[ effects of two traditional and post-activation potentiation warm-up methods on ground reaction forces during squat-jump]

Background and Aim: A proper warm-up method can be used as a strategy to improve performance of athletes in various sport fields. The purpose of the present study was to assess the effect of traditional and post-activation potentiation warm-up methods on ground reaction forces during squat jump

Materials and Methods: Fourteen trained male athletes [age=26.5+/-3.64 years, weight=70+/-10.65 kg, height=180 +/- 8.39 cm] participated voluntarily in this study. Athletes randomly performed three different warm-up protocols on three separate days: typical traditional warm-up method, static and dynamic post-activation potentiation implementing half-squat at 90% 1RM. After performing the warm-up protocols, the subjects completed squat jump test on a force platform in order to assess ground reaction forces

Results: In the jumping and landing phases, the peak values of horizontal and vertical ground reaction forces in the traditional warm-up method were significantly lower than those in the static [P=0.001 for both phases] and dynamic [P=0.001 for both phases] PAP warm-up methods. Also, we found a significant difference in the horizontal peak ground reaction force in the jumping phase between the static and dynamic PAP warm-up methods [P=0.003]. In addition, significant differences in the vertical jump height and rate of force development [RFD] were observed between the traditional and static PAP warm-up methods [P=0.001 for both methods], between the traditional and dynamic PAP warm-up methods [P=0.001 for both methods], and also between the static and dynamic PAP warm-up methods [P=0.002 and P=0.003, respectively]

Conclusion: According to the results of this study, it seems that the PAP warm-up method may have more advantage over traditional warm-up method in order to improve record and performance of the athletes during squat jump movement

[Effect of hip abductor muscles fatigue on plantar pressure characteristics during stance phase of walking]

Background and Objective: Muscles fatigue around the joint can altere the movement pattern and increasing the risk of muscle damage. This study was done to determine the effect of hip abductor muscles fatigue on plantar pressure characteristics during stance phase of gait

Methods: This quasi-experimental study was done on 22 males with age ranes of 15-21 years olds. Hip abduction protocol with 50% of one-repetition maximum was used to induce hip abductor muscles fatigue. Average pressure, plantar peak pressure, step duration and the plantar contact area in both feet distribution were collected using before and after the fatigue protocol during gait

Results: Despite the relative reduction in average pressure, contact area and step duration and plantar increase in peak pressure after abductors fatigue, but these differences were not significant

Conclusion: This study showed that the hip abductor muscles fatigue can not alter plantar pressure characteristics during stance phase of gait

[Comparison of spatial-temporal-distance gait parameters in male patients with different degrees of knee osteoarthritis]

Background and Aim: the effects of knee osteoarthritis on spatial, temporal and distance parameters of gait have been reviewed in the literature. But, the effect of osteoarthritis severity on gait parameters has not been clearly documented. The aim of this study was to compare the spatial, temporal and distance parameters in male patients according to severity of the knee osteoarthritis during gait

Materials and Methods: a Vicon [130 Hz] motion analysis system with four T-Series cameras was used to measure the spatial, temporal and distance parameters. Fifteen normal men and 30 patients with knee osteoarthritis participated in this study. According to Kellgren and Lawrence radiologic scale, patients were divided into three groups: mild [n = 10], moderate [n = 10] and severe [n = 10]. The spatiotemporal parameters of gait including cadence, double support, foot off, opposite foot contact, opposite foot off, single support, step length, step time, step width, stride length, stride time, walking speed, stance time and cycle time were calculated by Vicon Nexus 1.8.5 software. All data were then extracted by use of Polygon 3.5.1, Visual3D .v4 softwares. Using SPSS version 20, data were analyzed by one-way ANOVA test [p<0.05]

Results: there were no significant differences in all temporospatial parameters between the healthy and patient groups [P>0.05]. There was a significant decrease in cadence, step length, stride length and walking speed, while, step time, stride time, stance time, double support time were longer in the patients

Conclusion: changes of spatial-temporal,-distance gait parameters in the patients with knee osteoarthritis particularly among those with severe osteoarthritis may lead to loss of stability during gait and consequently, a higher fall risk

[ comparison of time to peak torque and acceleration time in elite karate athletes]

The purpose of the present study was to evaluate the differences between acceleration time and time to peak torque of the knee muscles of female elite karate athletes before and after muscular fatigue. Thirteen female elite karate athletes [age: 15.5 +/- 1.3 years] were evaluated using the Biodex system 3 isokinetic dynamometer at 60[degree]/s, 180[degree]/s and 300[degree]/s before and after hamstring and quadriceps muscular fatigue. There were no significant differences in time to peak torque and acceleration time variables at the 60 speed before and after fatigue [p>0.05]. At the 180[degree]/s speed, the quadriceps and hamstring presented a lower time to peak torque after muscular fatigue [p<0.05]. At the 300[degree]/s speed, only hamstring muscles showed a higher time to peak torque and acceleration time after muscular fatigue [p =0.04]. Results of the present study indicated that the functional demands of muscular fatigue among female elite karate athletes are not necessarily their muscular strength. This can be explained because the time to peak torque and acceleration time were changed after muscular fatigue. However, muscular fatigue could produce agonist-antagonist muscle asymmetries, particularly in high velocities that could influence the knee joint injuries

[Long-term effects of foot orthoseson leg muscles activity in individuals with pesplanus during walking]

Foot orthoses are widely prescribed to treat a range of lower extremity problems. Long-term biomechanical effects of foot orthosesare not clearly documented in the literature. The aim of this study was to examine long-term effects of foot orthoses on leg muscles activity in individuals with pesplanus during walking. In this clinical trial we selected 45 subjects after clinical examination. The subjects were divided into three equal groups: experimental pesplanus, control pesplanus and a healthy control group [with normal feet]. In the pre-test stage, electrical activity of leg muscles including tibialis anterior, peroneus longus, medial gastrocnemius and soleus were recorded at stance phase of walking, while all subjects walked barefoot along a 14m line. Experimental pesplanus group wore the custom-made orthoses for a period of six months. Then experimental pesplanus and control pesplanus groups underwent post-test. One-way ANOVA was used for data analysis. After six months of utilizing foot orthoses, the tibialis anterior activity significantly decreased in contact sub-phase [P=0.006]. The medial gastrocnemius activity showed a significant decrease in midstance sub-phase in the post-test [P=0.007]. Also, the soleus muscle had decreased activity in contact [P=0.033] and midstance [p=0.023] sub-phases in the post-test. According to the results of this study, we found that long term use of foot orthoses could change muscle activation and result in secondary adaptation

[ effect of genu varum deformity on balance control following postural perturbation in adolescent girls]

Despite the fact that balances has often been considered as a measure of lower extremity function, the effect of lower extremity malalignment on balance performance has received little attention. The aim of the present study was to examine postural control following a sudden external perturbation in adolescent girls with genu varum of the knees in comparison to age matched healthy controls. This comparative and interventional study included eight adolescent girls with genu varum [age: 13. 5 +/- 1.4 years] and eight age-matched healthy controls [age: 13.8 +/- 1.3]. The subjects underwent unexpected forward, backward and medio-lateral perturbations triggered by a weight equivalent to 10% of the body weight, of every subject while standing on a foot pressure system mounted on a movable plate. The displacement of the center of pressure [COP] of the feet was measured. Independent t-test was used for statistical analysis. p < =0.05 was considered significant. Subjects with genu varum of the knees showed a significantly greater COP displacement after perturbation in comparison to the control group [p=0.039]. Our findings revealed that postural control following balance perturbations is weaker in subjects with genu varum deformity than in control group. Consequently, abnormal lower limb alignment is a risk factor which can influence postural control in response to a balance perturbation

[ effect of knee bracing on plantar pressure variables of healthy females during stance phase of gait]

There is limited information regarding the effects of knee bracing on plantar pressure variables. The aim of this study was to determine the immediate effects of a supporting patellar brace on plantar pressure variables in healthy females during stance phase of gait 17 women [age: 22.3 +/- 1.31 years] participated in this study. Plantar foot pressure of the subjects was measured by foot scan pressure plate while walking barefoot with and without wearing supporting patellar brace. Dependent t-test was used for data analysis. P 0.05]. The center of pressure displacement [COPx] was more during propulsion phase of gait while using knee brace [P = 0.01]. The results of this study indicated that bracing could influence lower extremity function by delaying peak plantar pressure and consequently provide dynamic stability of the knee joint during stance phase of gait. Further studies are needed to advance our understanding of the effects of bracing on plantar pressure variables during gait

[Effects of soft orthotics on sEMG activity of superficial leg muscles during walking with supinated feet]

The purpose of this study was to evaluate the effects of a soft semi-custom foot orthotic on leg muscles activity during stance and swing phases of walking in three different conditions namely, bare foot, with shoes only, and wearing shoes with soft insoles in individuals with supinated feet. Ten subjects with bilateral idiopathic pescavus deformity were entered into the study. Foot types were defined by FPI method. Surface electromyographic signals from the tibialis anterior, peroneus longus, gastrocnemius medialis and lateralis and soleus were recorded using EMG system at a sampling rate of 1000 Hz according to the SENIAM protocol. Our findings showed a little change in muscle activation during walking, but no significant difference was detected in the muscles in the three conditions. Although use of orthotics resulted in no significant difference in the parameters in this study, different individuals showed different responses and the results of this study can be taken into consideration for designing orthotics

[Assessment of postural response after sudden perturbation in subjects with genu valgum]

The lower extremity deformities have been co nsidered to change the relations between body segments. Postural stability could be affected by these changes in the alignment and positioning of the body segments. The purpose of this study was to examine postural response and surface electromyographic activity of selected lower limb muscles to recover upright posture following a sudden external perturbation among individuals with genu valgum in comparison with age matched healthy controls. In this case-control study, sixteen subjects with genu valgum and sixteen agematched healthy controls were participated. With unexpected perturbation, the displacement of the center of pressure [COP] and surface electromyographic activity of selected lower limb muscles were collected. Data were analyzed using independent t-test [P<0.05]. The genu valgum group had a greater COP displacement after perturbation in comparison with the control group [P<0.05]. Activities of some of the lower limbs muscles were significantly higher in genu valgum group in comparison with controls group after perturbation in different directions. These findings illustrate that abnormal lower limb alignment as risk factor can decrease postural reaction strategy in response to a sudden balance perturbation. Designing a strength training program for vastus medialis muscle may have beneficial effects in the prevention of knee injuries in individuals with knee valgus deformity