LOCOMOZIONE UMANA E ANIMALE A DIFFERENTI GRAVITÀ: ADATTAMENTI BIOMECCANICI ED EFFETTI METABOLICI

A few years before Apollo Missions to Moon, locomotion physiologists promoted research and discussion about the potential adaptation of human body, the musculo-skeletal apparatus in particular, to an environment subject to a much smaller gravity acceleration than on Earth. Rodolfo Margaria and Giovanni Cavagna, who had just started investigating the fundamental mechanical paradigms of terrestrial locomotion, built a gravity-emulation facility in a 15 m tall vent shaft in Milano to study how jumping ability was affected by low-gravity. The combined knowledge led them to correctly predict that humans on the Moon would have walked at a very low pace and the alternative to an impaired running would have been a bouncing gait like hopping. Since then, other scientists around the world kept on researching on this subject, both experimentally and through mathematical models. Models based on 'dynamic similarity' (Froude Number) have confirmed that spontaneous locomotion adopted by astronauts was predictable. Recent biomechanical and metabolic experiments in the rebuilt emulation facility in Milano indicated that gaits with very different economy on Earth (running, skipping and hopping range from 2x to 10x, when compared to walking) progressively tend to have the same cost of transport when gravity decreases, and they are all alike at Moon gravity. This suggests that the energy devoted to sustain body weight represents a crucial determinant in the propulsion economy. Together with further biomechanical analysis, these data from emulated outer space are promising clues toward a better understanding of still unsolved mysteries of terrestrial locomotion (as the speed independence of metabolic cost of running)

Acute and long-term effects of ACE inhibition on renal haemodynamics in glomerular and interstitial nephropathies

Background Angiotensin-converting enzyme (ACE) inhibitors are the drugs of choice for the treatment of hypertension in patients with non-diabetic nephropathies. However, not every trial has reported better results with ACE inhibitors (ACE-I) than with other drugs. This study investigates whether the acute and chronic effects of ACE inhibition on renal and glomerular haemodynamics are similar in glomerular and interstitial nephropathies. Methods We studied 20 hypertensive patients, on their usual diet, with mild-to-moderate chronic renal failure secondary to non-diabetic nephropathy. After a three-week wash out period, we determined plasma clearances of para-amino-hippurate and inulin before, and after acute oral administration of either enalapril or ramipril. This same test was carried out after one and two years of treatment with the same drug. Results Acute ACE inhibition causes a decrease of renal perfusion, glomerular filtration and pressure with an increase of afferent resistances. Long-term ACE inhibition is associated only with a decrease in renal perfusion, with a non-significant tendency to higher filtration fraction and lower afferent resistances. All the renal haemodynamic modifications mentioned above are present only in patients with glomerular diseases. Conclusions Renal and glomerular haemodynamic responses are not similar after acute and chronic ACE inhibition. Only patients with glomerular diseases show acute or long-term responses to ACE inhibition

Cardiovascular Outcomes in Renal Transplant Recipients: Feasibility and Clinical Role of 2D Speckle Tracking to Assess Myocardial Function

however, few data are available about the role of 2D echocardiography (2DE) and 2D speckle tracking echocardiography (2DSTE) on renal transplant recipients (RTR). From a large cohort of RTR submitted to a supervised exercise as the prescription program, 10 subjects who were regularly trained were studied for sixth months. They underwent periodically an echo evaluation (ESAOTE MyLab 50), cardiopulmonary test (CPT) and strength test for the lower and upper limbs. The LV function study was completed with the speckle tracking longitudinal strain (Lo Strain) measure calculated by dedicated software (XStrain–Esaote) at the end of the protocol. All of the cardiovascular parameters were normal: the ejection fraction (EF) increased significantly (from 62.7 ± 4 to 67.2 ± 2.3 with p &l

Technical skills and movement coordination in elite, national and regional level race walkers

Introduction: Race walking (RW) is a very peculiar form of locomotion that requires athletes to walk as fast as possible following two main rules: keep the knee of the supporting leg locked “from the moment of first contact with the ground until the vertical upright position”; and, generate a progression of steps with no visible flight phase. Previous studies have attempted to characterize RW performance, but the use of conventional analytical tools, including kinematic, kinetic and physiological measures, has not been very successful in discriminating between different skill levels and identifying the factors for excellent performance. Improved experimental protocols and finer analytical tools are needed to unveil the subtle differences existing between athletes of different competitive standard.Aim: To compare coordination and coordination variability in RW, and highlight differences between elite-, national- and regional-standard athletes.Method: A cross-sectional design was used to study the changes in coordination variability as a factor of skill level. Fifteen competitive male race walkers were assigned to the Elite, National or Regional groups depending on their season best performance, and were asked to race walk on a treadmill at 15 km/h. Optoelectronic motion capture was used to record 40 gait cycles for each participant. Pelvis and lower limb kinematics was used to study coordination variability through a dynamical system approach [1]. Continuous relative phase and its variability across multiple strides were estimated (Figure 1a). Multiple joint couplings (e.g. hip-knee, knee-ankle) and movement phases (e.g. early and late stance, swing) were considered. Kruskal-Wallis tests were used to assess the between-group differences for each variable.Results and Discussion: Results appeared to support the hypothesis that coordination variability increases during transition phases (e.g. heel-strike and toe-off) (Figure 1b). Overall, less skilled athletes tended to produce larger coordination variability, with significantly higher values of deviation phase during the early-stance phase of the hip-knee (P=0.20), and pelvis-hip (P=0.09) couplings. Individual coordinative patterns showed the potential for characterizing individual peculiarities in specific phases of the movement and to improve the understanding of technical skills, however more work is needed to relate coordinative measures with features of the neuro-muscular-skeletal system organization.References[1] Preatoni, E., Hamill, J., Harrison, A.J., Hayes, K., Van Emmerik, R.E.A., Wilson, C., Rodano, R., 2013. Movement variability and skills monitoring in sports. Sports Biomechanics 12, 69-92.<br/

Recumbent vs. upright bicycles:3D trajectory of body centre of mass, limb mechanical work, and operative range of propulsive muscles

Recumbent bicycles (RB) are high performance, human-powered vehicles. In comparison to normal/upright bicycles (NB) the RB may allow individuals to reach higher speeds due to aerodynamic advantages. The purpose of this investigation was to compare the non-aerodynamic factors that may potentially influence the performance of the two bicycles. 3D body centre of mass (BCoM) trajectory, its symmetries, and the components of the total mechanical work necessary to sustain cycling were assessed through 3D kinematics and computer simulations. Data collected at 50, 70, 90 110\ua0rpm during stationary cycling were used to drive musculoskeletal modelling simulation and estimate muscle-tendon length. Results demonstrated that BCoM trajectory, confined in a 15-mm side cube, changed its orientation, maintaining a similar pattern across all cadences in both bicycles. RB displayed a reduced additional mechanical external power (16.1\ua0\ub1\ua09.7\ua0W on RB vs. 20.3\ua0\ub1\ua08.8\ua0W on NB), a greater symmetry on the progression axis, and no differences in the internal mechanical power compared to NB. Simulated muscle activity revealed small significant differences for only selected muscles. On the RB, quadriceps and gluteus demonstrated greater shortening, while biceps femoris, iliacus, and psoas exhibited greater stretch; however, aerodynamics still remains the principal benefit

Shoulder 3D range of motion and humerus rotation in two volleyball spike techniques:injury prevention and performance

Repetitive stresses and movements on the shoulder in the volleyball spike expose this joint to overuse injuries, bringing athletes to a career threatening injury. Assuming that specific spike techniques play an important role in injury risk, we compared the kinematic of the traditional (TT) and the alternative (AT) techniques in 21 elite athletes, evaluating their safety with respect to performance. Glenohumeral joint was set as the centre of an imaginary sphere, intersected by the distal end of the humerus at different angles. Shoulder range of motion and angular velocities were calculated and compared to the joint limits. Ball speed and jump height were also assessed. Results indicated the trajectory of the humerus to be different for the TT, with maximal flexion of the shoulder reduced by 10 degrees, and horizontal abduction 15 degrees higher. No difference was found for external rotation angles, while axial rotation velocities were significantly higher in AT, with a 5% higher ball speed. Results suggest AT as a potential preventive solution to shoulder chronic pathologies, reducing shoulder flexion during spiking. The proposed method allows visualisation of risks associated with different overhead manoeuvres, by depicting humerus angles and velocities with respect to joint limits in the same 3D space

Race Walking Ground Reaction Forces at Increasing Speeds: A Comparison with Walking and Running

Race walking has been theoretically described as a walking gait in which no flight time is allowed and high travelling speed, comparable to running (3.6\u20134.2 m s1), is achieved. The aim of this study was to mechanically understand such a \u201chybrid gait\u201d by analysing the ground reaction forces (GRFs) generated in a wide range of race walking speeds, while comparing them to running and walking. Fifteen athletes race-walked on an instrumented walkway (4 m) and three-dimensional GRFs were recorded at 1000 Hz. Subjects were asked to performed three self-selected speeds corresponding to a low, medium and high speed. Peak forces increased with speeds and medio-lateral and braking peaks were higher than in walking and running, whereas the vertical peaks were higher than walking but lower than running. Vertical GRF traces showed two characteristic patterns: one resembling the \u201cM-shape\u201d of walking and the second characterised by a first peak and a subsequent plateau. These dierent patterns were not related to the athletes\u2019 performance level. The analysis of the body centre of mass trajectory, which reaches its vertical minimum at mid-stance, showed that race walking should be considered a bouncing gait regardless of the presence or absence of a flight phase

The 3d body centre of mass trajectory before and after total knee arthroplasty:symmetry and mechanical work

The kinematics of walking on treadmill were collected and the 3D trajectory of the body centre of mass was computed in subjects suffering from mono-lateral knee osteoarthritis, before and after total knee arthroplasty. Experimental data showed after 6 months from surgery significant improvements in many biomechanical parameters as gait symmetry indices and total work done