Fausto A. Panizzolo

Ultrasound characterization of medial gastrocnemius tissue composition in children with spastic cerebral palsy

Introduction: In this study we aimed to characterize muscle composition of the medial gastrocnemius in children with spastic cerebral palsy (SCP) using quantitative ultrasound. Methods: Forty children with SCP, aged 4–14 years, participated in this study. Children were grouped according to the gross motor function classification system (GMFCS I–V) and compared with a cohort of age‐ and gender‐matched, typically developing children (TD; n = 12). Ultrasound scans were taken of the medial gastrocnemius. Images were then characterized using grayscale statistics to determine mean echo intensity (EI) and the size and number of spatially connected homogeneous regions (i.e., blobs). Results: Significant differences in skeletal muscle composition were found between children with SCP and their TD peers. Children classified as GMFCS III consistently exhibited the highest EI and blob area. Conclusions: This study demonstrates altered tissue composition in children with SCP visualized using ultrasound. Further work is required to determine the pathophysiology contributing to these alterations in SCP. Muscle Nerve 52:397–403, 2015

Soleus fascicle length changes are conserved between young and old adults at their preferred walking speed

Older adults have been shown to naturally select a walking speed approximately 20% slower than younger adults. We explored the possibility that a reduction in preferred speed in older adults represents a strategy to preserve the mechanical function of the leg muscles. We examined this question in the soleus muscle in eight healthy young (25.8±3.5 years) and eight healthy older adults (66.1±2.3 years) who were paired so that their preferred speed differed by ∼20%. Soleus muscle fascicle lengths were recorded dynamically using ultrasound, together with simultaneous measurements of soleus EMG activity and ankle joint kinematics while (a) older adults walked on a treadmill at a speed 20% above their preferred speed (speeds matched to the preferred speed of young adults), and (b) young and older adults walked at their preferred treadmill speeds. Analyses of mean muscle fascicle length changes revealed that, at matched speeds, older adults had a statistically different soleus fascicle length pattern compared to young adults, where the muscles stretch-shorten cycle during stance was diminished. However, older adults walking at their preferred speed exhibited a more pronounced stretch-shorten cycle that was not statistically different from young adults. Conserving muscle length patterns through a reduction in speed in older adults may represent a physiologically relevant modulation of muscle function that permits greater force and power production. Our findings offer a novel mechanical explanation for the slower walking speed in older adults, whereby a reduction in speed may permit muscles to function in a mechanically similar manner to that of younger adults.

IMU-based iterative control for hip extension assistance with a soft exosuit

In this paper we describe an IMU-based iterative controller for hip extension assistance where the onset timing of assistance is based on an estimate of the maximum hip flexion angle. The controller was implemented on a mono-articular soft exosuit coupled to a lab-based multi-joint actuation platform that enables rapid reconfiguration of different sensors and control strategy implementation. The controller design is motivated by a model of the suit-human interface and utilizes an iterative control methodology that includes gait detection and step-by-step actuator position profile generation to control the onset timing, peak timing, and peak magnitude of the delivered force. This controller was evaluated on eight subjects walking on a treadmill at a speed of 1.5 m/s while carrying a load of 23 kg. Results showed that assistance could be delivered reliably across subjects. Specifically, for a given profile, the average delivered force started concurrently with the timing of the maximum hip flexion angle and reached its peak timing 22.7 ± 0.63% later in the gait cycle (desired 23%) with a peak magnitude of 198.2 ± 1.6 N (desired 200 N), equivalent to an average peak torque of 30.5 ± 4.7 Nm. This control approach was used to assess the metabolic effect of four different assistive profiles. Metabolic reductions ranging from 5.7% to 8.5% were found when comparing the powered conditions with the unpowered condition. This work enables studies to assess the biomechanical and physiological responses to different assistive profiles to determine the optimal hip extension assistance during walking.

Soleus Muscle as a Surrogate for Health Status in Human Heart Failure

We propose the hypothesis that soleus muscle function may provide a surrogate measure of functional capacity in patients with heart failure. We summarize literature pertaining to skeletal muscle as a locus of fatigue and present our recent findings, using in vivo imaging in combination with biomechanical experimentation and modeling, to reveal novel structure-function relationships in chronic heart failure skeletal muscle and gait.

Reducing the metabolic cost of running with a tethered soft exosuit

A tethered exosuit reduces the metabolic cost of running. Assisting hip extension with a tethered exosuit and a simulation-optimized force profile reduces metabolic cost of running.

Biomechanical comparison of shorts with different pads: An Insight into the Perineum Protection Issue

Abstract An intensive use of the bicycle may increase the risk of erectile dysfunction and the compression of the perineal area has been showed to be a major mechanism leading to sexual alterations compromising the quality of life. Manufacturers claim that pads contribute to increase cyclists perineal protection ensuring a high level of comfort. To investigate the influence of various cycling pads with regard to perineal protection and level of comfort. Nine club road cyclists rode 20 min on a drum simulator, located at the Nutrition and Exercise Physiology Laboratory, at a constant speed and gear ratio wearing the shorts with 3 cycling pads of different design and thickness: basic (BAS), intermediate (INT), and endurance (END). Kinematics and pressure data were recorded at min 5, 15, and 20 of the test using a motion capture system and a pressure sensor mat. The variables of interest were: 3-dimensional pelvis excursions, peak pressure, mean pressure, and vertical force. The comfort level was assessed with a ranking order based on the subjects’ perception after the 20-min trials and measuring the vertical ground reaction force under the anterior wheel as well as the length of the center of pressure (COP) trajectory on the saddle. Results showed that the vertical force and the average value of mean pressure on the saddle significantly decreased during the 20-min period of testing for BAS and END. Mean peak pressure on the corresponding perineal cyclist area significantly increased only for BAS during the 20-min period. Interestingly objective comfort indexes measured did not match cyclists subjective comfort evaluation. The lower capacity of BAS to reduce the peak pressure on the corresponding perineal area after 20 min of testing, together with its positive comfort evaluation, suggest that a balance between protection and perceived comfort should be taken into account in the choice of the pad. Hence, the quantitative approach of objective comfort indexes introduced in this study could be helpful for manufacturers in the development of their protective pads.

Lower Limb Biomechanical Analysis During an Unanticipated Step on a Bump Reveals Specific Adaptations of Walking on Uneven Terrains

ABSTRACT Although it is clear that walking over different irregular terrain is associated with altered biomechanics, there is little understanding of how we quickly adapt to unexpected variations in terrain. This study aims to investigate which adaptive strategies humans adopt when performing an unanticipated step on an irregular surface, specifically a small bump. Nine healthy male participants walked at their preferred walking speed along a straight walkway during five conditions: four involving unanticipated bumps of two different heights, and one level walking condition. Muscle activation of eight lower limb muscles and three-dimensional gait analysis were evaluated during these testing conditions. Two distinct adaptive strategies were found, which involved no significant change in total lower limb mechanical work or walking speed. An ankle-based strategy was adopted when stepping on a bump with the forefoot, whereas a hip-based strategy was preferred when stepping with the rearfoot. These strategies were driven by a higher activation of the plantarflexor muscles (6–51%), which generated a higher ankle joint moment during the forefoot conditions and by a higher activation of the quadriceps muscles (36–93%), which produced a higher knee joint moment and hip joint power during the rearfoot conditions. These findings provide insights into how humans quickly react to unexpected events and could be used to inform the design of adaptive controllers for wearable robots intended for use in unstructured environments that can provide optimal assistance to the different lower limb joints. Summary: Investigation of an unanticipated step on uneven ground reveals two distinct adaptive strategies: an ankle-based strategy when stepping with the forefoot, and a hip-based strategy when stepping with the rearfoot.

Muscle size explains low passive skeletal muscle force in heart failure patients

Background Alterations in skeletal muscle function and architecture have been linked to the compromised exercise capacity characterizing chronic heart failure (CHF). However, how passive skeletal muscle force is affected in CHF is not clear. Understanding passive force characteristics in CHF can help further elucidate the extent to which altered contractile properties and/or architecture might affect muscle and locomotor function. Therefore, the aim of this study was to investigate passive force in a single muscle for which non-invasive measures of muscle size and estimates of fiber force are possible, the soleus (SOL), both in CHF patients and age- and physical activity-matched control participants. Methods Passive SOL muscle force and size were obtained by means of a novel approach combining experimental data (dynamometry, electromyography, ultrasound imaging) with a musculoskeletal model. Results We found reduced passive SOL forces (∼30%) (at the same relative levels of muscle stretch) in CHF vs. healthy individuals. This difference was eliminated when force was normalized by physiological cross sectional area, indicating that reduced force output may be most strongly associated with muscle size. Nevertheless, passive force was significantly higher in CHF at a given absolute muscle length (non length-normalized) and likely explained by the shorter muscle slack lengths and optimal muscle lengths measured in CHF compared to the control participants. This later factor may lead to altered performance of the SOL in functional tasks such gait. Discussion These findings suggest introducing exercise rehabilitation targeting muscle hypertrophy and, specifically for the calf muscles, exercise that promotes muscle lengthening.

Experimental methods for the mechanical characterization of cycling short pads

In cycling, non-traumatic injuries affecting the genitourinary tract have been the most extensively studied considering their effect in reducing the quality of life. The employment of saddle with specific geometries and of cycling shorts with pads can contribute to reduce the pressure on the perineal area and to increase the level of comfort. The aim of this study was to develop a method to quantify the mechanical properties of pads which can influence the cyclist’s perineal protection and its level of comfort. The proposed method consisted of both a laboratory and a field test component. The laboratory part included an accelerated fatigue test of 300,000 cycles performed with an hydraulic actuator. Loads employed were derived from pressure data collected on the saddle of a professional cyclist who pedalled both on asphalt and crossing potholes at a constant speed. The measurement of cylinder force and displacement allowed to calculate the damping and the stiffness over time for the pads tested. The field test allowed to collect the acceleration at the seatpost of the bike and at the back of the cyclist by means of two accelerometers. A transfer function ( H ( f ) ) allowed to quantify the vibration transmissibility of the pads. The application of our method characterized the pads tested concerning damping, stiffness and vibration transmissibility. This method could be useful for the manufacturer in the choice of density and thickness of foams, to obtain the desired level of protection, comfort and long-time efficacy of pads.

Different intensities of basketball drills affect jump shot accuracy of expert and junior players

Background In basketball a maximum accuracy at every game intensity is required while shooting. The aim of the present study was to investigate the acute effect of three different drill intensity simulation protocols on jump shot accuracy in expert and junior basketball players. Materials & Methods Eleven expert players (age 26 ± 6 yrs, weight 86 ± 11 kg, height 192 ± 8 cm) and ten junior players (age 18 ± 1 yrs, weight 75 ± 12 kg, height 184 ± 9 cm) completed three series of twenty jump shots at three different levels of exertion. Counter Movement Jump (CMJ) height was also measured after each series of jump shots. Exertion’s intensity was induced manipulating the basketball drills. Heart rate was measured for the whole duration of the tests while the rating of perceived exertion (RPE) was collected at the end of each series of shots. Results Heart rate and rating of perceived exertion (RPE) were statistically different in the three conditions for both expert and junior players. CMJ height remained almost unchanged in both groups. Jump shot accuracy decreased with increasing drills intensity both in experts and junior players. Expert players showed higher accuracy than junior players for all the three levels of exertion (83% vs 64%, p < 0.001; 75% vs 57%, p < 0.05; 76% vs 60%, p < 0.01). Moreover, for the most demanding level of exertion, experts showed a higher accuracy in the last ten shots compared to the first ten shots (82% vs 70%, p < 0.05). Discussion Experts coped better with the different exertion’s intensities, thus maintaining a higher level of performance. The introduction of technical short bouts of high-intensity sport-specific exercises into skill sessions should be proposed to improve jump shot accuracy during matches.