INSTANTANEOUS AND PROLONGED EFFECTS OF A TRIPLE DENSITY MIDSOLE DURING STANDING AND WALKING TASKS

The purpose of this study was to determine if there were any biomechanical differences between an unstable triple density midsole (TRIPLE) and a stable single density midsole (CONTROL). Twelve females completed 10 walking trials and three static trials followed by a two hour prolonged activity assessment during which participants alternated between standing and walking on a treadmill. Muscle activity, center of pressure, plantar forces and tissue oxygenation were measured for each footwear condition on two separate days. Standing in the TRIPLE condition resulted in better pressure distribution and lower peak forces, while walking in the TRIPLE condition resulted in greater tissue oxygenation. This midsole could be incorporated into other footwear where prolonged exposure to standing and walking tasks are the norm, such as work boots

Muscle tuning and preferred movement path – a paradigm shift

In the last 40 years, the scientific debate around running injuries and running shoes has been dominated by two paradigms, the ‘impact’ and the ‘pronation’ paradigms. However, the development of running shoe technologies aimed at reducing impact forces and pronation has not led to a decline of running-related injuries. This article recommends to abandon the ‘impact’ and ‘pronation’ paradigms due to a lack of biomechanical and epidemiological evidence and instead suggests a shift to new paradigms: ‘Muscle tuning’ and the ‘preferred movement path’. These paradigms represent new approaches to understanding the biomechanical patterns of each individual runner and how they are controlled by the neuromuscular system. Experimental evidence in support of the ‘muscle tuning’ and ‘preferred movement path’ paradigms are presented and discussed regarding their relevance for running performance, injuries, and footwear. Finally, this paper proposes that the concept of ‘functional groups’ should be used and further developed to overcome the challenge that groups of individuals respond differently to footwear interventions. First, groups of individuals who behave similarly (functional groups) should be identified. Second, running shoes should be selected to match the characteristics of the identified functional groups in order to optimize the beneficial effects of running shoes for improving running performance and reducing the risk of running injuries

Response to select comments on the proposed paradigm shifts in running

Background: Six experts in the field of running-related research have critically addressed a proposal to abandon the paradigms of ‘impact force’ and ‘pronation control’ when investigating running shoes, running injury, and running performance. Further, these experts have commented on the suggestion of the new paradigms of ‘muscle tuning’ and the ‘preferred movement path’ that can be used to investigate questions related to running injuries and performance as well running shoe design and comfort. This publication synthesizes and addresses the main criticisms of the experts and describes future directions to further develop the ‘muscle tuning and ‘preferred movement’ paradigms

Unstable shoes: Functional concepts and scientific evidence

The purpose of this study was to discuss (a) the conceptual idea behind unstable footwear and (b) the validity and scientific support of some selected claims made with respect to unstable shoes. The concept is that unstable shoes are built to provide a training device that uses instability as a strategy to train and strengthen muscles in the human locomotor system. Specific claims are: (1) evidence shows that unstable shoes currently on the market produce a substantial and significant increase in instability. The effects are most evident during standing but are also apparent in walking. (2) Unstable shoes increase the activity in certain muscles in about 80% of the population. The affected muscles change between different subjects. The highest relative increases were found in the small muscles crossing the ankle joint complex. (3) ‘Muscle toning’ is not defined and experimental data associating ‘muscle toning’ with unstable shoes are not available. (4) There is evidence that unstable shoes improve the static balance performance of users whose balance skills are low. (5) There is indirect evidence that unstable shoes reduce forces in the joints of the lower extremities. (6) There is evidence that unstable shoes can reduce the level of perceived pain. This has been confirmed in subjects suffering from pain in the knee joint and for subjects with low back pain. Based on these results, it seems that unstable shoes are associated with several possible benefits. However, the effects are not consistent between different subjects. In our experience, positive effects can be shown for about 80% of the test subjects

Relationship between lower limb muscle activity and platform acceleration during whole-body vibration exercise

International audienceThe purpose of this study was to identify the influence of different magnitudes and directions of the vibration platform acceleration on surface electromyography (sEMG) during whole-body vibration (WBV) exercises. Therefore, a WBV platform was used that delivers vertical vibrations via a side-alternating mode, horizontal vibrations via a circular mode, and vibrations in all three planes via a dual mode. sEMG signals of selected lower limb muscles were measured in thirty individuals while they performed a static squat on a vibration platform. The WBV trials included two side-alternating trials (Side-L: 6 Hz, 2.5 mm; Side-H: 16 Hz, 4 mm), two circular trials (Circ-L: 14 Hz, 0.8 mm; Circ-H: 43 Hz, 0.8 mm), and four dual mode trials that were the combinations of the single mode trials (Side-L/Circ-L, Side-L/Circ-H, Side-H/Circ-L, Side-H/Circ-H). Further, control trials without vibration were assessed, and 3D platform acceleration was quantified during the vibration. Significant increases in the root mean square of the sEMG (sEMGRMS) compared to the control trial were found in most muscles for Side-L/Circ-H (+17 to +63%, P < 0.05), Side-H/Circ-L (+7 to +227%, P < 0.05), and Side-H/Circ-H (+21 to +207%, P < 0.01), and in the lower leg muscles for Side-H (+35 to + 138%, P < 0.05). Further, only the vertical platform acceleration showed a linear relationship (r = 0.970, P < 0.001) with the averaged sEMGRMS of the lower limb muscles. Significant increases in sEMGRMS were found with a vertical acceleration threshold of 18 m.s and higher. The present results emphasize that WBV exercises should be performed on a platform that induces vertical accelerations of 18 m.s and higher