Gender differences on the age-related distal-to-proximal shift in joint kinetics during running.

The increased running participation in women and men over 40 years has contributed to scientific interest on the age-related and gender differences in running performance and biomechanics over the last decade. Gender differences in running biomechanics have been studied extensively in young runners, with inconsistent results. Understanding how gender influences the age-related differences in running mechanics could help develop population-specific training interventions or footwear to address any potential different mechanical demands. The purpose of this study was to assess gender and age effects on lower limb joint mechanics while running. Middle-aged men (57 ± 5 years) and women (57 ± 8 years) and young men (28 ± 6 years) and women (30 ± 6 years) completed five overground running trials at a set speed of 2.7 m/s while lower limb kinematics and ground reaction forces were collected. Lower limb joint kinetics were computed, normalized to body mass and compared between age and gender groups using two-factor analyses of variance. Women reported slower average running paces than men and middle-aged runners reported slower running paces than young runners. We confirmed that young runners run with more ankle, but less hip positive work and peak positive power compared to middle-aged runners (i.e., age-related distal-to-proximal shift in joint kinetics). We also present a novel finding that women run with more ankle, but less hip peak positive power compared to men suggesting an ankle dominant strategy in women at a preferred and comfortable running pace. However, the age-related distal-to-proximal shift in joint kinetics was not different between genders.

Age and training volume influence joint kinetics during running.

Recently, we proposed the hypothesis that weekly running volume and preferred running pace may play a role in preserving ankle joint kinetics in middle-age runners as ankle joint kinetics were generally similar in young and middle-aged runners with similar running volume and preferred pace. To further address this hypothesis, we compared lower extremity joint kinetics between high and low training volume runners in both young and middle-aged groups. Joint kinetics calculated from 3D kinematic and ground reaction force data during over-ground running at 2.7 m·s-1 from young and middle-aged runners who ran low or high weekly volume were analyzed. A two-factor analysis of variance was used to compare joint kinetics between age and running volume groups. Positive hip work was greater in middle-aged compared to young runners (P = .005). Plantarflexor torque (P = .009) and positive ankle work (P = .042) were greater in young compared to middle-aged runners. Positive ankle work was also greater in the high compared to the low volume group (P = .021). Finally, age by volume interactions were found for knee extensor torque (P = .024), negative knee work (P = .018), and positive knee work (P = .019) but not for ankle and hip joint kinetics. These findings suggest less distal-to-proximal difference in positive joint work with high running volume in both young and middle-aged runners as a result of greater power generation at the ankle. Given the age main effects, our findings are also the first to suggest the age-related distal-to-proximal shift in joint kinetics appears in middle-aged runners.

Joint work is not shifted proximally after a long run in rearfoot strike runners.

Distal-to-proximal redistribution of joint work occurs following exhaustive running in recreational but not competitive runners but the influence of a submaximal run on joint work is unknown. The purpose of this study was to assess if a long submaximal run produces a distal-to-proximal redistribution of positive joint work in well-trained runners. Thirteen rearfoot striking male runners (weekly distance: 72.6 ± 21.2 km) completed five running trials while three-dimensional kinematic and ground reaction force data were collected before and after a long submaximal treadmill run (19 ± 6 km). Joint kinetics were calculated from these data and percent contributions of joint work relative to total lower limb joint work were computed. Moderate reductions in absolute negative ankle work (p = 0.045, Cohen's d = 0.31), peak plantarflexor torque (p = 0.004, d = 0.34) and, peak negative ankle power (p = 0.005, d = 0.32) were observed following the long run. Positive ankle, knee and hip joint work were unchanged (p < 0.05) following the long run. These findings suggest no proximal shift in positive joint work in well-trained runners after a prolonged run. Runner population, running pace, distance, and relative intensity should be considered when examining changes in joint work following prolonged running.

Potential Predictors of Vertical Jump Performance: Lower Extremity Dimensions and Alignment, Relative Body Fat, and Kinetic Variables.

ABSTRACT: Daugherty, HJ, Weiss, LW, Paquette, MR, Powell, DW, and Allison, LE. Potential predictors of vertical jump performance: Lower extremity dimensions and alignment, relative body fat, and kinetic variables. J Strength Cond Res 35(3): 616-625, 2021-The association of structural and kinetic variables with restricted vertical jump (RVJ) displacement without and with added mass was examined in 60 men and women. Added mass (weighted vest) simulated a 5% increase in body fat (BF%). Independent variables included BF%, thigh length, and static Q-angle (Q-angles), and while performing RVJ, different expressions of frontal-plane knee angle (FPKA), dynamic Q-angle (Q-angled), vertical ground reaction force (vGRF), concentric vertical impulse (Iz), concentric rate of force development (CRFD), and vertical power (Pz). Variables having significant (p ≤ 0.05) negative correlations with RVJ displacement included BF% (r = -0.76) and Q-angles (r = -0.55). Those having significant (p ≤ 0.05) positive correlations with RVJ displacement included peak and average concentric Pz (r range = 0.74-0.81), peak and average concentric vGRF (r range = 0.46-0.67), Iz (r range = 0.32-0.54), thigh length (r = 0.31), minimum Q-angled (r = 0.31), and maximum FPKA (r = 0.28). Variables not associated (p > 0.05) with RVJ displacement included minimum and excursion FPKA (r = 0.11 and 0.23), maximum, excursion, and average Q-angled (r = 0.24, 0.11, and 0.22), and CRFD (r range = 0.19-0.24). A simple regression model predicted RVJ displacement (p = 1.00) for the simulated 5% increase in body fat. To maximize jumping performance, (a) high levels of body fat should be avoided, (b) peak and average Pz, vGRF, and Iz should be maximized through training, and (c) having a lower Q-angles is associated with better jumping ability.

Biomechanical Comparison of a New Dynamic Ankle Orthosis to a Standard Ankle-Foot Orthosis During Walking.

Patients who sustain irreversible cartilage damage or joint instability from ankle injuries are likely to develop ankle osteoarthritis (OA). A dynamic ankle orthosis (DAO) was recently designed with the intent to offload the foot and ankle using a distractive force, allowing more natural sagittal and frontal plane ankle motion during gait. To evaluate its efficacy, this study compared ankle joint kinematics and plantar pressures among the DAO, standard double upright ankle-foot orthosis (DUAFO), and a nonorthosis control (CON) condition in healthy adults during walking. Ten healthy subjects (26 ± 3.8 yr; 69.6 ± 12.7 kg; and 1.69 ± 0.07 m) walked on a treadmill at 1.4 m/s in three orthosis conditions: CON, DAO, and DUAFO. Ankle kinematics were assessed using a three-dimensional (3D) motion capture system and in-shoe plantar pressures were measured for seven areas of the foot. DAO reduced hallux peak plantar pressures (PPs) compared to CON and DUAFO. PPs under toes 2-5 were smaller in DAO than DUAFO, but greater in DUAFO compared to CON. Early stance peak plantarflexion (PF) angular velocity was smaller in DAO compared to CON and DUAFO. Eversion (EV) ROM was much smaller in DUAFO compared to CON and DAO. Early stance peak eversion angular velocity was smaller in DAO and much smaller in DUAFO compared to CON. This study demonstrates the capacity of the DAO to provide offloading during ambulation without greatly affecting kinematic parameters including frontal plane ankle motion compared to CON. Future work will assess the effectiveness of the DAO in a clinical osteoarthritic population.

Footwear and Sex Differences in Performance and Joint Kinetics During Maximal Vertical Jumping.

Smith, RE, Paquette, MR, Harry, JR, Powell, DW, and Weiss, LW. Footwear and sex differences in performance and joint kinetics during maximal vertical jumping. J Strength Cond Res 34(6): 1634-1642, 2020-This investigation examined the effects of footwear and sex on vertical jump displacement and joint power contributions. Twenty-three young adults with basketball experience performed 3 maximal countermovement vertical jumps in minimal and standard footwear. Ground reaction force and 3D kinematic data were collected during jumping. Footwear by sex analysis of variance for all dependent variables and effect sizes (d) was computed. An interaction effect showed that men produced greater lower-limb-positive work than women in standard footwear. Men jumped higher than women (d = 2.53) and produced greater peak ankle, knee and hip joint moments (d > 0.99), positive joint powers (d > 1.07) and, positive knee and hip joint work (d > 1.04) with no sex differences for negative joint powers and work (p > 0.05). Minimal footwear produced less peak-positive knee power (d = 0.27) and less positive ankle (d = 0.34) and knee (d = 0.21) joint work than standard footwear. Because negative joint power and work were similar between sexes, men may be better able to use the stretch-shortening cycle compared with women. Higher joint mechanical demands may provide a better vertical jumping training stimulus in standard compared with minimal footwear. Future studies should investigate footwear training effects on performance and joint mechanics during jumping.

Lower Limb Joint Kinetics During Walking in Middle-Aged Runners With Low or High Lifetime Running Exposure.

Aging is associated with a distal-to-proximal shift in joint kinetics during walking. This plasticity of gait is amplified rather than attenuated in old adults with high physical capacity. Because running is associated with greater kinetic demands at the ankle, older individuals with more versus less lifetime running exposure may retain a larger proportion of their ankle kinetics. The purpose of the study was to compare lower-extremity joint kinetics during walking between middle-aged runners with high and low lifetime running exposure. Eighteen middle-aged runners (9 per group) participated. Joint kinetics were calculated from kinematic and ground reaction force data during overground walking at 1.3 m·s-1 and compared between groups. High exposure runners produced 50% greater positive hip work (P = .03; Cohen d = 1.02) during walking compared with low exposure runners, but ankle kinetics were not different between groups. No other differences in joint kinetics or kinematics were observed between groups. These findings suggest that the age-related increase in hip joint kinetics during walking could be a compensatory gait strategy that is not attenuated by lifetime running exposure alone. Finally, the amount of lifetime running exposure did not affect ankle kinetics during walking in middle-aged runners.

Exercise prescription for weight management in obese adults at risk for osteoarthritis: synthesis from a systematic review.

BACKGROUND: The aim of this systematic review was to identify principles of exercise interventions associated with improved physical function, weight management or musculoskeletal pain relief among young and middle-aged adults with obesity and propose an evidence-based exercise prescription that could assist in secondary prevention of osteoarthritis. METHODS: A structured electronic review was conducted using MEDLINE, PubMed, and SPORTDiscus. The search string included 1) "obes*" AND "exercise" AND "interven*" AND "musculoskeletal pain OR knee pain OR hip pain". Studies 1) were randomized controlled trials of humans, with a non-exercise control, 2) included participants aged 18-50 years, and 3) had outcomes that included physical function, musculoskeletal pain, and/or body composition. Studies were excluded if participants had peri-menopausal status, cancer, or obesity-related co-morbidities. A recommended exercise prescription was developed based on common principles used in the included exercise interventions with greatest change in function or pain. RESULTS: Seven studies were included. Similarities in exercise intensity (40-80% VO2max), frequency (three times per week), duration (30-60 min), and exercise mode (treadmill, cross-trainer, stationary bike, aquatic exercise) were observed in exercise interventions that resulted in improved physical function and/or pain, compared to non-exercise control groups. CONCLUSION: Common principles in exercise prescription for improvements in weight management, physical function and pain relief among otherwise healthy people with obesity. Exercise prescription including moderate intensity exercise for 30-60 min, three times per week can be considered an effective treatment for weight management and obesity-related musculoskeletal symptoms. Exercise should be recommended to at-risk individuals as part of secondary prevention of osteoarthritis.

Sex and acute weighted vest differences in force production and joint work during countermovement vertical jumping.

It is unclear whether weighted vest (WV) use improves countermovement vertical jump (CMVJ) performance by enhancing stretch-shortening cycle (SSC) function via increased storage and utilisation of elastic strain energy. In is also unknown whether WV use stimulates different responses in men and women. WV effects on energy storage and utilisation during CMVJ were examined in men and women. Nine men (25 ± 3 y; 89.7 ± 18.7 kg; 1.8 ± 0.1 m) and 12 women (24 ± 3 y; 62.7 ± 10.3 kg; 1.6 ± 0.1 m) performed CMVJ wearing a WV with (loaded) and without (unloaded) 10% added mass while kinematic and ground reaction force (GRF) data were obtained. A longer eccentric sub-phase and increased storage of elastic strain energy occurred when loaded. Increased positive joint work occurred during the concentric portion of loaded CMVJ. Women exhibited less positive hip work and greater positive ankle work than men during the unloading and eccentric sub-phases, respectively. Joint work was similar between sexes during the concentric sub-phase, likely due to decreased trunk extension excursion in men when loaded. Women and men employ different SSC strategies during the CMVJ, though the different strategies do not alter energy storage or concentric mechanical output.

Effect of a rest-pause vs. traditional squat on electromyography and lifting volume in trained women.

PURPOSE: Rest-pause (4 s unloaded rest between repetitions) single session training effects on lifting volume, and muscle activity via electromyography (EMG) are currently vague in the literature and can benefit strength and conditioning professionals for resistance training program design. This study compared differences in volume lifted and muscle activity between a rest-pause vs. traditional protocol. METHODS: Trained females (N = 13) completed both a rest-pause and traditional squat protocol consisting of four sets to movement failure at 80% pretest 1 repetition maximum load with 2-min rest between sets. Total volume and muscle activity of the vastus lateralis, vastus medialis, rectus femoris, and gluteus maximus were measured on both training days. Differences in muscle activity were viewed as a percent change (%∆). RESULTS: A paired samples t test indicated total volume lifted was higher in the rest-pause compared to the traditional protocol (2532 vs. 2036 kg; p < .05). Furthermore, paired samples t tests showed muscle activity %∆ of the gluteus maximus was greater in the traditional protocol compared to the rest-pause protocol (p < .05). No other muscle activity differences were observed in the remaining muscles. CONCLUSIONS: The rest-pause allows for greater volume lifted via increased repetitions compared to a traditional protocol in trained women. The rest-pause method may be superior to a traditional method of training during a hypertrophy mesocycle, where a primary focus is total volume lifted. Furthermore, %∆ muscle activity in the GM will be greater while performing a traditional back squat protocol in comparison to a rest-pause.

The Impact of Different Cross-Training Modalities on Performance and Injury-Related Variables in High School Cross Country Runners.

Paquette, MR, Peel, SA, Smith, RE, Temme, M, and Dwyer, JN. The impact of different cross-training modalities on performance and injury-related variables in high school cross country runners. J Strength Cond Res 32(6): 1745-1753, 2018-There are many different types of aerobic cross-training modalities currently available. It is important to consider the effects that these different modalities have on running performance and injury risks. The purpose of this study was to compare movement quality, running economy (RE) and performance, injury-related biomechanical variables, and hip muscle strength before and after training with different cross-training modalities in high school runners. Thirty-one high school male runners trained for 4 weeks in 1 of 3 cross-training modalities, in addition to a running-only (n = 9) group, for which training sessions replaced 2 easy runs per week: cycling (CYCLE; n = 6), indoor elliptical (n = 7), and outdoor elliptical bike (EBIKE; n = 9). Functional movement screen (FMS), RE, 3,000-m performance, hip kinematics, and hip muscle strength were assessed. Paired t-tests and Cohen's d effect sizes were used to assess mean differences for each variable before and after training within each group. Elliptical bike training was the only modality that improved FMS scores (d = 1.36) and RE before and after training (d = 0.48). All groups showed improvements in 3,000-m performance, but large effects were found only for the CYCLE (d = 1.50) and EBIKE (d = 1.41) groups. Running-only (d = 1.25), CYCLE (d = 1.17), and EBIKE (d = 0.82) groups showed improvements in maximal hip extensor strength. Outdoor cycling and EBIKE cross-training may be the most effective cross-training modalities to incorporate in early season training to improve running performance in high school runners.

Muscle Activation Patterns of Lower-Body Musculature Among 3 Traditional Lower-Body Exercises in Trained Women.

Korak, JA, Paquette, MR, Fuller, DK, Caputo, JL, and Coons, JM. Muscle activation patterns of lower-body musculature among 3 traditional lower-body exercises in trained women. J Strength Cond Res 32(10): 2770-2775, 2018-The deadlift and back and front squats are common multijoint, lower-body resistance exercises that target similar musculature. To our knowledge, muscle activity measured using surface electromyography has never been analyzed among these 3 exercises. Furthermore, most literature examining this topic has included male participants creating a void in the literature for the female population. Knowledge of lower-body muscle activation among these 3 exercises can aid coaches, trainers, and therapists for training and rehabilitative purposes. Trained women (n = 13) completed 2 days of testing including a 1-repetition maximum (1RM) estimation, an actual 1RM, and 3 repetitions at 75% 1RM load for the deadlift and back and front squats. Muscle activity of the 3 repetitions of each muscle was averaged and normalized as a percentage to the 1RM lifts for the deadlift and front and back squats. Five separate repeated-measure analysis of variances were performed indicating muscle activity of the gluteus maximus (GM) differed among the 3 exercises (p = 0.01, (Equation is included in full-text article.)= 0.39). Specifically, post hoc analysis indicated greater muscle activity during the front squat (M = 94%, SD = 15%) compared with the deadlift (M = 72%, SD = 16%; p ≤ 0.05) in the GM. No significant differences were observed among the lifts in the vastus medialis, vastus lateralis, biceps femoris, and rectus femoris. Strength and conditioning specialist and trainers can use these findings by prescribing the front squat to recruit greater motor units of the GM.

Kinetic and Electromyographic Subphase Characteristics With Relation to Countermovement Vertical Jump Performance.

This study sought to identify kinetic and electromyographic subphase characteristics distinguishing good from poor jumpers during countermovement vertical jumps (CMVJs), as defined by the reactive strength index (RSI, CMVJ displacement divided by jump time; cutoff = 0.46 m·s-1). A total of 15 men (1.8 [0.6] m, 84.5 [8.5] kg, 24 [2] y) were stratified by RSI into good (n = 6; RSI = 0.57 [0.07] m·s-1) and poor (n = 9; RSI = 0.39 [0.06] m·s-1) performance groups. The following variables were compared between groups using independent t tests (α = .05) and Cohen's d effect sizes (d ≥ 0.8, large): jump height, propulsive impulse, eccentric rate of force development, and jump time, unloading, eccentric, and concentric subphase times, and average electromyographic amplitudes of 8 lower extremity muscles. Compared with the poor RSI group, the good RSI group exhibited a greater, though not statistically different CMVJ displacement (d = 1.07, P = .06). In addition, the good RSI group exhibited a significantly greater propulsive impulse (P = .04, d = 1.27) and a significantly more rapid unloading subphase (P = .04, d = 1.08). No other significant or noteworthy differences were detected. Enhanced RSI appears related to a quicker unloading phase, allowing a greater portion of the total jumping phase to be utilized generating positive net force. Poor jumpers should aim to use unloading strategies that emphasize quickness to enhance RSI during CMVJ.

Effect of rest-pause vs. traditional bench press training on muscle strength, electromyography, and lifting volume in randomized trial protocols.

PURPOSE: Rest-pause (4-s unloaded rest between repetitions) training effects on one repetition maximum (1 RM), lifting volume, and neural activation via electromyography (EMG) are currently vague in the literature and can benefit strength and conditioning professionals for resistance training programme design. Therefore, this study compared 1 RM, neural activation via (EMG), and volume differences between rest-pause vs. traditional resistance training. METHODS: Trained males (N = 20) were randomly assigned to either a rest-pause or a traditional training group. Pre- and post-1 RM testing was recorded. Training sessions were completed twice a week for 4 weeks and consisted of four sets of bench press to volitional fatigue at 80% of pre-test 1 RM with a 2-min rest between sets. Total volume completed was recorded on each training day. Neural activation of the pectoralis major was measured on the first and last training days. RESULTS: A two-way repeated-measures ANOVA indicated both groups significantly increased their 1 RMs following the 4-week training protocol (p < .05). However, no significant differences were found in 1 RM and neural activation between the two groups (p > .05). An independent samples t test indicated that total volume lifted was significantly higher for the rest-pause group (56,778 vs. 38,315 lbs; p < .05) throughout the protocol and independently during weeks 2, 3, and 4. CONCLUSIONS: While strength and neural activation changes did not differ between groups, both increased 1 RMs and the rest-pause group achieved greater increases in volume than the traditional group. If volume is the focus of training, the rest-pause method should be utilized.

Joint stiffness and running economy during imposed forefoot strike before and after a long run in rearfoot strike runners.

Research has focused on the effects of acute strike pattern modifications on lower extremity joint stiffness and running economy (RE). Strike pattern modifications on running biomechanics have mostly been studied while runners complete short running bouts. This study examined the effects of an imposed forefoot strike (FFS) on RE and ankle and knee joint stiffness before and after a long run in habitual rearfoot strike (RFS) runners. Joint kinetics and RE were collected before and after a long run. Sagittal joint kinetics were computed from kinematic and ground reaction force data that were collected during over-ground running trials in 13 male runners. RE was measured during treadmill running. Knee flexion range of motion, knee extensor moment and ankle joint stiffness were lower while plantarflexor moment and knee joint stiffness were greater during imposed FFS compared with RFS. The long run did not influence the difference in ankle and knee joint stiffness between strike patterns. Runners were more economical during RFS than imposed FFS and RE was not influenced by the long run. These findings suggest that using a FFS pattern towards the end of a long run may not be mechanically or metabolically beneficial for well-trained male RFS runners.

Impact of a Long Run on Injury-Related Biomechanics with Relation to Weekly Mileage in Trained Male Runners.

The purposes of this study were to compare selected biomechanical variables before and after a long run, and to assess the relationship between weekly running volume and changes in lower limb biomechanics after the run. Twelve trained habitual rearfoot strike male runners ran overground before and after a treadmill long run while kinematic and kinetic data were recorded. Repeated measures analysis of variance and Cohen's d effect sizes were used to compare kinematic and kinetic variables before and after the run. Loading rate was 6% higher after the run (p < .05) but this difference had a small effect size (d = .32). Moderate effects were found for a 25% increase in peak ankle eversion (d = 0.62) and a 10% increase in hip adduction (d = 0.60) after the run. These findings suggest that the completion of a submaximal long run does not yield potentially injurious lower limb biomechanics in uninjured rearfoot strike runners. Weekly running mileage was not correlated to biomechanical changes observed before and after the long run. Since biomechanical responses to the long run varied among runners, differences in other factors such as specific training regimens and neuromuscular control should be considered in future studies.

Do Lower-Body Dimensions and Body Composition Explain Vertical Jump Ability?

Caia, J, Weiss, LW, Chiu, LZF, Schilling, BK, Paquette, MR, and Relyea, GE. Do lower-body dimensions and body composition explain vertical jump ability? J Strength Cond Res 30(11): 3073-3083, 2016-Vertical jump (VJ) capability is integral to the level of success attained by individuals participating in numerous sport and physical activities. Knowledge of factors related to jump performance may help with talent identification and/or optimizing training prescription. Although myriad variables are likely related to VJ, this study focused on determining if various lower-body dimensions and/or body composition would explain some of the variability in performance. Selected anthropometric dimensions were obtained from 50 university students (25 men and 25 women) on 2 occasions separated by 48 or 72 hours. Estimated body fat percentage (BF%), height, body weight, hip width, pelvic width, bilateral quadriceps angle (Q-angle), and bilateral longitudinal dimensions of the feet, leg, thigh, and lower limb were obtained. Additionally, participants completed countermovement VJs. Analysis showed BF% to have the highest correlation with countermovement VJ displacement (r = -0.76, p < 0.001). When examining lower-body dimensions, right-side Q-angle displayed the strongest association with countermovement VJ displacement (r = -0.58, p < 0.001). Regression analysis revealed that 2 different pairs of variables accounted for the greatest variation (66%) in VJ: (a) BF% and sex and (b) BF% and body weight. Regression models involving BF% and lower-body dimensions explained up to 61% of the variance observed in VJ. Although the variance explained by BF% may be increased by using several lower-body dimensions, either sex identification or body weight explains comparatively more. Therefore, these data suggest that the lower-body dimensions measured herein have limited utility in explaining VJ performance.

Consistency of Lower-Body Dimensions Using Surface Landmarks and Simple Measurement Tools.

Caia, J, Weiss, LW, Chiu, LZF, Schilling, BK, and Paquette, MR. Consistency of lower-body dimensions using surface landmarks and simple measurement tools. J Strength Cond Res 30(9): 2600-2608, 2016-Body dimensions may influence various types of physical performance. This study was designed to establish the reliability and precision of bilateral lower-body dimensions using surface anatomic landmarks and either sliding calipers or goniometry. Fifty university students (25 men and 25 women) were measured on 2 separate occasions separated by 48 or 72 hours. A small digital caliper was used to acquire longitudinal dimensions of the feet, whereas a larger broad-blade caliper was used to measure lower-limb, hip, and pelvic dimensions. Quadriceps angle (Q-angle) was determined through surface goniometry. Data for all foot and lower-limb dimensions were both reliable and precise (intraclass correlation coefficient (ICC) ≥0.72, SEM 0.1-0.5 cm). Measures of Q-angle were also reliable and precise (ICC ≥0.85, SEM 0.2-0.4°). Findings from this investigation demonstrate that lower-body dimensions may be reliably and precisely measured through simple practical tests, when surface anatomic landmarks and standardized procedures are used. Although intertester reliability remains to be established, meticulous adherence to specific measurement protocols is likely to yield viable output for lower-body dimensions when more sophisticated methods are unavailable or inappropriate.

Lower Limb Kinematics and Metabolic Cost During Elliptical Exercises and Treadmill Running.

The purpose of this study was to compare knee and hip joint kinematics previously associated with anterior knee pain and metabolic cost among conditions including treadmill running (TR), standard elliptical (SE), and lateral elliptical (LE) in healthy runners. Joint kinematics and metabolic parameters of 16 runners were collected during all 3 modalities using motion capture and a metabolic system, respectively. Sagittal knee range of motion (ROM) was greater in LE (P < .001) and SE (P < .001) compared with TR. Frontal and transverse plane hip ROM were greater in LE compared with SE (P < .001) and TR (P < .001). Contralateral pelvic drop ROM was smaller in SE compared with TR (P = .002) and LE (P = .005). Similar oxygen consumption was found during LE and TR (P = .39), but LE (P < .001) and TR (P < .001) required greater oxygen consumption than SE. Although LE yields similar metabolic cost to TR and produces hip kinematics that may help strengthen hip abductors, greater knee flexion and abduction during LE may increase symptoms in runners with anterior knee pain. The findings suggest that research on the implications of elliptical exercise for injured runners is needed.

Effects of footwear condition on maximal jumping performance.

The purpose of this investigation was to examine the effects of footwear on kinetics and lower extremity electromyographic (EMG) activity during the vertical jump (VJ) and standing long jump. Fifteen men performed the 2 jump types in 3 footwear conditions: barefoot, minimal shoes, and cross-training shoes. Jump displacement and kinetic data were collected, along with EMG activity of the biceps femoris, medial gastrocnemius, peroneus longus, semitendinosus/semimembranosus, soleus (SOL), tibialis anterior, vastus lateralis, and vastus medialis. Subjective footwear performance and comfort were also assessed with a custom survey. No differences were found in jump displacement, peak ground reaction forces (GRF), countermovement and propulsive phase durations, vertical impulse, peak countermovement, or average propulsive EMG activity. Significant differences in peak propulsive root mean square EMG were found between barefoot and minimal shoes (p = 0.030) and minimal shoes and shod (p = 0.031) conditions for the SOL during the VJ, and for average countermovement EMG of the semitendinosus/semimembranosus during the VJ between barefoot and shod (p = 0.039). Moderate-to-large effect sizes (>0.59) were found between conditions for horizontal GRF, propulsive phase duration, average EMG amplitude, and duration of EMG activity during the countermovement. Participants reported higher comfort ratings when shod compared with barefoot and minimal shoes for both jumps. Participants also perceived better performance when shod compared with barefoot and minimal shoes for the VJ only. No acute differences in displacement were observed between barefoot, minimal shoes, and cross-trainer shoes during vertical and horizontal jumps. Some differences in muscle activation and timing seem to be present, and thus, training effects between footwear conditions should be examined. Footwear familiarization may prove beneficial, as acute increases in comfort seem unrelated to performance improvements.