Upper-body kinematics in team-handball throw, tennis serve, and volleyball spike.

Overarm movements are essential skills in many different sport games; however, the adaptations to different sports are not well understood. The aim of the study was to analyze upper-body kinematics in the team-handball throw, tennis serve, and volleyball spike, and to calculate differences in the proximal-to-distal sequencing and joint movements. Three-dimensional kinematic data were analyzed via the Vicon motion capturing system. The subjects (elite players) were instructed to perform a team-handball jump throw, tennis serve, and volleyball spike with a maximal ball velocity and to hit a specific target. Significant differences (P < 0.05) between the three overarm movements were found in 17 of 24 variables. The order of the proximal-to-distal sequencing was equal in the three analyzed overarm movements. Equal order of the proximal-to-distal sequencing and similar angles in the acceleration phase suggest there is a general motor pattern in overarm movements. However, overarm movements appear to be modifiable in situations such as for throwing or hitting a ball with or without a racket, and due to differences at takeoff (with one or two legs).

Effects of age on lower extremity joint kinematics and kinetics during level walking with Masai barefoot technology shoes.

BACKGROUND: The age-associated loss of physical function engenders gait patterns which jeopardise the knee and hip to osteoarthritis. Masai Barefoot Technology (MBT) shoes have been shown to provide a facility to address specific needs for load modification in terms of musculoskeletal disease prevention in people with restricted proprioceptive or strength abilities. Therefore, a readjustment of lower extremity joint loading profiles in the elderly was hypothesised when using this type of footwear. AIM: The aim of this study was to evaluate the effects of MBT shoes on gait kinematics and kinetics in both an elderly and young cohort during walking. DESIGN: This was a cross-sectional study. SETTING: A 3-dimensional motion analysis laboratory. POPULATION: Eleven healthy elderly men and 11 healthy young men. METHODS: A conventional sport shoe served as control situation to MBT. Subjects were advised to walk eight trials per shoe at a criterion speed of 1.5 ± 0.1 m·s(-1) in block-randomised order. Peak joint angles, moments and powers at the ankle, knee and hip were calculated through an inverse dynamic model. Data were compared by a two-way repeated measure ANOVA (α=0.05). RESULTS: MBT reduced external ankle joint moments and powers independent of age. At the hip, MBT footwear led to decreases in external hip flexion moments and concentric hip power output during early and late stance. Herein, no age-by-condition effects were present. Moreover, MBT reduced external knee flexion moments and concentric knee extensor powers at loading response, with the greater changes observed in the elderly. Additionally, a main effect of condition showing a general decrease in the MBT situation, but no interaction effect was noted for first peak external knee adduction moments. CONCLUSION: These results suggest that MBT shoes diminish joint loads among age groups, whereas compared to young adults, the elderly, in particular, benefited from MBT footwear with regard to relief stress on the knee joint region. CLINICAL REHABILITATION IMPACT: Based on these findings, the use of MBT shoes may attenuate the risk of developing knee and hip osteoarthritis in the elderly and may play an important role regarding pain avoidance and/or disability.

Effect of instability training equipment on lower limb kinematics and muscle activity.

To improve the effectiveness of training or therapy, it is important to know the benefits for each type of instability training equipment. The aim of this study was to show differences in lower limb kinematics and muscle activation during single leg standing on a slackline (SL) compared to a multi-functional rocker board (MD) and an air cushion (AC). In 14 subjects, mean angular velocity of the hip, knee and ankle, as well as the muscle activity (iEMG) from six lower limb muscles were recorded during 12 s of single leg standing task. Ankle in-/eversion and knee ab-/adduction angular velocity were highest for SL followed by MD and AC (all p < 0.05), as well as in the hip flex-/extension angular velocity with higher values for SL compared with AC (p < 0.01). Regarding iEMG, the rectus femoris muscle showed higher values for SL compared with MD (p < 0.05) and AC (p < 0.01). iEMG of biceps femoris muscle demonstrated higher values for MD compared to AC (p < 0.05), but with no difference to SL. Balancing on a SL is a more challenging exercise for the postural control system compared to MD and AC, and affects the knee and hip joint motion in particular.

Lower extremity joint loading during level walking with Masai barefoot technology shoes in overweight males.

The purpose of this study was to evaluate the effects of Masai barefoot technology (MBT) shoes on lower extremity joint loading in overweight males during level walking. Therefore, lower extremity kinematics, kinetics, and muscle electromyographic signals of the vastus lateralis (VL), biceps femoris (BF), and gastrocnemius medialis (GM) were recorded in 10 overweight males at a self-chosen walking speed with MBT shoes and conventional shoes. Selected peak joint moments, maximal joint force loading rates, mean muscle intensities, and co-activation indices of the VL/BF, as well as of the VL/GM were analyzed and compared for the two shoe conditions using paired Student's t-tests (α=0.05). Results showed that walking with MBT shoes reduced first peak knee adduction moments in overweight subjects. During midstance and terminal stance, increases in VL/GM co-activation, accompanied by increases in VL and GM (only terminal stance) intensities were found for the MBT situation. Kinetic variables analyzed to assess ankle and hip joint loading did not exhibit any statistical differences. These results suggest that using MBT shoes diminishes medial compartment loads at the knee without overloading hip or ankle joints in overweight males. However, the additional muscle loading should not be overlooked, and warrants further investigation.

Improved postural control after slackline training is accompanied by reduced H-reflexes.

"Slacklining" represents a modern sports activity where people have to keep balance on a tightened ribbon. The first trials on the slackline result in uncontrollable lateral swing of the supporting leg. Training decreases those oscillations and therefore improves postural control. However, the underlying neural mechanisms are not known. Therefore, the present study aimed to highlight spinal adaptations going along with slackline training. Twenty-four subjects were either assigned to a training or a control group and postural control was assessed before and after the 10 training sessions. Additionally, soleus Hoffmann (H)-reflexes were elicited to evaluate changes in the excitability of the spinal reflex circuitry. Trained subjects were able to maintain balance on the slackline for at least 20 s (P<0.001) and reduced platform movements on the balance board (P<0.05). The H-reflexes were significantly diminished (P<0.05) while no changes occurred in the background electromyography (bEMG). The control group showed no significant changes. From a functional point of view the reflex reduction may serve to suppress uncontrollable reflex mediated joint oscillations. As the bEMG remained unchanged, presynaptic rather than post-synaptic mechanisms are speculated to be responsible for the changes in the Ia-afferent transmission.