On physiological edema in man's lower extremity

To examine whether the so-called musculovenous pump counteracts the development of interstitial edema in the lower extremities of man in the upright position, the volume changes in the calf which occurred during twenty minutes of rhythmic muscular exercise were measured in twenty-three subjects by impedance-plethysmography. The results were compared with the volume increase found during quiet relaxed standing for the same length of time. Contrary to the hypothesis, and edema-protective effect of the musculovenous pump could only be shown in about half the number of the subjects. In the others, muscular exercise led to increases in calf volume which were higher than those measured in the normal upright position. These results show that the calf muscle pump does not generally have a edema-protective effect but rather that muscle contractions also activate mechanisms which stimulate the extravasation of fluid. In a second test-series with twenty subjects, changes in calf volume were measured during the course of the day. In nearly all cases, the calf volume was greater in the evening than in the morning. It could be shown that the volume increases in the evening are caused by an increase in extravascular fluid. Compared to the increase in extravascular volume occurring during twenty minutes, in a normal upright position, the accumulation of extravascular fluid during the day is, however, remarkably low. Although it is still unknown how interstitial edema in man's lower extremities is prevented during the day, these findings lead to the hypothesis that the edema-preventing mechanisms, for instance the muscle-lymphpump, do not become maximally effective until a certain volume has accumulated in the interstitial space.     

Joint forces and torques when walking in shallow water

This study reports for the first time an estimation of the internal net joint forces and torques on adults' lower limbs and pelvis when walking in shallow water, taking into account the drag forces generated by the movement of their bodies in the water and the equivalent data when they walk on land. A force plate and a video camera were used to perform a two-dimensional gait analysis at the sagittal plane of 10 healthy young adults walking at comfortable speeds on land and in water at a chest-high level. We estimated the drag force on each body segment and the joint forces and torques at the ankle, knee, and hip of the right side of their bodies using inverse dynamics. The observed subjects' apparent weight in water was about 35% of their weight on land and they were about 2.7 times slower when walking in water. When the subjects walked in water compared with walking on land, there were no differences in the angular displacements but there was a significant reduction in the joint torques which was related to the water's depth. The greatest reduction was observed for the ankle and then the knee and no reduction was observed for the hip. All joint powers were significantly reduced in water. The compressive and shear joint forces were on average about three times lower during walking in water than on land. These quantitative results substantiate the use of water as a safe environment for practicing low-impact exercises, particularly walking.     

Estimating the complete ground reaction forces with pressure insoles in walking

This study presented a method to estimate the complete ground reaction forces from pressure insoles in walking. Five male subjects performed 10 walking trials in a laboratory. The complete ground reaction forces were collected during a right foot stride by a force plate at 1000Hz. Simultaneous plantar pressure data were collected at 100Hz by a pressure insole system with 99 sensors covering the whole plantar area. Stepwise linear regressions were performed to individually reconstruct the complete ground reaction forces in three directions from the 99 individual pressure data until redundancy among the predictors occurred. An additional linear regression was performed to reconstruct the vertical ground reaction force by the sum of the value of the 99 pressure sensors. Five other subjects performed the same walking test for validation. Estimated ground reaction forces in three directions were calculated with the developed regression models, and were compared with the real data recorded from force plate. Accuracy was represented by the correlation coefficient and the root mean square error. Results showed very good correlation in anterior-posterior (0.928) and vertical (0.989) directions, and reasonable correlation in medial-lateral direction (0.719). The root mean square error was about 12%, 5% and 28% of the peak recorded value. Future studies should aim to generalize the methods or to establish specific methods to other subjects, patients, motions, footwear and floor conditions. The method gives an extra option to study an estimation of the complete ground reaction forces in any environment without the constraints from the number and location of force plates.     

Rocker-bottom, profile-type shoes do not increase lower extremity muscle activity or energy cost of walking

The purpose of this study was to determine if wearing rocker-bottom shoes with compliant midsoles (RB) influences muscle activity and metabolic cost of walking. Furthermore, we sought to determine if weight differences between shod conditions accounted for any potential change. Twenty-eight subjects (17 women, 11 men, age 22.8 ± 6.6 years; weight 72 ± 20 kg; height 170 ± 6.7 cm; percent body fat 23.0 ± 11.7) walked on a treadmill (0% grade) for 10 minutes at a self-selected speed plus 10% (1.3 ± 0.2 m·s) in each of the following laboratory-provided shoes: flat-bottomed shoe (W), flat-bottomed shoe weight-matched to RB (WM), and RB. Muscle activity of the right side biceps femoris (BF), rectus femoris (RF), gastrocnemius (GA), and tibalis anterior (TA) was recorded for 30 seconds at the beginning, middle, and ending of the 10-minute walk using an electromyography (EMG) system. The average (AVG) and root mean square (RMS) were calculated from full-wave rectified EMG data at each interval. The rate of oxygen consumption (V[Combining Dot Above]O2) was measured for 10 minutes during each condition. A 3 (shoe) × 3 (time) repeated-measures analysis of variance (ANOVA) was used to compare each EMG-dependent variable (AVG and RMS EMG of each muscle), and repeated measures ANOVA was used to test V[Combining Dot Above]O2. Muscle activity (for any muscle) was not influenced by the interaction of shoe and time (p > 0.05). The AVG and RMS for RF, BF, and GA, including V[Combining Dot Above]O2, were not different among shod conditions (W: 9.7 ± 0.6 ml·kg·min; WM: 10.0 ± 0.5 ml·kg·min; RB: 10.1 ± 0.5 ml·kg·min), whereas TA AVG and RMS were lower during RB (p < 0.05). It seems that there is no increase in muscle activity or metabolic cost while wearing RB beyond the flat-bottomed shoe despite there being the rocker-profile design and mass differences.     

Joint forces in the human pelvis-leg skeleton during walking

For the calculation of the forces in the hip, knee and ankle joints during walking the knowledge of the three-dimensional movements of the human body and of the forces between foot and ground is a prerequisite. It is shown how this information may be obtained and what accuracy is obtainable. For the calculation of the statically indeterminate system of the lower limbs, consisting of muscles, bones and joints an optimization method is applied. The optimization criterion is the minimization of the muscle forces. Measurements were taken with seventeen male and five female persons. The maximum joint forces are plotted against gait speed, body weight and body size. In addition some statistical distributions are presented.     

The forces and couples in the human trunk during level walking

The intersegmental force and couple exchanged between upper and lower body across a transverse section passing through the fourth lumbar vertebra were estimated during level walking on a straight line at speeds ranging from 0.99 to 2.23 ms-1. This was done using 3-D kinematic information relative to the head, upper limbs, and upper torso, obtained through a stereophotogrammetric technique, and the relevant inertial parameters obtained using anthropometric measurements and estimation techniques provided in the literature. Twenty walking cycles of five normal adult male subjects were analysed. The intersegmental force and couple components are presented as referenced to both a laboratory and pelvic set of axes. Using these results some considerations are made concerning the variations which the overall trunk muscles effort undergoes because of mean walking speed changes. The muscular action on the trunk is inferred from the intersegmental couple components. The various factors that contribute to the build-up of the intersegmental force and couple are analysed and their relative importance assessed.     

The MusIC method: a fast and quasi-optimal solution to the muscle forces estimation problem

The present paper aims at presenting a fast and quasi-optimal method of muscle forces estimation: the MusIC method. It consists in interpolating a first estimation in a database generated offline thanks to a classical optimization problem, and then correcting it to respect the motion dynamics. Three different cost functions – two polynomial criteria and a min/max criterion – were tested on a planar musculoskeletal model. The MusIC method provides a computation frequency approximately 10 times higher compared to a classical optimization problem with a relative mean error of 4% on cost function evaluation.     

Hyaluronan in human skeletal muscle of lower extremity: concentration, distribution, and effect of exercise.

The concentration and localization of hyaluronan (HYA) were determined in biopsy specimens from resting human quadriceps femoris and anterior tibial muscles. The influence of physical exercise on HYA concentrations in the quadriceps femoris muscle and in blood was also evaluated. A sensitive radioassay was used for the quantification of HYA. The distribution of the glycosaminoglycan was demonstrated using a histochemical method that involved microwave-aided fixation and an HYA-binding protein. At rest, the muscle HYA concentration was 34.9 +/- 23.6 (SD) micrograms/g muscle wet wt with a large interindividual variation. Exercise had no significant effect on the muscle HYA concentration. The serum HYA concentration increased from 35.9 +/- 22.7 to 53.4 +/- 57.1 micrograms/l during exercise, but 30 min after the exercise the HYA concentration was significantly lower (19.1 +/- 6.3 micrograms/l) than the initial preexercise value. In resting skeletal muscles of the lower extremity, HYA was heterogeneously distributed in the perimysium and endomysium. Perivascular and perineural connective tissues were distinctly HYA positive.     

Changes in relative work of the lower extremity joints and distal foot with walking speed

The modulation of walking speed results in adaptations to the lower limbs which can be quantified using mechanical work. A 6 degree-of-freedom (DOF) power analysis, which includes additional translations as compared to the 3 DOF (all rotational) approach, is a comprehensive approach for quantifying lower limb work during gait. The purpose of this study was to quantify the speed-related 6 DOF joint and distal foot work adaptations of all the lower extremity limb constituents (hip, knee, ankle, and distal foot) in healthy individuals. Relative constituent 6 DOF work, the amount of constituent work relative to absolute limb work, was calculated during the stance and swing phases of gait. Eight unimpaired adults walked on an instrumented split-belt treadmill at slow, moderate, and typical walking speeds (0.4, 0.6, and 0.8 statures/s, respectively). Using motion capture and force data, 6 DOF powers were calculated for each constituent. Contrary to previously published results, 6 DOF positive relative ankle work and negative relative distal foot work increased significantly with increased speed during stance phase (p < 0.05). Similar to previous rotational DOF results in the sagittal plane, negative relative ankle work decreased significantly with increased speed during stance phase (p < 0.05). Scientifically, these findings provide new insight into how healthy individuals adapt to increased walking speed and suggest limitations of the rotational DOF approach for quantifying limb work. Clinically, the data presented here for unimpaired limbs can be used to compare with speed-matched data from limbs with impairments.     

Comparison of forces developed by the leg of the rock lobster when walking free or on a treadmill

Summary In the free walking rock lobster the forces developed by legs 4 and 5 were investigated during the power stroke. Two orthogonal force components lying in the horizontal plane were measured. Based on these results the diffent tasks of the two legs during walking are discussed. The forces developed by leg 4 were compared when the animal walked freely and on a treadmill. In these two situations the results differ qualitatively as in driven walking the forces are nearly identical in a long series of consecutive steps whereas in free walking the forces can vary greatly from step to step. However, similar mean values of force were measured with those on the treadmill being somewhat higher. This shows that, although the treadmill is driven by a motor, the animal does perform active walking movements. In the treadmill situation the forces increase as the speed of treadmill motor is decreased.Supported by DAAD and DFG (Cr 58) for H. Cruse and by ATP (80 119.112) INSERM for F. Clarac     

Changes in lower limb muscle activity after walking on a split-belt treadmill in individuals post-stroke

Background: There is growing evidence that stroke survivors can adapt and improve step length symmetry in the context of split-belt treadmill (SBT) walking. However, less knowledge exists about the strategies involved for such adaptations. This study analyzed lower limb muscle activity in individuals post-stroke related to SBT-induced changes in step length. Methods: Step length and surface EMG activity of six lower limb muscles were evaluated in individuals post-stroke (n = 16) during (adaptation) and after (after-effects) walking at unequal belt speeds. Results: During adaptation, significant increases in EMG activity were mainly found in proximal muscles (p ⩽ 0.023), whereas after-effects were observed particularly in the distal muscles. The plantarflexor EMG increased after walking on the slow belt (p ⩽ 0.023) and the dorsiflexors predominantly after walking on the fast belt (p ⩽ 0.017) for both, non-paretic and paretic-fast conditions. Correlation analysis revealed that after-effects in step length were mainly associated with changes in distal paretic muscle activity (0.522 ⩽ r ⩽ 0.663) but not with functional deficits. Based on our results, SBT walking could be relevant for training individuals post-stroke who present shorter paretic step length combined with dorsiflexor weakness, or individuals with shorter nonparetic step length and plantarflexor weakness.     

Evaluation of a morphing based method to estimate muscle attachment sites of the lower extremity

To generate subject-specific musculoskeletal models for clinical use, the location of muscle attachment sites needs to be estimated with accurate, fast and preferably automated tools. For this purpose, an automatic method was used to estimate the muscle attachment sites of the lower extremity, based on the assumption of a relation between the bone geometry and the location of muscle attachment sites. The aim of this study was to evaluate the accuracy of this morphing based method. Two cadaver dissections were performed to measure the contours of 72 muscle attachment sites on the pelvis, femur, tibia and calcaneus. The geometry of the bones including the muscle attachment sites was morphed from one cadaver to the other and vice versa. For 69% of the muscle attachment sites, the mean distance between the measured and morphed muscle attachment sites was smaller than 15 mm. Furthermore, the muscle attachment sites that had relatively large distances had shown low sensitivity to these deviations. Therefore, this morphing based method is a promising tool for estimating subject-specific muscle attachment sites in the lower extremity in a fast and automated manner.     

Knee muscle forces during walking and running in patellofemoral pain patients and pain-free controls

One proposed mechanism of patellofemoral pain, increased stress in the joint, is dependent on forces generated by the quadriceps muscles. Describing causal relationships between muscle forces, tissue stresses, and pain is difficult due to the inability to directly measure these variables in vivo. The purpose of this study was to estimate quadriceps forces during walking and running in a group of male and female patients with patellofemoral pain (n=27, 16 female; 11 male) and compare these to pain-free controls (n=16, 8 female; 8 male). Subjects walked and ran at self-selected speeds in a gait laboratory. Lower limb kinematics and electromyography (EMG) data were input to an EMG-driven musculoskeletal model of the knee, which was scaled and calibrated to each individual to estimate forces in 10 muscles surrounding the joint. Compared to controls, the patellofemoral pain group had greater co-contraction of quadriceps and hamstrings (p=0.025) and greater normalized muscle forces during walking, even though the net knee moment was similar between groups. Muscle forces during running were similar between groups, but the net knee extension moment was less in the patellofemoral pain group compared to controls. Females displayed 30–50% greater normalized hamstring and gastrocnemius muscle forces during both walking and running compared to males (p<0.05). These results suggest that some patellofemoral pain patients might experience greater joint contact forces and joint stresses than pain-free subjects. The muscle force data are available as supplementary material.     

Hypothesis testing as a laboratory exercise: a simple analysis of human walking,with a physiological surprise

This paper describes a laboratory exercise designed to provide students with experience testing a hypothesis by systematically isolating and controlling determinant variables. The study involves an analysis of walking and is performed by the students on a subject from within their lab group. The study requires use of a motorized treadmill, tape measure, stop watch, metronome, personal cassette player, and calculator. The exercise is designed to include factors that the students are familiar with, so they can focus on the isolation of variables without being confused about the process they are investigating. However, the exercise will not turn out as the students anticipate, meaning they will be forced to reevaluate the assumptions that formed the basis of their original hypothesis. This exercise is designed for a college-level course in exercise science, physiology, or biology but could easily be managed by a high school honors class with appropriate guidance.     

Changes in lower extremity muscle function after 56 days of bed rest

Preservation of muscle function, known to decline in microgravity and simulation (bed rest), is important for successful spaceflight missions. Hence, there is great interest in developing interventions to prevent muscle-function loss. In this study, 20 males underwent 56 days of bed rest. Ten volunteers were randomized to do resistive vibration exercise (RVE). The other 10 served as controls. RVE consisted of muscle contractions against resistance and concurrent whole-body vibration. Main outcome parameters were maximal isometric plantar-flexion force (IPFF), electromyography (EMG)/force ratio, as well as jumping power and height. Measurements were obtained before and after bed rest, including a morning and evening assessment on the first day of recovery from bed rest. IPFF (-17.1%), jumping peak power (-24.1%), and height (-28.5%) declined (P < 0.05) in the control group. There was a trend to EMG/force ratio decrease (-20%; P = 0.051). RVE preserved IPFF and mitigated the decline of countermovement jump performance (peak power -12.2%; height -14.2%). In both groups, IPFF was reduced between the two measurements of the first day of reambulation. This study indicates that bed rest and countermeasure exercises differentially affect the various functions of skeletal muscle. Moreover, the time course during recovery needs to be considered more thoroughly in future studies, as IPFF declined not only with bed rest but also within the first day of reambulation. RVE was effective in maintaining IPFF but only mitigated the decline in jumping performance. More research is needed to develop countermeasures that maintain muscle strength as well as other muscle functions including power.     

Recovery of walking speed and symmetrical movement of the pelvis and lower extremity joints after unilateral THA

In 17 patients with unilateral hip disease who underwent total hip arthroplasty (THA), the gait was analyzed preoperatively and 1, 3, 6, and 12 months after unilateral THA using a Vicon system to assess the recovery of walking speed and symmetrical movement of the hip, knee, ankle, and pelvis. The walking speed of these patients reached that of normal Japanese persons by 12 months after surgery. Walking speed was correlated with the range of hip motion on the operated side at 1 month postoperatively, and was correlated with the hip joint extension moment of force on both sides from 3 to 6 months after surgery. Before THA, asymmetry was observed in the range of the hip motion, maximum hip flexion, maximum hip extension, maximum knee flexion, as well as in pelvic obliquity, pelvic tilt, and pelvic rotation. There were no differences of the stride length or step length between both sides throughout the observation period. The preoperative range of hip flexion on the operated side during a gait cycle (21.3+/-7.9 degrees ) was significantly smaller than on the non-operated side (46.7+/-7.1 degrees ), and the difference between sides was still significant at 12 months after surgery (35.1+/-6.2 degrees on the operated side and 43.6+/-5.7 degrees on the non-operated side). The majority (74%) of the difference in hip motion range during this period was due to the difference in maximum extension of the hip. The increase in the range of pelvic tilt and the range of motion of the opposite hip showed an inverse correlation with the range of motion of the operated hip, suggesting a compensatory preoperative role. However, this correlation became insignificant after 6 months postoperatively. Asymmetry of the range of hip motion persisted at 12 months after THA in patients with unilateral coxoarthropathy during free level walking, while the operation normalized the spatial asymmetry of other joints and the walking speed prior to the recovery of hip motion.     

Muscle flaps in osteomyelitis of the lower extremity: a 20-year account

Between 1977 and 1993, 64 patients had local muscle flap transposition as an integral portion of treatment for lower-extremity osteomyelitis. All muscle flaps were performed by a single surgeon. There were 54 men and 10 women with an average age of 45 years (range, 16 to 87 years). Median follow-up period was 9.3 years (range, 5 to 21 years). The muscles used included medial gastrocnemius (n = 28), soleus (n = 19), lateral gastrocnemius (n = 13), and peroneus tertius (n = 1). At final follow-up, the recurrence free rates at 5, 10, and 15 years were 94, 92.5, and 86 percent, respectively. These long-term results support the use of local muscle flap transposition as an important management method in the treatment of lower extremity osteomyelitis; however, the risk of treatment failure may arise after extended periods of time.