Zachary A. Sievert’s research while affiliated with University of Cincinnati and other places

Purpose Chewing duration can affect food particle size, gastric processing, and postprandial glycemia, but these effects have not been investigated with exercise. This study examined how the chewing duration of a food bar impacts glycemic and metabolic responses, gastrointestinal (GI) symptoms, psychological affect, and performance during endurance running. Methods This randomized, unblinded, crossover study had 15 males (35.2 ± 7.4 years, VO2peak: 56.1 ± 5.2 ml/kg/min) attend three laboratory visits. Visit 1 required a VO2peak test, 10 min familiarization run at 60% VO2peak, and familiarization time-to-exhaustion (TTE) test (10 min at 90% VO2peak, followed by TTE at 100% VO2peak). Visits 2 and 3 consisted of a 60 min run at 60% VO2peak, followed by TTE testing. Participants were fed 45 g of a bar (180 kcal, 4 g fat, 33 g carbohydrate, 3 g protein, 1 g fiber) in 9 g servings 30 min before running, and 27 g of bar in 9 g servings at three timepoints during the 60 min run. Participants consumed the servings in 20 (20CHEW) or 40 (40CHEW) masticatory cycles, at 1 chew/second. Outcomes included blood glucose, substrate use, GI symptoms, perceived exertion (RPE), overall feeling, and TTE. Results Post-prandial blood glucose, GI symptoms, and RPE increased over time, but there were no significant between-condition or condition-by-time effects. TTE showed no significant between-condition effect (20CHEW: 288 ± 133 s; 40CHEW: 335 ± 299 s; p = 0.240). Overall feeling demonstrated a time-by-condition effect (p = 0.006), suggesting possible better maintenance over time with 40CHEW. Conclusion Cumulatively, the results suggest that extended chewing minimally impacts physiology, perceptions, and performance during 60 min moderate-intensity running.

The squat is an essential exercise for strengthening lower body musculature. Although squats are frequently employed to improve lower extremity strength and neuromuscular control, differences between sexes and slight modifications, such as squat depth, can dramatically alter muscle recruitment and thus the foci of the exercise. The purpose of this study was to assess the effect of sex and squat depth on lower extremity coactivation and kinematics. Twenty recreationally active (women=10) participants were recruited. The first visit consisted of one repetition maximum testing. For the second visit, muscle activation was recorded of the gluteus maximus, semitendinosus, biceps femoris, vastus medialis, vastus lateralis, rectus femoris, and gastrocnemius. Reflective markers were placed on the lower body for 3D motion capture. Participants performed a series of squats to 90° knee flexion and 120° knee flexion. Benjamin-Hochberg procedure was employed and the alpha level was set at .05. Knee flexion (p<.001), adduction (p<.001), and external rotation (p=.008) were reduced during 90° compared to deep squats. Hip flexion, abduction, and external rotation were greater in deep squats (p<.001). Males had greater hip extensor to quad (HE:Q) co-contraction in 90° compared to deep squats (p=.007); females produced greater posterior chain activation in deep squats (p=.001) on ascent. When comparing sexes, males displayed greater HE:Q in the 90° squat during ascent (p=.013). The addition of deep squats into a preventative training program could be beneficial in reducing deficits prevalent in females and decrease injury incidence.

Purpose Knee sleeves have become widely popular in the exercise realm, especially for knee support during back squats. Knee sleeves are successful in providing frontal plane knee support during functional tasks, but have not been investigated in back squats. Knee wraps, a somewhat similar elastic material, provide elastic energy that increases weight lifted during back squats. Thus, it is possible the thick neoprene knee sleeves could prove advantageous for back squats. The purpose of this study was to examine the effects of knee sleeves on weight lifted, knee biomechanics, and muscle activations during back squats. Methods Fifteen resistance trained men and women performed 1-repetition maximum (1-RM) squats to full depth and 80% 1-RM to full and parallel depths during two separate randomized sessions: with/without knee sleeves. Three-dimensional motion capture, force platforms, and electromyography recorded knee biomechanics and activations of the rectus femoris, vastus medialis, biceps femoris long head, and gluteus maximus during all squats. Results Maximal weight lifted did not improve when using knee sleeves. Frontal plane knee biomechanics did not differ for 1-RM or submaximal squats to either depth between conditions. Knee external rotation moments during descent were larger with sleeves during submaximal squats. Reduced integrated ascent phase gluteus maximus activations occurred during both 1-RM and submaximal squats with knee sleeves. Conclusions The results of this study show that wearing knee sleeves does not provide additive effects to weight lifted and do not appear to alter frontal plane mechanics during weighted back squats.

Walking is the most common mode of physical activity for individuals who are blind. However, this population tends to be physically inactive, possibly due to alterations in coordination patterns during walking. Therefore, the purpose of this study was to examine lower extremity coordination patterns during walking in persons who are blind, and age-, sex-, and body mass index–matched sighted controls. Five persons who are blind performed level walking independently (with a cane) and with a human guide. Sighted controls walked at matched speeds for both conditions. A 10-camera motion capture system was used to record segmental kinematics during both walking conditions. Angle–angle plots and modified vector coding was used to present inter-limb (left/right thigh) and intra-limb (ankle–hip, ankle–knee, and knee–hip) couplings across both walking conditions for each group. Frequency of coupling patterns was compared between groups using Mann–Whitney’s U tests. Inter- and intra-limb coordination patterns were similar between both groups during independent and guided walking conditions (all p > .05). Angle–angle plots depict reduced segmental and joint motion in persons who are blind compared with sighted controls. Although the visual feedback system is integral for coordination during complex tasks, persons who are blind perform level walking with similar lower extremity coordination patterns to sighted controls. Reductions in spatiotemporal and range of motion are likely linked to a more hesitant stepping pattern due to unfamiliarity with the environment.

The back squat is a complex movement with significant demands on the lower extremities and trunk to raise an external load. The back squat is simultaneously an open and closed kinetic chain movement that requires coordination of the entire body for successful completion of the lift. Therefore, this study aimed to examine coordination of the thigh and shank, trunk and thigh, and the hip and knee during the concentric phase of maximum, supra-maximum (at 105% max), and sub-maximum (at 80% max) back squats. Fourteen resistance trained adults participated in this study. Maximum back squat loads were determined using a previously determined progressive load protocol. Motion capture of the trunk and lower extremities and ground reaction force data were recorded during all squats. Angle-angle plots and modified vector coding were performed to analyze segment and joint coupling angles and knee-hip moments. Overall, the concentric phase of back squats depict a transition from early knee dominance to hip dominance as the system ascends. Interestingly, all squats presented with coupling of thigh-rising and trunk-falling. Based on the angle-angle plots and the modified vector coding results, the prolonged coupling of trunk falling and thigh rising likely resulted in too large of a moment arm for the external load for the participants to overcome during Supramax conditions.

Diagnostic ultrasound has accurately and reliably been utilized by clinicians to determine ACL morphology at the tibial insertion site, specifically measuring the entire ACL diameter, the anteromedial bundle (AM), and the posterolateral bundle. However, intra- and inter-rater reliability of these measures in a research setting is unknown. The purpose of this study was to determine intra- and inter-rater reliability of ultrasound measures of ACL diameter and AM diameter in researchers with low-to-moderate ultrasound experience. We hypothesized that intra- and inter-rater reliability of ACL and AM diameters would reach acceptable levels, a minimal intraclass correlation (ICC) of 0.6 and a desired ICC of 0.8 with an α of 0.05 and β of 0.20. Fourteen volunteers participated in this study. During the ACL ultrasound measures, participants were seated with their knee flexed to at least 90°. Each rater recorded two images of both the right and left ACL and AM bundles. Next, participants were re-examined by rater one for intra-rater reliability analyses. Two-way random ICCs were conducted for intra-rater (between sessions) and inter-rater reliability for both the full ACL and the AM bundle diameters. Standard errors between sessions for Rater 1’s AM bundle and ACL diameters were less than 0.03 cm. Intra-rater reliability was higher in AM bundles compared to full ACL, 0.76 versus 0.59, respectively. Standard errors between Rater 1 and Rater 2 were less than 0.03 cm. Inter-rater reliability was higher in AM bundles compared to full ACL, 0.71 versus 0.41, respectively. The results of the study indicate researchers with low-to-moderate training with ultrasound measures can locate and measure the ACL, but with greater reliability using the AM.

The purpose of this study was to examine the relationship between ACL injury risk factors in unanticipated cutting and decelerating. Three-dimensional kinematics and ground reaction forces were collected on eleven females (22±2yrs, 1.67±0.08m, 68.5±9.8kg) during two unanticipated tasks. Paired samples t-tests were performed to compare dependent variables between tasks. Spearman rank correlation coefficients were calculated to analyze the relationship between peak internal knee adduction moment and peak anterior tibial shear force during two unanticipated tasks. Significantly greater knee abduction angles, peak knee adduction moments, and peak anterior tibial shear forces were observed during cutting (p≤0.05). A strong positive correlation existed between decelerating anterior tibial shear force and cutting anterior tibial shear force (ρ=0.67), while correlations between decelerating knee adduction moment and cutting knee adduction moment and decelerating anterior tibial shear force and cutting knee adduction moment were not significant. In situations where time management is a necessity, and only one task can be evaluated, it may be more appropriate to utilize an unanticipated cutting task rather than an unanticipated deceleration task because of the increased knee adduction moment and anterior tibial shear force. These data can help future clinicians in better designing more effective ACL injury risk screening methods.

Alterations in hip joint loading have been associated with diseases such as arthritis and osteoporosis. Understanding the relationship between gait speed and hip joint loading in healthy hips may illuminate changes in gait mechanics as walking speed deviates from preferred. The purpose of this study was to quantify hip joint loading during the gait cycle and identify differences with varying speed using musculoskeletal modeling. Ten, healthy, physically active individuals performed walking trials at their preferred speed, 10% faster, and 10% slower. Kinematic, kinetic, and electromyographic data were collected and used to estimate hip joint force via a musculoskeletal model. Vertical ground reaction forces, hip joint force planar components, and the resultant hip joint force were compared between speeds. There were significant increases in vertical ground reaction forces and hip joint forces as walking speed increased. Furthermore, the musculoskeletal modeling approach employed yielded hip joint forces that were comparable to previous simulation studies and in vivo measurements and was able to detect changes in hip loading due to small deviations in gait speed. Applying this approach to pathological and aging populations could identify specific areas within the gait cycle where force discrepancies may occur which could help focus management of care.