Non-preferred Leg Research Articles

Kinematic comparison of the preferred and non-preferred foot punt kick

Kicking with the non-preferred leg is important in Australian Football and becoming important in the rugby codes. The aim of this study was to examine differences between preferred and non-preferred leg kicking in the drop punt kick. Seventeen elite Australian Football players performed kicks with the preferred and non-preferred leg. Optotrak Certus collected kinematic data of the kick leg and pelvis (200 Hz) from kick leg toe-off until ball contact. Foot speed, knee and shank angular velocity at ball contact, and pelvis range of motion were significantly larger for the preferred leg (P < 0.05). In contrast, hip and thigh angular velocity at ball contact and hip range of motion were significantly larger for the non-preferred leg. This indicates different movement patterns, with preferred-leg kicks making greater use of the pelvis, knee, and shank while non-preferred leg kicks rely relatively more on the hip and thigh (P < 0.05). Reasons for this difference might be due to locking degrees of freedom or sub-optimal sequencing in the non-preferred leg. The thigh–knee continuum identified by Ball (2008) was also evident in this study. Findings have implications for training non-preferred leg kicking for performance and injury prevention.

An Obese Body Mass Increases the Adverse Effects of HIV/AIDS on Balance and Gait

Balance and gait problems have been detected among patients with HIV/AIDS. The extent to which these problems are exacerbated by either frailty or obesity has not been examined. Objective The purpose of this study was to compare participants who differed in body mass and the presence or absence of HIV/AIDS. This was a cross-sectional study. Quantitative measurements were obtained from 86 participants who were HIV-type 1 (HIV-1) seronegative and 121 participants who were seropositive divided into subgroups based on their body mass index (BMI <21, 21-29, or >29 kg/m(2)). Participants who were seropositive were impaired relative to seronegative controls on several indices, including the limit of stability, sway amplitude and sway strategy, gait initiation time, and gait speed during a fast pace condition. Participants who were obese also exhibited impairments, which were evident during assessments of the limit of stability, nonpreferred leg stance time, sway strategy, normal and fast gait speed, fast gait initiation time, and 360-degree turn time. Importantly, the analysis revealed that participants with both attributes were more impaired than those with either or neither attribute: patients who were obese and seropositive were more impaired in fast gait initiation time and cadence, nonpreferred leg stance time, 360-degree turn time, and sway strategy scores. Limitations The validity of BMI as a measure of body mass can be challenged. In addition, the validity of chair rise time and 360-degree turn time as estimates of lower-extremity strength (force-generating capacity) can be argued. The present findings have an obvious and unfortunate implication: as more patients who are HIV-1 seropositive join the seronegative community in becoming obese, the effects of obesity and their disease may summate and their risk for balance and gait problems may increase.

Influence of leg preference on bilateral muscle activation during cycling

The purpose of this study was to investigate asymmetry of muscle activation in participants with different levels of experience and performance with cycling. Two separate experiments were conducted, one with nine cyclists and one with nine non-cyclists. The experiments involved incremental maximal and sub-maximal constant load cycling tests. Bilateral surface electromyography (EMG) and gross and net muscle efficiency were assessed. Analyses of variance in mixed linear models and t-tests were conducted. The cyclists in Experiment 1 presented higher gross efficiency (P < 0.05), whereas net efficiency did not differ between the two experiments (21.3 ± 1.4% and 19.8 ± 1.0% for cyclists and non-cyclists, respectively). The electrical muscle activity increased significantly with exercise intensity regardless of leg preference in both experiments. The coefficient of variation of EMG indicated main effects of leg in both experiments. The non-preferred leg of non-cyclists (Experiment 2) presented statistically higher variability of muscle activity in the gastrocnemius medialis and vastus lateralis. Our findings suggest similar electrical muscle activity between legs in both cyclists and non-cyclists regardless of exercise intensity. However, EMG variability was asymmetric and appears to be strongly influenced by exercise intensity for cyclists and non-cyclists, especially during sub-maximal intensity. Neural factors per se do not seem to fully explain previous reports of pedalling asymmetries.

Control of medio-lateral stability during rapid voluntary step initiation with preferred and non-preferred leg: is it symmetrical?

Control of medio-lateral stability during rapid voluntary step initiation with preferred and non-preferred leg: is it symmetrical?

Does leg preference affect muscle activation and efficiency?

The aim of this study was to investigate the effect of leg preference and cycling experience on unilateral muscle efficiency and muscle activation. To achieve this purpose, two experiments were performed. Experiment 1 involved eight cyclists and experiment 2 included eight non-cyclists. Subjects underwent an incremental maximal test and submaximal trials of one-legged cycling for preferred and non-preferred leg. Oxygen uptake and muscle efficiency were compared between legs. The magnitude of muscle activation (RMS) and the inter-limb excitation were monitored for the vastus lateralis, biceps femoris and gastrocnemius (medial head) muscles during one-legged cycling with preferred and non-preferred leg. Variables of muscle activation, oxygen uptake and muscle efficiency (gross and net) did not differ between legs ( P > 0.05). The magnitude of muscle activation and its variability were similar between legs while performing the unilateral pedaling. Inter-limb communication did not differ between experiments ( P > 0.05). Similar activation between legs was consistent with the influence of bilateral practice for attaining similar performance between sides. These results do not support asymmetry in magnitude of muscle activation during pedaling.

Control of mediolateral stability during rapid step initiation with preferred and non-preferred leg: Is it symmetrical?

During voluntary stepping initiation, postural stability along the mediolateral direction is controlled via “anticipatory postural adjustment” (APA). This study tested the hypothesis that, in young healthy subjects, the biomechanical features of mediolateral APA depend on the leg that initiates stepping. Subjects ( N = 10) initiated a rapid single step with the preferred (P condition) and the non-preferred leg (NP condition) on a force-plate. Results showed that mediolateral APA duration ( P = 0.020) and amplitude were higher (as attested by the increase in maximal center-of-gravity velocity ( P = 0.003) and displacement ( P < 0.001) during APA), and that mediolateral stability was better (as attested by the attenuation in center-of-gravity velocity at time of swing-foot contact ( P = 0.007)) in P than in NP. These results support the view that stepping initiation in healthy subjects involves postural asymmetry. This statement may have relevant implications in clinical evaluation where postural asymmetry is generally considered as reflecting postural impairment.

The epidemiology of knee injuries in Iranian male professional soccer players

Detailed injury epidemiology is an invaluable tool for minimising risk associated with sporting injuries. The aim of this study was to investigate epidemiology of knee injuries in Iranian male professional soccer players. In total, 390 soccer players of 16 clubs were studied during one season. A total of 43 injured soccer players were interviewed and 16 team physicians were consulted. All information was collected through standard questionnaires. Furthermore, medical personal prospectively reported time-loss injuries sustained by players over one season and the knee injuries were evaluated. The results showed that in total, from 390 players, 43 of them suffered knee injuries (14.9 per 100 players). The anterior cruciate ligament was the most commonly injured ligament of the knee, in which 12.5% were accompanied by injuries to the medial meniscus and medial collateral ligament. There was a significant difference in incidence of injury between the preferred (62.9%) and non-preferred leg (37.1%). Most injuries were characteristically severe (82.3%). Most injuries occurred in away games (52.94%), mostly in the second half and most commonly in the final 15 min (35.3%). The incidence of non-contact injuries (66.12%) was significantly higher than contact injuries (33.87%). It can be concluded that the incidence of knee injury was high (0.12 injuries per team per match). Injury tends to be more common in match play and mostly at the end of season. Midfielders suffered more knee injuries. Most injuries occurred in the losing teams.

Balance Ability and Muscle Response of the Preferred and Nonpreferred Leg in Soccer Players

The aim of this study was to evaluate balance abilities and electromyographic (EMG) latency times of the preferred and nonpreferred leg in soccer players. Whereas side differences between the two legs in force, kicking speed, and joint laxity have been demonstrated in athletes in previous studies, no data are so far available on balance differences. Low balance ability is generally associated with an increased risk of ligament injuries, and the detection of a possible asymmetry in balance is important because a bilateral difference may be a contributing factor to injury. Twenty-one amateur soccer players were tested. Two different balance test instruments were used: the Biodex Stability System and the Tetrax System. For the evaluation of muscle latency times, EMGs were recorded by means of the EquiTest system. None of the tests performed in this study revealed statistically significant differences in balance ability between the preferred and the nonpreferred leg. The investigations of balance function and muscle response in amateur soccer players did not reveal significant differences between the preferred and nonpreferred leg in the current study. However, a certain tendency to better balance in the nonpreferred leg was observed.

Years of Training and Hamstring-Quadriceps Ratio of Soccer Players

To investigate the effect of the years of training on the hamstring-quadriceps isokinetic strength and establish normative data for the cardiorespiratory fitness of first and second division Greek male professional soccer players (M=25.1, SD=5.1 yr.) a representative sample of 72 soccer players was chosen randomly from six teams of these divisions. Hamstring-quadriceps ratios of the preferred and nonpreferred leg correlated with years of training weekly (r = .51) in the preferred leg. In conclusion, data indicated that the training background of the players (years of training) might have a small effect on the strength balance of quadriceps and hamstrings of the preferred leg.

MUSCLE DYNAMICS DIFFERENCES BETWEEN LEGS IN HEALTHY ADULTS

Differences in muscle dynamics between the preferred and nonpreferred jumping legs of subjects in maximal, explosive exercise were examined. Eight subjects performed nonfatiguing bouts of single-legged drop jumps and rebound jumps on a force sledge apparatus. Measures of flight time, reactive strength index, peak vertical force, and vertical leg-spring stiffness were obtained for 3 drop jumps and 3 rebound jumps on both legs. Subjects utilized a stiffer leg spring and a more explosive jumping action in the nonpreferred leg when performing a cyclical rebound jumping task in comparison to a single drop jump task (observed through differences in vertical leg-spring stiffness, peak vertical force, and reactive strength index, p < 0.05). The preferred leg performed equally well in both tasks. Between-leg analysis showed no differences in dependent variables between the preferred and the nonpreferred leg in the rebound jumping protocol. However, the drop jump protocol showed significant performance differences, with flight time and reactive strength index greater in the preferred leg than the nonpreferred leg (p < 0.05). We hypothesize that, throughout the lifespan, both legs are equally trained in cyclical rebound jumping tasks through running. However, because a preferred leg must be selected when performing any one-off, single-legged jump, imbalances in this specific task develop over time with consistent selection of a preferred jumping leg. The data demonstrate that the rebound jump protocol is representative of the symmetrical mechanics of forward running and that leg-spring stiffness is modulated depending on the demands of the specific task involved. Strength and conditioning practitioners should give careful consideration to appropriate jump protocol selection and should exercise caution when comparing laboratory results to data gathered in field testing.

Segmental dynamics of soccer instep kicking with the preferred and non-preferred leg

Detailed time-series of the resultant joint moments and segmental interactions during soccer instep kicking were compared between the preferred and non-preferred kicking leg. The kicking motions of both legs were captured for five highly skilled players using a three-dimensional cinematographic technique at 200 Hz. The resultant joint moment (muscle moment) and moment due to segmental interactions (interaction moment) were computed using a two-link kinetic chain model composed of the thigh and lower leg (including shank and foot). The mechanical functioning of the muscle and interaction moments during kicking were clearly illustrated. Significantly greater ball velocity (32.1 vs. 27.1 m · s−1), shank angular velocity (39.4 vs. 31.8 rad · s−1) and final foot velocity (22.7 vs. 19.6 m · s−1) were observed for the preferred leg. The preferred leg showed a significantly greater knee muscle moment (129.9 N · m) than the non-preferred leg (93.5 N · m), while no substantial differences were found for the interaction moment between the two legs (79.3 vs. 55.7 N · m). These results indicate that the highly skilled soccer players achieved a well-coordinated inter-segmental motion for both the preferred and non-preferred leg. The faster leg swing observed for the preferred leg was most likely the result of the larger muscle moment.

A comparison of muscle strength and flexibility between the preferred and non-preferred leg in English soccer players

Most soccer players have a favoured foot for kicking the ball, and it is believed that this preference may lead to an asymmetry in the strength and flexibility of the lower extremities. This study was designed to determine whether asymmetry in strength and flexibility are present in the legs of soccer players. Forty-one elite and sub-elite soccer players (age 23.4 ± 3.8 years; height 1.81 ± 0.06 m; body mass 81.7 ± 9.9 kg) were studied (data are presented as mean ± SD). The dynamic strength of knee flexors (hamstrings) and knee extensors (quadriceps) was measured using an isokinetic dynamometer at angular velocities of 1.05, 2.09, 5.23 rad/s (in a concentric mode) and 2.09 rad/s (in an eccentric mode). The concentric strength ratio (hamstringsconc/quadricepsconc) and the dynamic control ratio (hamstringsecc/quadricepsconc) were computed. Hip joint flexibility (in flexion) was measured using a goniometer. A significant difference between the preferred and non-preferred leg was found in the knee flexors at 2.09 rad/s (119 ± 22 versus 126 ± 24 Nm; P < 0.05) and for the dynamic control ratio (0.79 ± 0.13 versus 0.84 ± 0.16 Nm; P < 0.05). In both cases the knee flexors of the preferred leg were weaker than those of the non-preferred leg. A total of 28 of the 41 players (68%) had significant musculoskeletal abnormality (imbalance >10%) in one or more specific muscle groups. No significant differences were found in flexibility of the hip joint between the preferred and non-preferred leg (P > 0.05). It is concluded that the lower strength of the knee flexor muscles of the preferred leg may be associated with the differential use of these muscle during the kicking action and thus constitutes a unique training effect associated with soccer. This in turn can lead to muscular imbalance which is generally regarded as an injury risk factor.

Temporal differences in relative phasing of gait initiation and first step length in patients with cervical and lumbosacral spinal cord injuries

Comparison group design. To compare the temporal distance factors during gait initiation between patients with incomplete cervical spinal cord injury, incomplete lumbosacral spinal lesion, and unimpaired control adults. Human performance and movement analysis laboratory, Taiwan. Five patients with an incomplete cervical spinal cord injury (Group 1), five patients with an incomplete lumbosacral spinal lesion (Group 2) and nine unimpaired control adults (Group 3). Subjects underwent a three-dimensional gait analysis. The total gait initiation period, reaction time, each relative phasing of gait initiation and the length of the first step were identified by using the kinematic measurement system. The total gait initiation period (start of the auditory cue for gait initiation to heel-strike of the first swing leg); each relative phasing of gait initiation indicated that the duration of the preparatory phase (start of auditory cue for gait initiation to heel-off of the first swing leg), the duration of the push-up phase (heel-off to toe-off of the first swing leg), and the duration of the single-stance phase (toe-off to heel-strike of the first swing leg) established by the total gait initiation period; and the length of the first step. The gait initiation period was greater in Groups 1 and 2 than that of Group 3 (P<0.05). Each relative phasing including the duration of the preparatory phase, the push-up phase, and the swing phase relative to the total gait initiation period, did not differ among Groups 1-3 (P>0.05). The length of the first step, measured while the nonpreferred leg stepped first in Groups 1 and 2, was shorter than that of Group 3 (P<0.05). Patients with incomplete cervical spinal cord injuries or lumbosacral spinal lesions took more time in gait initiation than unimpaired control adults. The first step length also reduced in these patients while the nonpreferred leg stepped first, as compared to unimpaired control adults. The data indicated that centrally programmed gait initiation might be preserved in ASIA-D spinal patients who, in this study, executed gait initiation with varying temporal distance strategies to compensate for peripheral impairments, as compared to unimpaired control adults.

Static balance in children with hand-eye co-ordination problems.

The aim of the present study was to examine static balance on one leg in 10-year-old children with and without hand-eye co-ordination problems (HECP) in an attempt to come closer to an understanding of developmental co-ordination disorder in children. The children were compared on three different balance tasks with the right and/or left leg together with a systematic manipulation of vision. The results showed that when the scores for both legs were combined, the control group, in general, had superior performance in all conditions. Separate preferred and non-preferred leg analyses demonstrated that the differences between the HECP group and control group could be accounted for by lowered performances when the non-preferred leg was used in only one static balance task, stork stand with vision. In the two other balance tasks, balance on beam and one-board balance, the HECP group displayed significantly worse performance than the control group irrespective of the use of the preferred or non-preferred leg. Explanation related to the development of the hemispheres controlling the preferred and non-preferred leg is invoked to account for the poor performance in the HECP group.

Static balance and developmental coordination disorder

The development of static balance is a basic characteristic of normal motor development. Most of the developmental motor tests include a measure of static balance. Children with a developmental coordination disorder (DCD) often fail this item. Twenty-four children at risk for DCD with balance problems (DCD-BP) and 24 matched control children in the age range of 6–12 years participated in a detailed study of balance control. Additional groups of children (6–7 years, N=25; 10–11 years, n=16; with M-ABC scores >15th percentile) were selected randomly to study developmental changes in balance control in the age range of interest. Three experiments were conducted to examine developmental and clinical differences in the control of static balance. In the first, we measured the excursion of the centre of pressure (force-plate) in conditions with and without vision while standing still on one or two legs for 20 s. In the second experiment, EMGs were measured while standing on one leg. In the third experiment, in which only a subgroup of the DCD-BP and matched control children participated, a short unexpected force in the back lightly perturbed normal standing and EMG and force-plate responses were measured during balance recovery. In conditions of one-leg stance, children were not always able to maintain balance. Only epochs of stable postural control (7.5–20 s) were analysed. The results showed improvement of static balance with age, but only subtle differences between the DCD and control groups. Centre of pressure measures differed in the more difficult conditions. DCD-BP children had more difficulty standing on one leg with eyes closed. While standing on the non-preferred leg the EMGs of the DCD-BP children showed slightly more co-activation of the muscles of lower and upper leg. Perturbation of standing resulted in longer duration of recovery in the first trial in this group. Apparently DCD children learn to compensate for the perturbation within a few trials as well as control children do. The clear improvement with age shows that our measures of balance control are sensitive to detect changes. The general conclusion that may be drawn from this study is that under normal conditions static balance control is not a problem for children with DCD. Only in difficult or novel situations they seem to suffer from increased postural sway as a result of non-optimal balance control.

Reduction of lateral asymmetries in dribbling: The role of bilateral practice

The influence of bilateral practice on the modification of well-established lateral asymmetries of performance was investigated in overlearned motor skills related to soccer in 12- to 14-year-old adolescent players. The participants had extensive practice before entering the experiment and were trained 2 hours per day, five times per week, during a period of 4 months. In the training, the participants were assigned to one of two groups: practice with emphasis on the preferred leg (PL), or practice with emphasis on the nonpreferred leg (NpL). Lateral asymmetries of performance were assessed before and after training on three motor tasks: kicking for force, kicking for accuracy, and speed of dribbling. The analysis of the results indicated a consistent asymmetry of performance throughout the tests, favouring the preferred leg. The asymmetry of performance was maintained at a constant level across the tests for the kicking tasks in both experimental groups. For speed of dribbling, however, the index of lateral asymmetry was reduced from the pre- to the post-test in the NpL group only, which was due to a higher rate of improvement with the nonpreferred leg after the experimental training. These results are indicative of the role played by bilateral practice in modifying lateral asymmetries of performance established as a consequence of previous unilateral training.

Biomechanical differences in soccer kicking with the preferred and the non-preferred leg

The aims of this study were to examine the release speed of the ball in maximal instep kicking with the preferred and the non-preferred leg and to relate ball speed to biomechanical differences observed during the kicking action. Seven skilled soccer players performed maximal speed place kicks with the preferred and the nonpreferred leg; their movements were filmed at 400 Hz. The inter-segmental kinematics and kinetics were derived. A coefficient of restitution between the foot and the ball was calculated and rate of force development in the hip flexors and the knee extensors was measured using a Kin-Com dynamometer. Higher ball speeds were achieved with the preferred leg as a result of the higher foot speed and coefficient of restitution at the time of impact compared with the non-preferred leg. These higher foot speeds were caused by a greater amount of work on the shank originating from the angular velocity of the thigh. No differences were found in muscle moments or rate of force development. We conclude that the difference in maximal ball speed between the preferred and the non-preferred leg is caused by a better inter-segmental motion pattern and a transfer of velocity from the foot to the ball when kicking with the preferred leg.

Transfer and motor skill learning in association football

Transfer of learning involves the influence of previous experiences on the performance or learning of new skills. It is defined as a gain (or loss) in the capability for performance on one task as a result of practice on another. The aim of the study was to examine the degree of transfer between various association football skills. Twenty intermediate male players participated in the study. During pre- and post-training tests, participants juggled a football as many times as possible within 30 s using feet or knees. Further tests required participants to control an approaching football inside a restricted area using the preferred and non-preferred kicking leg. Following performance on the pretest, two matched skill groups were obtained. One group participated in a 4-week training period in which feet-only ball juggling was practised for 10 min daily, while the remaining group acted as a control. Trained participants exhibited superior post-test performance on knee juggling and ball control with preferred and non-preferred leg tasks relative to the control group (p< 0.05). Findings indicate positive transfer of learning from juggling practice with the feet to juggling with the knees and a football control task. Implications for theory and practice are highlighted.

Changes in Resultant Pedal Reaction Forces Due to Ankle Immobilization during Pedaling

The purpose of this study was to determine the effects of limiting ankle motion on pedal forces. Sixteen adults pedaled an instrumented ergometer against constant cadence and frictional load while wearing hinged braces. Ankle motion was limited under four randomly assigned conditions: both braces unlocked (UL), only the preferred leg (PL) brace locked, only the nonpreferred leg (NPL) brace locked, and braces on both legs (BL) locked. Measurements of pedal force, crank, and pedal angles were sampled at 200/s for 20 s. With both braces locked, resultant force mean magnitude decreased during the downstroke, due to reduced radial crank force. Asymmetry between PL and NPL decreased during the power phase when only PL was braced but increased when only NPL was braced. It was concluded that constrained ankle motion, as may occur with ankle injury or hemiplegia, reduces the ability to transmit power during the downstroke while enhancing ability during the upstroke.

A COMPARISON OF CONTRACTILE PROPERTIES IN THE PREFERRED AND NONPREFERRED LEG IN A MIXED SAMPLE OF DYSTROPHIC PATIENTS

No study of how muscle contractile function is related to limb preference in human muscular dystrophy is presently available. The purpose of this study was to determine if the ankle plantarflexor (PF) and dorsiflexor (DF) muscle groups of the preferred leg are more or less affected than the nonpreferred one in a mixed sample of myotonic and limb-girdle patients. Measurements of lower limb preference were made as well as of PF and DF evoked and voluntary contractile responses. Isometric contractile properties and peak values for torque production during maximum isometric twitch and voluntary contractions were measured. No significant difference was found in terms of contractile properties between the preferred and nonpreferred leg for both DF and PF muscle groups, except for the large PF twitch torque observed in the nonpreferred side (P less than 0.05). These results, however, reveal a clear tendency for both muscle groups on the preferred side to be weaker than those on the nonpreferred side. This last finding, in conjunction with the equally if not presumably stronger PF/DF muscles on the preferred leg of healthy adult subjects, would suggest that the equivalent bilateral muscle force observed in the present study may be interpreted as giving support to the hypothesis that overwork or overuse of dystrophic muscles may be harmful in weakening the musculature.