Update and extension of the 'equivalent slope' of speed-changing level locomotion in humans : a computational model for shuttle running

Controlled experimental protocols for metabolic cost assessment of speed-changing locomotion are quite complex to design and manage. The use of the 'equivalent slope', i.e. the gradient locomotion at constant speed metabolically equivalent to a level progression in acceleration, has proved valuable in the estimation of the metabolic cost of speed-changing gaits. However, its use with steep slopes requires extrapolation of the experimental cost versus gradient function for constant running speed, resulting in less-reliable estimates. The present study extended the model to also work with deceleration, and revised the predictive equation to enable it to be applied to much higher levels of speed change. Shuttle running at different distances (from 5+5 to 20+20\u2005m) was then investigated using the novel approach and software, and the predictions in terms of metabolic cost and efficiency compare well with the experimental data

THE EFFECTS OF GRAVITY ON HUMAN LOCOMOTION REPERTOIRE: COST OF TRANSPORT & BODY CENTRE OF MASS ANALYSIS

Human legged locomotion has been widely studied from both mechanical and bioenergetics points of view, however some aspects are still unaddressed and this thesis aimed to analysed some of them. One of the two methods for calculating muscular work during locomotion, which is an interesting parameters that can describe locomotion and subjective featuring, concerns the body centre of mass (BCoM) movements. The BCoM is the ideal point of the body where all forces act, and especially in a multi segment body as the human body, it is much easier and useful to calculate and follow its trajectory as the movement of the whole body. In order to compute BCoM two methods can be used: a double integration of the ground reaction forces, the forces exerted by feet when in contact to the ground, based on Newton\u2019s second law, which is considered the gold standard, and called Direct Dynamics; and the weighted mean of segments centre of mass (COM) obtained by motion analysis, called Inverse Dynamics. Segments mass and COM location are based on anthropometric tables, which are scaled on subjects\u2019 lengths; this is an approximation and assumes that segments are rigid, introducing potential errors. Even if there is not a complete 3D validation of Inverse Dynamics as a function of speed in the human gaits, Inverse and Direct Dynamics are often used interchangeably. In the first part of the thesis Inverse and Direct Dynamics in the human locomotion repertoire were compared in order to analyse different models, based on different anthropometric tables, and validate Inverse Dynamics. BCoM trajectory in walking, running and skipping is well described by Inverse Dynamics models employing a whole body marker set, where the main body segments are considered for BCoM calculation. On the contrary, simplified estimation models employing few markers, such as just one marker on the trunk or the mean of the pelvis, poorly match Direct Dynamics trajectory. Same results come from the further analysis of muscular work, where whole body models better describe and match Direct Dynamics data. Some interesting observations emerged from these analyses: i) two anthropometric tables with quite different segments definition reach the same results; ii) whole body models of Inverse Dynamics well matched Direct Dynamics values, validating this methods, whereas poor models should not be employed anymore; iii) the difference between Inverse and Direct Dynamics in the same gait is almost speed independent highlighting a systematic error, and among gaits it shows the same trend; iv) race walking BCoM trajectory cannot be described with any Inverse Dynamics models, therefore only ground reaction forces should be used for computation. Skipping is the third paradigm of human locomotion. Differently from walking and running, it was only investigated on level ground, addressing the much expensive cost of transport as the reason for its under use in day life activity; conversely it was displayed by astronauts of Apollo missions on the Moon. In the second part of this thesis the mechanics and bioenergetics of skipping on gradient was investigated since Ed Mitchell during Apollo 14 mission explicitly said \u201cThat nice skipping gait that I liked was very easy to do going downhill\u201d. Gradient range was \ub115%, the range of gradient presents on the Moon. On Earth skipping cost is higher than walking and running at all gradients and it decreases with speed, differently from the other gaits no minimum was found during downhill skipping, and it is impossible to skip at positive gradient steeper than 5% due to muscular demand and consequent fraction of metabolic power. When analysing mechanical parameters, the work done by muscles to move BCoM (WEXT) and the work done to accelerate limbs with respect to BCoM (WINT), skipping changes are similar to running with WEXT decreasing with downhill gradient and increasing speed, whereas WINT increases with speed. These results show that skipping on gradient can be performed on Earth only downhill due to the great metabolic demand. However, skipping cost of transport is always higher than walking and running at the same slopes. Based on these findings and astronauts\u2019 choices, we could expect that gravity plays an important role on skipping and locomotion cost of transport, which are analysed and discussed in the third part of this thesis. Low gravity locomotion can be studied on Earth with different methods, the gold standard is the parabolic flight, since with the adequate angle of the airplane parabola it is possible to obtain gravity levels ranging from hypo-gravity (including 0 g) to hyper-gravity. However the time available at low gravity simulation is only about 30 seconds, which is too short for metabolic measurements. The second most used method is based on the body weight suspension, where subjects are unloaded of the desired body weight by the suspension of the body via bungee cords or springs. We re-vamped the Margaria\u2019s low- gravity \u2018cavedium\u2019 with a treadmill and two bungee cords free to stretch until 16 m and let subjects walk, run and skip on a range of speed with Moon and Mars gravity, in order to study cost of transport and biomechanical parameters. Walking range of speed decreases with gravity and cost of transport decreases by 18% in hypo-gravity; higher decrements are shown in bouncing gaits, running and skipping. On the Moon their cost is the same and comparable with terrestrial walking values. Being on Earth was almost 40% higher than running, skipping shows the best decrease and a threefold gain in operative speed. This means that on the Moon human can skip three times faster than on Earth with the same metabolic power, whereas running gain is only twofold. Mechanically these cost changes can be explained by a reduction in pendulum-like recovery of energy in walking that needs a higher muscular work, whereas in skipping it is not shown. Moreover WEXT is lower in low gravity and a greater reduction of WINT in skipping compared with running can partially explain the major reduction in skipping cost. Another interesting aspect related to gait mechanics regards stability, and when the surface is slippery, as on the Moon due to regoliths, balance during support phase becomes an important issue. Skipping, compared to running, involves a shorter stance phase and also a double support, in which the trajectory of the flight can be adjusted. Moreover higher vertical forces on the ground and a greater angle at take off let the foot to be less slippery when pushing the body forward. Based on this biomechanical and bioenergetics analyses it can be concluded that human locomotion on hypo-gravity planets will be a bouncing gait and probably skipping could be preferred to running. Secondly the decrease of skipping cost up to walking values on Earth can explain the astronauts\u2019 choice of skipping during Apollo missions

Body center of mass trajectory and mechanical energy using inertial sensors: a feasible stride?

Background: The description of the three-dimensional (3D) trajectory of the body center of mass (BCoM) provides useful insights on the mechanics of locomotion. The BCoM trajectory can be estimated from ground reaction forces, recorded by force platforms (GRF, gold standard), or from marker trajectories recorded by stereophotogrammetric systems (MKR). However, both instruments do not allow for monitoring locomotion in the real-life environment. In this perspective, magneto-inertial measurement units (MIMUs) are particularly attractive being wearable, thus enabling to collect movement data out of the laboratory. Research questions: To investigate the feasibility and accuracy of a recent marketed full-body MIMU-based method for the estimation of the 3D BCoM trajectory and energetics during walking. Methods: Twelve subjects walked at self-selected and slow speed along a 12 m long walkway. GRF and MKR were acquired using three force platforms and a stereophotogrammetric system. MIMU data were collected using a full-body MIMU-based motion capture system (Xsens MTw Awinda). The 3D BCoM trajectory, external mechanical work and energy recovery were extracted from the data acquired by the three measurement systems, using state-of-the-art methods. The accuracy of both MKR- and MIMU-based estimates compared with GRF was assessed for the BCoM trajectory (maximum, minimum, range, and RMSD), as well as for mechanical work and energy recovery. Results: A total number of 108 strides were analyzed. MIMU-based BCoM trajectory displayed larger errors in comparison with GRF (and MKR) for the trajectory ranges: 89 ± 47(93 ± 44)% in antero-posterior, 46 ± 25(40 ± 79)% medio-lateral and -13 ± 23(-5 ± 25)% vertical directions, leading to a 3D RMSD of 17 ± 5(12 ± 5) mm (mean ± SD). These discrepancies largely affected the estimation of both mechanical work and energy recovery (+115 ± 85% and -28 ± 21%, respectively). Significance: Preliminary findings highlighted that the tested MIMU-based method for BCoM trajectory estimation still lacks accuracy and that the quantification of energetics in real-life situations remains an open challenge

A "wearable" test for maximum aerobic power : real-time analysis of a 60-m sprint performance and heart rate off-kinetics

Maximum aerobic power (V.O2peak) as an indicator of body fitness is today a very well-known concept not just for athletes but also for the layman. Unfortunately, the accurate measurement of that variable has remained a complex and exhaustive laboratory procedure, which makes it inaccessible to many active people. In this paper we propose a quick estimate of it, mainly based on the heart rate off-kinetics immediately after an all-out 60-m sprint run. The design of this test took into account the recent availability of wrist wearable, heart band free, multi-sensor smart devices, which could also inertially detect the different phases of the sprint and check the distance run. 25 subjects undertook the 60-m test outdoor and a V.O2peak test on the laboratory treadmill. Running average speed, HR excursion during the sprint and the time constant (t) of HR exponential decay in the off-kinetics were fed into a multiple regression, with measured V.O2peak as the dependent variable. Statistics revealed that within the investigated range (25-55 ml O2/(kg min)), despite a tendency to overestimate low values and underestimate high values, the three predictors confidently estimate individual V.O2peak (R2= 0.65, p < 0.001). The same analysis has been performed on a 5-s averaged time course of the same measured HR off-kinetics, as these are the most time resolved data for HR provided by many modern smart watches. Results indicate that despite of the substantial reduction in sample size, predicted V.O2peak still explain 59% of the variability of the measured V.O2peak

Ground reaction forces of Olympic and World Championship race walkers.

Abstract Race walking is an Olympic event where no visible loss of contact should occur and the knee must be straightened until midstance. The purpose of this study was to analyse ground reaction forces of world-class race walkers and associate them with key spatiotemporal variables. Nineteen athletes race walked along an indoor track and made contact with two force plates (1000 Hz) while being filmed using high-speed videography (100 Hz). Race walking speed was correlated with flight time (r = .46, p = .049) and flight distance (r = .69, p = .001). The knee's movement from hyperextension to flexion during late stance meant the vertical push-off force that followed midstance was smaller than the earlier loading peak (p < .001), resulting in a flattened profile. Athletes with narrower stride widths experienced reduced peak braking forces (r = .49, p = .046), peak propulsive forces (r = .54, p = .027), peak medial forces (r = .63, p = .007) and peak vertical push-off forces (r = .60, p = .011). Lower fluctuations in speed during stance were associated with higher stride frequencies (r = .69, p = .001), and highlighted the importance of avoiding too much braking in early stance. The flattened trajectory and consequential decrease in vertical propulsion might help the race walker avoid visible loss of contact (although non-visible flight times were useful in increasing stride length), while a narrow stride width was important in reducing peak forces in all three directions and could improve movement efficiency

Determination of galangin in commercial extracts of Alpinia officinarum by RP-HPLC-DAD

Alpinia officinarum has been used by long time in the traditional medicine and several commercial extracts containing it are available on the market. In this paper a reversed phase high performance liquid chromatography-diode array detection (RP-HPLC-DAD) method for Alpinia officinarum preparations was proposed using galangin as a marker. The quantification was undertaken by a combination of RP-HPLC-DAD. The LC system employed a Gemini Phenomenex RP-18 column with phosphoric acid, tetrahydrofuran and acetonitrile as mobile phase and detection at 267 nm. The method validation was throughout satisfactory. The determination coefficient was r2 = 0.998 with LOD 0.48 µg mL-1 and LOQ 1.59 µg mL-1 The results of precision (RSD < 2.82) and accuracy (99.9 %, 100.4 %, 102.2 %) with . RSD less than 2.7 %, were satisfactory. The analytical method was applied to commercial extracts, and was suitable to provide qualitative and quantitative information for the quality control to commercial preparations.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Different training modalities improve energy cost and performance in master runners

Purpose: The aim of this study was to compare the effects of continuous moderate-intensity and discontinuous high-intensity training on running performance in master runners.Methods: Thirty-four male master runners (47.2 ± 7.4 years) were assigned to three different groups: continuous moderate-intensity training (CMIT), discontinuous high-intensity training (DHIT), and control group (CON). CMIT and DHIT performed 8-week of supervised training (3 session·wk−1; ~35 km·wk−1) while CON maintained their normal training habits (3–4 session·wk−1; ~50 km·wk−1). Peak oxygen consumption (V˙O2peak) and peak running speed (vpeak) during incremental treadmill exercise, gas exchange threshold (GET), speed at GET, energy cost of running (Cr), and 5-km performance were evaluated before and after training.Results: Following the training period, both CMIT and DHIT significantly reduced Cr (−4.4 and −4.9%, respectively, P &lt; 0.05), increased speed at GET (3.4 and 5.7%, P &lt; 0.05) and improved 5-km time-trial performance (3.1 and 2.2%, P &lt; 0.05) whereas no differences were found for V˙O2peak and GET (as %V˙O2peak). After training, vpeak improved only for DHIT (6%, P &lt; 0.05). No differences were found in any variable for CON.Conclusions: This study indicates that both CMIT and DHIT may positively affect running performance in middle-aged master runners. This improvement was achieved despite a significant reduction of the amount of weekly training volume

Start of SPIDER operation towards ITER neutral beams

Heating Neutral Beam (HNB) Injectors will constitute the main plasma heating and current drive tool both in ITER and JT60-SA, which are the next major experimental steps for demonstrating nuclear fusion as viable energy source. In ITER, in order to achieve the required thermonuclear fusion power gain Q=10 for short pulse operation and Q=5 for long pulse operation (up to 3600s), two HNB injectors will be needed [1], each delivering a total power of about 16.5 MW into the magnetically-confined plasma, by means of neutral hydrogen or deuterium particles having a specific energy of about 1 MeV. Since only negatively charged particles can be efficiently neutralized at such energy, the ITER HNB injectors [2] will be based on negative ions, generated by caesium-catalysed surface conversion of atoms in a radio-frequency driven plasma source. A negative deuterium ion current of more than 40 A will be extracted, accelerated and focused in a multi-aperture, multi-stage electrostatic accelerator, having 1280 apertures (~ 14 mm diam.) and 5 acceleration stages (~200 kV each) [3]. After passing through a narrow gas-cell neutralizer, the residual ions will be deflected and discarded, whereas the neutralized particles will continue their trajectory through a duct into the tokamak vessels to deliver the required heating power to the ITER plasma for a pulse duration of about 3600 s. Although the operating principles and the implementation of the most critical parts of the injector have been tested in different experiments, the ITER NBI requirements have never been simultaneously attained. In order to reduce the risks and to optimize the design and operating procedures of the HNB for ITER, a dedicated Neutral Beam Test Facility (NBTF) [4] has been promoted by the ITER Organization with the contribution of the European Union\u2019s Joint Undertaking for ITER and of the Italian Government, with the participation of the Japanese and Indian Domestic Agencies (JADA and INDA) and of several European laboratories, such as IPP-Garching, KIT-Karlsruhe, CCFE-Culham, CEA-Cadarache. The NBTF, nicknamed PRIMA, has been set up at Consorzio RFX in Padova, Italy [5]. The planned experiments will verify continuous HNB operation for one hour, under stringent requirements for beam divergence (< 7 mrad) and aiming (within 2 mrad). To study and optimise HNB performances, the NBTF includes two experiments: MITICA, full-scale NBI prototype with 1 MeV particle energy and SPIDER, with 100 keV particle energy and 40 A current, aiming at testing and optimizing the full-scale ion source. SPIDER will focus on source uniformity, negative ion current density and beam optics. In June 2018 the experimental operation of SPIDER has started

Moderate aerobic exercise (brisk walking) increases bone density in cART-treated persons

Moderate intensity aerobic activity reduces the risk of cardiovascular disease, diabetes and metabolic syndrome in the general population and has a potential in preventing bone loss. We evaluated the effects of brisk walking, with or without strength exercise, on bone mineral density in HIV-infected treated persons. Twenty-eight HIV-infected, cART-treated, sedentary subjects with VL&#60;50 c/mL were enrolled in a 12-week exercise program, consisting of 3 outdoor sessions/week of 60 min walking at 67&#x2013;70% of HR (heart rate) max&#x00B1;30 min circuit training at 65% of 1-RM (repetition maximum). Subjects were examined at baseline (BL) and 12 weeks (W12) by 6-minute walking test (6MWT) and by counting the number of repetitions for each strength exercise; and by dual energy X-ray absorptiometry (DEXA) to evaluate lumbar spine and femoral bone mineral density with t- and z-scores - in addition to morphometric (BMI, waist, hip and leg circumference) and blood examination (cytometry, fasting total, HDL and LDL cholesterol, triglycerides, glucose, insulin; AST/ALT, ALP, gGT, creatinine, CPK, HbA1c; CD4+ and CD8+, plasma HIV-RNA). Differences over time were tested by Wilcoxon-signed rank test and between groups by Mann-Whitney test. Twenty-seven (96%) participants (19M, 8F; median 48 y-o, IQR 43&#x2013;54; median CD4+624/&#x00B5;L, IQR 478&#x2013;708; ART with PI: 13 patients, with NNRTI: 7 patients, and including TDF: 15 patients) completed the 12-week program with a median adherence of 61% (IQR 50&#x2013;70): 18 in the &#x2018;walk only&#x2019; only group and 9 in the &#x2018;walk and strength&#x2019; group. At W12, participants showed significant improvement of distance by 6MWT (Table), and of performance in all strength exercises (crunch p=0.023, lat machine p=0.016, chest press p=0.016, leg extension p=0.016, sitting calf p=0.008, leg press p=0.016). DEXA spine z-score improved significantly in the whole group, and femoral z-scores in the &#x2018;walk only&#x2019; group. There was no z-score difference at BL between patients with/out PIs, NNRTIs or TDF. However, spine z-score improved significantly in patients receiving TDF. At W12 BMI, waist circumference, and LDL also improved significantly in the whole group, whereas no significant changes were observed for the other variables, The above 12-week program improved fitness and bone density in HIV-infected treated subjects, in addition to some morphometric variables and serum LDL. Brisk walking, with or without strength exercise, might help control the long-term consequences of cART