1994), J. Solid State Chem.110, 397–398; Vegas (2000), Crystallogr. Rev.7, 189–286; Vegas et al. (2002), Solid State Sci.4, 1077–1081]. These structural changes suggest that if M2SO2 would exist, its cation array might well have an anti-CaF2 structure. On the other hand, in an analysis of the existing thermodynamic data for M2S, M2SO3 and M2SO4 we have identified, and report, a series of unique linear relationships between the known ΔfHo and ΔfGo values of the alkali metal (M) sulfide (x = 0) and their oxyanion salts M2SOx (x = 3 and 4), and the similarly between M2S2 disulfide (x = 0) and disulfur oxyanion salts M2S2Ox (x = 3, 4, 5, 6 and 7) and the number of O atoms in their anions x. These linear relationships appear to be unique to sulfur compounds and their inherent simplicity permits us to interpolate thermochemical data (ΔfHo) for as yet unprepared compounds, M2SO (x = 1) and M2SO2 (x = 2). The excellent linearity indicates the reliability of the interpolated data. Making use of the volume-based thermodynamics, VBT [Jenkins et al. (1999), Inorg. Chem.38, 3609–3620], the values of the absolute entropies were estimated and from them, the standard ΔfSo values, and then the ΔfGo values of the salts. A tentative proposal is made for the synthesis of Na2SO2 which involves bubbling SO2 through a solution of sodium in liquid ammonia. For this attractive thermodynamic route, we estimate ΔGo to be approximately −500 kJ mol−1. However, examination of the stability of Na2SO2 raises doubts and Na2SeO2 emerges as a more attractive target material. Its synthesis is likely to be easier and it is stable to disproportionation into Na2S and Na2SeO4. Like Na2SO2, this compound is predicted to have an anti-CaF2 Na2Se subnet.