The influence of footwear on foot motion during walking and running

There are evidences to suggest that wearing footwear constrains the natural barefoot motion during locomotion. Unlike prior studies that deduced foot motions from shoe sole displacement parameters, the aim of this study was to examine the effect of footwear motion on forefoot to rearfoot relative motion during walking and running. The use of a multi-segment foot model allowed accurate both shoe sole and foot motions (barefoot and shod) to be quantified. Two pairs of identical sandals with different midsole hardness were used. Ten healthy male subjects walked and ran in each of the shod condition.The results showed that for barefoot locomotion there was more eversion of the forefoot and it occurred faster than for shod locomotion. In this later condition, the range of eversion was reduced by 20% and the rate of eversion in late stance by 60% in comparison to the barefoot condition. The sole constrained both the torsional (eversion/inversion) and adduction range of motion of the foot. Interestingly, during the push-off phase of barefoot locomotion the rate and direction of forefoot torsion varied between individuals. However, most subjects displayed a forefoot inversion direction of motion while shod. Therefore, this experiment showed that the shoes not only restricted the natural motion of the barefoot but also appeared to impose a specific foot motion pattern on individuals during the push-off phase. These findings have implications for the matching of footwear design characteristics to individual natural foot function.     

Effect of endurance training on oxygen uptake kinetics during treadmill running.

The purpose of this study was to examine the effect of endurance training on oxygen uptake (VO(2)) kinetics during moderate [below the lactate threshold (LT)] and heavy (above LT) treadmill running. Twenty-three healthy physical education students undertook 6 wk of endurance training that involved continuous and interval running training 3-5 days per week for 20-30 min per session. Before and after the training program, the subjects performed an incremental treadmill test to exhaustion for determination of the LT and the VO(2 max) and a series of 6-min square-wave transitions from rest to running speeds calculated to require 80% of the LT and 50% of the difference between LT and maximal VO(2). The training program caused small (3-4%) but significant increases in LT and maximal VO(2) (P<0.05). The VO(2) kinetics for moderate exercise were not significantly affected by training. For heavy exercise, the time constant and amplitude of the fast component were not significantly affected by training, but the amplitude of the VO(2) slow component was significantly reduced from 321+/-32 to 217+/-23 ml/min (P<0.05). The reduction in the slow component was not significantly correlated to the reduction in blood lactate concentration (r = 0. 39). Although the reduction in the slow component was significantly related to the reduction in minute ventilation (r = 0.46; P<0.05), it was calculated that only 9-14% of the slow component could be attributed to the change in minute ventilation. We conclude that the VO(2) slow component during treadmill running can be attenuated with a short-term program of endurance running training.     

Maximal oxygen uptake during treadmill walking and running at various speeds.

Three groups of male subjects, average fitness (AF, N = 12), high fitness (HF, N = 7) and highly fit competitive race walkers (CRW, N = 3) performed maximal treadmill tests walking at 3.5 and 4.5 mph and running at 4.5, 5.5, 7.0, and 8.5 mph. In addition, the HF group performed a running test at 10.0 mph and the CRW group performed a walking test at 5.5 mph. All maximal oxygen uptake (VO2 max) tests with the exception of the 3.5 mph walking test (modified Balke test) were discontinuous in nature. VO2 max obtained from walking tests was similar regardless of speed within each group. Walking VO2 max was significantly lower than running VO2 max which was found to be similar over a speed range of 4.5 to 8.5 mph in the AF group. Running at 4.5 mph (HF group) and 4.5 and 5.5 mph (CRW group) resulted in lower VO2 max levels than running at speeds greater than or equal to 7.0 mph. Associated physiological variables (heart rate, ventilation, and respiratory exchange ratio) did not demonstrate a discernable pattern with reference to mode of locomotion (walking versus running) or speed. It was concluded that VO2 max elicited during walking is independent of speed and less than VO2 max obtained during running. Running VO2 max was interrelated with speed of running and state of training.     

Relation between endurance time and maximal oxygen consumption during supramaximal running

The relationship between speed and the maximal length of time supramaximal runs can be sustained (temps-limite, tlim) has been studied in seven male subjects (physical education students). Within the range of intensity studied, tlim strictly depends on maximal oxygen consumption (VO2max). The relationship between tlim and the relative energy cost of the exercises per unit of time (E), calculated by subtracting the maximal power of aerobic metabolism (Emaxox) from E, removes the interindividual differences of tlim. The function tlim = f(E-Emaxox) is described by an empirical equation of the form: tlim = a.exp[-b(E-Emaxox)] (r = 0.979; P less than 0.001), where the parameters a and b are respectively equal to 330.8 and 0.14 and where tlim, E and Emaxox are respectively expressed in seconds and in watts per kg of body weight.     

Effects of footwear on three-dimensional tibiotalar and subtalar joint motion during running

Running is a popular form of recreation, but injuries are common and may be associated with abnormal joint motion. The objective of this study was to determine the effect of three footwear conditions – barefoot (BF), an ultraflexible training shoe (FREE), and a motion control shoe (MC) – on 3D foot and ankle motion. Dynamic, biplane radiographic images were acquired from 12 runners during overground running. 3D rotations of the tibiotalar and subtalar joints were quantified in terms of plantarflexion/dorsiflexion (PF/DF), inversion/eversion (IN/EV) and internal/external rotation (IR/ER). Across the early stance phase (defined as footstrike to heel-off), BF running demonstrated greater tibiotalar joint range of motion for PF/DF (28.2±8.3°) and IR/ER (7.0±1.4°) than the shod conditions (FREE: PF/DF=15.1±5.9°, IR/ER=4.8±2.1°; MC: PF/DF=15.0±6.2°, IR/ER=4.3±0.7°). Also at the tibiotalar joint, BF running resulted in a position significantly more plantarflexed (BF: 2.0±12.5°, FREE: 15.7±12.2°, MC: 16.5±9.3°) and internally rotated (BF: 12.9±4.5°, FREE: 10.7±4.3°, MC: 10.6±3.9°) at footstrike compared to both shod conditions. No differences were detected between the shod conditions at any point in the early stance phase at the tibiotalar joint. The MC condition demonstrated significant differences compared to FREE at several points throughout the early stance phase at the subtalar joint, with the greatest differences seen at 30% in PF/DF (MC −1.4±8.8°: FREE: −0.5±9.0°), IN/EV (MC −8.1±5.7°: FREE −6.3±5.5°) and IR/ER (MC −9.5±5.3°: FREE: −8.7±5.2°). These findings indicate that footwear has subtle effects on joint motion mainly between BF and shod conditions at the tibiotalar joint and between shod conditions at the subtalar joint.     

Influence of training status on maximal accumulated oxygen deficit during all-out cycle exercise

The influence of training status on the maximal accumulated oxygen deficit (MAOD) was used to assess the validity of the MAOD method during supramaximal all-out cycle exercise. Sprint trained (ST; n = 6), endurance trained (ET; n = 8), and active untrained controls (UT; n = 8) completed a 90 s all-out variable resistance test on a modified Monark cycle ergometer. Pretests included the determination of peak oxygen uptake ( O_2peak) and a series (5–8) of 5-min discontinuous rides at submaximal exercise intensities. The regression of steady-state oxygen uptake on power output to establish individual efficiency relationships was extrapolated to determine the theoretical oxygen cost of the supramaximal power output achieved in the 90 s all-out test. Total work output in 90 s was significantly greater in the trained groups (P<0.05), although no differences existed between ET and ST. Anaerobic capacity, as assessed by MAOD, was larger in ST compared to ET and UT. While the relative contributions of the aerobic and anaerobic energy systems were not significantly different among the groups, ET were able to achieve significantly more aerobic work than the other two groups, while ST were able to achieve significantly more anaerobic work. Peak power and peak pedalling rate were significantly higher in ST. The results suggested that MAOD determined during all-out exercise was sensitive to training status and provided a useful assessment of anaerobic capacity. In our study sprint training, compared with endurance training, appeared to enhance significantly power output and high intensity performance over brief periods (up to 60 s), yet few overall differences in performance (i.e. total work) existed during 90 s of all-out exercise.     

Effect of footwear on intramuscular EMG activity of plantar flexor muscles in walking

One of the purposes of footwear is to assist locomotion, but some footwear types seem to restrict natural foot motion, which may affect the contribution of ankle plantar flexor muscles to propulsion. This study examined the effects of different footwear conditions on the activity of ankle plantar flexors during walking. Ten healthy habitually shod individuals walked overground in shoes, barefoot and in flip-flops while fine-wire electromyography (EMG) activity was recorded from flexor hallucis longus (FHL), soleus (SOL), and medial and lateral gastrocnemius (MG and LG) muscles. EMG signals were peak-normalised and analysed in the stance phase using Statistical Parametric Mapping (SPM). We found highly individual EMG patterns. Although walking with shoes required higher muscle activity for propulsion than walking barefoot or with flip-flops in most participants, this did not result in statistically significant differences in EMG amplitude between footwear conditions in any muscle (p > 0.05). Time to peak activity showed the lowest coefficient of variation in shod walking (3.5, 7.0, 8.0 and 3.4 for FHL, SOL, MG and LG, respectively). Future studies should clarify the sources and consequences of individual EMG responses to different footwear.     

有氧运动训练影响大鼠胸主动脉环内皮依赖性舒张功能机制的研究

目的:探讨有氧运动对大鼠胸主动脉内皮依赖性舒张功能影响的机制。方法:12只SD大鼠随机分为有氧运动和对照两组(n=6),经过8周每天1 h的游泳训练后(每周5天),测定比较2组间大鼠胸主动脉舒张功能的改变。结果:有氧运动组一氧化氮(NO)和前列环素PGI2途径胸主动脉舒张功能的Rmax值较对照组明显提高(P<0.05)。结论:有氧运动对大鼠胸主动脉舒张功能的有益影响,主要是由NO和PGI2途径介导的。     

Effect of bilateral carotid cooling on thermal responses during cycling and arm cranking work due to identical oxygen consumption

1. During the control, tympanic temperature (T_ty), skin blood flow (SkBF), local sweating rate (LSR) and heart rate (HR) of the AC were markedly higher than those of the BE. No significant differences were finally observed in rectal (T_re) and mean skin (T_sk) temperatures or oxygen uptake (VO₂). In contrast, mechanical work efficiency (ME) was significantly higher in the BE than in the AC.

2. During ice cooling, T_ty and the increasing rate in T_ty began to be suppressed at 25–35 min after the beginning in both kinds of work. During the AC, SkBF, LSR, HR and mean T_sk in the ice cooling tended to be lower compared those in the control. There were no significant difference between the control and the ice cooling in ME, VO₂ or T_re in either kind of work.     

The therapeutic effect of aerobic exercise with resistance training in elderly men with type 2 diabetes mellitus

Objective: This study was conducted to examine the effects of aerobic exercise alone and aerobic exercise with resistance training on the quality of life in men over the age of 55 years with type 2 diabetes mellitus. Methods: A total of 54 participants were divided into the following three groups so that there were no significant differences in blood chemistry or physical ability indexes among the three groups: control, aerobic exercise, and aerobic exercise with resistance training. The latter two groups exercised for 24 weeks, while the control group performed no exercise. Blood chemistry levels and measures of physical ability in each group members were examined one day before and one day after the exercise regimens. Results: Compared with those before the study, blood glucose, glycated hemoglobin, triglycerides, cholesterol, and low-density lipoprotein levels as well as vital capacity, reaction time, sit-and-reach ability, and balancing while standing on one leg with closed eyes were significantly improved in the aerobic exercise only group(P 0.05). All these measures as well as high-density lipoprotein levels and grip, back, and leg strength were significantly improved in the combined aerobic and resistance training group(P 0.05). By contrast, no significant differences before and after the experiment were found in any measure for the control group(P 0.05). Conclusion: Although both aerobic exercise and aerobic exercise combined with resistance training for 24 weeks effectively improved the quality of life in patients with type 2 diabetes, the effect of the combined training was better than that of aerobic exercise alone. These results suggest that resistance training may be safely added to the rehabilitation training regimen of patients with type 2 diabetes mellitus.     

Three-dimensional acceleration of the tibia during walking and running.

Measurements of tibial acceleration during walking and running were obtained by means of a triaxial accelerometer. The accelerometer was fixed to the free end of a Steinmann pin inserted into the right tibia of one volunteer subject. The patterns of tibial acceleration showed little step-to-step variation within each experimental condition. Following foot strike and depending upon footwear, the resultant tibial acceleration reached between 2.7 and 3.7 g during walking. The tibia experienced maximal accelerations of 10.6 g during running. The high values of tibial acceleration recorded in the antero-posterior (AP) and medio-lateral (ML) directions clearly revealed the importance of measuring all three components of acceleration to quantify the magnitude of the shock experienced by the lower limbs during locomotor activities.     

Effect of work rate increment on peak oxygen uptake during wheelchair ergometry in men with quadriplegia

The purpose of this study was to determine the effect of work rate increment on peak oxygen uptake (VO2 peak) during wheelchair ergometry (WCE) in men with quadriplegia due to cervical spinal cord injuries (CSCI). Twenty-two non-ambulatory subjects (aged 20-38 years) with CSCI were divided into two groups based on wheelchair sports classification (n = 12 for IA group and n = 10 for IB/IC group). Subjects underwent three different, continuous graded exercise tests (spaced at least 1 week apart) on an electronically braked wheelchair ergometer. Following a 3-min warmup, the work rate was increased 2, 4, or 6 W.min-1 for the IA group and 4, 6, or 8 W.min-1 for the IB/IC group. Ventilation and gas exchange were measured breath-by-breath with a computerized system. Repeated-measures ANOVA showed no significant difference among the three protocols for VO2 peak in the IA group (P greater than 0.05). The mean (SD) VO2 peak values (ml.kg-1.min-1) were 9.3 (2.4), 9.4 (3.2), and 8.4 (2.6) for the 2, 4, and 6 W.min-1 protocols, respectively. In contrast, the IB/IC group showed a significant difference among the protocols for VO2 peak (P less than 0.05). The mean (SD) VO2 peak values (ml.kg-1,min-1) were 15.1 (4.0), 14.1 (4.4), and 12.7 (4.0) for the 4, 6, and 8 W.min-1 protocols, respectively. Post hoc analysis revealed a difference between the 4 and 8 W.min-1 protocols. Our results suggest that graded exercise testing of men with quadriplegia due to CSCI, using WCE, should employ work rate increments between 2 and 6 W.min-1 and that work rate increments of 8 W.min-1 or greater will result in an underestimate of VO2 peak.     

力竭性运动锻炼和饥饿对南方鲇运动后过量耗氧的影响

为了检验力竭性运动锻炼和饥饿是否对南方鲇Silurus meridonalis Chen维持能量消耗和无氧代谢能力产生影响,在25℃条件下测定了维持日粮(1.5%body mass per day)和饥饿条件下南方鲇15d力竭性锻炼(5min chasing)和随后5d恢复过程静止代谢率(VO2rest)和运动后过量耗氧(Excess post-exercise VO2,EPOC)的变化.另外两组非锻炼组分别作为摄食和饥饿对照组.实验过程中摄食和饥饿对照组VO2rest显著下降(P＜0.05),而摄食和饥饿对照组经过15d的锻炼显著上升(P＜0.05).经过5d的恢复2锻炼组VO2rest显著下降与对照组无显著差异.摄食和饥饿对照组力竭运动后代谢率峰值(VO2peak)在实验过程中显著下降(P＜0.05),而摄食和饥饿锻炼组经过15d没有显著变化.锻炼取消后2锻炼组VO2peak显著下降至对照组水平.各锻炼组和对照组间过量耗氧均无显著差异.实验提示:(1)锻炼导致VO2rest和VO2peak显著提高,但影响可塑性大,5d恢复期后影响消失;(2)锻炼导致力竭运动后代谢恢复速率加快,5d恢复期后锻炼影响依然存在;(3)对饥饿和摄食组,锻炼的生理影响相似,但饥饿组VO2rest对锻炼更为敏感.     

Foot structure and knee joint kinetics during walking with and without wedged footwear insoles

The relationship between static foot structure characteristics and knee joint biomechanics during walking, or the biomechanical response to wedged insoles are currently unknown. In this study, 3D foot scanning, dual X-ray absorptiometry and gait analysis methods were used to determine structural parameters of the foot and assess their relation to knee joint loading and biomechanical response to wedged insoles in 30 patients with knee osteoarthritis. In multiple linear regression models, foot fat content, height of the medial longitudinal arch and static hind foot angle were not associated with the magnitude of the knee adduction moment (R² = 0.24, p = 0.060), knee adduction angular impulse (R² = 0.21, p = 0.099) or 3D resultant knee moment (R² = 0.23, p = 0.073) during gait. Furthermore, these foot structure parameters were not associated with the patients’ biomechanical response to medial or lateral wedge footwear insoles (all p < 0.01). These findings suggest that static foot structure is not associated with gait mechanics at the knee, and that static foot structure alone cannot be utilized to predict an individual’s biomechanical response to wedged footwear insoles in patients with knee osteoarthritis.     

The influence of footwear on the electromyographic activity of selected lower limb muscles during walking

The purpose of this study was to compare the effects of a standard flexible shoe and a stability running shoe on lower limb muscle activity during walking. Twenty-eight young asymptomatic adults with flat-arched feet were recruited. While walking, electromyographic (EMG) activity was recorded from tibialis posterior and peroneus longus via intramuscular electrodes; and from tibialis anterior and medial gastrocnemius via surface electrodes. Three experimental conditions were assessed: (i) barefoot, (ii) a standard flexible shoe, (iii) a stability running shoe. Results showed significant differences for the peak amplitude and the time of peak amplitude for tibialis anterior, peroneus longus and medial gastrocnemius when comparing the three experimental conditions (p < 0.05). Significant differences were detected primarily between the barefoot and shoe conditions and with relatively small effect sizes for peroneus longus, tibialis anterior and medial gastrocnemius. Few significant differences were found between the two shoe styles. We discuss how these changes are most likely associated with the shoe upper bracing the foot, the shape of the shoe outer-sole and weight of the shoes. Further research is needed to investigate differences between these shoe styles when participants walk for longer distances (i.e. over 1000 m) and following fatigue.     

Relationship between record time and maximal oxygen consumption in middle-distance running.

The relationship between record time (tr) and maximal oxygen uptake (VO2max) has been examined in 69 male physical education students who had taken part in 800-m and 1500-m footraces. It was found that tr and VO2max were inversely related. The relationships tr = f(VO2max) have been fitted by two exponential equations: tr (1500 m) = 698e-0.0145VO2max; tr (800 m) = 272e-0.011VO2max; P less than 0.001. A mathematical formulation of the energy conservation principle in supramaximal running, based on the exponential increase of the oxygen uptake as a function of time with a rate constant of 0.025 s-1 has been applied to the tr calculation from VO2max. As calculated tr were highly correlated to measured tr (P less than 0.001), it was concluded that the relationships tr = f(VO2max) can be interpreted on the basis of the model described in this study.     

Effect of aerobic exercise training on non-alcoholic fatty liver disease induced by a high fat diet in C57BL/6 mice

[Purpose]

The aim of this study was to investigate the effects of aerobic exercise training on a high fat diet (HFD)-induced fatty liver and its metabolic complications in C57BL/6 mice.

[Methods]

Mice at 5-month old (n = 30) were randomly assigned to standard chow (SC + CON, n = 10) and high-fat diet (HFD, n = 20), and they were subjected to SC and HFD, respectively, for 23-week. After 15-week of HFD, mice in the HFD group were further assigned to HFD (HFD + CON, n = 10) or exercise training (HFD + EX, n = 10) groups. The HFD + EX mice were subjected to aerobic treadmill running during the last 8-week of the 23-week HFD course. Outcomes included hepatic steatosis, insulin resistance, and expression of genes involved in mitochondrial function and/or fatty oxidation as well as de novo lipogenesis and/or triacylglycerol (TAG) synthesis.

[Results]

Treadmill running ameliorated impaired glucose tolerance and insulin resistance secondary to the HFD. The beneficial effects of treadmill running were associated with enhanced molecular markers of mitochondrial function and/or fatty acids oxidation (i.e., PPARα and CPT1a mRNAs, pAMPK/AMPK, pACC, and SIRT1 protein) as well as suppressed expression of de novo lipogenesis and/or TAG synthesis (i.e., SREBP1c, lipin1 and FAS mRNAs) in the liver.

[Conclusion]

The current findings suggest that aerobic exercise training is an effective and non-pharmacological means to combat fatty liver and its metabolic complications in HFD-induced obese mice.