Metabolic Energy Expenditure Research Articles

Dynamic Work Analysis of Manual Material Handling With Digital Human Modeling

The activity of loading and unloading rice in Indonesia is still carried out using human power. Porters transport rice manually from truck to warehouse or the otherwise. Manual material handling work (MMH) will pose a risk of musculoskeletal disorders (MSDs). The application of the work analysis method generates an analysis per one body position only. There is a need for a model that can perform a work analysis quickly for any change in body movement if it is carried out in dynamic work, for instances on rice porters. In this research, Digital Human Modeling Tecnomatix Jack is used in the Task Simulation Builder menu to simulate dynamic work and generate analysis. The dynamic work carried out is to compare the risk of transporting rice weighing 10 kg and 25 kg. The results obtained are Ergonomic Report, Static Strength Prediction (SSP), Low Back Compression Analysis (LBA), Fatigue, Cumulative Loading and Metabolic Energy Expenditure (MEE). The simulator also provides the SSV file extension as in SSP. If needed, this result can be entered in a formula according to work analysis method such as RULA or REBA so that every change in movement obtained results related to the risk that may occur.

O equivalente metabólico estimado e o gasto energético verificam o esforço físico de diabéticos tipo 1 em repouso e exercícios? Um ensaio cruzado randomizado

ABSTRACT To compare measured and estimated metabolic equivalent (MET) and energy expenditure (EE) in different situations with Type-1 diabetes (T1DM) patients. Ten T1DM patients performed three 30-minute sessions (resting, running-RS, and exergame-VS) at moderate intensity. MET and EE were measured by direct gas analyzer and estimated using the formula applying heart rate and V̇02peak. MET values (measured vs. estimated) were statistically different during RS (4.58±1.11 vs.7.59±1.36) and VS (3.98± 0.84 vs. 5.77±0.84) (p<0.001). EE values were similar: RS (147±43 vs. 246±157) and VS (129±33 vs. 184±20) (p<0.001). The error between the methods: 0.41, 1.51, and 1.07 METs and 20.1, 51.5, and 32.5 Kcals for resting, RS, and VS. Estimation could be used in resting and with caution for RS and VS.

Maternal propionate supplementation ameliorates glucose and lipid metabolic disturbance in hypoxia-induced fetal growth restriction.

Intrauterine growth restriction (IUGR), one of the major complications of pregnancy, is characterized by low birth weight and results in higher risks for long-term problems including developing metabolic and cardiovascular diseases. Short-chain fatty acids (SCFAs), especially propionate, have been reported to correct glucose and lipid disorders in metabolic diseases. We hypothesized that maternal propionate supplementation could prevent glucose and lipid metabolic disturbance in hypoxia-induced IUGR. Here, in our study, maternal hypoxia was induced from gestational day (GD) 11 to GD 17.5 to establish an IUGR mouse model. Maternal propionate treatment reversed reduced birth weight in male IUGR offspring. Hepatic transcriptomics demonstrated that SP treatment significantly lowered glucose and lipid metabolism-related genes (Scd1, G6pc, Pck1 and Fasl) in IUGR offspring. KOG enrichment analysis showed that propionate-induced down-regulated differential expressed genes (DEGs) mainly belonged to lipid transport and metabolism. KEGG enrichment results showed that the down-regulated DEGs were mostly enriched in PPAR and FoxO signaling pathways. We also found that maternal oral administration of SP decreased serum lipid content, attenuated hepatic insulin resistance and liver lipid accumulation, reduced hepatic key gene expressions of gluconeogenesis and lipogenesis, increased energy expenditure and improved liver function in 11-week-old male IUGR offspring. These results indicate that maternal propionate supplementation increases birth weight and corrects hepatic glucose and lipid metabolic disturbance and energy expenditure in male mice born with IUGR, which may provide a basis for using propionate to treat IUGR disease.

Water-soluble vitamins in the feed of high-yield lactating cows during the milking period

The aim of the work is to show how to increase the productivity of cows, to improve the feeding system, to introduce intensive, promising, effective, resource-saving milk production technologies, including the implementation of measures for the production and use of domestic vitamin feed products (preparations). The studies were carried out by the example of highly productive dairy cows with an annual productivity of over 6000 kg of milk per lactation. The type of feeding is the silage – hayage silage concentrate, the rations are balanced in terms of nutrients, biologically active substances and metabolic energy. It corresponded to the generally accepted norms of animal feeding in the country (M., RAAS, 2003). The diets of cows during the milking period included Vitaminol and a phytocomplex (of 13 medicinal forage herbs), 10 g, 15 g and 20 g per head per day. When milking cows (100 days), fed with Vitaminol, more milk was produced ranging from 2.7 to 9.9 %, the phytocomplex increased milk yield from 8.4 to 16.3 %. The consumption of metabolic energy of diets per 1 kg of milk is lower in cows of the experimental groups when using different doses of Vitaminol ranging from 2.8 to 9.9 %, and the phytocomplex allowed ranging it from 8.3 to 16.1 % compared to the control variant. To increase metabolic processes in the body, productivity and supply of water-soluble vitamins and mineral macronutrients in cows under the conditions of a year-round stable method of keeping, the rations included the optimal dose of Vitaminol and the phytocomplex (separately) amounting to 20 g per head a day. Vitaminol serves to replenish the body of highly productive lactating cows during the period of milk production with missing biologically active substances, vitamin nutritional value of milk, increase the digestibility of organic substances in rations, and improve metabolic processes.

Effect of Walking Speed on Gait Parameters and Energy Expenditure in Individuals with Unilateral Trans-tibial Amputatio

Background and Objectives: Analysis of gait parameters and energy expenditure in different walking speeds in trans-tibial amputees has been less investigated. This may provide an insight into how they respond to it. The main aim of this study was to investigate the effect of walking speed changes on gait parameters and metabolic energy consumption in unilateral trans-tibial amputees using the prosthesis. Methods: Thirty trans-tibial amputees fulfilling inclusion criteria were investigated for gait parameters using a ten-meter walk test while these subjects walked with three different walking speeds (comfortable, fast, and slow). Temporal-spatial gait parameters, such as step length, stride length, velocity and cadence, and Physiological Cost Index (PCI) for metabolic energy consumption were analyzed by repeated-measures ANOVA. Results: Step length of a prosthetic side in the fast walking speed (0.67±0.10 m) was higher than the normal comfortable speed (0.56±0.13 m) and least in slow walking (0.42±0.06 m). A similar trend was observed for all gait parameters. PCI (beats/m) was least in normal comfortable speed (0.08±0.09), followed by fast walking speed (0.11±0.08). It was highest when patients walked at a slow speed (0.18±0.12). There was a significant difference in all temporal-spatial gait parameters and PCI in three walking speed conditions (p<0.05). Conclusion: Walking speed significantly affected all temporal-spatial and energy parameters in unilateral trans-tibial amputees.

Oxygen consumption and energy budget of the barnacle Balanus amphitrite amphitrite (Darwin, 1854) in an estuarine ecosystem, Basrah-Iraq

The annual O2 consumption, annual energy budget and the ecological efficiencies of a population of the barnacle Balanus amphitrite amphitrite were estimated in Garmat-Ali river, in the period October 1994-September 1995. The annual O2 consumption was 2156 kJ/ m2/yr, the rate of O2 consumption increased with increasing temperature and body weight, the barnacle consumes oxygen at a rate of 0.622 µlO2/mg/h at 15°C, 0.84 µlO2/mg/h at 23°C and 0.954 µlO2/mg/h at 30°C. The Q10 values increased with increasing size of barnacle. The food items provided were the alga, Chlorella sp. with a calorific contents of 3.2 kcal/g DW, and a flesh of the clam C. fluminea with 5.4 kcal/g DW. The barnacle assimilates the flesh of the clam about 7 times more than assimilating the Chlorella. The barnacle allocates 45-55% of the assimilated energy for net growth and 27-37% for metabolic energy expenditure, whereas 18% is channeled for faeces production. The respiratory coefficient (R/P) of this barnacle was 0.6. The assimilation efficiency for the plant and animal food were 88-91%. The annual energy budget equation for a population of barnacle at Garmat-Ali river is: Cp 16271.14 = Pp 11639.55 + Rp 2156 + Fp 2475.60.

Metabolic profiles, energy expenditures, and body compositions of the weight regain versus sustained weight loss patients who underwent Roux-en-Y gastric bypass.

Weight regain (WR) has been an emerging problem after Roux-en Y gastric bypass (RYGB) and little is known about the mechanisms of WR after RYGB. To evaluate the mechanisms of WR after RYGB through the postprandial gut hormones response, particularly glucagon-like peptide-1 (GLP-1), which regulates appetite control, energy expenditure, body composition, physical activities, dietary intake, and psychological factors. Duke University Medical Center, Durham, North Carolina. A cross sectional study of 34 patients who underwent RYGB at least 2 years and achieved ≥50% of excess weight loss at 1year was conducted. The subjects were categorized into WR group or sustained weight loss group, based upon whether their WR was ≥15% of postoperative lowest weight. The WR group had less augmented postprandial GLP-1 response but exaggerated hyperinsulinemia. Postprandial peptide YY, ghrelin, and glucose were not different between group. Patients who regained weight required less weight-adjusted energy expenditure and had more percentage body fat and less percentage lean mass. The caloric intake and diet composition were comparable between groups; however, the WR group had higher depression scores, binge eating scales, and hunger rating and spent significantly less time on vigorous exercise. The mechanisms of WR in patients who were initially successful after RYGB are complex and involved not only the role of postprandial gut hormone response but are also related to energy expenditure adaptation and body composition changes. Moreover, food preference and physical activity may play roles in weight control after bariatric surgery. Further prospective controlled trial is needed to explore the mechanisms of WR.

Modeling the Metabolic Costs of Heavy Military Backpacking.

ABSTRACTIntroductionExisting predictive equations underestimate the metabolic costs of heavy military load carriage. Metabolic costs are specific to each type of military equipment, and backpack loads often impose the most sustained burden on the dismounted warfighter.PurposeThis study aimed to develop and validate an equation for estimating metabolic rates during heavy backpacking for the US Army Load Carriage Decision Aid (LCDA), an integrated software mission planning tool.MethodsThirty healthy, active military-age adults (3 women, 27 men; age, 25 ± 7 yr; height, 1.74 ± 0.07 m; body mass, 77 ± 15 kg) walked for 6–21 min while carrying backpacks loaded up to 66% body mass at speeds between 0.45 and 1.97 m·s−1. A new predictive model, the LCDA backpacking equation, was developed on metabolic rate data calculated from indirect calorimetry. Model estimation performance was evaluated internally by k-fold cross-validation and externally against seven historical reference data sets. We tested if the 90% confidence interval of the mean paired difference was within equivalence limits equal to 10% of the measured metabolic rate. Estimation accuracy and level of agreement were also evaluated by the bias and concordance correlation coefficient (CCC), respectively.ResultsEstimates from the LCDA backpacking equation were statistically equivalent (P < 0.01) to metabolic rates measured in the current study (bias, −0.01 ± 0.62 W·kg−1; CCC, 0.965) and from the seven independent data sets (bias, −0.08 ± 0.59 W·kg−1; CCC, 0.926).ConclusionsThe newly derived LCDA backpacking equation provides close estimates of steady-state metabolic energy expenditure during heavy load carriage. These advances enable further optimization of thermal-work strain monitoring, sports nutrition, and hydration strategies.

Runners Employ Different Strategies to Cope With Increased Speeds Based on Their Initial Strike Patterns.

In this paper we examined how runners with different initial foot strike pattern (FSP) develop their pattern over increasing speeds. The foot strike index (FSI) of 47 runners [66% initially rearfoot strikers (RFS)] was measured in six speeds (2.5–5.0 ms−1), with the hypotheses that the FSI would increase (i.e., move toward the fore of the foot) in RFS strikers, but remain similar in mid- or forefoot strikers (MFS) runners. The majority of runners (77%) maintained their original FSP by increasing speed. However, we detected a significant (16.8%) decrease in the FSI in the MFS group as a function of running speed, showing changes in the running strategy, despite the absence of a shift from one FSP to another. Further, while both groups showed a decrease in contact times, we found a group by speed interaction (p < 0.001) and specifically that this decrease was lower in the MFS group with increasing running speeds. This could have implications in the metabolic energy consumption for MFS-runners, typically measured at low speeds for the assessment of running economy.

Thyroid Function and Obesity: From Mechanisms to the Benefits of Levothyroxine in Obese Patients

Thyroid disease and obesity are widespread clinical conditions in the population. They can occur together in the same subject, but their relationship does not seem exclusively stochastic. Literature was critically reviewed to explain the association between thyroid disease and obesity and to understand the possible benefits of levothyroxine therapy in euthyroid obese patients. A low energy expenditure rate can lead to obesity. Maintaining Basal Metabolic Rate (BMR) is the leading cause of energy expenditure in the body, which is regulated by thermogenesis. Thyroid hormone receptors (TR) play different roles in the induction of thermogenetic mechanisms; TRα is fundamental to induce thermogenesis, and TRβ triggers the expression of uncoupling protein 1(UCP1). Despite such mechanisms, there is no current evidence related to the treatment of subjects suffering from obesity with thyroid hormones. Replacement therapy should be reserved only for patients with clear signs of subclinical or clinical hypothyroidism. Basal metabolic rate (BMR) or basal energy expenditure (BEE): measurement obtained under total inactivity and controlled research conditions; resting energy expenditure (REE): measurement obtained when an individual is sitting quietly (is mildly higher than BMR/BEE).

Innovative exoskeleton mechanics

The authors have developed an integrated approach and technology for building an exoskeleton that minimizes human energy expenditures while walking. Optimized torque characteristics from an exoskeleton worn on one knee have reduced metabolic and electrical energy consumption. Studies have shown practical value and significance for application, namely, the lift increase of the exoskeleton and possibilities opening in medicine, for rescuers, tourists. Comparative analysis showed the way to solve the problems of mechanics when creating an exoskeleton to improve the quality of performing complex tasks.

Engineering microbial metabolic energy homeostasis for improved bioproduction

Metabolic energy (ME) homeostasis is essential for the survival and proper functioning of microbial cell factories. However, it is often disrupted during bioproduction because of inefficient ME supply and excessive ME consumption. In this review, we propose strategies, including reinforcement of the capacity of ME-harvesting systems in autotrophic microorganisms; enhancement of the efficiency of ME-supplying pathways in heterotrophic microorganisms; and reduction of unessential ME consumption by microbial cells, to address these issues. This review highlights the potential of biotechnology in the engineering of microbial ME homeostasis and provides guidance for the higher efficient bioproduction of microbial cell factories.

Lower-Limb Exosuits for Rehabilitation or Assistance of Human Movement: A Systematic Review

Background: The aim of this review is to provide a comprehensive overview of the technological state-of-the-art of exosuits and the clinical results obtained when applied to users with mobility impairment. Methods: Searches are carried out in the COCHRANE, PubMed, IEEE Xplore and MEDLINE databases. Titles, abstracts and full texts are screened for inclusion criteria. Technological and clinical data are extracted. The quality of the studies is evaluated via a study quality assessment tool. Results: 19 studies are identified as relevant. Active (47%) and passive exosuits (53%) are used. Most are used untethered (84%), accommodating the demand of mobility. No study reports power consumption, which is important for dimensioning power systems. Fields of applications are post-stroke (79%), osteoarthritis (16%) and post-trauma (5%). Mostly the ankle joint is addressed (57%), while less studies address multiple joints (21%). The outcomes of clinical evaluations of lower-limb exosuits with patients suffering from mobility impairments are positive in the correction of gait pattern and reducing metabolic energy consumption during hemiparetic walking. Conclusions: Lower-limb exosuits for clinical applications are still facing technological challenges. Fields of application are limited to stroke, osteoarthritis and trauma. While clinical outcomes are overall positive, improvements in the study protocols are suggested.

Path tortuosity changes the transport cost paradigm in terrestrial animals

The time that animals spend travelling at various speeds and the tortuosity of their movement paths are two of the many things that affect space‐use by animals. In this, high turn rates are predicted to be energetically costly, especially at high travel speeds, which implies that animals should modulate their speed according to path characteristics. When animals move so as to maximize distance and minimize metabolic energy expenditure, they travel most efficiently at the speed that gives them a minimum cost of transport (COTmin), a well‐defined point for animals that move entirely in fluid media. Theoretical considerations show though, that land animals should travel at their maximum speed to minimize COT, which they do not, instead travelling at walking pace. So, to what extent does COTmin depend on speed and turn rate and how might this relate to movement paths? We measured oxygen consumption in humans walking along paths with varied tortuosity at defined speeds to demonstrate that the energetic costs of negotiating these paths increase disproportionately with both speed and angular velocity. This resulted in the COTmin occurring at very low speeds, and these COTmin speeds reduced with increased path tortuosity and angular velocity. Logged movement data from six free‐ranging terrestrial species underpinned this because all individuals turned with greater angular velocity the slower their travel speeds across their full speed range. It seems, therefore, that land animals may strive to achieve minimum movement costs by reducing speed with increasing path variability, providing one of many possible explanations as to why speed is much lower than currently predicted based on lab measurements of mammalian locomotor performance.

Effects of prosthetic feet on metabolic energy expenditure in people with transtibial amputation: A systematic review and meta-analysis.

To assess the effects of different prosthetic feet on energy costs associated with walking and running in people with transtibial amputation. The Pubmed, CINAHL, and Web-of-Science bibliographic databases were searched for original research published through June 30, 2018. References from identified articles were also reviewed. Two reviewers screened titles, abstracts, and articles for pertinent studies. Details were extracted with a standardized template. Risk of bias was assessed using domain-based methods. Prosthetic feet were grouped into categories and compared according to energy costs associated with walking or running over various terrain conditions. Meta-analyses were conducted when data quantity and homogeneity permitted. Evidence statements were formed when results were consistent or undisputed. Fifteen studies were included. Participants (n=141) were predominantly male (87.9%), had unilateral amputation (95.7%) from non-dysvascular causes (87.9%), and were classified as unlimited community ambulators or active adults (56.0%). Participants were often young but varied in age (mean age 24.8-66.6 years). Available evidence indicates that feet with powered dorsiflexion reduce energy costs relative to dynamic response feet in unlimited community ambulators or active adults when walking on level or declined surfaces. Dynamic response feet do not significantly reduce energy costs compared to energy storing, flexible keel, or solid ankle feet when walking on level terrain. Running feet do not reduce energy costs relative to dynamic response in active adults when running. Select feet may reduce energy costs under specific conditions, but additional research is needed to confirm preliminary results. The overall body of evidence is based on small samples, comprised mostly of participants who may not well represent the population of prosthesis users and test conditions that may not well reflect how prostheses are used in daily life. However, evidence suggests energy costs are affected by prosthetic foot type only under select conditions.

Identification of Movements and Postures Using Wearable Sensors for Implementation in a Bi-Hormonal Artificial Pancreas System.

Background: Closed loop bi-hormonal artificial pancreas systems, such as the artificial pancreas (AP™) developed by Inreda Diabetic B.V., control blood glucose levels of type 1 diabetes mellitus patients via closed loop regulation. As the AP™ currently does not classify postures and movements to estimate metabolic energy consumption to correct hormone administration levels, considerable improvements to the system can be made. Therefore, this research aimed to investigate the possibility to use the current system to identify several postures and movements. Methods: seven healthy participants took part in an experiment where sequences of postures and movements were performed to train and assess a computationally sparing algorithm. Results: Using accelerometers, one on the hip and two on the abdomen, user-specific models achieved classification accuracies of 86.5% using only the hip sensor and 87.3% when including the abdomen sensors. With additional accelerometers on the sternum and upper leg for identification, 90.0% of the classified postures and movements were correct. Conclusions: The current hardware configuration of the AP™ poses no limitation to the identification of postures and movements. If future research shows that identification can still be done accurately in a daily life setting, this algorithm may be an improvement for the AP™ to sense physical activity.

Energy Expenditure of Level Overground Walking in Young Adults: Comparison With Prediction Equations

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. 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 6km/h were measured by indirect calorimetry, walking energy expenditure was estimated by 3 published equations. 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 etal 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 etal, and Weyand etal was 12.4%, 16.8%, 1.4% (4km/h); 21.6%, 15.8%, 7.1% (5km/h); and 27.6%, 12%, 6.6% (6km/h). Bland-Altman plots and prediction error analysis showed that the Weyand etal was the most accurate in 3 existing equations. The Weyand etal equation appears to be the most suitable for the prediction of overground walking energy expenditure in young adults.

Is starvation a cause of overmortality of the Mediterranean sardine?

Animal mortality is difficult to observe in marine systems, preventing a mechanistic understanding of major drivers of fish population dynamics. In particular, starvation is known to be a major cause of mortality at larval stages, but adult mortality is often unknown. In this study, we used a laboratory food-deprivation experiment, on wild caught sardine Sardina pilchardus from the Gulf of Lions. This population is interesting because mean individual phenotype shifted around 2008, becoming dominated by small, young individuals in poor body condition, a phenomenon that may result from declines in energy availability. Continuous monitoring of body mass loss and metabolic rate in 78 captive food-deprived individuals revealed that sardines could survive for up to 57 days on body reserves. Sardines submitted to long-term caloric restriction prior to food-deprivation displayed adaptive phenotypic plasticity, reducing metabolic energy expenditure and enduring starvation for longer than sardines that had not been calorie-restricted. Overall, entry into critical fasting phase 3 occurred at a body condition of 0.72. Such a degree of leanness has rarely been observed over 34 years of wild population monitoring. Still, the proportion of sardines below this threshold has doubled since 2008 and is maximal in January and February (the peak of the reproductive season), now reaching almost 10 % of the population at that time. These results indicate that the demographic changes observed in the wild may result in part from starvation-related adult mortality at the end of the winter reproductive period, despite adaptive plastic responses.

The Effect Of Split-belt Treadmill Training On Gait Efficiency In Hip Osteoarthritis Patients: Preliminary Study

Reduced gait efficiency has been found in hip osteoarthritis (OA) measured as decreased mechanical energy exchange (MEE) or increased metabolic energy expenditure. Step length asymmetry (SLA) is commonly reported in hip OA patients and could potentially influence gait efficiency. Modifying step length through split-belt treadmill training may improve gait efficiency in hip OA patients. PURPOSE: To determine the effect of split-belt treadmill training modifying step length on gait efficiency in hip OA patients. METHODS: We evaluated 5 women with hip OA (66.8 ± 6.0 yrs; 33.6 ± 7.2 kg/m2) who provided informed consent for this IRB-approved study. We conducted split-belt treadmill testing with 4 periods: Warm-up (3 minutes), Baseline (1 minute), Adaptation (10 minutes), and Post-adaptation (1 minute) with motion analysis and metabolic energy analysis. During the adaptation period, the involved limb was assigned to the slow speed belt (half of the self-selected walking speed), and the uninvolved limb was assigned to the fast speed belt (self-selected walking speed). Both belts were at the self-selected speed during the other periods. Repeated measures ANOVA was used to determine the effect of the training period on SLA, MEE, and O2 rate in each period. LSD post hoc test was used to compare each condition. RESULTS: There was a significant effect of training period (Wilks’ Lambda = 0.17, F (9, 24.5) = 2.88, p = 0.02) in the multivariate test. There were no significant differences between the periods in SLA (p > 0.05). MEE significantly increased from the baseline period (24.68 ± 3.37) to the end of adaptation period (31.51 ± 4.00) (p = 0.01). MEE significantly decreased from the end of adaptation period to post-adaptation period (25.21 ± 5.10) (p = 0.04). O2 rate significantly increased from the end of adaptation period (7.77 ± 2.60) to post-adaptation period (9.22 ± 1.65) (p = 0.04). CONCLUSIONS: Although SLA did not change significantly through split-belt treadmill training, beneficial modifications in MEE and O2 rate were seen. Split-belt treadmill training could potentially become a rehabilitation strategy to improve gait efficiency in hip OA patients. Support from a National Institute on Aging Roybal Center for Health and Promotion and Translation Doctoral Pilot Grant.

Sensing leg movement enhances wearable monitoring of energy expenditure

Physical inactivity is the fourth leading cause of global mortality. Health organizations have requested a tool to objectively measure physical activity. Respirometry and doubly labeled water accurately estimate energy expenditure, but are infeasible for everyday use. Smartwatches are portable, but have significant errors. Existing wearable methods poorly estimate time-varying activity, which comprises 40% of daily steps. Here, we present a Wearable System that estimates metabolic energy expenditure in real-time during common steady-state and time-varying activities with substantially lower error than state-of-the-art methods. We perform experiments to select sensors, collect training data, and validate the Wearable System with new subjects and new conditions for walking, running, stair climbing, and biking. The Wearable System uses inertial measurement units worn on the shank and thigh as they distinguish lower-limb activity better than wrist or trunk kinematics and converge more quickly than physiological signals. When evaluated with a diverse group of new subjects, the Wearable System has a cumulative error of 13% across common activities, significantly less than 42% for a smartwatch and 44% for an activity-specific smartwatch. This approach enables accurate physical activity monitoring which could enable new energy balance systems for weight management or large-scale activity monitoring.