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Predictive equations are widely employed for estimating the volume of oxygen consumption (VO 2 ) while walking, which is ultimately employed to determine energy expenditure and tailor exercise prescription. This study aimed to test the agreement between the measured VO 2 and estimated VO 2 during a walking protocol on a treadmill at 3.5, 4.5, 5.5, and 6.5 km/h. Thirty-eight young adults (50% women) participated in this cross-sectional study. The Omnical (Maastricht Instruments, Maastricht, The Netherlands) and K5 (Cosmed, Rome, Italy) metabolic systems were used to measure VO 2 . To determine the predictive equations, a comprehensive literature search was conducted using the MEDLINE database from May 2022 to July 2023. Seven predictive equations were found and included for estimating VO 2 values. We calculated the mean bias (mean difference between measured VO 2 and estimated VO 2 ) obtained at each speed using one-sample t-tests. We compared the VO 2 measured and estimated values using repeated measures analysis of variance and the Bland-Altman method. One-sample t-tests showed that all score errors were different from zero (ranging from 1.1 to 5.4 mL/kg/min). Thus, no predictive equation estimated similar VO 2 values in comparison with the Omnical and K5 metabolic systems at all intensities. However, the Weyand equation showed the lowest bias across all intensities (score error of 1.1 mL/kg/min). This study showed a lack of agreement between the Omnical and K5 systems compared to diverse predictive equations specially designed to estimate VO 2 during walking. Nevertheless, based on our results, the Weyand equation should be the preferred option., (© 2024 The Author(s). European Journal of Sport Science published by Wiley‐VCH GmbH on behalf of European College of Sport Science.)

Purpose: We have previously shown that accelerated running on flat terrain is biomechanically equivalent to running uphill at a constant speed. This hypothesis was further investigated comparing the energy cost of running at a constant speed either uphill, or on flat terrain against an equivalent horizontal impeding force, mimicking acceleration., Methods: Steady-state O 2 consumption and the corresponding energy cost (per unit body mass and distance) were determined on 12 male subjects during treadmill running at speeds between 2.11 and 2.89 m/s: (i) on the level, (ii) uphill at 10 or 20% incline ( I ), or (iii) on the level against a horizontal traction force of 10 or 20% of the subject's body weight ( TF ). This allowed us to estimate the net efficiency ( n e t η ) of running against horizontal or vertical forces, as given by the ratio between the additional mechanical work output under TF , or the corresponding I condition, and the difference between the appropriate energy cost above that for running at constant speed on flat terrain., Results: The n e t η values when running uphill ( I ) amount to 0.35-0.40, whereas those for running against an equivalent impeding force ( TF ) are about 10% greater (0.45-0.50), a fact that may be due to a greater recovery of elastic energy in the TF as compared to the I condition., Conclusion: Making allowance for these small differences, these data support the view of considering accelerated running on flat terrain biomechanically equivalent to running at a constant speed, up an equivalent slope., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Penguins are proficient swimmers, and their survival depends on their ability to catch prey. The diving behaviour of these fascinating birds should then minimize the associated energy cost. For the first time, the energy cost of penguin dives is computed from the free-ranging dive data, on the basis of an existing biomechanical model. Time-resolved acceleration and depth data collected for 300 dives of little penguins (Eudyptula minor) are specifically employed to compute the bird dive angles and swimming speeds, which are needed for the energy estimate. We find that the numerically obtained energy cost by using the free-ranging dive data is not far from the minimum cost predicted by the model. The outcome, therefore, supports the physical soundness of the chosen model; however, it also suggests that, for closer agreement, one should consider previously neglected effects, such as those due to water currents and those associated with motion unsteadiness. Additionally, from the free-ranging dive data, we calculate hydrodynamic forces and non-dimensional indicators of propulsion performance - Strouhal and Reynolds numbers. The obtained values further confirm that little penguins employ efficient propulsion mechanisms, in agreement with previous investigations., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

This article focuses on the tradeoff analysis between time and energy costs for fixed-time synchronization (FXTS) of discontinuous neural networks (DNNs) with time-varying delays and mismatched parameters. First, a more comprehensive lemma is systematically established to study fixed-time stability, which is less conservative than those in most current results. Besides, theoretical proof has proven that the upper bounds of the settling time (ST) in this article are more accurate compared to existing results. Second, on the grounds of the new fixed-time stability lemma, fixed-time synchronization problem for discontinuous neural networks with time-varying delays and mismatched parameters is explored, and sufficient conditions for fixed-time synchronization are obtained. Further, the upper bounds of energy cost during the synchronization process are estimated. Third, in order to achieve a balance between time cost and energy cost, the genetic algorithm is utilized to find the satisfactory control parameter. Finally, a numerical example is provided to verify the theoretical analysis's correctness and the control mechanism's feasibility., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Prior studies investigated selected discrete sagittal-plane outcomes (e.g., peak knee flexion) in relation to running economy, hereby discarding the potential relevance of running technique parameters during noninvestigated phases of the gait cycle and in other movement planes., Purpose: Investigate which components of running technique distinguish groups of runners with better and poorer economy and higher and lower weekly running distance using an artificial neural network (ANN) approach with layer-wise relevance propagation., Methods: Forty-one participants (22 males and 19 females) ran at 2.78 m∙s -1 while three-dimensional kinematics and gas exchange data were collected. Two groups were created that differed in running economy or weekly training distance. The three-dimensional kinematic data were used as input to an ANN to predict group allocations. Layer-wise relevance propagation was used to determine the relevance of three-dimensional kinematics for group classification., Results: The ANN classified runners in the correct economy or distance group with accuracies of up to 62% and 71%, respectively. Knee, hip, and ankle flexion were most relevant to both classifications. Runners with poorer running economy showed higher knee flexion during swing, more hip flexion during early stance, and more ankle extension after toe-off. Runners with higher running distance showed less trunk rotation during swing., Conclusion: The ANN accuracy was moderate when predicting whether runners had better, or poorer running economy, or had a higher or lower weekly training distance based on their running technique. The kinematic components that contributed the most to the classification may nevertheless inform future research and training., (© 2024 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.)

Background: Walking speed and energy economy tend to decline with age. Lower-limb exoskeletons have demonstrated potential to improve either measure, but primarily in studies conducted on healthy younger adults. Promising techniques like optimization of exoskeleton assistance have yet to be tested with older populations, while speed and energy consumption have yet to be simultaneously optimized for any population., Methods: We investigated the effectiveness of human-in-the-loop optimization of ankle exoskeletons with older adults. Ten healthy adults > 65 years of age (5 females; mean age: 72 ± 3 yrs) participated in approximately 240 min of training and optimization with tethered ankle exoskeletons on a self-paced treadmill. Multi-objective human-in-the-loop optimization was used to identify assistive ankle plantarflexion torque patterns that simultaneously improved self-selected walking speed and metabolic rate. The effects of optimized exoskeleton assistance were evaluated in separate trials., Results: Optimized exoskeleton assistance improved walking performance for older adults. Both objectives were simultaneously improved; self-selected walking speed increased by 8% (0.10 m/s; p = 0.001) and metabolic rate decreased by 19% (p = 0.007), resulting in a 25% decrease in energetic cost of transport (p = 8e-4) compared to walking with exoskeletons applying zero torque. Compared to younger participants in studies optimizing a single objective, our participants required lower exoskeleton torques, experienced smaller improvements in energy use, and required more time for motor adaptation., Conclusions: Our results confirm that exoskeleton assistance can improve walking performance for older adults and show that multiple objectives can be simultaneously addressed through human-in-the-loop optimization., (© 2023. The Author(s).)

Waste management has been a chronic environmental challenge in Nigeria, coupled with declining economic performance due to energy crises. This study was designed to estimate electricity potential of sewage sludge to meet the 2030 Renewable Energy target. However, there was a need to fill the gap in data related to wastewater management in Nigeria. The wastewater and sludge generated from households were evaluated based on data on population, access to water, and coverage of sewer networks. Consequently, the technical and economic feasibility of electricity generation was assessed using Anaerobic Digestion (AD) 1 and Incineration (INC) 2 scenarios. The core results found that North Central had the highest potential for wastewater generation (142.8-403.6 billion litres/yr) and collection (8.3-37.5 billion litres/yr) over 20 years. However, the South East had the highest average sewer collection rate of 9.08 %. The AD technology was the most technically viable, with a maximum generation of 6.8 GWh/yr in the North Central. In comparison, the INC outperformed AD in most of the financial viability indicators considered viz-a-viz: Life Cycle Cost (LCC), 3 Net Present Value (NPV), 4 Pay Back Period (PBP), 5 Internal Rate of Return (IRR), 6 Levelized Cost of Energy (LCOE). 7 The AD had a higher NPV of 16.3-69.58 million USD and a shorter PBP of about 4 years. The INC had a lower LCC of 0.1-0.34 million USD, LCOE of 0.046-0.094 USD/kWh, and a higher IRR of 19.3-25 %. Additionally, the sensitivity of NPV and INC to changes in economic factors would be noteworthy for investors and policymakers. Ultimately, the choice of technology should reflect the fiscal goal and priorities of a project., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The aim of this study is to investigate the performance of advanced electrocoagulation (EC) process for the treatment of olive mill wastewater. In EC process, iron plates were used as electrodes, and peroxydisulfate (PS) and peroxymonosulfate (PMS) were added as oxidants. The effects of the initial pH value, current density, oxidant dose, and electrolysis time were optimized for pollutant removal from olive mill wastewater by EC-PS and EC-PMS processes. Control experiments showed that addition of oxidants to the conventional EC process increased the pollutant removal efficiency. Classical optimization method was used to determine optimum conditions, which were initial pH 4, current density 40 mA/cm 2 , oxidant dose 5 g/L, and electrolysis time 30 min for both processes. Under these conditions, EC-PS and EC-PMS processes achieved 50.5% and 48.9% chemical oxygen demand (COD), 93.8% and 89.3% total phenol, 87.7% and 83% UV 254 , and 74.5% and 64.1% total suspended solid removal efficiencies. Quenching experiments were performed to determine the dominant radical species participating in the processes. It was observed that hydroxyl and sulfate radicals were involved in both processes but hydroxyl radicals were more active. Specific energy consumption was calculated as 5.90 kWh/kg COD for EC process, 4.95 kWh/kg COD for EC-PS process, and 5.20 kWh/kg COD for EC-PMS process. The organic removal/sludge ratio of EC-PS process was found to be higher with 17.5 g/L value. Although the application of EC-PS and EC-PMS processes alone is insufficient to meet the discharge limits, they have been found to be effective in olive mill wastewater treatment. PRACTITIONER POINTS: Peroxydisulfate (PS) and peroxymonosulfate (PMS)-based advanced electrocoagulation (EC) was used in olive mill wastewater treatment. 50.5% chemical oxygen demand (COD), 93.8% TP, 87.7% UV 254 , and 74.5% TSS removals were achieved by EC-PS. 48.9% COD, 89.3% TP, 83% UV 254 , and 64.1% TSS removals were obtained by EC-PMS. Hydroxyl and sulfate radicals were involved in both processes., (© 2023 Water Environment Federation.)

Background: The ever-increasing sport level makes every single detail of the athlete's cardiorespiratory profile count, and therefore, it is deemed crucial to clarify how the anterior cruciate ligament (ACL) reconstruction (ACLR) affects the energy economy of an athlete compared to the ACL-deficient and healthy subjects. The purpose of this review was to systematically analyze the studies investigating the correlation between the energy-oxygen cost in patients following ACLR in unreconstructed and intact ACLs., Methods: We conducted this systematic review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. PubMed, Cochrane, and Google Scholar databases were searched, and eight articles describing miscellaneous methods for the assessment of oxygen consumption in patients with ACL deficiency or ACL reconstructed knees were included., Results: In total, 285 subjects were recorded with a mean age of 29.61 years. The type of exercise the patients were subjected to varied among the studies, including one-leg cycling, exercise in the closed kinetic chain, walking, jogging, or running at various speeds, and treadmill inclinations. The energy expenditure of an ACL-deficient patient is considerably higher than a healthy subject. Additionally, chronicity of the ACL tear is not correlated with energy expenditure. ACL deficiency leads to higher energy consumption, not only during walking but during jogging as well. ACLR could improve the efficiency of walking by lowering the energy demands. After ACLR, professional soccer players' aerobic capacity (VO 2 max) is improved significantly., Conclusions: ACL insufficiency affects substantially the metabolic energy costs, resulting in increased energy expenditure. According to current literature, ACLR can help to partially reverse this condition, as significant improvements and a more efficient, energy-wise, locomotion are expected. However, further research is necessary to clarify if ACLR can completely normalize energy expenditure again. HIPPOKRATIA 2023, 27 (4):119-125., Competing Interests: The authors declare no conflict of interest. This research received no external funding., (Copyright 2023, Hippokratio General Hospital of Thessaloniki.)

Purpose: Advanced footwear technology is prevalent in distance running, with research focusing on these "super shoes" in competitive athletes, with less understanding of their value for slower runners. The aim of this study was to compare physiological and biomechanical variables between a model of super shoes (Saucony Endorphin Speed 2) and regular running shoes (Saucony Cohesion 13) in recreational athletes., Methods: We measured peak oxygen uptake (VO2peak) in 10 runners before testing each subject 4 times in a randomly ordered crossover design (ie, Endorphin shoe or Cohesion shoe, running at 65% or 80% of velocity at VO2peak [vVO2peak]). We recorded video data using a high-speed camera (300 Hz) to calculate vertical and leg stiffnesses., Results: 65% vVO2peak was equivalent to a speed of 9.4 km·h-1 (0.4), whereas 80% vVO2peak was equivalent to 11.5 km·h-1 (0.5). Two-way mixed-design analysis of variance showed that oxygen consumption in the Endorphin shoe was 3.9% lower than in the Cohesion shoe at 65% vVO2peak, with an interaction between shoes and speed (P = .020) meaning an increased difference of 5.0% at 80% vVO2peak. There were small increases in vertical and leg stiffnesses in the Endorphin shoes (P < .001); the Endorphin shoe condition also showed trivial to moderate differences in step length, step rate, contact time, and flight time (P < .001)., Conclusions: There was a physiological benefit to running in the super shoes even at the slower speed. There were also spatiotemporal and global stiffness improvements indicating that recreational runners benefit from wearing super shoes.

The main objective of this study was to determine the differences in energy expenditure (EE) according to sex during and after two different squat training protocols in a group of healthy young adults. Twenty-nine Sports Sciences students volunteered to participate in this study. They attended the laboratory on four different days and completed four sessions: two sessions with 3 sets of 12 repetitions at 75% of their one-repetition maximum (RM) and two sessions with 3 sets of 30 repetitions at 50% of their 1RM. Energy expenditure was evaluated using an indirect calorimeter. Males consistently demonstrated higher EE in all sessions and intensities. The linear regression model identified a significant association between sex, BMI, and total EE across all sessions and intensities. In conclusion, males exhibited higher EE in both protocols (50% and 75% of 1RM) throughout all sessions. Furthermore, sex and BMI were found to influence EE in healthy young adults. Therefore, coaches should consider sex when assessing EE, as the metabolic response differs between males and females.

One of the central paradigms of modern neuroscience is the connectionist concept suggesting that the brain's cognitive functions are carried out at the level of neural networks through complex interactions among neurons. This concept considers neurons as simple network elements whose function is limited to generating electrical potentials and transmitting signals to other neurons. Here, I focus on the neuroenergetic aspect of cognitive functions and argue that many findings from this field challenge the concept that cognitive functions are performed exclusively at the level of neural circuits. Two of these findings are particularly foretelling. First, activation of the cerebral cortex in humans (sensory stimulation or solving cognitive problems) is not associated with a significant increase in energy demand. Second, the energetic cost of the brain per unit mass in primates, including Homo sapiens , is approximately proportional to the number of cerebral neurons but not to the number of synapses, the complexity of neural networks, or the level of brain's intellectual abilities. These findings contradict the predictions of the connectionist concept. Rather, they suggest that cognitive functions are generated by intraneuronal mechanisms that do not require much energy. In this context, interactions among neurons would serve to coordinate activities of neurons performing elementary cognitive functions. This function of the network mechanisms also does not require much energy.

Paddles and fins are used in swimmers training with different objectives (e.g., increase propulsive areas of hands and feet, improve the feeling of water flow). These artificial modifications of the stroke might be viewed as external constraints of the stroke task, both will either disturb or facilitate swimming modalities, so the coaches should manipulate its use to extract benefits for performance. This study seeks to investigate the precise effects of wearing either paddles (PAD) or fins (FINS) vs. a no-equipment (NE) trial in three all-out front crawl exercises on swimmer kinematics, arm stroke efficiency ( η p ), upper-limbs coordination patterns (Index of Coordination, IdC), and estimated energy cost (C). Eleven regional to national-level male swimmers participated in the study (age: 25.8 ± 5.5 years, body mass: 75.2 ± 5.5 kg, height: 177 ± 6.5 cm) and were recorded from both sides of the swimming pool to collect all variables. Repeated measures ANOVA and Bonferroni post hoc were used to compare the variables. Effects sizes were calculated. Time to cover the distance and velocity were higher in FINS swimming, with larger values of stroke length (SL) and lower kick amplitude in comparison to the other trials (PAD and NE). The use of FINS also modified the stroke phases durations by presenting significant lower propulsion time during the stroke in comparison to PAD or NE. Values of IdC were lower (IdC < -1%, so catch-up pattern of coordination) for FINS in comparison to NE. In terms of η p , using PAD or FINS demonstrate higher arm stroke efficiency than swimming without equipment. Finally, C was significantly higher in FINS swimming in comparison to NE and PAD. From the present results, it should be noted that the use of equipment such as fins deeply modify the structure of the swimming stroke (from the performance-related parameters through the kinematics of both upper and lower limbs to the stroke efficiency and coordination pattern). So, using equipment should be appropriately scaled by the coaches to the objectives of the training session in swimming, and in emergent sports such as "SwimRun", paddles and fins must be viewed as tools to achieve higher velocities to cover a given distance., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 De Matos, Guignard, Castro and Guimard.)

Introduction: The relationship between the Achilles tendon moment arm length (AT MA ) and the energy cost of running (E run ) has been disputed. Some studies suggest a short AT MA reduces E run while others claim a long AT MA reduces E run . For a given ankle joint moment, a short AT MA permits a higher tendon strain energy storage, whereas a long AT MA reduces muscle fascicle force and muscle energy cost but shortening velocity is increased, elevating the metabolic cost. These are all conflicting mechanisms to reduce E run , since AT energy storage comes at a metabolic cost. Neither of these proposed mechanisms have been examined together., Methods: We measured AT MA using the tendon travel method in 17 males and 3 females (24 ± 3 years, 75 ± 11 kg, 177 ± 7 cm). They ran on a motorized treadmill for 10 min at 2.5 m · s -1 while E run was measured. AT strain energy storage, muscle lengths, velocities and muscle energy cost were calculated during time-normalized stance from force and ultrasound data. A short (SHORT n  = 11, AT MA  = 29.5 ± 2.0 mm) and long (LONG, n  = 9, AT MA  = 36.6 ± 2.5 mm) AT MA group was considered based on a bimodal distribution of measured AT MA., Results: Mean E run was 4.9 ± 0.4 J · kg -1  · m -1 . The relationship between AT MA and E run was not significant ( r 2  = 0.13, p  = 0.12). Maximum AT force during stance was significantly lower in LONG (5,819 ± 1,202 N) compared to SHORT (6,990 ± 920 N, p  = 0.028). Neither AT stretch nor AT strain energy storage was different between groups (mean difference: 0.3 ± 1 J · step -1 , p  = 0.84). Fascicle force was significantly higher in SHORT (508 ± 93 N) compared to LONG (468 ± 84 N. p  > 0.72). Muscle energy cost was significantly lower in LONG (0.028 ± 0.08 J · kg · step p  > 0.72). Muscle energy cost was significantly lower in LONG (0.028 ± 0.08 J · kg · step -1 ) compared to SHORT (0.045 ± 0.14 J · kg · step -1 and total muscle energy cost relative to body mass across the stance phase ( p  = 0.004). There was a significant negative relationship between AT MA and total muscle energy cost relative to body mass across the stance phase ( r  = -0.699, p  < 0.001)., Discussion: Together these results suggest that a LONG AT MA serves to potentially reduce E run by reducing the muscle energy cost of the plantarflexors during stance. The relative importance of AT energy storage and return in reducing E run should be re-considered., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Bennett, Machado and Fletcher.)

Objective: Individuals after stroke are less active, experience more fatigue, and perform activities at a slower pace than peers with no impairments. These problems might be caused by an increased aerobic energy expenditure during daily tasks and a decreased aerobic capacity after stroke. The aim of this study was to quantify relative aerobic load (ie, the ratio between aerobic energy expenditure and aerobic capacity) during daily-life activities after stroke., Methods: Seventy-nine individuals after stroke (14 in Functional Ambulation Category [FAC] 3, 25 in FAC 4, and 40 in FAC 5) and 22 peers matched for age, sex, and body mass index performed a maximal exercise test and 5 daily-life activities at a preferred pace for 5 minutes. Aerobic energy expenditure (mL O2/kg/min) and economy (mL O2/kg/unit of distance) were derived from oxygen uptake ($\dot{\mathrm{V}}{\mathrm{O}}&#95;2$). Relative aerobic load was defined as aerobic energy expenditure divided by peak aerobic capacity (%$\dot{\mathrm{V}}{\mathrm{O}}&#95;2$peak) and by $\dot{\mathrm{V}}{\mathrm{o}}&#95;2$ at the ventilatory threshold (%$\dot{\mathrm{V}}{\mathrm{o}}&#95;2$-VT) and compared in individuals after stroke and individuals with no impairments., Results: Individuals after stroke performed activities at a significantly higher relative aerobic load (39%-82% $\dot{\mathrm{V}}{\mathrm{o}}&#95;2$peak) than peers with no impairments (38%-66% $\dot{\mathrm{V}}{\mathrm{o}}&#95;2$peak), despite moving at a significantly slower pace. Aerobic capacity in individuals after stroke was significantly lower than that in peers with no impairments. Movement was less economical in individuals after stroke than in peers with no impairments., Conclusion: Individuals after stroke experience a high relative aerobic load during cyclic daily-life activities, despite adopting a slower movement pace than peers with no impairments. Perhaps individuals after stroke limit their movement pace to operate at sustainable relative aerobic load levels at the expense of pace and economy., Impact: Improving aerobic capacity through structured aerobic training in a rehabilitation program should be further investigated as a potential intervention to improve mobility and functioning after stroke., (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Physical Therapy Association.)

Background: Compared to typically developing children, children with cerebral palsy (CP) have increased energy expenditure during walking, limiting activity and participation. Insight into whether the also deviating and more asymmetric gait with increased muscle co-activation contributes to this increased energy expenditure is important for clinical decision making. The aim of this study was to investigate the relation between energy cost of walking with gait deviation, asymmetry, and muscle co-activation in children with CP., Methods: Forty ambulant children with CP, with Gross Motor Function Classification System (GMFCS) level I (N = 35) and II (N = 5), aged between 5-17y, were tested at one or two occasions with 24 weeks in between, resulting in 71 observations. Gross energy cost (J/kg/m) was measured during a 5-min walk test at self-selected speed. From a 3-dimensional gait analyses, kinematic variables and electromyography were extracted to calculate the gait deviation index (GDI) and co-activation index. The relation between energy cost and GDI, GDI asymmetry, and co-activation index of the lower limb muscles was evaluated through mixed model analyses. Height was included to control for growth-related variation., Results: Gait deviation and height combined explained about 40% of the variance in gross energy cost. No significant contribution was found for gait asymmetry or co-activation index., Conclusions: This cross-sectional study indicates that increased gait deviation contributes to increased energy cost of walking in children with GMFCS level I and II., (© 2023. The Author(s).)

Objective: To assess the impact of cognitive Dual Task (DT) during walking on the energy cost of walking (Cw) in individuals with subacute stroke. The secondary objective was to determine whether there is an association between the Cw and cortical activity of the prefrontal area., Methods: Any individual with stroke localized in the temporal-parietal regions and able to walk without human assistance was included. Cw and prefrontal cortical activity, recorded by fNIRS, were measured during simple task walking activity and cognitive dual task during walking., Results: Nineteen individuals with stroke (age = 67.7 ± 9.6 yrs) were included. The cognitive DT during walking resulted in an increase in Cw of 23.1%; 95%CI [13.1%; 34.5%]. The increase in Cw in cognitive DT was correlated with the Cw for the single task walking activity (r = 0.48, p < 0.01) as well as the predominance of cortical activity of the prefrontal area in the contralesional hemisphere (r = -0.33, p < 0.01)., Conclusion: There is an increase in Cw during the cognitive DT. This increase is even more significant, as the Cw of the single task walking activity is high, and the cortical activity of the prefrontal areas predominates in the contralesional hemisphere.

New Findings: What is the central question of the study? Are the changes in force potentials (at the muscle level) related with metabolic changes at speeds above and below the walk-to-run transition? What is the main finding and its importance? The force-length and force-velocity potentials of gastrocnemius medialis during human walking decrease as a function of speed; this decrease is associated with an increase in cumulative EMG activity and in the energy cost of locomotion. Switching from fast walking to running is associated to an increase in the force potentials, supporting the idea that the 'metabolic trigger' that determines the transition from walking to running is ultimately driven by a reduction of the muscle's contractile capacity., Abstract: The aim of this study was to investigate the interplay between the force-length (F-L) and force-velocity (F-V) potentials of gastrocnemius medialis (GM) muscle fascicles, the cumulative muscle activity per distance travelled (CMAPD) of the lower limb muscles (GM, vastus lateralis, biceps femori, tibialis anterior) and net energy cost (C net ) during walking and running at speeds above and below the walk-to-run transition speed (walking: 2-8 km h -1 ; running: 6-10 km h -1 ). A strong association was observed between C net and CMAPD: both changed significantly with walking speed but were unaffected by speed in running. The F-L and F-V potentials decreased with speed in both gaits and, at 6-8 km h -1 , were significantly larger in running. At low to moderate walking speeds (2-6 km h -1 ), the changes in GM force potentials were not associated with substantial changes in CMAPD (and C net ), whereas at walking speeds of 7-8 km h -1 , even small changes in force potentials were associated with steep increases in CMAPD (and C net ). These data suggest that: (i) the walk to run transition could be explained by an abrupt increase in C net driven by an upregulation of the EMG activity (e.g., in CMAPD) at sustained walking speeds (>7 km h -1 ) and (ii) the reduction in the muscle's ability to produce force (e.g., in the F-L and F-V potentials) contributes to the increase in CMAPD (and C net ). Switching to running allows regaining of high force potentials, thus limiting the increase in CMAPD (and C net ) that would otherwise occur to sustain the increase in locomotion speed., (© 2022 The Authors. Experimental Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.)

Energy consumption is increasing daily, and with that comes a continuous increase in energy costs. Predicting future energy consumption and building an effective energy management system for smart homes has become essential for many industrialists to solve the problem of energy wastage. Machine learning has shown significant outcomes in the field of energy management systems. This paper presents a comprehensive predictive-learning based framework for smart home energy management systems. We propose five modules: classification, prediction, optimization, scheduling, and controllers. In the classification module, we classify the category of users and appliances by using k-means clustering and support vector machine based classification. We predict the future energy consumption and energy cost for each user category using long-term memory in the prediction module. We define objective functions for optimization and use grey wolf optimization and particle swarm optimization for scheduling appliances. For each case, we give priority to user preferences and indoor and outdoor environmental conditions. We define control rules to control the usage of appliances according to the schedule while prioritizing user preferences and minimizing energy consumption and cost. We perform experiments to evaluate the performance of our proposed methodology, and the results show that our proposed approach significantly reduces energy cost while providing an optimized solution for energy consumption that prioritizes user preferences and considers both indoor and outdoor environmental factors.

Background: Modern pentathlon includes horse riding, fencing, swimming, shooting and cross-country running. Events can last many hours during which the athletes face almost maximal energy and physiological demands, and fatigue. Early recognition and prevention of injuries and overuse syndromes can be achieved by refining the individual training loads. The purpose of the study was to determine which parameter could be the most accurate predictor of swimming working capacity determinants in pentathletes., Methods: Fourteen male pentathletes performed a continuous maximal incremental test in the swimming flume ergometer to measure peak oxygen uptake (VO 2 peak), and five swimming tests in a 50 m swimming pool to detect critical velocity (CV); velocity at 2 and 4 mM·L -1 of blood lactate (v2, v4) and energy cost (EC)., Results: The 200 m swimming time was 2:18-2:32 m:s (340 FINA points). CV was 1.21 ± 0.04 m·s -1 , v2 was 1.14 ± 0.09 and v4 1.23 ± 0.08 m·s -1 . VO 2 peak was 3540.1 ± 306.2 mL·min -1 or 48.8 ± 4.6 mL·kg -1 ·min -1 . EC at 1.24 m·s -1 was 45.7 ± 2.4 mL·kg -1 ·min -1 . Our main finding was the large correlation of CV with 200 m swimming performance; Conclusions: Among all the protocols analysed, CV is the most predictive and discriminative of individual swimming performance in this group of pentathletes. It appears as the most suitable test to constantly refine their swimming training loads for both performance enhancement and health promotion.

This paper focuses on comprehensive analysis of fixed-time stability and energy consumed by controller in nonlinear neural networks with time-varying delays. A sufficient condition is provided to assure fixed-time stability by developing a global composite switched controller and employing inequality techniques. Then the specific expression of the upper of energy required for achieving control is deduced. Moreover, the comprehensive analysis of the energy cost and fixed-time stability is investigated utilizing a dual-objective optimization function. It illustrates that adjusting the control parameters can make the system converge to the equilibrium point under better control state. Finally, one numerical example is presented to verify the effectiveness of the provided control scheme., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Several constraints, including environmental (e.g., aquatic resistance, temperature and viscosity), organismic (e.g., anthropometry, buoyancy) and task-related (e.g., imposed swim speed or stroke rate) impact motor coordination and swimming performance. As motor coordination requires structurally organising intra- and inter-limb coupling, the purpose of this review was to update the literature concerning coordination between the upper-limbs in front crawl swimming. We focused on the effects of biomechanical, physiological, and personal (gender, skill level, and age) factors on coordination and performance. In fact, it could be highlighted that upper-limbs coordination varies with organismic, task and environmental constraints, resulting in several available motor solutions that should be adopted according to how each swimmer deals with occurring constraints. As such, there is no ideal or optimal coordination pattern that youth, learners and less-skilled swimmers should imitate.

Background: The increased energy cost of walking (Cw) for stroke patients affects the walking function and walking independence of stroke patients. However, its impact on quality of life (QoL) has never been studied., Objective: Assess the association between Cw and QoL for post-stroke individuals in the year following hospital discharge., Method: Thirty-seven individuals with stroke were included. QoL was assessed by the EuroQol-5 Dimensions on the day after hospital discharge (T0), at six months (T1) and at one year after hospital discharge (T2). Concomitant an evaluation of Cw, mood disorders (HADS), fatigue, independence in activities of daily living and the presence of a family caregiver was performed. The association between QoL and the different covariates was analyzed using multiple regression analysis., Results: At T2, data from 29 individuals were analyzable. Multiple regression analyses showed Cw had a significant influence on the QoL at T1 (coeff -0.42 (-0.71 to -0.12), P = .008) and T2 (coeff -0.49 (-0.71 to -0.26), P < .001). HADS score was the only other variable to significantly impact variances of QoL at T0, T1 and T2. Moreover, we showed that Cw at T0 explained 29% of variances of QoL at T1 and 42% at T2., Conclusion: Cw appears to be an independent factor in the QoL of individuals with stroke at six months and one year after hospital discharge. In addition, the initial Cw and HADS are predictive of QoL at one year highlighting the importance of early interventions in these two dimensions to improve QoL over the long term., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Treadmills are utilized as a training tool to improve aerobic fitness, but precise understanding of intensity and the corresponding physiological strain is critical for optimizing exercise prescription and associated adaptations. Running on non-motorized, curved treadmills may result in greater oxygen uptake (VO 2 ), increased heart rate (HR), and increased rating of perceived exertion (RPE) compared to traditional motorized treadmills. The purpose of this study was to investigate the physiological responses on non-motorized versus traditional motorized treadmills during speed-matched running. Participants were 4 college-aged, recreationally active females. HR, VO 2 , respiratory exchange ratio (RER), and RPE were monitored during 3 speed-matched stages of incremental exercise in two conditions: the non-motorized Assault AirRunner and a traditional motorized treadmill, as well as for 5 minutes post-exercise. VO 2 , RER, and HR were greater in the Assault condition (ES VO2 = 0.998, ES RER = 0.839, ES HR = 0.972, p < 0.05). While not significant between groups, RPE showed a greater increase with increasing speeds in the Assault condition (ES = 0.728), as did RER (ES = 0.800, p < 0.05). Cumulative excess-post exercise oxygen consumption (EPOC) during a five-minute period post-exercise was also greater in the Assault condition, and HR and RER remained higher five minutes post-exercise in the Assault condition (ES EPOC = 0.738, ES HR = 1.600, ES RER = 2.075, p < 0.05). The Assault AirRunner elicited greater physiological responses (VO 2 , carbohydrate usage, and HR) in response to speed-matched running in comparison to a traditional motorized treadmill in active college-aged females. Collectively, aerobic exercise conducted on the Assault AirRunner has a greater physiological and perceived intensity and need to be taken into consideration when designing and implementing training programs or testing.

In human upper-arm reaching movements, the variance of the hand position increases until the middle of the movement and then decreases toward the endpoint. Such decrease in positional variance has been suggested as an evidence to support the hypothesis that our nervous system uses feedback control, rather than feedforward control, for arm reaching tasks. In this study, we computed the optimal trajectories based on feedforward control under several criteria for a one-link two-muscle arm model with considering the stochastic property of muscle activities in order to reexamine the hypothesis. The results showed that the feedforward control also represents the decrease in positional variance in the latter half of the movement when the control signal is planned under the minimum energy cost and minimum variance models. Furthermore, the optimal trajectory that minimizes energy cost represents not only the decrease in positional variance but also many other characteristics of the human reaching movements, e.g., the three-phasic activity of antagonistic muscle, bell-shaped speed curve, N-shaped equilibrium trajectory, and bimodal profile of joint stiffness. These results suggest that minimum energy cost model well expresses the characteristics of hand reaching movements, and our central nervous system would make use of not only a feedback control but also feedforward control., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Traditional movement economy (ME) measures the energetic cost of in-line running. However, it is debatable whether such a measure is representative of movement efficiency for team sport athletes who are required to run and change direction repeatedly. This study evaluated ME during both in-line running and runs with directional changes and provided a preliminary exploration as to whether these abilities discriminate soccer players according to playing position, level, and sex. Forty-three soccer players were assessed for ME as extrapolated from oxygen uptake during in-line running (RE) and running with changes of directions (using 20 and 10 m shuttle runs [SRE 20 and SRE 10 ]) at 8.4 km/h mean speed. ME worsened with change of direction frequency ( p  < 0.001). Coefficient of determination was high between RE and SRE 20 ( r 2  =   0.601) but dropped below 0.5 for RE and SRE 10 ( r 2  = 0.280) as change of direction frequency increased. No significant differences were observed between different player positions, however, centre midfielders reported the best ME across any position and running mode, with the largest differences observed in centre backs over SRE 10 (41.9 ± 2.7 ml/kg/min [centre midfielders] vs 45 ± 1.8 ml/kg/min [centre backs]; ES = 1.19). No significant differences were observed for ME over any running condition for male players of different playing levels. Female players exhibited better ME than male players with significant differences observed for SRE 10 (41.5 ± 2.6 ml/kg/min [females] vs 44 ± 2.6 ml/kg/min [males]; p  = 0.013; ES = 0.94). RE does not adequately account for efficiency during activities that involve changes of direction. SRE 10 is a stronger discriminator of ME between soccer players of different position and sex.

This paper presents a method to model and optimise the substrate feeding rate of an anaerobic digestion (AD) system. The method is demonstrated for a case study plant in Bangalore, India, using onsite kitchen waste to provide biogas for cooking. The AD system is modelled using Anaerobic Digestion Model No. 1 (ADM1) and a genetic algorithm (GA) is applied to control the substrate feeding rate in order to simultaneously minimise the volume of flared biogas, unmet gas demand and energy cost. Our results show that ADM1 can predict biogas yield from a continuously operated digester well with mean percentage errors between daily predicted and measured data values of only 5.7% for March 2017 and 17.8% for July 2017. When biogas flaring and unmet gas demand were minimised, the amount of biogas flared reduced from 886.62 m 3 to 88.87 m 3 in March and from 73.79 m 3 to 68.49 m 3 in July. When the energy cost was also considered within the objective function, the biogas flared reduced from 886.62 m 3 to 281.27 m 3 for March, but increased from 73.79 m 3 to 180.11 m 3 for July. The amount of flaring increased in July as the energy cost function increased biogas yield without considering surplus gas production beyond demand and storage capacity. As AD systems are often operated to maximise biogas production, these results highlight the need for multi-objective optimisation, particularly for off-grid AD systems., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Flagellar-driven motility grants unicellular organisms the ability to gather more food and avoid predators, but the energetic costs of construction and operation of flagella are considerable. Paths of flagellar evolution depend on the deviations between fitness gains and energy costs. Using structural data available for all three major flagellar types (bacterial, archaeal, and eukaryotic), flagellar construction costs were determined for Escherichia coli , Pyrococcus furiosus , and Chlamydomonas reinhardtii . Estimates of cell volumes, flagella numbers, and flagellum lengths from the literature yield flagellar costs for another ~200 species. The benefits of flagellar investment were analysed in terms of swimming speed, nutrient collection, and growth rate; showing, among other things, that the cost-effectiveness of bacterial and eukaryotic flagella follows a common trend. However, a comparison of whole-cell costs and flagellum costs across the Tree of Life reveals that only cells with larger cell volumes than the typical bacterium could evolve the more expensive eukaryotic flagellum. These findings provide insight into the unsolved evolutionary question of why the three domains of life each carry their own type of flagellum., Competing Interests: PS, ML No competing interests declared, (© 2022, Schavemaker and Lynch.)

A Chinese Compilation of Physical Activities was compiled to estimate the energy costs of physical activities (PAs) using data on adults aged 18-64. Data were obtained from published articles and laboratory measurements. Databases, including PubMed, Embase, Scopus, Ebsco, Web of Science, Chinese National Knowledge Infrastructure, Wan Fang Data, National Science and Technology Report Service, Public Health Scientific Data were searched to collect data from inception to January 2022, on energy expenditure associated with PA in the healthy Chinese population. Two reviewers independently screened the literature and extracted, classified, and summarized data. Data were measured for 36 PAs using indirect calorimetry. Detailed descriptions of specific activities and metabolic equivalent values were provided by summarizing 241 physical activities in 13 categories. The first edition of the Chinese Compilation of PAs in Healthy Adults Aged 18-64(CCPA) was created. It provides valuable resources for people who regularly engage in physical exercise, researchers, educators, fitness professionals, and health or commercial sectors to quickly obtain various PA MET intensities. In the future, the energy expenditure of various PAs of different ages within the Chinese population can be measured based on the CCPA., Competing Interests: The author declares no conflicts of interest relevant to the content of this paper., (© 2022 Chengdu Sport University. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.)

Water exercise provides a workload in every direction of motion for training in a reduced impact environment. The selection of an appropriate physical activity and an individual exercise prescription are essential to obtain training effects. The aim of the present study was to determine individualised relative exercise intensities at four speeds of motion for water cycling and water running. Running was tested both in buoyancy and with the feet in contact with the bottom of the pool. To this purpose, gas exchanges, heart rate, and blood lactate were measured in each test session. Fourteen active, healthy females (23.2 ± 1.6 years) underwent a dry land maximal incremental protocol to exhaustion on a treadmill and hydrobike (HB); they engaged in water running with ground contact (RC) and water running suspended (RS) tests in a swimming pool at 30, 40, 50, and 60 cycles per minute (cpm), submerged at the individual xiphoid level. The four motion speeds of the three water exercise modalities ranged from 50% to 95% of the maximal heart rate and the maximal oxygen uptake, representing a moderate-to-vigorous training stimulus. RS elicited the lowest oxygen consumption, whereas HB demanded the significantly highest oxygen consumption and presented the highest blood lactate accumulation, with vigorous intensity being reached at 50 cpm and near maximal intensity at 60 cpm. It appears that water cycling could be more suitable for athletic training, whereas water running could be more appropriate for health and fitness purposes.

The energetics of cycling represents a well-studied area of exercise science, yet there are still many questions that remain. Efficiency, broadly defined as the ratio of energy output to energy input, is one key metric that, despite its importance from both a scientific as well as performance perspective, is commonly misunderstood. There are many factors that may affect cycling efficiency, both intrinsic (e.g., muscle fiber type composition) and extrinsic (e.g., cycling cadence, prior exercise, and training), creating a complex interplay of many components. Due to its relative simplicity, the measurement of oxygen uptake continues to be the most common means of measuring the energy cost of exercise (and thus efficiency); however, it is limited to only a small proportion of the range of outputs humans are capable of, further limiting our understanding of the energetics of high-intensity exercise and any mechanistic bases therein. This review presents evidence that delta efficiency does not represent muscular efficiency and challenges the notion that the slow component of oxygen uptake represents decreasing efficiency. It is noted that gross efficiency increases as intensity of exercise increases in spite of the fact that fast-twitch fibers are recruited to achieve this high power output. Understanding the energetics of high-intensity exercise will require critical evaluation of the available data., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

In elite oarsmen, the rowing ergometer is a valuable tool for both training and studying rowing performance determinants. However, the energy cost of rowing, often reported as a determinant of performance, has never been described for ergometer rowing. Therefore, this study aimed to characterize the energy cost of ergometer rowing (ECR) in elite oarsmen, its contribution to 2,000 m performance, and its determinants. This study was conducted on 21 elite oarsmen from the French national team. It included an incremental exercise test up to exhaustion and an all-out performance test over 2,000 m, both conducted on a rowing ergometer. Gas exchange analysis was performed to calculate oxygen uptake and substrate utilization rate. Whole blood lactate concentrations during the incremental test were obtained from the earlobe. During the incremental test, ECR displayed a significant linear increase up to a plateau that reached a mean rowing speed of 5.23 ± 0.02 m⋅s -1 . The ECR values at 300, 350, and 400 W were positively correlated with performance expressed as the time required to perform the 2,000 m distance on the rowing ergometer. The same ECR values were found to be significantly related to fat oxidation (expressed in percentage of total energy supply) and blood lactate concentrations. This study provides the first description of ECR and of its relationship to exercise intensity on the rowing ergometer in elite oarsmen. ECR appeared to be a factor of performance and interestingly was related to energy supply from fat and blood lactate concentrations., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Blervaque, Bowen, Chatel, Corbex, Dalmais and Messonnier.)

While many studies for material extrusion-based additive manufacturing (AM) of polymers focus on experimental approaches to evaluate relevant performance measures from process parameters, there is a lack of discussion to connect experimental results with useful applications. Also, one of the major deficiencies in the application literature is a trade-off analysis between energy costs and cycle time (time to produce an item from the beginning to the end) since improving these two measures simultaneously is challenging. Thus, this paper proposes an energy simulation method for performing a trade-off analysis between energy costs and cycle time using combinations of major AM process parameters for material extrusion. We conduct experiments using carbon fiber-reinforced poly-ether-ether-ketone (CFR-PEEK), which is increasingly used in material extrusion. From experimental results, we build a power model in which power (kW) is derived as a linear function of material addition rates (MAR). This MAR regression model is then used in a proposed simulation model that integrates discrete event simulation and numerical simulation. In our simulation case study of 50 machines and 40 scenarios, we investigate trade-offs between energy costs and cycle time with three control policies (P 1 , P 25 , and P 50 ) that allow 1, 25, or 50 machines to start heating, respectively. The trade-off analysis results show that P 25 can be preferred when a balance between cycle time and energy costs is pursued, while P 1 or P 50 can be chosen if either energy cost (with P 1 ) or cycle time (with P 50 ) is more important than the other measure. Moreover, we find that the machine utilization, variability, and product volume have significant effects on energy costs and cycle time., Competing Interests: Conflict of interestThe authors declare no competing interests., (© The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2022.)

The new concept of energy solvency is defined as the ability of a person buying or renting a dwelling to meet the energy costs necessary to keep the dwelling comfortable, without falling into energy poverty. The energy efficiency certificate information is used to calculate the economic expenditure that is theoretically necessary to maintain the property comfortable. This is a more robust value for calculating the energy poverty indicator 2 M than the available data on real expenditure. Dwellings' maximum surface may be determined in order to guarantee the energy solvency, depending on the climate zone, the energy class, the energy sources used, and the household's net income. The results indicate that in 15% of situations, it is not possible to have a dwelling that exceeds the minimum surface area stipulated by law without incurring an energy risk situation. It is also observed that in 86% of the cases, energy solvency is achieved for dwellings with energy classes A, B, C, and D, up to 120 m 2 . It is concluded that, by knowing the energy solvency before renting or buying a home, it is possible to prevent energy poverty by avoiding those operations in which it is known that this will happen., Competing Interests: Conflict of interestThe authors declare no competing interests., (© The Author(s), under exclusive licence to Springer Nature B.V. 2022, Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.)

Background: The net metabolic cost of walking (NCw) and the co-activation of leg muscles are both higher in old adults (OG) than in young adults (YG). Nevertheless, the relation between the two remains unresolved, mainly due to the controversial co-activation measurement method used in previous studies., Research Question: To compare ankle and knee co-contraction (CCI), calculated using an EMG-driven method, between the groups and to examine their relationship with NCw., Methods: Nine young (YG = 25.2 +/- 3.3 years old) and nine older (OG = 68.7 +/5.9 years old) adults walked on a treadmill at five speeds (YG: 1; 1.2; 1.4; 1.6; 1.8 m/s; OG: 0.6; 0.8; 1; 1.2; 1.4 m/s) while electromyography (sEMG) and oxygen consumption were measured. CCI were calculated around the ankle and knee for different parts of the gait cycle (entire gait cycle 0-100 %, stance phase 0-60 %, swing phase 60-100 %)., Results: NCw was significantly higher (25 %, averaged over the walking speeds) in OG as were Knee&#95;CCI, Knee&#95;CCI&#95;swing and Knee&#95;CCI&#95;stance. Multiple regression models in YG, OG and YG + OG highlighted Ankle&#95;CCI as the main contributor in NCw (β = 0.08-0.188, p < 0.05) with a positive relation between the two variables., Significance: The present findings provide a better understanding of the association between muscle co-contraction and metabolic cost in older adults. It may help scientists and clinicians to further develop strategies aimed at neuromuscular rehabilitation as a means of improving mobility and independence among older adults., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Higher mass-normalized net energy cost of walking (NetC w/kg ) and mechanical pendular recovery are observed in obese compared to lean adults. This study aimed to investigate the effect of different classes of obesity on the energetics and mechanics of walking and to explore the relationships between body mass, NetC w/kg and gait mechanics by using principal component analysis (PCA). NetC w/kg and gait mechanics were computed in severely obese (SOG; n = 18, BMI = 40.1 ± 4.4 kg·m -2 ), moderately obese (MOG; n = 17, BMI = 32.2 ± 1.5 kg·m -2 ) and normal-weight (NWG; n = 13, BMI = 22.0 ± 1.5 kg·m -2 ) adults during five walking trials (0.56, 0.83, 1.11, 1.39, 1.67 m·s -1 ) on an instrumented treadmill. NetC w/kg was significantly higher in SOG compared to NWG ( p = 0.019), with no significant difference between SOG and MOG ( p = 0.14), nor between MOG and NWG ( p = 0.27). Recovery was significantly higher in SOG than in NWG ( p = 0.028), with no significant difference between SOG and MOG ( p = 0.13), nor between MOG and NWG ( p = 0.35). PCA models explained between 17.0% and 44.2% of the data variance. This study showed that: (1) obesity class influences the gait energetics and mechanics; (2) PCA was able to identify two components, showing that the obesity class is associated with lower walking efficiency and better pendulum-like characteristics.

The COVID-19 pandemic has renewed interest in assessing how the operation of HVAC systems influences the risk of airborne disease transmission in buildings. Various processes, such as ventilation and filtration, have been shown to reduce the probability of disease spread by removing or deactivating exhaled aerosols that potentially contain infectious material. However, such qualitative recommendations fail to specify how much of these or other disinfection techniques are needed to achieve acceptable risk levels in a particular space. An additional complication is that application of these techniques inevitably increases energy costs, the magnitude of which can vary significantly based on local weather. Moreover, the operational flexibility available to the HVAC system may be inherently limited by equipment capacities and occupant comfort requirements. Given this knowledge gap, we propose a set of dynamical models that can be used to estimate airborne transmission risk and energy consumption for building HVAC systems based on controller setpoints and a forecast of weather conditions. By combining physics-based material balances with phenomenological models of the HVAC control system, it is possible to predict time-varying airflows and other HVAC variables, which are then used to calculate key metrics. Through a variety of examples involving real and simulated commercial buildings, we show that our models can be used for monitoring purposes by applying them directly to transient building data as operated, or they may be embedded within a multi-objective optimization framework to evaluate the tradeoff between infection risk and energy consumption. By combining these applications, building managers can determine which spaces are in need of infection risk reduction and how to provide that reduction at the lowest energy cost. The key finding is that both the baseline infection risk and the most energy-efficient disinfection strategy can vary significantly from space to space and depend sensitively on the weather, thus underscoring the importance of the quantitative predictions provided by the models., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 Elsevier B.V. All rights reserved.)

Purpose: To investigate the acute effect of repeated-sprint activity (RSA) on change-of-direction economy (assessed using shuttle running economy [SRE]) in soccer players and explore neuromuscular and cardiorespiratory characteristics that may modulate this effect., Methods: Eleven young elite male soccer players (18.5 [1.4] y old) were tested on 2 different days during a 2-week period in their preseason. On day 1, lower-body stiffness, power and force were assessed via countermovement jumps, followed by an incremental treadmill test to exhaustion to measure maximal aerobic capacity. On day 2, 2 SRE tests were performed before and after a repeated-sprint protocol with heart rate, minute ventilation, and blood lactate measured., Results: Pooled group analysis indicated no significant changes for SRE following RSA due to variability in individual responses, with a potentiation or impairment effect of up to 4.5% evident across soccer players. The SRE responses to RSA were significantly and largely correlated to players' lower-body stiffness (r = .670; P = .024), and moderately (but not significantly) correlated to players' force production (r = -.455; P = .237) and blood lactate after RSA (r = .327; P = .326)., Conclusions: In summary, SRE response to RSA in elite male soccer players appears to be highly individual. Higher lower-body stiffness appears as a relevant physical contributor to preserve or improve SRE following RSA.

Implementation of an ultraviolet (UV)-induced advanced oxidation process (AOP) before coagulation was found to enhance the removal of algae cells. However, the effect of UV-induced AOPs on extracellular cellular organic matter (EOM) and on its coagulation and removal was neglected. This study investigated the impact of UV-induced AOPs (UV/Cl 2 , UV/ClO 2 , and UV/H 2 O 2 ) on EOM from Microcystis aeruginosa, and its coagulation and removal by a conventional gravity system (CGS), dissolved air flotation, and a low-energy flash-pressurized flotation (FPF) process. The changes in EOM characteristics before and after the UV-induced AOPs were based on UV absorbance (UV 254 ) and liquid chromatography with organic carbon detection analysis. The reduction in UV 254 increased with an increasing dose of oxidant and UV irradiation. The reduction in UV 254 for UV/Cl 2 , UV/ClO 2 and UV/H 2 O 2 was 59.5%, 26.5%, and 17.5% respectively, for 0.71 mM equimolar concentration of oxidant and 1920 mJ/cm 2 UV irradiation, as evident from a pseudo-first order kinetics study. Similarly, degradation of the high molecular weight to low molecular weight (LMW) fraction was pronounced for UV/Cl 2 . The coagulation efficiency decreased after UV-induced AOP in the following order: UV/H 2 O 2  > UV/ClO 2  > UV/Cl 2 . By contrast, the low-energy FPF process showed a higher removal of LMW fractions than CGS. Thus, low-energy FPF could be an alternative technology for the UV-induced AOP treatment system., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: In boys with DMD, muscle weakness progresses in a proximal to distal pattern, leading to compensatory gait strategies, including hyperlordosis and equinus, that increase energy cost and accelerate the loss of walking capacity., Research Question: The purpose of this study was to determine the changes in the energy cost of walking that occur with disease progression and to determine the optimal normalization scheme for the longitudinal assessment of the energy cost of walking in boys with DMD., Methods: Energy cost was assessed with the COSMED K4b 2 . Three normalization schemes were examined: gross energy cost (EC), net non-dimensional oxygen cost (NNcost) and speed-matched control energy cost (SMC-EC). Nonlinear mixed modeling procedures determined the rate of change with age. Linear regression was used to asses the relationship between each normalization scheme and age and body height., Results: 74 boys with DMD were assessed for the energy cost of walking. Velocity decreased at a significant rate (-.00245/month, p = .03) across time; (Fig. 2), while gross EC (.003248/month, p = 0.0026), NNcost (.006155/month, p < 0.0001) and SMC-EC (.001690/month, p = 0.03) all increased significantly. Age and height were significantly associated with NNcost and SMC-EC. The sensitivity of NNcost and SMC-EC to age over time were similar, while SMC-EC was less sensitive to changes in height over time than NNcost., Significance: In contrast to able-bodied peers, boys with DMD decrease their velocity while all walking energy cost measures increased over time. Both SMC-EC and NNcost proved appropriate normalization schemes for boys with DMD. Compared to gross EC, both NNcost and SMC-EC were less sensitive to changes in age over time, while SMC-EC was less sensitive to changes in height than NNcost. Therefore, both NNCost and SMC-EC are suggested normalization schemes for the longitudinal assessment of energy cost in boys with DMD., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Background: Physical activity becomes increasingly fragmented with age, which may be an early marker of functional decline. Energetic cost of walking and energy capacity are also linked with functional decline, but their associations with activity fragmentation, and the potential modifying roles of total daily physical activity and age, remains unclear., Method: A total of 493 participants (50-93 years) from the Baltimore Longitudinal Study of Aging underwent measures of energetic cost of usual-paced overground walking (mL/kg/m), energy demand during slow walking (mL/kg/min) on a treadmill (0.67 m/s, 0% grade), and average peak walking energy expenditure (mL/kg/min) during a fast-paced 400-m walk. A ratio of slow walking to peak walking energy expenditure ("cost-to-capacity ratio") was calculated. Activity fragmentation was quantified as an active-to-sedentary transition probability (ASTP) using Actiheart accelerometer data. Linear regression models with ASTP as the dependent variable were used to test whether poorer energy cost and capacity were associated with higher ASTP and whether the associations differed by daily physical activity or age., Results: After adjusting for demographics, body composition, comorbidities, and daily physical activity, every 10% higher cost-to-capacity ratio was associated with 0.4% greater ASTP (p = .005). This association was primarily driven by the least active participants (pinteraction = .023). Peak walking energy expenditure was only associated with ASTP among participants aged ≥70 years., Conclusions: Higher cost-to-capacity ratio and lower energy capacity may manifest as more fragmented physical activity, especially among those less active or aged ≥70 years. Future studies should examine whether an increasing cost-to-capacity ratio or declining energy capacity predicts subsequent activity fragmentation., (© The Author(s) 2021. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: The oxygen cost of walking (Cw) represents the energy expenditure involved in walking, which is a major concern when quantifying physical activity in stroke. Recent studies have reported that Cw may be estimated accurately with a prediction equation using the self-self-selected walking speed (S free )., Research Question: To evaluate the validity of Cw estimates according to different modalities of S free measurements (10-m walking test, 6-minute walking test, GaitRite system)., Methods: Twenty-one stroke individuals in subacute phase who were able to walk without human aid were included. Cw was estimated from the walking speed measured during a 10-m walking test, a 6-minute walking test and a recording on a GaitRite system. The values of the Cw estimates were compared to those measured by a respiratory gas exchange analyzer (Metamax3b)., Results: The findings showed that there is no significant difference between the Cw measured by Metamax3b and the Cw estimates regardless of the modalities used to measure S free (Fvalue = 0.02; pvalue = 0.99). The mean bias between Cw measured by the Metamax3b and those estimated using the different S free measurement modalities was less than 2.5 % of the mean Cw value. Test retest reliability was excellent with an intraclass correlation coefficient higher than 0.95., Significance: in stroke survivors who are able to walk independently without human aid, the use of a 10-m walking test, a 6-minute walking test or a GaitRite recording can be considered validated for estimating Cw., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The primary aim of this study was to compare the measured oxygen consumption (Measured -V O 2 ) in a simulated futsal game (S-Game) with the estimated oxygen consumption (Estimated -V O 2 ) through a regression equation between heart rate (HR) and oxygen consumption ( V O 2 ) (HR- V O 2 ) in treadmill running, and a secondary aim was to calculate the total energy expenditure (EE) in S-Game. Ten professional players (22.20 ± 3.22 years) were evaluated. HR- V O 2 was determined individually in the continuous test on the treadmill (Cont Test ). The Measured -V O 2 in S-Game was compared with the Estimated -V O 2 in the Cont Test . Alactic and lactic pathways were estimated by V O 2 . The Estimated -V O 2 presented no statistically significant difference with the Measured -V O 2 , using the paired t -test ( p = 0.38). However, the correlation between Estimated- and Measured- V O 2 was very weak ( r = -0.05), and it presented poor agreement (concordance correlation coefficient = -0.04). In addition, a Bland-Altman plot presented bias of -2.8 ml/kg/min and individual difference as large as 19 ml/kg/min. The HR- V O 2 determined by the Cont Test was not a good individual predictor of V O 2 . The high intensity and intermittent nature of the futsal game possibly caused dissociation in the HR- V O 2 relationship. Cont Test is not recommended for estimating V O 2 and calculating individual EE in the futsal game. This is recommended only for the group mean. The total EE in S-Game was 13.10 ± 1.25 kcal.min -1 (10.81 ± 1.57 metabolic equivalents). The contributions from the metabolic pathways were as follows: aerobic (93%), alactic (5%), and lactic (2%)., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Silva, Nakamura, Papoti, da Silva and Dos-Santos.)

Purpose: This study aimed to compare physiological factors and cycle characteristics during cross-country (XC) roller-skiing at matched inclines and speeds using the double-poling (DP) and diagonal-stride (DS) sub-techniques in junior female and male XC skiers., Methods: Twenty-three well-trained junior XC skiers (11 women, 12 men; age 18.2 ± 1.2 yr.) completed two treadmill roller-skiing tests in a randomized order using either DP or DS. The exercise protocols were identical and included a 5 min warm-up, 4 × 5 min submaximal stages, and an incremental test to exhaustion, all performed at a 5° incline., Results: No significant three-way interactions were observed between sex, submaximal exercise intensity, and sub-technique. For the pooled sample, higher values were observed for DP versus DS during submaximal exercise for the mean oxygen uptake kinetics response time (33%), energy cost (18%), heart rate (HR) (9%), blood lactate concentration (5.1 versus 2.1 mmol·L -1 ), rating of perceived exertion (12%), and cycle rate (25%), while cycle length was lower (19%) (all P < 0.001). During the time-to-exhaustion (TTE) test, peak oxygen uptake ([Formula: see text]O 2 peak), peak HR, and peak oxygen pulse were 8%, 2%, and 6% lower, respectively, for DP than DS, with a 29% shorter TTE during DP (pooled data, all P < 0.001)., Conclusion: In well-trained junior XC skiers, DP was found to exert a greater physiological load than DS during uphill XC roller-skiing at submaximal intensities. During the TTE test, both female and male athletes were able to ski for longer and reached markedly higher [Formula: see text]O 2 peak values when using DS compared to DP.

The aim of this study was first to determine if level, uphill, and downhill energy cost of running (ECR) values were correlated at different slopes and for different running speeds, and second, to determine the influence of lower limb strength on ECR. Twenty-nine healthy subjects completed a randomized series of 4-min running bouts on an instrumented treadmill to determine their cardiorespiratory and mechanical (i.e., ground reaction forces) responses at different constant speeds (8, 10, 12, and 14 km·h -1 ) and different slopes (-20, -10, -5, 0, +5, +10, +15, and +20%). The subjects also performed a knee extensor (KE) strength assessment. Oxygen and energy costs of running values were correlated between all slopes by pooling all running speeds (all r 2 ≥ 0.27; p ≤ 0.021), except between the steepest uphill vs. level and the steepest downhill slope (i.e., +20% vs. 0% and -20% slopes; both p ≥ 0.214). When pooled across all running speeds, the ECR was inversely correlated with KE isometric maximal torque for the level and downhill running conditions (all r 2 ≥ 0.24; p ≤ 0.049) except for the steepest downhill slope (-20%), but not for any uphill slopes. The optimal downhill grade (i.e., lowest oxygen cost) varied between running speeds and ranged from -14% and -20% (all p < 0.001). The present results suggest that compared to level and shallow slopes, on steep slopes ~±20%, running energetics are determined by different factors (i.e., reduced bouncing mechanism, greater muscle strength for negative slopes, and cardiopulmonary fitness for positive slopes). On shallow negative slopes and during level running, ECR is related to KE strength., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Lemire, Falbriard, Aminian, Millet and Meyer.)

The metabolic cost of walking in healthy individuals increases with spatiotemporal gait asymmetries. Pathological gait, such as post-stroke, often has asymmetry in step length and step time which may contribute to an increased energy cost. But paradoxically, enforcing step length symmetry does not reduce metabolic cost of post-stroke walking. The isolated and interacting costs of asymmetry in step time and step length remain unclear, because previous studies did not simultaneously enforce spatial and temporal gait asymmetries. Here, we delineate the isolated costs of asymmetry in step time and step length in healthy human walking. We first show that the cost of step length asymmetry is predicted by the cost of taking two non-preferred step lengths (one short and one long), but that step time asymmetry adds an extra cost beyond the cost of non-preferred step times. The metabolic power of step time asymmetry is about 2.5 times greater than the cost of step length asymmetry. Furthermore, the costs are not additive when walking with asymmetric step time and asymmetric step length: the metabolic power of concurrent asymmetry in step length and step time is driven by the cost of step time asymmetry alone. The metabolic power of asymmetry is explained by positive mechanical power produced during single support phases to compensate for a net loss of center of mass power incurred during double support phases. These data may explain why metabolic cost remains invariant to step length asymmetry in post-stroke walking and suggest how effects of asymmetry on energy cost can be attenuated., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2021. Published by The Company of Biologists Ltd.)

Radiant cooling-assisted natural ventilation is an innovative technical approach that combines new radiant cooling technology with natural ventilation to increase fresh air delivery into buildings year-round with minimal energy cost and improvment of air quality. Currently, the standard paradigm for HVAC (heating, ventilation and air conditioning) is based on central air systems that tie the delivery of heating and cooling to the delivery of fresh air. To prevent heat loss, the delivery of fresh air must be tightly controlled and is often limited through recirculation of already heated or cooled air. Buildings are designed with airtight envelopes, which do not allow for natural ventilation, and depend on energy-intensive central-air systems. As closed environments, buildings have become sites of rapid COVID-19 transmission. In this research, we demonstrate the energy cost of increasing outdoor air supply with standard systems per COVID-19 recommendations and introduce an alternative HVAC paradigm that maximizes the decoupling of ventilation and thermal control. We first consider a novel analysis of the energy costs of increasing the amount of conditioned fresh air using standard HVAC systems to address COVID-19 concerns. We then present an alternative that includes a novel membrane-assisted radiant system we have studied for cooling in humid climates, in place of an air conditioning system. The proposed system can work in conjunction with natural ventilation and thus decreases the risk of indoor spread of infectious diseases and significantly lowers energy consumption in buildings. Our results for modeling HVAC energy in different climates show that increasing outdoor air in standard systems can double cooling costs, while increasing natural ventilation with radiant systems can halve costs. More specifically, it is possible to add up to 100 days' worth of natural ventilation while saving energy when coupling natural ventilation and radiant systems. This combination decreases energy costs by 10-45% in 60 major cities globally, while increasing fresh air intake., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 Elsevier Ltd. All rights reserved.)

Background: The purpose of this study was to investigate the accuracy of the published prediction equations for determining level overground walking energy cost in young adults., Methods: In total, 148 healthy young adults volunteered to participate in this study. Resting metabolic rate and energy expenditure variables at speeds of 4, 5, and 6 km/h were measured by indirect calorimetry, walking energy expenditure was estimated by 3 published equations., Results: The gross and net metabolic rate per mile of level overground walking increased with increased speed (all P < .01). Females were less economical than males. The present findings revealed that the American College of Sports Medicine and Pandolf et al equations significantly underestimated the energy cost of overground walking at all speeds (all P < .01) in young adults. The percentage mean bias for American College of Sports Medicine, Pandolf et al, and Weyand et al was 12.4%, 16.8%, 1.4% (4 km/h); 21.6%, 15.8%, 7.1% (5 km/h); and 27.6%, 12%, 6.6% (6 km/h). Bland-Altman plots and prediction error analysis showed that the Weyand et al was the most accurate in 3 existing equations., Conclusions: The Weyand et al equation appears to be the most suitable for the prediction of overground walking energy expenditure in young adults.