Effect of very large body mass loss on energetics, mechanics and efficiency of walking in adults with obesity: mass-driven versus behavioural adaptations.

Understanding the mechanisms involved in the higher energy cost of walking (NCw : the energy expenditure above resting per unit distance) in adults with obesity is pivotal to optimizing the use of walking in weight management programmes. Therefore, this study aimed to investigate the mechanics, energetics and mechanical efficiency of walking after a large body mass loss induced by bariatric surgery in individuals with obesity. Nine adults (39.5 ± 8.6 year; BMI: 42.7 ± 4.6 kg m-2 ) walked at five fixed speeds before (baseline) and after the bariatric surgery (post 1 and post 2). Gas exchanges were measured to obtain NCw . A motion analysis system and instrumented treadmill were combined to assess total mechanical work (Wtot ). Mechanical efficiency (Wtot NCw-1 ) was also calculated. Participants lost 25.7 ± 3.4% of their body mass at post 1 (6.6 months; P < 0.001) and 6.1 ± 4.9% more at post 2 (12 months; P = 0.014). Mass-normalized NCw was similar between baseline and post 1 and decreased at post 2 compared to that at baseline (-6.2 ± 2.7%) and post 1 (-8.1 ± 1.9%; P ≤ 0.007). No difference was found in mass-normalized Wtot during follow-up (P = 0.36). Mechanical efficiency was similar at post 1 and post 2 when compared to that at baseline (P ≥ 0.19), but it was higher (+14.1 ± 4.6%) at post 2 than at post 1 (P = 0.013). These findings showed that after a very large body mass loss, individuals with obesity may reorganize their walking pattern into a gait more similar to that of lean adults, thus decreasing their NCw by making their muscles work more efficiently. KEY POINTS: A higher net (above resting) energy cost of walking (lower gait economy) is observed in adults with obesity compared to lean individuals. Understanding the mechanisms (i.e. mass driven, gait pattern and behavioural changes) involved in this extra cost of walking in adults with obesity is pivotal to optimizing the use of walking to promote daily physical activity and improve health in these individuals. We found that very large weight loss induced by bariatric surgery significantly decreased the energy cost of walking per kg of body mass after 1 year with similar total mechanical work per kg of body mass, resulting in an increased mechanical efficiency of walking. Individuals with obesity may reorganize their walking pattern into a gait more similar to that of adults of normal body mass, thus decreasing their energy cost of walking by making their muscles work more efficiently.

Time course of muscle activation, energetics and mechanics of running in minimalist and traditional cushioned shoes during level running.

The study aimed to compare the ankle muscles activation, biomechanics and energetics of running in male runners during submaximal level run using minimalist (MinRS) and traditional cushioned (TrdRS) running shoes. During 45-min running in MinRS and TrdRS, the ankle muscles pre- and co-activation, biomechanics, and energetics of running of 16 male endurance runners (25.5 ± 3.5 yr) were assessed using surface electromyography (tibialis anterior and gastrocnemius lateralis), instrumented treadmill and indirect calorimetry, respectively. The net energy cost of running (Cr) was similar for both conditions (P = 0.25) with a significant increase over time (P < 0.0001). Step frequency (P < 0.001), and total mechanical work (P = 0.001) were significantly higher in MinRS than in TrdRS with no evolution over time (P = 0.28 and P = 0.85, respectively). The ankle muscles pre- and co-activation during the contact phase did not differ between the two shoe conditions (P ≥ 0.33) or over time (P ≥ 0.15). In conclusion, during 45-min running, Cr and muscle pre- and co-activation were not significantly different between MinRS and TrdRS with significantly higher step frequency and total mechanical work noted in the former than in the latter. Moreover, Cr significantly increased during the 45-min trial in both shoe conditions along with no significant change over time in muscle activation and biomechanical variables.

The Effect of Obesity Class on the Energetics and Mechanics of Walking.

Higher mass-normalized net energy cost of walking (NetCw/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, NetCw/kg and gait mechanics by using principal component analysis (PCA). NetCw/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. NetCw/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.

Mass-normalized internal mechanical work in walking is not impaired in adults with class III obesity.

This study aimed to investigate the effects of obesity on the internal mechanical work, and its influence on the total mechanical work, energy cost, and mechanical efficiency in obese and nonobese adults while walking at different speeds. Body composition and anthropometrical characteristics were obtained for eleven obese [O; 39.9 ± 7.9 yr; body mass index (BMI): 43.0 ± 4.2 kg/m2] and thirteen lean adults (L; 29.6 ± 5.7 yr; BMI: 22.0 ± 1.5 kg/m2). Participants walked at five speeds (0.56, 0.83, 1.11, 1.39, 1.67 m/s) while oxygen consumption was measured to obtain net energy cost of walking (NCw). A motion analysis system and instrumented treadmill were combined to obtain external (Wext), internal (Wint), and total (Wtot) mechanical work, and pendular energy recovery. Mechanical efficiency was calculated as the ratio of Wtot to NCw. Relative NCw (per unit body mass) was significantly higher in O than L (P ≤ 0.001). Relative Wext was significantly lower in O compared with L (P = 0.002), whereas no significant difference was found in relative Wint (P = 0.16) and Wtot (P = 0.6). Recovery was significantly higher (P ≤ 0.001), while mechanical efficiency was significantly lower in O than in L (P ≤ 0.001). These results suggest that individuals with obesity class III have similar mass-normalized Wint and Wtot compared with their lean counterparts, along with a higher relative NCw. Consequently, the efficiency of walking was reduced in this population. These results suggest that mass-normalized Wint is unaffected by obesity and is not responsible for the higher relative NCw and lower efficiency of walking in these individuals.NEW & NOTEWORTHY It has been suggested that internal mechanical work (i.e., the work required to move the limbs with respect to the center of mass, Wint) may be responsible for the higher net cost of walking in obese adults, but this variable has not yet been studied in individuals with obesity. The main finding of the present study is that individuals with class III obesity exhibit a similar amount of mass-normalized Wint to that of adults with a normal body weight, suggesting that body mass-relative Wint is not affected by obesity and is not responsible for the higher energy cost and the lower efficiency of walking in this population.

Energy-saving walking mechanisms in obese adults.

Energy-saving mechanisms are used in human walking. In obese adults the energy cost of walking (Cw) is higher compared with normal-body mass adults. However, the biomechanical factors involved in this extra cost should result in a higher Cw. The aim of this study was to compare energy-saving walking mechanisms [i.e., mechanical energy saved via pendulum (Recovery) and maximum possible elastic energy usage (MPEEu)] and their influence on Cw in obese vs. lean individuals. The net Cw (NetCw), external work (Wext), Recovery, MPEEu, and gait weight transfer duration (gWT) were computed for 13 lean [L; body mass index (BMI) 21.9 ± 1.5 kg/m2] and 13 obese (O; BMI 33.8 ± 2.5 kg/m2) individuals during treadmill walking at five speeds (0.56, 0.83, 1.11, 1.39, 1.67 m/s). No significant difference was found between groups in relative (per kg of body mass) NetCw (P = 0.13). Relative positive Wext was significantly lower at the three fastest speeds (P ≤ 0.003) whereas Recovery was higher at the two fastest speeds (P ≤ 0.01) in O than in L individuals. MPEEu tended to be lower in O than in L (P = 0.06), with significantly lower values in O compared with L at 1.39 and 1.67 m/s (P ≤ 0.017). gWT was significantly shorter in O than in L individuals at 1.67 m/s (P = 0.001). The present results reveal that obese adults rely more on the pendular mechanism than on the storage and release of elastic energy for decreasing the amount of positive Wext and thus limiting the increase in the relative NetCw. NEW & NOTEWORTHY We observed that obese individuals had a lower maximum possible elastic energy usage per kilogram of body mass than their lean counterparts and they may rely more on the pendular mechanism of walking than on the storage and release of elastic energy for decreasing the external mechanical work and thus limiting the increase in the relative net energy cost of walking.

The Determinants of the Preferred Walking Speed in Individuals with Obesity.

BACKGROUND: The preferred walking speed (PWS), also known as the "spontaneous" or "self-selected" walking speed, is the speed normally used during daily living activities and may represent an appropriate exercise intensity for weight reduction programs aiming to enhance a more negative energy balance. OBJECTIVES: The aim of this study was to examine, simultaneously, the energetics, mechanics, and perceived exertion determinants of PWS in individuals with obesity. METHODS: Twenty-three adults with obesity (age 32.7 ± 6.8 years, body mass index 33.6 ± 2.6 kg/m2) were recruited. The participants performed 10 min of treadmill familiarization, and PWS was determined. Each subject performed six 5-min walking trials (PWS 0.56, 0.83, 1.11, 1.39, and 1.67 m/s). Gas exchanges were collected and analyzed to obtain the gross energy cost of walking (GCw), rated perceived exertion (RPE) was measured using a 6-20 Borg scale, and the external mechanical work (Wext) and the fraction of mechanical energy recovered by the pendular mechanism (Recovery) were computed using an instrumented treadmill. Second-order least-squares regression was used to calculate the optimal walking speed (OWS) of each variable. RESULTS: No significant difference was found between PWS (1.28 ± 0.13 m/s) and OWS for GCw (1.28 ± 0.10 m/s), RPE cost of walking (1.38 ± 0.14 m/s), and Recovery (1.48 ± 0.27 m/s; p > 0.06 for all), but the PWS was significantly faster than the OWS for Wext (0.98 ± 0.56 m/s; p < 0.02). Multiple regression (r = 0.72; p = 0.003) showed that ∼52% of the variance in PWS was explained by Recovery, Wext, and height. CONCLUSION: The main finding of this study was that obese adults may select their PWS in function of several competing demands, since this speed simultaneously minimizes pendular energy transduction, energy cost, and perceived exertion during walking. Moreover, recovery of mechanical work, external work, and height seem to be the major determinants of PWS in these individuals.

Effects of Short-Term Normobaric Hypoxic Walking Training on Energetics and Mechanics of Gait in Adults with Obesity.

OBJECTIVE: The aim of this study was to compare the effects of short-term hypoxic versus normoxic training at preferred walking speed (PWS) on energetics, mechanics, efficiency, and metabolic risk markers in individuals with obesity. METHODS: Twenty-three subjects with obesity performed nine 1-hour sessions at PWS under hypoxia (3,000 m, n = 12; BMI: 34.0 ± 0.8 kg/m2 ) or normoxia (360 m, n = 11; BMI: 32.9 ± 0.8 kg/m2 ). Participants performed six 5-minute walking trials at different speeds (PWS, 0.56, 0.83, 1.11, 1.39, and 1.67 m/s). The net energy cost, external mechanical work, and rated perceived exertion (RPE) were measured at these speeds. Body composition and blood samples were collected. RESULTS: PWS tended to be slower under hypoxia than normoxia (-6.7%; P = 0.092) during the training, and this difference reached significance the third week (-8.9%; P = 0.05). After training, PWS significantly increased (+ 8.2%; P ≤ 0.001), while RPE decreased (P = 0.005). Ankle range of motion (P = 0.03) and vertical displacement of the center of mass (P = 0.02) significantly increased in both groups. CONCLUSIONS: A walking training program under hypoxia at slower PWS than in normoxia elicited similar responses in metabolic risk factors, energetics, and mechanics of walking in individuals with obesity. Both programs increased PWS, decreased RPE, and induced gait-pattern adaptations, which protected against orthopedic injury in these individuals.