Rui Macedo

Influence of wearing an unstable shoe on thigh and leg muscle activity and venous response in upright standing.

PURPOSE To quantify the effect of unstable shoe wearing on muscle activity and haemodynamic response during standing. METHODS Thirty volunteers were divided into 2 groups: the experimental group wore an unstable shoe for 8 weeks, while the control group used a conventional shoe for the same period. Muscle activity of the medial gastrocnemius, tibialis anterior, rectus femoris and biceps femoris and venous circulation were assessed in quiet standing with the unstable shoe and barefoot. RESULTS In the first measurement there was an increase in medial gastrocnemius activity in all volunteers while wearing the unstable shoe. On the other hand, after wearing the unstable shoe for eight weeks these differences were not verified. Venous return increased in subjects wearing the unstable shoe before and after training. CONCLUSIONS The unstable shoe produced changes in electromyographic characteristics which were advantageous for venous circulation even after training accommodation by the neuromuscular system.

Influence of wearing an unstable shoe construction on compensatory control of posture.

This study investigated the influence of wearing unstable shoe construction (WUS) on compensatory postural adjustments (CPA) associated with external perturbations. Thirty-two subjects stood on a force platform resisting an anterior-posterior horizontal force applied to a pelvic belt via a cable, which was suddenly released. They stood under two conditions: barefoot and WUS. The electromyographic (EMG) activity of gastrocnemius medialis, tibialis anterior, rectus femoris, biceps femoris, rectus abdominis, and erector spinae muscles and the center of pressure (CoP) displacement were acquired to study CPA. The EMG signal was used to assess individual muscle activity and latency, antagonist co-activation and reciprocal activation at joint and muscle group levels. Compared to barefoot, WUS led to: (1) increased gastrocnemius medialis activity, (2) increased total agonist activity, (3) decreased antagonist co-activation at the ankle joint and muscle group levels, (4) increased reciprocal activation at the ankle joint and muscle group levels, and (5) decrease in all muscle latencies. No differences were observed in CoP displacement between conditions. These findings demonstrate that WUS led to a reorganization of the postural control system associated to improved performance of some components of postural control responses.

Effect of the contraction of medial rotators of the tibia on the electromyographic activity of vastus medialis and vastus lateralis

PURPOSE This study attempted to assess if the resisted contraction of medial rotators of the tibia increases the ratio between the activity of vastus medialis (VM) and vastus lateralis (VL) during maximal isometric contractions (MIC) of the quadriceps femoral (QF) muscle at 90 degrees of knee flexion. METHODS About 24 female subjects participated in this study, performing four series MIC of the QF. In the first series subjects performed only MIC of the QF muscle, whereas in the other three there was MIC of the QF with resisted contraction of medial rotators of the tibia, with the tibia positioned in medial, neutral and lateral rotation. During each contraction, VM and VL electromyographic signal (EMGs) and QF force were collected, being the EMGs root mean square (RMS) used to access the activity level of these muscles. RESULTS The use of the General Linear Model (GLM) test showed that for alpha=0.05 there was a significant increase in the VM:VL ratio when the resisted contraction of medial rotators of the tibia was performed with the tibia in medial (p=<0.0001), neutral (p=<0.0001) and lateral rotation (p=0.001). The same test showed that during MIC of the QF associated to resisted contraction of medial rotators of the tibia there were no significant differences in the VM:VL ratio between the three tibial rotation positions adopted (p=0.866 [medial-neutral]; p=0.106 [medial-lateral]; p=0.068 [neutral-lateral]). CONCLUSIONS The resisted contraction of medial rotators of the tibia increases the VM:VL ratio during MIC of the QF and the tibial rotation position does not influence the VM:VL ratio during MIC associated to resisted contraction of medial rotators of the tibia.

Influence of prolonged wearing of unstable shoes on upright standing postural control

OBJECTIVE To study the influence of prolonged wearing of unstable shoes on standing postural control in prolonged standing workers. METHODS The participants were divided into two groups: one wore unstable shoes while the other wore conventional shoes for 8weeks. Stabilometry parameters related to centre of pressure (CoP), rambling (RM) and trembling (TR) as well as the total agonist/antagonist muscle activity, antagonist co-activation and reciprocal activation were evaluated during upright standing, before and after the 8weeks period. In both moments, the subjects were evaluated wearing the unstable shoes and in barefoot. RESULTS The unstable shoe condition presented increased CoP displacement related variables and decreased co-activation command compared to barefoot before and after the intervention. The prolonged wearing of unstable shoes led to: (1) reduction of medial-lateral CoP root mean square and area; (2) decreased anteroposterior RM displacement; (3) increased anteroposterior RM mean velocity and mediolateral RM displacement; (4) decreased anteroposterior TR RMS; and (5) increased thigh antagonist co-activation in the unstable shoe condition. CONCLUSION The unstable shoe condition is associated to a higher destabilising effect that leads to a selection of more efficient and accurate postural commands compared to barefoot. Prolonged wearing of unstable shoes provides increased effectiveness and performance of the postural control system, while wearing of unstable shoes in upright standing, that are reflected by changes in CoP related variables and by a reorganisation of postural control commands.

The influence of different soccer cleat type on kinetic, kinematic and neuromuscular ankle variables in artificial turf

Lateral ankle sprain is the most prevalent injury in soccer athletes. Enhanced by the variety of soccer cleats and by increased use of artificial turf, the interaction between the ground and the footwear has taken high importance as a lateral ankle sprain risk factor. The higher incidence of injuries in the second half of the match reflects the need of studying this interaction during tasks involving muscle fatigue. To evaluate the influence of different soccer cleats on kinetic, kinematic and neuromuscular ankle variables in artificial turf under two conditions: with and without fatigue of lateral ankle dynamic stabilizers. Study design: Experimental study within-subjects design. Twenty-four healthy athletes participated in this study. All subjects performed three sets of five medial-lateral unipodal jumps, each one with one of three models of cleats (Turf, Hard and Firm ground) on two conditions: with and without fatigue induced by the isokinetic dynamometer. The electromyographic activity of long and short peroneal heads, ground reaction forces and the movement of the rear-foot were collected and used to calculate kinematic (ankle eversion/inversion, centre of pressure displacement and velocity), kinetic (loading rate of the ground reaction forces) and neuromuscular variables (activation time of peroneal muscles). With the exception of decreased peroneal activation time with the Hard ground model (without fatigue vs. with fatigue), no statistically significant differences were identified in the ankle variables, between cleats, neither between the two evaluated conditions. In healthy soccer athletes, the contributor variables for ankle sprain were not influenced by the kind of soccer cleat in a functional test on a third generation artificial turf.

Influence of Cleats-Surface Interaction on the Performance and Risk of Injury in Soccer: A Systematic Review

Objective To review the influence of cleats-surface interaction on the performance and risk of injury in soccer athletes. Design Systematic review. Data Sources Scopus, Web of science, PubMed, and B-on. Eligibility Criteria Full experimental and original papers, written in English that studied the influence of soccer cleats on sports performance and injury risk in artificial or natural grass. Results Twenty-three articles were included in this review: nine related to performance and fourteen to injury risk. On artificial grass, the soft ground model on dry and wet conditions and the turf model in wet conditions are related to worse performance. Compared to rounded studs, bladed ones improve performance during changes of directions in both natural and synthetic grass. Cleat models presenting better traction on the stance leg improve ball velocity while those presenting a homogeneous pressure across the foot promote better kicking accuracy. Bladed studs can be considered less secure by increasing plantar pressure on lateral border. The turf model decrease peak plantar pressure compared to other studded models. Conclusion The soft ground model provides lower performance especially on artificial grass, while the turf model provides a high protective effect in both fields.