Inter-joint coordination patterns differ between younger and older runners.

Older runners are at greater risk of certain running-related injuries. Previous work demonstrated that aging influences running biomechanics, and suggest a compensatory relation between changes in the proximal and distal joints. Previous comparisons of interjoint coordination strategies between young and older runners could potentially have missed relevant differences by averaging coordination measures across time. OBJECTIVE: To compare coordination strategies between male runners under the age of 30 to those over the age of 60. METHODS: Twelve young (22 ±â€¯3 yrs, 1.80 ±â€¯0.07 m, 78.0 ±â€¯12.1 kg) and 12 older (63 ±â€¯3 yrs, 1.78 ±â€¯0.06 m, 73.2 ±â€¯15.8 kg) male runners ran at 3.35 m/s on an instrumented treadmill. Ankle frontal plane, tibial transverse plane, knee sagittal plane, and hip frontal plane motion were measured. Inter-joint coordination was calculated using a modified vector coding technique. Coordination patterns and variability time series were compared between groups throughout stance using ANOVA for circular data. RESULTS: At the ankle, older runners use in-phase propulsion (inversion, tibia external rotation) pattern following midstance (46-47% stance) while young runners are still in an in-phase collapse pattern (eversion, tibia external rotation). In coordination of the knee and hip, older runners maintained an in-phase collapse pattern (knee flexion, hip adduction) approaching midstance (35-37% stance), while younger runners use an out of phase strategy (knee extension, hip adduction). In coordination of the ankle and hip in the frontal plane, older runners again maintained an in phase collapse pattern up to midstance (34-39% stance), while younger runners used an out of phase strategy (ankle inversion, hip adduction). Variability was similar between age groups. CONCLUSION: Older runners appear to display altered coordination patterns during mid-stance, which may indicate protective biomechanical adaptations. These changes may also have implications for performance in older runners.

Tibiofemoral Joint Forces in Female Recreational Runners Vary with Step Frequency.

PURPOSE: Elevated tibiofemoral joint (TFJ) contact forces have been linked to the development and progression of knee osteoarthritis. The primary objective of this study was to determine the association between peak TFJ shear and compression forces during running at different self-selected step frequencies (SF) in female recreational runners. METHODS: Fifty-five healthy female recreational runners ran at 2.98 m·s on an instrumented treadmill. Peak TFJ anterior shear force, peak axial TFJ compression force, and peak medial compartment TFJ compression force were estimated using a musculoskeletal model with inputs from 3D joint kinematics and inverse dynamics calculations. Three SF groups were generated using tertiles, and differences between the groups were compared using one-way ANOVA (α = 0.05). RESULTS: Runners with an SF of ≥178 steps per minute demonstrated the lowest peak TFJ anterior shear force (P = 0.04), peak axial TFJ compression force (P = 0.01), and peak TFJ medial compartment compression forces (P = 0.01) compared with runners using lower SF. CONCLUSION: Female recreational runners with low SF of ≤166 steps per minute experience greater TFJ contact forces. This study provides evidence of an association between SF and both shear and axial peak TFJ contact forces during running.

The effect of variable rest intervals and chronic ankle instability on triplanar ankle motion during performance of the Star Excursion Balance Test.

Inadequate rest intervals may contribute to impaired performance during functional tests. However, the effect of different rest intervals on performance of the SEBT in individuals with and without CAI is not known. Our purposes were to determine whether different rest intervals impact ankle kinematics during the SEBT and whether there differences between those two populations. 24 controls and 24 CAI completed 3 trials in 3 reach directions (anteromedial; AM, medial; M, posteromedial; PM). The order of rest intervals and reach distance were randomized and counterbalanced. Three visits were required to complete the 3 rest interval conditions (10, 20, 40s). Rest interval did not impact ankle kinematics between controls and CAI during the SEBT. Dorsiflexion (DF) (AM:partial η2=0.18; M:partial η2=0.23; PM:partial η2=0.23) for all directions and tibial internal rotation (TIR) excursions (AM:partial η2=0.20) for AM direction were greater in individuals with CAI regardless of rest interval length. Rest intervals ranging from 10 to 40s did not influence ankle kinematics. Differences exist in DF and TIR between controls and CAI during the SEBT. These findings suggest that clinicians can use any rest interval between 10 and 40s when administrating the SEBT. However, triplanar motion differs during a complex functional movement in controls compared to CAI.

Frontal and sagittal plane biomechanics during drop jump landing in boys who are obese.

PURPOSE: To investigate the frontal and sagittal plane lower extremity biomechanics during drop jump landings in boys who were obese and boys who were of healthy weight. METHODS: Twelve boys participated, 6 were considered as healthy weight (body mass index for age <85%, age 11.0 +/- 0.8 years), and 6 were considered as obese (body mass index for age >95%, age 12.1 +/- 0.7 years). Three-dimensional data were collected during landing from a drop jump. Group means were compared using Student t tests (alpha = 0.05). RESULTS: Significant differences were found in peak hip adduction moment, timing of peak dorsiflexion and knee flexion angles, and timing of peak knee extension and abduction moments. CONCLUSIONS: Boys who were obese exhibited significant differences in frontal and sagittal plane biomechanics when landing from a jump compared with healthy weight peers. These differences could place boys who are obese at greater risk for lower extremity injuries when they engage in jump-landing activities.

Frontal plane lower extremity biomechanics during walking in boys who are overweight versus healthy weight.

PURPOSE: To compare frontal plane lower extremity biomechanics during walking in adolescent boys who were overweight (OW) versus healthy weight (HW). METHODS: Fourteen boys (7 considered HW, body mass index for age <85th percentile; age 10.8 +/- 0.7 years; 7 considered OW, body mass index for age >95th percentile; age 12.0 +/- 0.7 years) participated. Three-dimensional kinematic data were collected during walking at self-selected speeds. Group means were compared using Student's t tests (alpha = 0.05). RESULTS: Significant differences were found in timing of rearfoot motions and moments, amplitude of knee motion peaks, timing of knee moment peaks, and timing and amplitudes of peak hip motion and moments. CONCLUSION: Boys who were OW collapsed into hip adduction and knee valgus during stance and attempted to compensate with rearfoot inversion. Observed differences in frontal plane kinematics during walking suggest that boys who are OW have increased risk of lower extremity musculoskeletal injuries and dysfunction.