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1.
BMC Res Notes ; 16(1): 254, 2023 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-37798737

RESUMO

OBJECTIVE: A U-shaped relationship between energy cost of walking (Cw) and walking speed indicates that there is a specific speed minimizing the Cw, called economical speed (ES). It is mostly slower in older adults than young adults; however, effects of leg length on the ES have been ignored. We investigated effects of aging and exercise habituation on the normalized ES by leg length (ESnormalized). We quantified time delay of stride length and step frequency in sedentary young (SY), active young (AY), and active elderly (AE) adults in response to sinusoidal gait speed change at 30-s and 180-s periods with an amplitude of ± 0.56 mï½¥s- 1. RESULTS: The ES was significantly slower in the following sequence: AE, SY, and AY, whereas ESnormalized was slower in the AE than in other young groups, with no difference between AY and SY. AE and SY showed greater step variabilities at the 180-s period, whereas AY showed relatively smaller step variabilities at both periods. Collectively, the ESnormalized slowed due to aging, not due to exercise habituation. When optimizing the appropriate SL-SF combination for sinusoidal speed changes, young and elderly adults may adopt different strategies. Exercise habituation may reduce step variabilities in young adults.


Assuntos
Marcha , Habituação Psicofisiológica , Adulto Jovem , Humanos , Idoso , Marcha/fisiologia , Fenômenos Biomecânicos , Caminhada/fisiologia , Velocidade de Caminhada , Envelhecimento/fisiologia
2.
J Cardiovasc Aging ; 2(1)2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36816983

RESUMO

Introduction: Aortic stiffness offers important insight into vascular aging and cardiovascular disease (CVD) risk. The referent measure of aortic stiffness is carotid-femoral pulse wave velocity (cfPWV). cfPWV can be estimated (ePWV) from age and mean arterial pressure. Few studies have directly compared the association of ePWV to measured cfPWV, particularly in non-White adults. Moreover, whether ePWV and cfPWV correlate similarly with CVD risk remains unexplored. Aim: (1) To estimate the strength of the agreement between ePWV and cfPWV in both Black and White older adults; and (2) to compare the associations of ePWV and cfPWV with CVD risk factors and determine whether these associations were consistent across races. Methods and Results: We evaluated 4478 [75.2 (SD 5.0) years] Black and White older adults in the Atherosclerosis Risk in Communities (ARIC) Study. cfPWV was measured using an automated pulse waveform analyzer. ePWV was derived from an equation based on age and mean arterial pressure. Association and agreement between the two measurements were determined using Pearson's correlation coefficient (r), standard error of estimate (SEE), and Bland-Altman analysis. Associations between traditional risk factors with ePWV and cfPWV were evaluated using linear mixed regression models. We observed weak correlations between ePWV and cfPWV within White adults (r = 0.36) and Black adults (r = 0.31). The mean bias for Bland-Altman analysis was low at -0.17 m/s (95%CI: -0.25 to -0.09). However, the inspection of the Bland-Altman plots indicated systematic bias (P < 0.001), which was consistent across race strata. The SEE, or typical absolute error, was 2.8 m/s suggesting high variability across measures. In models adjusted for sex, prevalent diabetes, the number of prevalent cardiovascular diseases, and medication count, both cfPWV and ePWV were positively associated with heart rate, triglycerides, and fasting glucose, and negatively associated with body mass index (BMI) and smoking status in White adults (P < 0.05). cfPWV and ePWV were not associated with heart rate, triglycerides, and fasting glucose in Black adults, while both measures were negatively associated with BMI in Black adults. Conclusions: Findings suggest a weak association between ePWV and cfPWV in older White and Black adults from ARIC. There were similar weak associations between CVD risk factors with ePWV and cfPWV in White adults with subtle differences in associations in Black adults.

3.
BMC Sports Sci Med Rehabil ; 13(1): 107, 2021 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-34488873

RESUMO

BACKGROUND: A specific walking speed minimizing the U-shaped relationship between energy cost of transport per unit distance (CoT) and speed is called economical speed (ES). To investigate the effects of reduced body weight on the ES, we installed a body weight support (BWS) apparatus with a spring-like characteristics. We also examined whether the 'calculated' ES was equivalent to the 'preferred' walking speed (PWS) with 30% BWS. METHODS: We measured oxygen uptake and carbon dioxide output to calculate CoT values at seven treadmill walking speeds (0.67-2.00 m s- 1) in 40 healthy young males under normal walking (NW) and BWS. The PWS was determined under both conditions on a different day. RESULTS: A spring-like behavior of our BWS apparatus reduced the CoT values at 1.56, 1.78, and 2.00 m s- 1. The ES with BWS (1.61 ± 0.11 m s- 1) was faster than NW condition (1.39 ± 0.06 m s- 1). A Bland-Altman analysis indicated that there were no systematic biases between ES and PWS in both conditions. CONCLUSIONS: The use of BWS apparatus with a spring-like behavior reduced the CoT values at faster walking speeds, resulting in the faster ES with 30% BWS compared to NW. Since the ES was equivalent to the PWS in both conditions, the PWS could be mainly determined by the metabolic minimization in healthy young males. This result also derives that the PWS can be a substitutable index of the individual ES in these populations.

4.
PeerJ ; 7: e8290, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31871846

RESUMO

BACKGROUND: Minimization of the energetic cost of transport (CoT) has been suggested for the walk-run transition in human locomotion. More recent literature argues that lower leg muscle activities are the potential triggers of the walk-run transition. We examined both metabolic and muscular aspects for explaining walk-run transition under body weight support (BWS; supported 30% of body weight) and normal walking (NW), because the BWS can reduce both leg muscle activity and metabolic rate. METHODS: Thirteen healthy young males participated in this study. The energetically optimal transition speed (EOTS) was determined as the intersection between linear CoT and speed relationship in running and quadratic CoT-speed relationship in walking under BWS and NW conditions. Preferred transition speed (PTS) was determined during constant acceleration protocol (velocity ramp protocol at 0.00463 m·s-2 = 1 km·h-1 per min) starting from 1.11 m·s-1. Muscle activities and mean power frequency (MPF) were measured using electromyography of the primary ankle dorsiflexor (tibialis anterior; TA) and synergetic plantar flexors (calf muscles including soleus) before and after the walk-run transition. RESULTS: The EOTS was significantly faster than the PTS under both conditions, and both were faster under BWS than in NW. In both conditions, MPF decreased after the walk-run transition in the dorsiflexor and the combined plantar flexor activities, especially the soleus. DISCUSSION: The walk-run transition is not triggered solely by the minimization of whole-body energy expenditure. Walk-run transition is associated with reduced TA and soleus activities with evidence of greater slow twitch fiber recruitment, perhaps to avoid early onset of localized muscle fatigue.

5.
Sci Rep ; 9(1): 9550, 2019 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-31266961

RESUMO

Energy expenditure (EE) during treadmill walking under normal conditions (normobaric normoxia, 21% O2) and moderate hypoxia (13% O2) was measured. Ten healthy young men and ten healthy young women walked on a level (0°) gradient a range of speeds (0.67-1.67 m s-1). During walking, there were no significant differences in reductions in arterial oxygen saturation (SpO2) between the sexes. The hypoxia-induced increase in EE, heart rate (HR [bpm]) and ventilation ([Formula: see text] [L min-1]) were calculated. Using a multivariate model that combined EE, [Formula: see text], and HR to predict ΔSpO2 (hypoxia-induced reduction), a very strong fit model both for men (r2 = 0.900, P < 0.001) and for women was obtained (r2 = 0.957, P < 0.001). The contributions of EE, VE, and HR to ΔSpO2 were markedly different between men and women. [Formula: see text] and EE had a stronger effect on ΔSpO2 in women ([Formula: see text]: 4.1% in women vs. 1.7% in men; EE: 28.1% in women vs. 15.8% in men), while HR had a greater effect in men (82.5% in men and 67.9% in women). These findings suggested that high-altitude adaptation in response to hypoxemia has different underlying mechanisms between men and women. These results can help to explain how to adapt high-altitude for men and women, respectively.


Assuntos
Sistema Cardiovascular/metabolismo , Hipóxia/metabolismo , Consumo de Oxigênio , Sistema Respiratório/metabolismo , Caminhada , Adolescente , Adulto , Biomarcadores , Sistema Cardiovascular/fisiopatologia , Feminino , Humanos , Hipóxia/fisiopatologia , Masculino , Testes de Função Respiratória , Sistema Respiratório/fisiopatologia , Adulto Jovem
6.
J Sports Sci ; 37(14): 1638-1647, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30774004

RESUMO

We investigated combined effects of ambient temperature (23°C or 13°C) and fraction of inspired oxygen (21%O2 or 13%O2) on energy cost of walking (Cw: J·kg-1·km-1) and economical speed (ES). Eighteen healthy young adults (11 males, seven females) walked at seven speeds from 0.67 to 1.67 m s-1 (four min per stage). Environmental conditions were set; thermoneutral (N: 23°C) with normoxia (N: 21%O2) = NN; 23°C (N) with hypoxia (H: 13%O2) = NH; cool (C: 13°C) with 21%O2 (N) = CN, and 13°C (C) with 13%O2 (H) = CH. Muscle deoxygenation (HHb) and tissue O2 saturation (StO2) were measured at tibialis anterior. We found a significantly slower ES in NH (1.289 ± 0.091 m s-1) and CH (1.275 ± 0.099 m s-1) than in NN (1.334 ± 0.112 m s-1) and CN (1.332 ± 0.104 m s-1). Changes in HHb and StO2 were related to the ES. These results suggested that the combined effects (exposure to hypoxia and cool) is nearly equal to exposure to hypoxia and cool individually. Specifically, acute moderate hypoxia slowed the ES by approx. 4%, but acute cool environment did not affect the ES. Further, HHb and StO2 may partly account for an individual ES.


Assuntos
Temperatura Baixa , Metabolismo Energético , Hipóxia , Músculo Esquelético/metabolismo , Consumo de Oxigênio , Velocidade de Caminhada/fisiologia , Adaptação Fisiológica , Adulto , Teste de Esforço , Feminino , Frequência Cardíaca , Humanos , Masculino , Oxigênio/sangue , Troca Gasosa Pulmonar , Temperatura Cutânea , Adulto Jovem
7.
Biol Open ; 7(7)2018 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-29970478

RESUMO

We measured oxygen consumption and carbon dioxide output during walking [per unit distance (Cw) values] for 14 healthy young human males at seven speeds from 0.67 to 1.67 m s-1 (4 min per stage) in thermoneutral (23°C), cool (13°C), and hot (33°C) environments. The Cw at faster gait speeds in the 33°C trial was slightly higher compared to those in the 23°C and 13°C trials. We found the speed at which the young males walked had a significant effect on the Cw values (P<0.05), but the different environmental temperatures showed no significant effect (P>0.05). Economical speed (ES) which can minimize the Cw in each individual was calculated from a U-shaped relationship. We found a significantly slower ES at 33°C [1.265 (0.060) m s-1 mean (s.d.)] compared to 23°C [1.349 (0.077) m s-1] and 13°C [1.356 (0.078) m s-1, P<0.05, respectively] with no differences between 23°C and 13°C (P>0.05). Heart rate and mean skin temperature responses in the 33°C condition increased throughout the walking trial compared to 23°C and 13°C (all P<0.05). These results suggest that an acutely hot environment slowed the ES by ∼7%, but an acutely cool environment did not affect the Cw and ES.

8.
J Physiol Anthropol ; 37(1): 18, 2018 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-29914562

RESUMO

BACKGROUND: Energy cost of transport per unit distance (CoT) against speed shows U-shaped fashion in walking and linear fashion in running, indicating that there exists a specific walking speed minimizing the CoT, being defined as economical speed (ES). Another specific gait speed is the intersection speed between both fashions, being called energetically optimal transition speed (EOTS). We measured the ES, EOTS, and muscle activities during walking and running at the EOTS under hyperoxia (40% fraction of inspired oxygen) on the level and uphill gradients (+ 5%). METHODS: Oxygen consumption [Formula: see text] and carbon dioxide output [Formula: see text] were measured to calculate the CoT values at eight walking speeds (2.4-7.3 km h-1) and four running speeds (7.3-9.4 km h- 1) in 17 young males. Electromyography was recorded from gastrocnemius medialis, gastrocnemius lateralis (GL), and tibialis anterior (TA) to evaluate muscle activities. Mean power frequency (MPF) was obtained to compare motor unit recruitment patterns between walking and running. RESULTS: [Formula: see text], [Formula: see text], and CoT values were lower under hyperoxia than normoxia at faster walking speeds and any running speeds. A faster ES on the uphill gradient and slower EOTS on both gradients were observed under hyperoxia than normoxia. GL and TA activities became lower when switching from walking to running at the EOTS under both FiO2 conditions on both gradients, so did the MPF in the TA. CONCLUSIONS: ES and EOTS were influenced by reduced metabolic demands induced by hyperoxia. GL and TA activities in association with a lower shift of motor unit recruitment patterns in the TA would be related to the gait selection when walking or running at the EOTS. TRIAL REGISTRATION: UMIN000017690 ( R000020501 ). Registered May 26, 2015, before the first trial.


Assuntos
Metabolismo Energético/fisiologia , Hiperóxia/metabolismo , Perna (Membro)/fisiologia , Caminhada/fisiologia , Adulto , Dióxido de Carbono/metabolismo , Eletromiografia , Marcha/fisiologia , Humanos , Hiperóxia/fisiopatologia , Masculino , Consumo de Oxigênio/fisiologia , Adulto Jovem
9.
Biol Open ; 5(10): 1408-1414, 2016 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-27744292

RESUMO

We measured oxygen consumption during walking per unit distance (Cw) values for 12 human healthy young males at six speeds from 0.667 to 1.639 m s-1 (four min per stage) on a level gradient under normobaric normoxia, moderate hypoxia (15% O2), and severe hypoxia (11% O2). Muscle deoxygenation (HHb) was measured at the vastus lateralis muscle using near-infrared spectroscopy. Economical speed which can minimize the Cw in each individual was calculated from a U-shaped relationship. We found a significantly slower economical speed (ES) under severe hypoxia [1.237 (0.056) m s-1; mean (s.d.)] compared to normoxia [1.334 (0.070) m s-1] and moderate hypoxia [1.314 (0.070) m s-1, P<0.05 respectively] with no differences between normoxia and moderate hypoxia (P>0.05). HHb gradually increased with increasing speed under severe hypoxia, while it did not increase under normoxia and moderate hypoxia. Changes in HHb between standing baseline and the final minute at faster gait speeds were significantly related to individual ES (r=0.393 at 1.250 m s-1, r=0.376 at 1.444 m s-1, and r=0.409 at 1.639 m s-1, P<0.05, respectively). These results suggested that acute severe hypoxia slowed ES by ∼8%, but moderate hypoxia left ES unchanged.

10.
PLoS One ; 10(9): e0138154, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26383249

RESUMO

The oxygen cost of transport per unit distance (CoT; mL·kg(-1)·km(-1)) shows a U-shaped curve as a function of walking speed (v), which includes a particular walking speed minimizing the CoT, so called economical speed (ES). The CoT-v relationship in running is approximately linear. These distinctive walking and running CoT-v relationships give an intersection between U-shaped and linear CoT relationships, termed the energetically optimal transition speed (EOTS). This study investigated the effects of subtracting the standing oxygen cost for calculating the CoT and its relevant effects on the ES and EOTS at the level and gradient slopes (±5%) in eleven male trained athletes. The percent effects of subtracting the standing oxygen cost (4.8 ± 0.4 mL·kg(-1)·min(-1)) on the CoT were significantly greater as the walking speed was slower, but it was not significant at faster running speeds over 9.4 km·h(-1). The percent effect was significantly dependent on the gradient (downhill > level > uphill, P < 0.001). The net ES (level 4.09 ± 0.31, uphill 4.22 ± 0.37, and downhill 4.16 ± 0.44 km·h(-1)) was approximately 20% slower than the gross ES (level 5.15 ± 0.18, uphill 5.27 ± 0.20, and downhill 5.37 ± 0.22 km·h(-1), P < 0.001). Both net and gross ES were not significantly dependent on the gradient. In contrast, the gross EOTS was slower than the net EOTS at the level (7.49 ± 0.32 vs. 7.63 ± 0.36 km·h(-1), P = 0.003) and downhill gradients (7.78 ± 0.33 vs. 8.01 ± 0.41 km·h(-1), P < 0.001), but not at the uphill gradient (7.55 ± 0.37 vs. 7.63 ± 0.51 km·h(-1), P = 0.080). Note that those percent differences were less than 2.9%. Given these results, a subtraction of the standing oxygen cost should be carefully considered depending on the purpose of each study.


Assuntos
Metabolismo Energético/fisiologia , Consumo de Oxigênio/fisiologia , Oxigênio/metabolismo , Corrida/fisiologia , Aceleração , Adolescente , Adulto , Desempenho Atlético/fisiologia , Teste de Esforço , Marcha/fisiologia , Humanos , Masculino , Caminhada/fisiologia , Adulto Jovem
11.
J Exerc Sci Fit ; 13(2): 79-85, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-29541103

RESUMO

BACKGROUND/OBJECTIVE: Oxygen consumption during walking per unit distance (Cw ; mL/kg/m) is known to be greater for older adults than younger adults, although its underlying process is controversial. METHODS: We measured the Cw values at six gait speeds from 30 m/min to 105 m/min on level ground and gradient slopes (±5%) in healthy younger and older male adults. A quadratic approximation was applied for a relationship between Cw and gait speeds (v; m/min). It gives a U-shaped Cw -v relationship, which includes a particular gait speed minimizing the Cw , the so-called economical speed (ES). The age-related difference of the Cw -v relationship was assessed by comparisons of ES and/or Cw . RESULTS: A significantly greater Cw at 30 m/min and slower ES were found for older adults at the downhill gradient, suggesting that a combination of leftward and upward shifts of the Cw -v relationship was found at that gradient. Only a slower ES was found for older adults at the uphill gradient, suggesting that a leftward shift was found for older adults at that gradient. Neither a significant leftward nor an upward shift was found at the level gradient. Leg length significantly correlated to the ES for younger adults at the level and downhill gradients, while such a significant relationship was observed only at the level gradient for older adults. The maximal quadriceps muscle strength significantly correlated to the ES for older adults at all gradients, but not for younger adults. CONCLUSION: The age-related alteration of the Cw -v relationship depends on the gradient, and its related factors were different between age groups.

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