Sex Differences in Spatiotemporal Gait Parameters of Transtibial Amputees.

Research addressing lower limb amputee gait and prosthetic design often focuses on men, despite female lower limb amputees having different risk factors and lower success with their prosthetics overall. It is widely agreed that sex differences exist in able-bodied gait, but research analyzing sex differences in amputee gait is rare. This study compared male and female transtibial amputee gait to ascertain potential sex differences. Forty-five transtibial amputees were asked to walk at their self-selected speed, and spatiotemporal gait data were obtained. Both the mean and variability metric of parameters were analyzed for 10 male and 10 female participants. For all participants, amputated limbs had a shorter stance time, longer swing time, and larger step length. Females had a 10% shorter stance time and 26% larger normalized step and stride length than males. Female participants also walked over 20% faster than male participants. Finally, significant interactions were found in the mean and variability metric of stride velocity, indicating greater variability in women. These findings suggest that sex differences exist in transtibial amputee gait, offering possible explanations for the different comorbidities experienced by female lower limb amputees. These results have major implications for female amputees and for sex-specific research, rehabilitation, and prosthetic design.

Age-related erosion of obstacle avoidance reflexes evoked with electrical stimulation of tibial nerve during walking.

In young healthy adults, characteristic obstacle avoidance reflexes have been demonstrated in response to electrical stimulation of cutaneous afferents of the foot during walking. It is unknown whether there is an age-related erosion of this obstacle avoidance reflex evoked with stimulation to the tibial nerve innervating the sole of the foot. The purpose of this study was to identify age-dependent differences in obstacle avoidance reflexes evoked with electrical stimulation of the tibial nerve at the ankle during walking in healthy young and older (70 yr and older) adults with no history of falls. Toe clearance, ankle and knee joint displacement and angular velocity, and electromyograms (EMG) of the tibialis anterior, medial gastrocnemius, biceps femoris, and vastus lateralis were measured. A significant erosion of kinematic and EMG obstacle avoidance reflexes was seen in the older adults compared with the young. Specifically, during swing phase, there was reduced toe clearance, ankle dorsiflexion, and knee flexion angular displacement in older adults compared with the young as well as changes in muscle activation. These degraded reflexes were superimposed on altered kinematics seen during unperturbed walking in the older adults including reduced toe clearance and knee flexion and increased ankle dorsiflexion compared with the young. Notably, during mid-swing the toe clearance was reduced in the older adults compared with the young by 2 cm overall, resulting from a combination of 1-cm reduced reflex response in the older adults superimposed on 1-cm less toe clearance during unperturbed walking. Together, these age-related differences could represent the prodromal phase of fall risk. NEW & NOTEWORTHY This study demonstrated age-dependent erosion of obstacle avoidance reflexes evoked with electrical stimulation of the tibial nerve at the ankle during walking. There was significant reduction in toe clearance, ankle dorsiflexion, and knee flexion reflexes as well as changes in muscle activation during swing phase in older adults with no history of falls compared with the young. These degraded reflexes, superimposed on altered kinematics seen during unperturbed walking, likely represent the prodromal phase of fall risk.

Anthropometric and Physical Qualities of International Level Female Rugby Sevens Athletes Based on Playing Position.

Agar-Newman, DJ, Goodale, TL, and Klimstra, MD. Anthropometric and Physical Qualities of International Level Female Rugby Sevens Athletes Based on Playing Position. J Strength Cond Res 31(5): 1346-1352, 2017-The purpose of this study was to profile international level female sevens athletes and determine whether anthropometric and physical qualities are able to differentiate between backs and forwards. Twenty-four subjects with a mean (±SD) age of 22.8 ± 4.0 years and body weight of 69.4 ± 5.2 kg were sampled from a national team training program, ranked in the top 3 on the IRB Women's Sevens World Series. Anthropometric (height, body mass, and sum of 7 skinfolds) and performance measures (power clean, front squat, bench press, neutral grip pull-up, 40-m sprint, and 1,600-m run) were collected across the 2013-2014 centralized period and compared across playing position. The 13 backs (mean age ± SD = 21.3 ± 3.5 years) and 11 forwards (mean age ± SD = 24.5 ± 4.0 years) had significant differences in body mass (66.40 ± 3.48 vs. 72.87 ± 4.79 kg) and initial sprint momentum (366.8 ± 19.8 vs. 399.2 ± 22.4 kg·m·s). However no other measures showed positional differences. The lack of positional differences in female rugby sevens may be due to the multifarious physical requirements of a sevens athlete, leading to a generic athletic profile, or perhaps due to a lack of selective pressure. Also, it is conceivable that the anthropometric and physical qualities measured in this study lacked the necessary precision or failed to capture the unique attributes of each position. In conclusion, this is the first investigation profiling international level female sevens athletes. The normative data presented within this article highlight the physical requirements of female sevens athletes for strength and conditioning practitioners. In addition, the lack of positional differences discovered should impact the training program design.

Efficacy of horizontal jumping tasks as a method for talent identification of female rugby players.

The purpose of this study was to explore the relationship between horizontal jumping tasks (standing long jump [SLJ] and standing triple jump [STJ]) and sprint speed (initial sprint speed [ISS] and maximum sprint speed [MSS]) in elite female rugby athletes. Data were collected from provincial, under 20 international fifteens players, in addition to senior sevens international level female rugby athletes (n = 114). Body weight, SLJ, STJ, 10-m sprint speed (ISS), 30- to 40-m sprint speed (MSS), initial sprint momentum, and maximal sprint momentum were analyzed. When categorized by horizontal jumping ability, there was a significant difference in sprint speeds (p < 0.001) between the top 50% and bottom 50% groups. Examining the relationship between horizontal jumping tasks and sprinting speed revealed a stronger correlation in the slowest 50% of athletes compared with the fastest 50%. A linear regression developed from STJ and body weight adequately predicted ISS (r = 0.645, p < 0.001) and MSS (r = 0.761, p < 0.001). In conclusion, horizontal jumping tasks can be used as a valuable performance test to identify differences of sprinting ability in elite female rugby players. However, the relationship between horizontal jumping tasks and sprinting speed seems to decrease in faster athletes. Further, STJ and body weight can be used to predict both ISS and MSS. Based on these data, it is suggested that only STJ be collected when identifying potential sprinting talent in female rugby athletes and caution be used when generalizing results across varying levels of athletes.

Physical performance and electromyographic responses to an acute bout of paired set strength training versus traditional strength training.

The objective of this study was to investigate the acute effects of performing paired set (PS) vs. traditional set (TS) training over 3 consecutive sets on volume load (VL) and electromyographic (EMG) activity of the pectoralis major, anterior deltoid, latissimus dorsi, and trapezius muscles. Following a familiarization session 16 trained males performed 2 testing protocols using 4 repetition maximum loads: TS (3 sets of bench pull [Bpull] followed by 3 sets of bench press [Bpress] performed in approximately 20 minutes) or PS (3 sets of Bpull and 3 sets of Bpress performed in an alternating manner in approximately 10 minutes). Bpull and Bpress VL decreased significantly from set 1 to set 2 and from set 2 to set 3 under both conditions. There was no difference between VL per set, or over the sessions, between the 2 conditions. PS was determined to be more efficient (VL/time) as compared to TS. EMG activity of the 4 monitored muscles was not different for the 2 conditions or within each condition over the 3 sets. However, there was a significant within-set response in EMG activity in the Bpress exercise. The data suggest that a 4-minute rest interval between sets may not be adequate to maintain VL using either protocol. The data further suggest that PS training may be as effective as TS training in terms of VL maintenance and more effective in terms of efficiency. The comparison of EMG activity between the PS and TS protocols suggests that the level of neuromuscular fatigue does not differ under the 2 conditions. PS training would appear to be an effective method of exercise with respect to VL maintenance and efficiency.

Neuromechanical considerations for incorporating rhythmic arm movement in the rehabilitation of walking.

We have extensively used arm cycling to study the neural control of rhythmic movements such as arm swing during walking. Recently rhythmic movement of the arms has also been shown to enhance and shape muscle activity in the legs. However, restricted information is available concerning the conditions necessary to maximally alter lumbar spinal cord excitability. Knowledge on the neuromechanics of a task can assist in the determination of the type, level, and timing of neural signals, yet arm swing during walking and arm cycling have not received a detailed neuromechanical comparison. The purpose of this research was to provide a combined neural and mechanical measurement approach that could be used to assist in the determination of the necessary and sufficient conditions for arm movement to assist in lower limb rehabilitation after stroke and spinal cord injury. Subjects performed three rhythmic arm movement tasks: (1) cycling (cycle); (2) swinging while standing (swing); and (3) swinging while treadmill walking (walk). We hypothesized that any difference in neural control between tasks (i.e., pattern of muscle activity) would reflect changes in the mechanical constraints unique to each task. Three-dimensional kinematics were collected simultaneously with force measurement at the hand and electromyography from the arms and trunk. All data were appropriately segmented to allow a comparison between and across conditions and were normalized and averaged to 100% movement cycle based on shoulder excursion. Separate mathematical principal components analysis of kinematic and neural variables was performed to determine common task features and muscle synergies. The results highlight important neural and mechanical features that distinguish differences between tasks. For example, there are considerable differences in the anatomical positions of the arms during each task, which relate to the moments experienced about the elbow and shoulder. Also, there are differences between tasks in elbow flexion/extension kinematics alongside differential muscle activation profiles. As well, mechanical assistance and constraints during all tasks could affect muscle recruitment and the functional role of muscles. Overall, despite neural and mechanical differences, the results are consistent with conserved common central motor control mechanisms operational for cycle, walk, and swing but appropriately sculpted to demands unique to each task. However, changing the mechanical parameters could affect the role of afferent feedback altering neural control and the coupling to the lower limbs.

Biomechanical outcomes and neural correlates of cutaneous reflexes evoked during rhythmic arm cycling.

During walking cutaneous stimulation of the foot yields neural and mechanical reflexes that serve a functional purpose to correct or assist the ongoing movement. Concurrently, while cutaneous stimulation of the hand during rhythmic arm movement parallel the neural responses observed in the legs, studies of rhythmic arm movement have only limited mechanical measurements. Therefore it is difficult to determine whether reflex responses in the arms during rhythmic arm movement serve a functional purpose similar to those seen in the lower limbs. The purpose of this study was to explore the mechanical outcomes of stimulating a cutaneous nerve innervating the hand during arm cycling. We hypothesized that there would be measurable mechanical effects to cutaneous stimulation during arm cycling that function to correct or assist the task of arm cycling. Specifically, kinetic responses measured at the handle would be considered assistive if they were tangential to the arm cycling path in the direction of forward progression. Also, limb kinematic responses would be considered corrective if they allowed limb movement that would result in removal of the limb from stimulus while not altering the kinetic profile at the handle necessary for arm cycling progression. Participants performed seated arm cycling while EMG was recorded from the arm and trunk muscles, kinematic data was recorded from the right arm, and kinetic data was recorded from the handle. Cutaneous reflexes were evoked by stimulating the superficial radial nerve. The results show that there are observable mechanical responses to cutaneous stimulation of the hand during arm cycling. Subjects responded to cutaneous stimulation of the hand during arm cycling with significant changes in backward and lateral forces at the handle as well as wrist abduction/adduction and wrist flexion/extension kinematics. These responses, related to the task and phase of movement, are consistent with the anatomical location of the stimulus and are correlated to the neural responses. Therefore, these responses are comparable to functionally relevant responses in the legs during rhythmic movement. However, while there is a single observation of a kinematic corrective strategy, the kinetics measured at the handle are not tangential to the arm cycling path and therefore not considered an assistive response. Therefore, unlike the observations in the lower limbs, the mechanical responses during arm cycling are not clearly related to the functional context of the ongoing task.