NEW IDEAS AND CONCEPTS IN SPORT SHOE DEVELOPMENT

The sport biomechanist is often challenged to ‘test performance’ during competition and not in the laboratory environment. While ecological validity of data must always be of concern, measurement error (both system, and modelling) and the characteristics of equipment used (manual or automatic?), often mean that data are collected under ‘simulated match’ conditions. This paper will review the vexing question of laboratory versus field testing from a biomechanical perspective. Current data suggest that for movements involving out of plane rotations, laboratory testing with an opto-reflective system (cluster based model), provides a more accurate measure of elbow angle when compared with the same angle collected with a video-based system (vector model) during a simulated cricket bowling task

IMPACT FORCES AND MOVEMENT CONTROL -TWO NEW PARADIGMS

In the last century, participation in physical activities has developed dramatically. The best documented development was in running with millions of participants (6, 24). Between 1978 and 1983, the number of runners in Canada has more than doubled from 15 % to 31 %, but has decreased in 1988 to about 18 % of the total population (50, 56). The high incidence of injuries in runners has been proposed as one possible reason for this decrease. Between 37 to 56 % of all runners are injured during a year of running (31) and running injuries make up the majority of sport related injuries in the young (31.5 %) and the old (40.5 %) physically active population (29). Major reasons for the development of exercise related injuries proposed in the literature include previous injuries, training errors, excessive impact forces and excessive foot movement or movement control (8, 9, 21, 31). From a biomechanical point of view impact forces and movement control are of interest since they can be influenced with the sport shoe. This paper will concentrate on these two aspects and propose two new paradigms for the functional understanding of impact forces and movement control

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

TRANSMISSIBILITY OF WHOLE BODY VIBRATIONS TO THE TRICEPS SURAE

In order to evaluate potential risks of long term whole body vibration (WBV) training, the transmissibility of vibrations from the WBV platform to the muscles needs to be determined. The purpose of this study was to quantify the transmissibility of vibrations from the WBV platform to the triceps surae muscle. Sixteen healthy male subjects were exposed to WBV at 2.5 mm amplitude and to frequencies of 10, 17 and 28 Hz. Transmissibility of peak acceleration, frequency, and amplitude were quantified using tri-axial accelerometers. The results showed high transmissibility of acceleration and amplitude, especially at low platform frequencies. Since high amounts of acceleration were related to tissue damage, animal or computational muscle models might use the current results as input parameters to study eventual long term risks of WBV training

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

Can Porous Tantalum Be Used to Achieve Ankle and Subtalar Arthrodesis?: A Pilot Study

A structural graft often is needed to fill gaps during reconstructive procedures of the ankle and hindfoot. Autograft, the current gold standard, is limited in availability and configuration and is associated with donor-site morbidity in as much as 48%, whereas the alternative allograft carries risks of disease transmission and collapse. Trabecular metal (tantalum), with a healing rate similar to that of autograft, high stability, and no donor-site morbidity, has been used in surgery of the hip, knee, and spine. However, its use has not been documented in foot and ankle surgery. We retrospectively reviewed nine patients with complex foot and ankle arthrodeses using a tantalum spacer. Minimum followup was 1.9years (average, 2years; range, 1.9-2.4years). Bone ingrowth into the tantalum was analyzed with micro-CT in three of the nine patients. All arthrodeses were fused clinically and radiographically at the 1- and 2year followups and no complications occurred. The American Orthopaedic Foot and Ankle Society score increased from 32 to 74. The micro-CT showed bony trabeculae growing onto the tantalum. Our data suggest tantalum may be used as a structural graft option for ankle and subtalar arthrodesis. All nine of our patients achieved fusion and had no complications. Using tantalum obviated the need for harvesting of the iliac spine. Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidenc

LOWER LIMB MUSCLE RECRUITMENT STRATEGIES DIFFER BETWEEN ELITE AND RECREATIONAL ICE HOCKEY PLAYERS

Understanding the muscle recruitment strategies that have the largest contribution to performance is essential in sports biomechanics. The aims of this study were to characterise principal muscle activation patterns during accelerative hockey skating and to classify skill levels of players based on their principal muscle activation patterns. Key features of lower limb muscle activation strategies during accelerative skating were extracted and used to classify, with 83% success, elite and recreational players’ acceleration strides. Classification and functional interpretation of muscle coordination is important to understand the differences in muscle recruitment strategies across skill levels, and to monitor changes that result from training

CAN INCREASED MIDSOLE BENDING STIFFNESS OF SPORT SHOES DELAY THE ONSET OF LOWER LIMB JOINT WORK REDISTRIBUTION DURING A PROLONGED RUN?

Prolonged running has been shown to result in a redistribution of positive lower limb joint work from distal to proximal joints. Running footwear with increased midsole bending stiffness (MBS) has been shown to redistribute lower limb joint work from proximal to distal joints. How increased MBS of running shoes can affect joint work redistribution during a prolonged run, however, is unknown. Therefore, the purpose of this study was to investigate if increasing the MBS of running shoes can delay the onset of positive lower limb joint work redistribution during a prolonged run. Thirteen trained male runners (current 10 km time \u3c 44 min.) performed 10-km runs at 90% of their speed at lactate threshold (sLT) in a control and stiff shoe condition, respectively. Prolonged running resulted in a redistribution of positive lower limb joint work from distal to proximal joints in both shoe conditions. The onset of joint work redistribution, however, was delayed at the metatarsophalangeal and ankle joint when running in the stiff shoe condition. A delayed onset of lower limb joint work redistribution in the stiff condition may result in greater energy stored and returned in distal passive-elastic structures (i.e., Achilles tendon), reducing lower limb muscle work later into the prolonged run. Also, less active muscle volume would be required to perform the same total amount of positive mechanical work when running in the stiff condition because the ankle plantarflexor muscles have less volume than the knee extensor muscles. These results contribute to the notion that footwear with increased MBS likely result in lower metabolic cost, due to delays in distal to proximal lower limb joint work redistribution