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

The Effects of Resistance Strength Training and Functional Strength Training on Risk Factors for Running Injury

Reduced muscular strength and relatively larger magnitudes of movements and moments at the lower extremity joints during running have been proposed as risk factors for sustaining an injury. Some have suggested that increased movements at the joints are partially due to reduced muscular strength. However, the influence of strength training on running mechanics has yet to be evaluated in a group of novice runners, which have been shown to be particularly prone to injury. Therefore, the purposes of this thesis were to 1) compare changes in strength, running mechanics, and balance and 2) to explore injury risk for novice runners enrolled in a resistance strength training program, a functional movement strength training program or a stretching control program. One hundred and twenty nine novice runners (18-60 years old, less than two years running experience) were randomly assigned to one of three groups: a “resistance” strength training group (n=43), a “functional” strength training group (n=43) or a stretching “control” group (n=43). Participants were asked to complete a home-based training program three to five times a week for the eight week training period. Following this training period, participants were asked to complete their respective training at least twice a week for a sixteen week maintenance period. Changes in strength, running mechanics, and balance pre- to post-training were compared between groups. Running injuries were self-reported and defined as any complaint sustained in relation to running that caused a restriction in running for at least one week. Eighty-six participants completed the follow up assessment (functional=34, resistance=28, control=24). Changes in lower extremity strength were similar between the training groups with all groups demonstrating strength gains at multiple lower extremity joints. Changes in running mechanics were small in magnitude and within the measurement error of the testing protocol. The functional training group demonstrated improved balance using force plate and field based measures of balance. Though exploratory in nature, injury rates were not different between the three training groups. The results of this thesis indicate that running and completing a home-based strength training program did not increase strength or reduce joint movements more than running and stretching for a group of novice runners

Shoe midsole hardness, sex and age effects on lower extremity kinematics during running

Previous studies investigating the effects of shoe midsole hardness on running kinematics have often used male subjects from within a narrow age range. It is unknown whether shoe midsole hardness has the same kinematic effect on male and female runners as well as runners from different age categories. As sex and age have an effect on running kinematics, it is important to understand if shoe midsole hardness affects the kinematics of these groups in a similar fashion. However, current literature on the effects of sex and age on running kinematics are also limited to a narrow age range distribution in their study population. Therefore, this study tested the influence of three different midsole hardness conditions, sex and age on the lower extremity kinematics during heel-toe running. A comprehensive analysis approach was used to analyze the lower-extremity kinematic gait variables for 93 runners (male and female) aged 16–75 years. Participants ran at 3.33±0.15 m/s on a 30 m-long runway with soft, medium and hard midsoles. A principal component analysis combined with a support vector machine showed that running kinematics based on shoe midsole hardness, sex, and age were separable and classifiable. Shoe midsole hardness demonstrated a subject-independent effect on the kinematics of running. Additionally, it was found that age differences affected the more dominant movement components of running compared to differences due to the sex of a runner

Increased vertical impact forces and altered running mechanics with softer midsole shoes.

To date it has been thought that shoe midsole hardness does not affect vertical impact peak forces during running. This conclusion is based partially on results from experimental data using homogeneous samples of participants that found no difference in vertical impact peaks when running in shoes with different midsole properties. However, it is currently unknown how apparent joint stiffness is affected by shoe midsole hardness. An increase in apparent joint stiffness could result in a harder landing, which should result in increased vertical impact peaks during running. The purpose of this study was to quantify the effect of shoe midsole hardness on apparent ankle and knee joint stiffness and the associated vertical ground reaction force for age and sex subgroups during heel-toe running. 93 runners (male and female) aged 16-75 years ran at 3.33 ± 0.15 m/s on a 30 m-long runway with soft, medium and hard midsole shoes. The vertical impact peak increased as the shoe midsole hardness decreased (mean(SE); soft: 1.70BW(0.03), medium: 1.64BW(0.03), hard: 1.54BW(0.03)). Similar results were found for the apparent ankle joint stiffness where apparent stiffness increased as the shoe midsole hardness decreased (soft: 2.08BWm/º x 100 (0.05), medium: 1.92 BWm/º x 100 (0.05), hard: 1.85 BWm/º x 100 (0.05)). Apparent knee joint stiffness increased for soft (1.06BWm/º x 100 (0.04)) midsole compared to the medium (0.95BWm/º x 100 (0.04)) and hard (0.96BWm/º x 100 (0.04)) midsoles for female participants. The results from this study confirm that shoe midsole hardness can have an effect on vertical impact force peaks and that this may be connected to the hardness of the landing. The results from this study may provide useful information regarding the development of cushioning guidelines for running shoes

Statistics.

<p>Descriptive statistics (mean and standard deviation (SE)) for the variables tested.</p

Individuality decoded by running patterns: Movement characteristics that determine the uniqueness of human running.

Human gait is as unique to an individual as is their fingerprint. It remains unknown, however, what gait characteristics differentiate well between individuals that could define the uniqueness of human gait. The purpose of this work was to determine the gait characteristics that were most relevant for a neural network to identify individuals based on their running patterns. An artificial neural network was trained to recognize kinetic and kinematic movement trajectories of overground running from 50 healthy novice runners (males and females). Using layer-wise relevance propagation, the contribution of each variable to the classification result of the neural network was determined. It was found that gait characteristics of the coronal and transverse plane as well as medio-lateral ground reaction forces provided more information for subject identification than gait characteristics of the sagittal plane and ground reaction forces in vertical or anterior-posterior direction. Additionally, gait characteristics during the early stance were more relevant for gait recognition than those of the mid and late stance phase. It was concluded that the uniqueness of human gait is predominantly encoded in movements of the coronal and transverse plane during early stance

Methods.

<p>A) Illustration of apparent ankle joint stiffness (stiffness = slope), and B) vertical force during running highlighting the impact peak during the first part of stance.</p

Apparent Knee Stiffness.

<p>Average apparent knee joint stiffness (mean ± SEM) for the soft (blue), medium (red) and hard (green) midsole shoes for the female participants (left) and male participants (right). Significant differences were found between the soft midsole and the medium and hard midsoles for the female participants and between the soft midsole and the medium midsole for the male participants. Covariates were evaluated at the following values: weight = 66.7kg, Height = 170.9cm.</p

Vertical Impact Peak.

<p>Average vertical impact peak force (mean ± SEM) for the soft (blue), medium (red) and hard (green) midsole shoes for the female participants (left) and male participants (right). Significant differences were found between soft, medium and hard midsole shoes. Covariates were evaluated at the following values: weight = 66.7kg, Height = 170.9cm.</p