Age-related changes in upper body contribution to braking forward locomotion in women

Introduction Gait termination is a transitory task that requires the lower body to produce braking forces and inhibit forward propulsion. However, it is still unknown whether the upper body plays an active role in braking of gait and whether this mechanism is impaired with ageing. Research question Do older women exhibit an impaired control of upper body segments during gait termination with respect to young women? Methods Ten young and 10 older women performed three gait termination trials at comfortable speed while fixing the gaze on a visual target. A 3D motion analysis system was used to measure head, trunk and pelvis angular displacement and velocity, and estimate neck, waist and hip moments through Plug-in Gait modeling. Cross-correlation analysis of kinematic waveforms between paired adjacent segments (head-trunk and trunk-pelvis) was performed to investigate upper body coordination. Surface EMG activity of erector spinae (L3), sternocleidomastoid and neck extensor muscles was recorded. Statistics was carried out by MANOVA. Results Older participants exhibited delayed peak extensor torques of neck, waist and hip compared to young participants, along with lower progression speed. Both groups showed a slight flexion of the trunk counteracted by a backward tilt of head and pelvis during braking. In addition, older women displayed a peculiar upper body coordination pattern, with the head coupling with trunk motion, as shown by cross-correlation. Older women displayed shorter lumbar erector spinae onset latency relative to last heel contact than young (16 ± 68 ms vs 92 ± 37 ms). Significance The upper body plays an active role in the braking of gait and this mechanism is impaired in older women. Moreover, the age-related coupling of head and trunk motion may produce an unbalancing effect on whole-body stability during the braking mechanism, thus leading to a higher risk of falls

Comparison of walking energy cost between an anterior and a posterior ankle-foot orthosis in people with foot drop.

To compare walking energy cost between an anterior and a posterior ankle-foot orthosis in people with foot drop.Within-group comparisons.Twenty-three adults (14 women, 9 men; mean age 56.8 years (standard deviation 15.4)) with foot drop.PARTICIPANTS were asked to walk for 5 min at their self-selected walking speed under 3 conditions: (i) with shoes only; (ii) with a posterior ankle-foot orthosis; (iii) with an anterior ankle-foot orthosis. Spatio-temporal gait para-meters (speed, step length and step frequency) and walking energy cost per unit of distance were assessed for each walking condition. A visual analogue scale was used to quantify participants' level of perceived comfort for the 2 orthosis.Gait spatio-temporal parameters were higher with anterior ankle-foot orthoses than with posterior ankle-foot orthoses or shoes only. Walking energy cost per unit of distance was lower with anterior than posterior ankle-foot orthosis or shoes only ((mean ± standard error) 3.53 ± 1.00 vs 3.94 ± 1.27 and 3.98 ± 1.53 J·kg-1·m-1 respectively; p  0.05) and level of perceived comfort was higher with anterior ((mean ± standard error) 8.00 ± 1.32) than with posterior ankle-foot orthosis ((mean ± standard error) 4.52 ± 2.57; p  0.05).In people with foot drop the use of anterior ankle-foot orthoses resulted in lower energy costs of walking and higher levels of perceived comfort compared with posterior ankle-foot orthoses. Anterior ankle-foot orthoses may enable people with foot drop to walk further with less physical effort than posterior ankle-foot orthoses

No Relationship Between Preoperative and Early Postoperative Strength After ACL Reconstruction

Context: All rehabilitative programs before ACL reconstructive surgery, which are focused on recovery of proprioception and muscular strength, are defined as prehabilitation. While it has shown that prehabilitation positively affects the overall outcome after ACL reconstruction, it is still controversial whether enhancing preoperatively quadriceps strength has some beneficial effect on postoperative strength, mainly during the first period. Objective: To determine whether there is any relationship between pre- and early postoperative quadriceps strength. Design: Case control. Setting: University research laboratory. Participants: Fifty-nine males (18-33 y; age: 23.69 (0.71) y) who underwent ACL reconstruction with patellar-tendon autograft were examined the day before surgery, at 60 and at 90 days after surgery. Main Outcome Measures: The limb-symmetry-index (LSI) was quantified for maximal voluntary isometric contraction (MVIC) of the knee extensor muscles and of the knee flexor muscles at 90° joint angle. K-means analysis was performed on either quadriceps or hamstrings LSI before surgery to classify the patients in high and low preoperative LSI clusters. Differences in postoperative LSI were then evaluated between the high and low preoperative LSI clusters. Results: Following surgery, there were no differences in the quadriceps LSI between patients with high and low preoperative quadriceps LSI. Sixty days after surgery, the hamstrings LSI was higher in patients with high than low preoperative hamstrings LSI (84.0±13.0% vs 75.4±15.9%; P<0.05). Conclusions: Findings suggest that quadriceps strength deficit is related to the ACL injury and increases further after the reconstruction without any correlation between the pre-operative and postoperative values. Therefore, it appears that there is no need to delay surgery in order to increase the preoperative quadriceps strength before surgery

Quadriceps muscle compensatory activations are delayed following anterior cruciate ligament reconstruction using hamstring tendon graft

Objective: To investigate compensatory and anticipatory quadriceps muscle activations before and after anterior cruciate ligament reconstruction (ACLR) using hamstrings tendon graft. Design:Twelve participants who underwent ACLR and 12 healthy controls were exposed to 10 either unpredictable or predictable perturbations of the knee joint before ACLR (T1), 2 months (T2) and 6 months (T3) after surgery. Latencies of compensatory and anticipatory postural activations in the vastus lateralis (VL), rectus femoris (RF) and vastus medialis (VM) muscles were recorded by surface electromyography with respect to the arrival of the perturbations. Results:Latency of compensatory activations was significantly delayed in ACLR compared to that in healthy participants at T1 for VL (105 ± 25 vs. 57 ± 9 ms; P<0.001), RF (102 ± 23 vs. 56 ± 9 ms; P<0.001) and VM (107 ± 24 vs. 66 ± 16 ms;P<0.001), at T2 for VL (68 ± 14 vs. 55 ± 10 ms;29 P<0.01) and at T3 for VL (105 ± 22 vs. 58 ± 7 ms;P<0.001), RF (102 ± 22 vs. 58 ± 12 ms; P<0.001) and VM (106 ± 20 vs. 63 ± 8 ms;P<0.001). Anticipatory activations occurred earlier in ACLR than in healthy participants at T1 for VL (-82 ± 64 vs. -14 ± 11 ms; P<0.05) and VM (-105 ± 32 68 vs. -9 ± 12 ms;P<0.05). Conclusion:While anticipatory quadriceps activations show no alterations, compensatory muscle activations are delayed following ACLR with hamstring graft. Post-surgical rehabilitation should address alterations in compensatory lower limb postural control

Asymmetrical lower extremity loading early after ACL reconstruction is a significant predictor of asymmetrical loading at the time of return to sport

OBJECTIVES: The aim of this study was to examine whether asymmetrical lower limb loading early after anterior cruciate ligament reconstruction (1 mo) can predict asymmetrical lower limb loading at the time of return to sport (6 mos) and whether other early predictors as knee joint range of motion or maximal isometric strength affect this relationship. DESIGN: Ground reaction forces were measured during a sit-to-stand task 1 mo after anterior cruciate ligament reconstruction and a vertical countermovement jump 6 mos after anterior cruciate ligament reconstruction in 58 athletes. Other early postoperative measurements were knee joint range of motion (2 wks, 1 mo, and 2 mos after surgery) and maximal isometric strength of the knee extensor and flexor muscles (2 mos after surgery). Linear regression models were developed using side-to-side limb symmetry index (LSI) of countermovement jump as the dependent variable. RESULTS: LSI of sit-to-stand task 1 mo after surgery was a significant independent predictor of LSI of countermovement jump 6 mos after surgery. After accounting for deficits in knee joint range of motion and LSI of maximal isometric strength (ΔR² = 0.35, P < 0.01), LSI of sit-to-stand task predicted LSI of countermovement jump (ΔR² = 0.14 P < 0.01). CONCLUSIONS: Asymmetrical lower extremity loading 1 mo after anterior cruciate ligament reconstruction is an early predictor of asymmetrical lower extremity loading 6 mos after surgery

Non-specific chronic low back pain elicits kinematic and neuromuscular changes in walking and gait termination

Background: Chronic low back pain (CLBP) is associated with an increased trunk stiffness and muscle coactivation duringwalking. However, it is still unclear whether CLBP individuals are unable to control neuromechanically their upper body motion during a sudden termination of gait (GT), which involves achallenging balancetransition from walking to standing.Research question: Does CLBP elicit neuromuscular and kinematic changes which are specific towalking and GT?Methods: Eleven individuals with non-specific CLBP and 11 healthy controls performed walking and sudden GT in response to an external visual cue. 3D kinematiccharacteristicsof thorax, lumbar and pelvis wereobtained, with measures of range of motion (ROM) and intra-subject variability of segmental movement being calculated. Electromyographic activity of lumbar and abdominal muscles was recorded to calculate bilateral as well as dorsoventral muscle coactivation.Results: CLBP group reported greater transverseROM of the lumbar segment during walking and GTcompared to healthy controls. Thorax sagittal ROM was higher in CLBP than healthy participants during GT. Greater overall movement variability in the transverseplane was observed in the CLBP group while walking, whereas GT produced greater variability of lumbar frontal motion. CLBP participants showed higher bilateral lumbar coactivation compared to healthy participants after the stopping stimulus delivery during GT.Significance: These results suggest that CLBP can elicit a wider and more variable movement of the upper body during walking and GT, especially in the transverseplane and at lumbar level. Alterations in upper body motor control appeared to depend on task, plane of motion and segmental level. Therefore, these findings should be considered by practitioners when screening before planning specific training interventions for recovery of motor control patterns in CLBP population

Association between physical activity levels and physiological factors underlying mobility in young, middle-aged and older individuals living in a city district

Maintaining adequate levels of physical activity is known to preserve health status and functional independence as individuals grow older. However, the relationship between determinants of physical activity (volume and intensity) and physiological factors underlying mobility (cardio-respiratory fitness, neuromuscular function and functional abilities) is still unclear. The aim of this study was to investigate the association between objectively quantified physical activity and a spectrum of physiological factors underlying mobility in young, middle-aged and older individuals living in a city district. Experiments were carried out on 24 young (28±2 years), 24 middle-aged (48±2 years) and 24 older (70±3 years) gender-matched volunteers. Physical activity was monitored by a wearable activity monitor to quantify volume and intensity of overall physical activity and selected habitual activities over 24 hours. Ventilatory threshold was assessed during an incremental cycling test. Torque, muscle fiber conduction velocity and agonist-antagonist coactivation were measured during maximal voluntary contraction of knee extensors and flexors. Ground reaction forces were measured during sit-to-stand and counter-movement jump. K-means cluster analysis was used to classify the participants’ physical activity levels based on parameters of volume and intensity. Two clusters of physical activity volume (i.e., high and low volume) and three clusters of physical activity intensity (i.e. high, medium and low intensity) were identified in all participants. Cardio-respiratory fitness was associated with volume of overall physical activity as well as lying, sitting, standing, walking and stair climbing. On the other hand, neuromuscular function and functional abilities showed a significant association with intensity of overall physical activity as well as postural transition, walking and stair climbing. As a practical application, the relative role played by volume and intensity of overall physical activity and selected habitual activities should be taken into account in the design of preventative training interventions to preserve mobility as individuals grow older

Age differences in anticipatory and executory mechanisms of gait initiation following unexpected balance perturbations

Purpose. An age-related decline in anticipatory postural mechanisms has been reported during gait initiation; however, it is unclear whether such decline may jeopardize whole-body stability following unexpected balance perturbations. This study aimed to compare young and older individuals’ ability to generate postural responses and preserve stability in response to external waist perturbations delivered within gait initiation. Methods. Ten young and ten older participants performed 10 gait initiation trials followed by 48 unperturbed and 12 perturbed trials in a random order. A stereophotogrammetric system and three force platforms were used to quantify mechanical parameters from the preparatory phase (e.g., timing and amplitude of postural adjustments) and from the stepping phase (e.g., step characteristics and dynamic stability). Activation patterns of lower leg muscles were determined by surface electromyography. Results. Older participants responded to perturbation with lower increase in both magnitude (p<0.001; η 2 p=0.62) and duration of (p=0.001; η 2 p=0.39) preparatory parameters and soleus muscle activity (p<0.001; η 2 p=0.55), causing shorter (p<0.001; η 2 p=0.59) and lower (p<0.001; η 2 p=0.43) stepping, compared to young participants. Interestingly, young participants showed greater correlations between preparatory phase parameters and dynamic stability of the first step than older participants (average r of -0.40 and -0.06, respectively). Conclusion. The results suggest that young participants took more time than older to adjust the anticipatory biomechanical response to perturbation attempting to preserve balance during stepping. In contrast, older adults were unable to modify their anticipatory adjustments in response to perturbation and mainly relied on compensatory mechanisms attempting to preserve stability via a more cautious stepping strategy

Effects of Functional Electrical Stimulation Cycling of Different Duration on Viscoelastic and Electromyographic Properties of the Knee in Patients with Spinal Cord Injury

The benefits of functional electrical stimulation during cycling (FES-cycling) have been ascertained following spinal cord injury. The instrumented pendulum test was applied to chronic paraplegic patients to investigate the effects of FES-cycling of different duration (20-min vs. 40-min) on biomechanical and electromyographic characterization of knee mobility. Seven adults with post-traumatic paraplegia attended two FES-cycling sessions, a 20-min and a 40-min one, in a random order. Knee angular excursion, stiffness and viscosity were measured using the pendulum test before and after each session. Surface electromyographic activity was recorded from the rectus femoris (RF) and biceps femoris (BF) muscles. FES-cycling led to reduced excursion (p < 0.001) and increased stiffness (p = 0.005) of the knee, which was more evident after the 20-min than 40-min session. Noteworthy, biomechanical changes were associated with an increase of muscle activity and changes in latency of muscle activity only for 20-min, with anticipated response times for RF (p < 0.001) and delayed responses for BF (p = 0.033). These results indicate that significant functional changes in knee mobility can be achieved by FES-cycling for 20 min, as evaluated by the pendulum test in patients with chronic paraplegia. The observed muscle behaviour suggests modulatory effects of exercise on spinal network aimed to partially restore automatic neuronal processes

Neuromechanics of repeated stepping with external loading in young and older women

An understanding of the neuromechanical responses to bench stepping with external loading is important for exercise prescription, especially in older women who are more at risk than men for disability. This study was designed to describe and compare such responses to repeated bench stepping with external loading between young and older women. Eight young (25 ± 2.7 years) and nine older (70 ± 3.3 years) medically stable women performed repeated stepping on a bench of either 20 or 25 cm either unloaded or with 2.5, 5, 7.5 or 10 % of body mass (BM) incorporated into a weighted vest. Ground reaction forces, peak power output and agonist-antagonist neuromuscular activation around the knee joint were evaluated. Peak power output was 44 % lower in the older than in the younger women. At a step height of 25 cm, peak power (PP) in the young women was 7 % greater with an external load of 7.5 % body mass compared with no loading, while in the older women there was a tendency for PP to be higher with an external load of 2.5 % body mass. Neuromuscular activation of the vastus lateralis muscle was 60 % higher in the older than in the young women. Older women performed repeated weighted-vest stepping with lower power output but greater knee muscle activation compared to younger counterparts. Peak power output during stepping may be achieved at 7.5 % BM loading in young women and either 2.5 or 10 % BM in older women, depending on desired step height