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

Functional Relevance of the Small Muscles Crossing the Ankle Joint

It has been suggested that increasing muscle strength could help reducing the frequency of running injuries and that a top-down approach using an increase in hip muscle strength will result in a reduced range of movement and reduced external moments at the knee and ankle level. This paper suggests, that a bottom-up approach using an increase of strength of the small muscles crossing the ankle joint, should reduce movement and loading at the ankle, knee and hip. This bottom-up approach is discussed in detail in this paper from a conceptional point of view. The ankle joint has two relatively “large” extrinsic muscles and seven relatively small extrinsic muscles. The large muscles have large levers for plantar-dorsi flexion but small levers for pro-supination. In the absence of strong small muscles the large muscles are loaded substantially when providing balancing with respect to pro-supination. Specifically, the Achilles tendon will be loaded in this situation asymmetrically with high local stresses. Furthermore, a mechanical model with springs shows that (a) the amplitude of the displacement with the strong small springs is smaller and (b) that the loading in the joints of the springs is substantially smaller for the model with the strong small springs. Additionally, strong and active small muscles crossing the ankle joint provide stability for the ankle joint (base). If they are weak, forces in the ankle, knee and hip joint increase substantially due to multiple co-contractions at the joints. Finally, movement transfer between foot and tibia is high for movements induced from the bottom and small for movements induced from the top. Based on these considerations one should speculate that the bottom-up approach may be substantially more effective in preventing running injuries than the top down approach. Various possible strategies to strengthen the small muscles of the ankle joint are presented

EFFECT OF BASKETBALL SHOES OF DIFFERENT WEIGHTS ON PERFORMANCE IN A GAME-LIKE SCENARIO

Lighter shoes have been shown to improve running economy; however this same phenomenon has not been investigated in basketball shoes. The purpose of this study was to investigate the physiological effects of basketball shoes of different masses during an on-court, game like scenario. Twelve male basketball players participated in this study. One shoe that was modified to have three different masses (Light, Medium, and Heavy) was evaluated in this study. Subjects completed a basketball-specific 20 minute fieldbased work protocol (Basketball-20) in each shoe on three different days while five physiological variables of interest were collected. The light shoe condition resulted in significantly lower oxygen consumption, ventilation, and rate of energy expenditure than the medium and heavy conditions

The effects of a 9-week hip focused weight training program on hip and knee kinematics and kinetics in experienced female dancers

Increased involvement of the hip musculature during some movements is associated with enhanced performance and reduced injury risk. However, the impact of hip dominant weight training methods on movement strategy has seen limited attention within the literature. The aim of this study was to evaluate if a 9-week hip dominant weight training intervention promotes a more hip dominant movement strategy leading to an improvement in countermovement jump performance. Twenty-two experienced female dancers were recruited and separated into an intervention (age 24.4 ± 6.3 years, body height 165.5 ± 5.8 cm, body mass 65.9 ± 5.6 kg) and a control (age 22.9 ± 5.6 years, body height 163.3 ± 5.4 cm, body mass 57.4 ± 6.8 kg) group. The intervention group participated in a 9-week hip dominant training intervention, which consisted of a wide stance back squat, Romanian deadlift, hip thrusters, and a bent over row. Hip and knee kinematics and kinetics, and countermovement jump performance were assessed pre and post training. Significant interaction effects were found for peak hip joint moment (p = 0.030, η2 = 0.214) and countermovement jump performance (p = 0.003, η2 = 0.356), indicating an increase in peak hip joint moment and countermovement jump performance for the intervention group. Specifically, the intervention group showed a mean increase in jump height of 11.5%. The data show that the use of a hip dominant weight training strategy can improve hip contribution in the propulsion phase of the countermovement jump. Strength and conditioning specialists should incorporate hip dominant weight training exercises to increase hip strength and improve performance

Impact of Self-Selected Customized Orthotics on Lower Limbs Biomechanics

Customized insoles are commonly prescribed to prevent or treat a variety of foot pathologies and to reduce foot and lower limb fatigue. Due to the patient-specific design and production of such orthotics, the concept of self-selected customized orthotics (SSCO) has recently been developed. The goal of this study was to assess the impact of SSCO technology on several physiological and biomechanical variables during uphill power walking. Thirty male participants underwent an uphill power walking intervention at constant speed in two insoles conditions (control and SSCO). The electromyographic (EMG) activity of their right gastrocnemii and vastii muscles was measured. Perceived fatigue was assessed every 5 minutes and the intervention stopped when the targeted fatigue level was reached. Baseline and post-intervention assessments were also performed. Sixty-three percent of the participants experienced an improvement in foot fatigue while wearing the SSCO. The foot arch seemed to collapse less when participants wore the SSCO, but statistical significance was not reached. The changes in mean EMG activity was not consistent between the 50% isometric contraction and the walking trial. In conclusion, while some interesting trends were observed when wearing SSCO, further investigations should be performed to try and reach statistical significance

The preferred movement path paradigm: influence of running shoes on joint movement

PURPOSE: (a) to quantify differences in lower extremity joint kinematics for groups of runners subjected to different running footwear conditions, and (b) to quantify differences in lower extremity joint kinematics on an individual basis for runners subjected to different running footwear conditions. METHODS: Three-dimensional ankle and knee joint kinematics were collected for 35 heel-toe runners when wearing three different running shoes and when running barefoot. Absolute mean differences in ankle and knee joint kinematics were computed between running shoe conditions. The percentage of individual runners who displayed differences below a 2°, 3° and 5° threshold were also calculated. RESULTS: The results indicate that the mean kinematics of the ankle and knee joints were similar between running shoe conditions. Aside from ankle dorsi-flexion and knee flexion, the percentage of runners maintaining their movement path between running shoes (i.e. less than 3°) was in the order of magnitude of about 80 to 100%. Many runners showed ankle and knee joint kinematics that differed between a conventional running shoe and barefoot by more than 3°, especially for ankle dorsiflexion and knee flexion CONCLUSION: Many runners stay in the same movement path (the preferred movement path) when running in various different footwear conditions. The percentage of runners maintaining their preferred movement path depends on the magnitude of the change introduced by the footwear condition

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