Kinetic coupling in distal foot joints during walking.

BACKGROUND: Kinematic coupling between the first metatarsophalangeal (MTP) and midtarsal joints is evident during gait and other movement tasks, however kinetic foot coupling during walking has not been examined. Furthermore, contributing factors to foot coupling are still unclear. Therefore, the purpose of this study was to investigate kinematic and kinetic coupling within the foot by restricting MTP motion during overground walking. We hypothesized that when the MTP joint was prevented from fully extending, the midtarsal joint would achieve less peak motion and generate less positive work compared to walking with normal MTP motion. METHODS: Twenty-six individuals participated in this randomized cross-over study. Using motion capture to track motion, participants walked at 1.3 m/s while wearing a brace that restricted MTP motion in a neutral (BR_NT) or extended (BR_EX) position. Additionally, participants walked while wearing the brace in a freely moveable setting (BR_UN) and with no brace (CON). A pressure/shear sensing device was used to capture forces under each foot segment. During stance, peak joint motion and work were calculated for the MTP and midtarsal joints using inverse dynamics. A series of ANOVAs and Holm post hoc tests were performed for all metrics (alpha = 0.05). RESULTS: The brace successfully decreased peak MTP motion by 19% compared to BR_UN and CON. This was coupled with 9.8% less midtarsal motion. Kinetically, the work absorbed by the MTP joint (26-51%) and generated by the midtarsal joint (30-38%) were both less in BR_EX and BR_NT compared to BR_UN. CONCLUSION: Implications and sources of coupling between the MTP and midtarsal joints are discussed within the context of center of pressure shifts and changes to segmental foot forces. Our results suggest that interventions aimed at modulating MTP negative work (such as footwear or assistive device design) should not ignore the midtarsal joint.

Design of the Building Research in CRC prevention (BRIDGE-CRC) trial: a 6-month, parallel group Mediterranean diet and weight loss randomized controlled lifestyle intervention targeting the bile acid-gut microbiome axis to reduce colorectal cancer risk among African American/Black adults with obesity.

BACKGROUND: Among all racial/ethnic groups, people who identify as African American/Blacks have the second highest colorectal cancer (CRC) incidence in the USA. This disparity may exist because African American/Blacks, compared to other racial/ethnic groups, have a higher prevalence of risk factors for CRC, including obesity, low fiber consumption, and higher intakes of fat and animal protein. One unexplored, underlying mechanism of this relationship is the bile acid-gut microbiome axis. High saturated fat, low fiber diets, and obesity lead to increases in tumor promoting secondary bile acids. Diets high in fiber, such as a Mediterranean diet, and intentional weight loss may reduce CRC risk by modulating the bile acid-gut microbiome axis. The purpose of this study is to test the impact of a Mediterranean diet alone, weight loss alone, or both, compared to typical diet controls on the bile acid-gut microbiome axis and CRC risk factors among African American/Blacks with obesity. Because weight loss or a Mediterranean diet alone can reduce CRC risk, we hypothesize that weight loss plus a Mediterranean diet will reduce CRC risk the most. METHODS: This randomized controlled lifestyle intervention will randomize 192 African American/Blacks with obesity, aged 45-75 years to one of four arms: Mediterranean diet, weight loss, weight loss plus Mediterranean diet, or typical diet controls, for 6 months (48 per arm). Data will be collected at baseline, mid-study, and study end. Primary outcomes include total circulating and fecal bile acids, taurine-conjugated bile acids, and deoxycholic acid. Secondary outcomes include body weight, body composition, dietary change, physical activity, metabolic risk, circulating cytokines, gut microbial community structure and composition, fecal short-chain fatty acids, and expression levels of genes from exfoliated intestinal cells linked to carcinogenesis. DISCUSSION: This study will be the first randomized controlled trial to examine the effects of a Mediterranean diet, weight loss, or both on bile acid metabolism, the gut microbiome, and intestinal epithelial genes associated with carcinogenesis. This approach to CRC risk reduction may be especially important among African American/Blacks given their higher risk factor profile and increased CRC incidence. TRIAL REGISTRATION: ClinicalTrials.gov NCT04753359 . Registered on 15 February 2021.

The influence of the windlass mechanism on kinematic and kinetic foot joint coupling.

BACKGROUND: Previous research shows kinematic and kinetic coupling between the metatarsophalangeal (MTP) and midtarsal joints during gait. Studying the effects of MTP position as well as foot structure on this coupling may help determine to what extent foot coupling during dynamic and active movement is due to the windlass mechanism. This study's purpose was to investigate the kinematic and kinetic foot coupling during controlled passive, active, and dynamic movements. METHODS: After arch height and flexibility were measured, participants performed four conditions: Seated Passive MTP Extension, Seated Active MTP Extension, Standing Passive MTP Extension, and Standing Active MTP Extension. Next, participants performed three heel raise conditions that manipulated the starting position of the MTP joint: Neutral, Toe Extension, and Toe Flexion. A multisegment foot model was created in Visual 3D and used to calculate ankle, midtarsal, and MTP joint kinematics and kinetics. RESULTS: Kinematic coupling (ratio of midtarsal to MTP angular displacement) was approximately six times greater in Neutral heel raises compared to Seated Passive MTP Extension, suggesting that the windlass only plays a small kinematic role in dynamic tasks. As the starting position of the MTP joint became increasingly extended during heel raises, the amount of negative work at the MTP joint and positive work at the midtarsal joint increased proportionally, while distal-to-hindfoot work remained unchanged. Correlations suggest that there is not a strong relationship between static arch height/flexibility and kinematic foot coupling. CONCLUSIONS: Our results show that there is kinematic and kinetic coupling within the distal foot, but this coupling is attributed only in small measure to the windlass mechanism. Additional sources of coupling include foot muscles and elastic energy storage and return within ligaments and tendons. Furthermore, our results suggest that the plantar aponeurosis does not function as a rigid cable but likely has extensibility that affects the effectiveness of the windlass mechanism. Arch structure did not affect foot coupling, suggesting that static arch height or arch flexibility alone may not be adequate predictors of dynamic foot function.

Ground reaction force profiles during inclined running at iso-efficiency speeds.

While running provides an accessible form of cardiovascular stimulus, many runners report lower extremity musculoskeletal injuries. Additionally, runners who develop overuse injuries, such as tibial stress fractures, also have higher loading rates (LR) and impact forces. PURPOSE: Therefore, the purpose of this study was to investigate how uphill treadmill running at iso-efficient speeds (IES; a speed-incline combination having the same metabolic intensity as level running) influences impact LR, and peak vertical ground reaction forces (GRF). METHODS: Eleven collegiate distance runners completed 3 experimental running conditions (0%, 4%, and 8% treadmill inclination). During each running condition, the metabolic intensity was controlled by implementing an IES for each runner. RESULTS: All variables of interest were significantly reduced as treadmill incline increased (0% > 4% > 8%). CONCLUSION: Incline running is more metabolically demanding compared to level running at the same speed. But, if speed is controlled to maintain metabolic output, runners could decrease LR and peak vertical GRF while achieving the same metabolic training stimulus as level running.