Allometric Grip Strength Norms for American Children.

Kocher, MH, Oba, Y, Kimura, IF, Stickley, CD, Morgan, CF, and Hetzler, RK. Allometric grip strength norms for American children. J Strength Cond Res 33(8): 2251-2261, 2019-To develop normative data from a large cohort of American school children (ages 6-18) for unscaled and allometrically scaled handgrip strength data that are uninfluenced by body size (body mass [BM] and stature [Ht]). Data (age, handgrip strength, BM, and Ht) were collected from the 2011-2012 and 2013-2014 National Health and Nutrition Examination Survey databases, resulting in 4,665 cases (2,384 boys and 2,281 girls). Multiple log-linear regressions were used to determine allometric exponents for BM and Ht separately for each age and sex to satisfy the common exponent and group difference principles described by Vanderburgh. Appropriateness of the allometric model was assessed through regression diagnostics, including normality and homoscedasticity of residuals. Allometrically scaled, ratio-scaled, and unscaled grip strength were then correlated with BM and Ht to examine the effectiveness of the procedure in controlling for body size. The data did not allow for development of a common exponent across age and sex that did not violate the common exponent and group difference principles. Correlations between allometrically scaled handgrip strength with BM and Ht were not significant (p ≤ 0.479) and approached zero, unlike correlations of unscaled handgrip strength with BM and Ht (p < 0.001 for all), indicating that allometric scaling was successful in removing the influence of body size. Allometric scaling handgrip strength by age and sex effectively controls for body size (Ht and BM) and perhaps maturation (Ht). The allometric exponents and normative values developed can be used to compare handgrip strength within age and sex while controlling for body size.

Standard Radiographs Are Not Sufficient for Assessing Knee Mechanical Axis in Patients With Advanced Osteoarthritis.

BACKGROUND: The use of standard radiographs, and measured tibiofemoral angle (TFA), to assess lower extremity alignment is commonly practiced despite limited knowledge of its relationship to the mechanical axis (MA), as measured on hip-to-ankle (HTA) radiographs. This study assessed the predictive accuracy of previously developed equations, developed gender-specific regression equations using predictors from standard radiographs, and the clinical effectiveness of these equations in a large sample of cases using HTA radiographs as a gold standard. METHODS: The MA was measured on HTA radiographs, whereas TFA and femoral angle were measured on standard radiographs in 788 cases diagnosed with knee osteoarthritis. RESULTS: Multiple regression analyses indicated that TFA, femoral angle, and height were the strongest factors associated with the predicting MA, accounting for 83% of the variance for men and 86% for women, but were able to predict only the actual MA within ±3° in 66% of men and 69% of women. When applied to previously reported regression equations with similar results, the best predicative accuracy obtained within ±3° was 61% and 63% of men and women, respectively. CONCLUSION: Standard radiographs are not sufficient for determining MA, and HTA radiographs should be used while making surgical decisions aimed at correcting alignment to within ±3° or for assessing alignment post-total knee arthroplasty. In addition, surgical alignment outcomes reported in previous research using standard radiographs should be viewed with caution.

Allometric Grip Strength Norms for Children of Hawaiian Lineage.

The purpose of the study was to determine allometric exponents for scaling grip strength in children that effectively control for body mass (BM) and stature (Ht) and to develop normative grip strength data for Hawaiian children. One thousand, four hundred thirty-seven students (754 boys) from a rural community in Hawaii participated in this 5-year study, resulting in 2,567 data points. Handgrip strength, BM, and Ht were collected every year. Multiple log-linear regression was used to determine allometric exponents for BM and Ht. Appropriateness of the allometric model was assessed through regression diagnostics, including normality of residuals and homoscedasticity. Allometrically scaled, ratio-scaled, and unscaled grip strength were then correlated with BM and Ht to examine the effectiveness of the procedure in controlling for body size. Allometric exponents for BM and Ht were calculated separately for each age group of boys and girls to satisfy the common exponent and group difference principles described by Vanderburgh. Unscaled grip strength had moderate to strong positive correlations with BM and Ht (p ≤ 0.05 for all) for all age groups. Ratio-scaled handgrip strength had significant moderate to strong negative correlations with BM (p ≤ 0.05 for all) and, to a lesser extent, Ht (p ≤ 0.05 for 8- to 12-year-old boys; p ≤ 0.05 for 8- to 12- and 14-year-old girls). Correlations between allometrically scaled handgrip strength and BM and Ht were not significant and approached zero. This study was the first to allometrically scale handgrip strength for BM and Ht in Hawaiian children. Allometric scaling applied to grip strength provides a useful expression of grip strength free of the confounding influence of body size.

Aerobic fitness levels and validation of a non exercise VO2max prediction equation for HIV-infected patients on HAART.

BACKGROUND: Non-exercise (N-EX) questionnaires have been developed to determine maximal oxygen consumption (VO2max) in healthy populations. There are limited reliable and validated N-EX questionnaires for the HIV+ population that provide estimates of habitual physical activity and not VO2max. OBJECTIVES: To determine how well regression equations developed previously on healthy populations, including N-EX prediction equations for VO2max and age-predicted maximal heart rates (APMHR), worked on an HIV+ population; and to develop a specific N-EX prediction equation for VO2max and APMHR for HIV+ individuals. METHODS: Sixty-six HIV+ participants on stable HAART completed 4 N-EX questionnaires and performed a maximal graded exercise test. RESULTS: Sixty males and 6 females were included; mean (SD) age was 49.2 (8.2) years; CD4 count was 516.0 ± 253.0 cells·mm-3; and 92% had undetectable HIV PCR. Mean VO2max was 29.2 ± 7.6 (range, 14.4-49.4) mL·kg-1·min-1 Despite positive correlations with VO2max, previously published N-EX VO2max equations produced results significantly different than actual VO2 scores (P < .0001). An HIV+ specific N-EX equation was developed and produced similar mean VO2max values, R = 0.71, when compared to achieved VO2max (P = .53). CONCLUSION: HIV+ individuals tend to be sedentary and unfit, putting them at increased risk for the development of chronic diseases associated with a sedentary lifestyle. Based on the level of error associated with utilizing APMHR and N-EX VO2max equations with HIV+ individuals, neither should be used in this population for exercise prescription.

Validity and reliability of the Hawaii anaerobic run test.

This study examined the reliability and validity of the Hawaii anaerobic run test (HART) by comparing anaerobic capacity measures obtained to those during the Wingate Anaerobic Test (WAnT). Ninety-six healthy physically active volunteers (age, 22.0 ± 2.8 years; height, 163.9 ± 9.5 cm; body mass, 70.6 ± 14.7 kg; body fat %, 19.29 ± 5.39%) participated in this study. Each participant performed 2 anaerobic capacity tests: the WAnT and the HART by random assignment on separate days. The reliability of the HART was calculated from 2 separate trials of the test and then determined through intraclass correlation coefficients (ICCs). Blood samples were collected, and lactate was analyzed both pretest and posttest for each of the 2 exercise modes. Heart rate and rate of perceived exertion were also measured pre- and post-exercise. Hawaii anaerobic run test peak and mean momentum were calculated as body mass times highest or average split velocity, respectively. Intraclass correlation coefficients between trials of the HART for peak and mean momentum were 0.98 and 0.99, respectively (SEM = 18.8 and 25.7, respectively). Validity of the HART was established through comparison of momentum on the HART with power on the WAnT. High correlations were found between peak power and peak momentum (r = 0.88), as well as mean power and mean momentum (r = 0.94). The HART was considered to be a reliable test of anaerobic power. The HART was also determined to be a valid test of anaerobic power when compared with the WAnT. When testing healthy college-aged individuals, the HART offers an easy and inexpensive alternative maximal effort anaerobic power test to other established tests.

Allometric scaling of strength scores in NCAA division I-A football athletes.

This study examined population-specific allometric exponents to control for the effect of body mass (BM) on bench press, clean, and squat strength measures among Division I-A collegiate football athletes. One repetition maximum data were obtained from a university pre-season football strength assessment (bench press, n = 207; clean, n = 88; and squat n = 86) and categorized into 3 groups by positions (line, linebacker, and skill). Regression diagnostics and correlations of scaled strength data to BM were used to assess the efficacy of the allometric scaling model and contrasted with that of ratio scaling and theoretically based allometric exponents of 0.67 and 0.33. The log-linear regression models yielded the following exponents (b): b = 0.559, 0.287, and 0.496 for bench press, clean, and squat, respectively. Correlations between bench press, clean, and squat to BM were r = -0.024, -0.047, and -0.018, respectively, suggesting that the derived allometric exponents were effective in partialling out the effect of BM on these lifts and removing between-group differences. Conversely, unscaled, ratio-scaled, and allometrically scaled (b = 0.67 or 0.33) data resulted in significant differences between groups. It is suggested that the exponents derived in the present study be used for allometrically scaling strength measures in National Collegiate Athletic Association Division I-A football athletes. Use of the normative percentile rank scores provide coaches and trainers with a valid means of judging the effectiveness of their training programs by allowing comparisons between individuals without the confounding influence of BM.

Allometric scaling of Wingate anaerobic power test scores in men.

This study examined the appropriate magnitude of allometric scaling of the Wingate anaerobic test (WAnT) power data for body mass (BM) and established normative data for the WAnT for adult men. Eighty-three men completed a standard WAnT using 0.1 kg·kg(-1) BM resistance. Allometric exponents and percentile ranks for 1-second peak power (PP), 5-second PP, and mean power (MP) were established. The Predicted Residual Sum of Squares (PRESS) procedure was used to assess external validity while avoiding data splitting. The mean 1-second PP, 5-second PP, and MP were 1,049.1 ± 168.8 W, 1,013.4 ± 158.6 W, and 777.9 ± 105.0 W, respectively. Allometric exponents for 1-second PP, 5-second PP, and MP scaled for BM were b = 0.89, 0.88, and 0.86, respectively. Correlations between allometrically scaled 1-second PP, 5-second PP, and MP, and BM were r = -0.03, -0.03, and -0.02, respectively, suggesting that the allometric exponents derived were effective in partialling out the effect of BM on WAnT values. The PRESS procedure values resulted in small decreases in R² (0.03, 0.04, and 0.02 for 1-second PP, 5-second PP, and MP, respectively) suggesting acceptable levels of external validity when applied to independent samples. The allometric exponents and normative values provide a useful tool for comparing WAnT scores in college-aged females without the confounding effect of BM. It is suggested that exponents of b = 0.89 (1-second PP), b = 0.88 (5-second PP), and b = 0.86 (MP) be used for allometrically scaling WAnT power values in healthy adult men and that the confidence limits for these allometric exponents be considered as 0.66-1.0 for PP and 0.69-1.0 for MP. The use of these exponents in allometric scaling of male WAnT power values provide coaches and practitioners with valid means for comparing power production between individuals without the confounding influence of BM.

Validation of a nonexercise prediction equation of anaerobic power.

This study examined the validity of estimating anaerobic power in college-aged students using anthropometric data and a paper and pencil test. Peak power (PP) and mean power (MP) were determined for 157 subjects (92 men and 65 women) using a standard Wingate anaerobic test (WAnT) at a resistance of 0.075 and 0.10 kg·body mass for women and men, respectively. Subjects completed previously established paper and pencil tests for assessing aerobic capacity and rated their ability to perform tasks related to anaerobic power, such as their vertical jump height relative to peers. Descriptive statistics were generated, and multiple regression was performed using SAS v9.1 to assess the ability of paper and pencil tests to predict PP and MP from the WAnT. Mean (±SD) age, height, body mass, body mass index, PP, and MP for subjects were 22.1 ± 2.5 years, 175.6 ± 7.5 cm, 78.5 ± 11.4 kg, 25.4 ± 3.0 kg·m, 1015.2 ± 169.7 W, and 784.5 ± 122.1 W and 22.0 ± 3.0 years, 163.6 ± 7.4 cm, 61.1 ± 10.4 kg, 22.8 ± 3.4 kg·m, 593.0 ± 102.4 W, and 478.8 ± 72.8 W, respectively. Mean estimated jump height (EJHt) rating values were 5.8 ± 1.5 and 4.7 ± 1.5 (on a 1-9 Likert-type scale) for men and women, respectively. The following multiple regression models were developed:PP = -34.5 + 249.6 (gender; female = 0, male = 1) + 8.1 (BMkg) + 27.8 (EJHt) (R = 0.82, SEE = 106.6 W);MP = -37.7 + 163.7 (gender) + 6.7 (BMkg) + 22.8 (EJHt) (R = 0.87, SEE = 65.5 W).It was concluded that valid estimates for PP and MP could be obtained from anthropometric data and a single question paper and pencil test asking subjects to estimate relative jumping ability, without the need for performing the Wingate anaerobic cycle test.

Comparisons of age-predicted maximum heart rate equations in college-aged subjects.

This study investigated the accuracy of age-predicted equations to predict heart rate maximum (HRmax) in a college-age sample and establish efficacy of short-duration anaerobic capacity tests to determine the actual HRmax. A criterion HRmax (CHRmax) was obtained from 96 (52 men and 44 women, age = 22.0 ± 2.8 years, height = 163.9 ± 9.5 cm, 70.6 ± 14.7 kg, resting HR = 68.9 ± 11.2 b·min) healthy volunteers during 2 200-m sprint trials on a standard track. Maximal effort was confirmed via plasma lactate ≥7 mmol·L(-1) and rating of perceived exertion ≥17 points. The CHRmax was compared to 7 age-predicted HRmax equations: Fox et al., 3 equations from Gellish et al., Tanaka et al., and gender-specific equations from Fairbarn et al., and Hossack et al. Descriptive statistics and standard errors of estimate (SEEs) were calculated. One-way analysis of variance was used to assess differences between the criterion HRmax and the age-predicted HRmax from the 7 equations. The predicted HRmax from the Fox equation and those of Gellish(3), Tanaka, and Hossack were all significantly higher (p ≤ 0.05) than the CHRmax. The Fox equation resulted in overpredicting HRmax in 88.5% of the cases compared to the CHRmax. Compared to the CHRmax, the age-predicted HRmax equations resulted in the following percentages of the CHRmax: Fox = 104.8%, SEE = 12.7; Gellish(1) = 95.2%, SEE = 12.2; Gellish(2) = 99.6%, SEE = 8.3; Gellish(3) = 101.8%, SEE = 9.1; Tanaka = 102.0%, SEE = 9.3; Fairbarn = 100.1%, SEE = 8.5; and Hossack = 105.2%, SEE = 13.9 of CHRmax. It was concluded that the Gellish(2) and Fairbarn equations were the most accurate of the age-predicted HRmax equations in a college-age population. In practical application, 2 200-m sprint trials provide a reasonable estimate of HRmax compared to a graded exercise test.

Development of a modified Margaria-Kalamen anaerobic power test for American football athletes.

This study examined a modification of the Margaria-Kalamen test for football players. The football stair climb test (FST) protocol used in this study increased the vertical displacement (20 steps, 3.12 m) so that the mean best time for the test was 2.048 +/- 0.267 seconds. Fifty-eight Division I-A football players volunteered to participate (mean +/- SD age = 20.2 +/- 1.8 yr, height = 184.1 +/- 7.7 cm, weight = 102.5 +/- 19.4 kg). Subjects performed 25 trials with 30 to 40 seconds of rest between trials. Test-retest reliability was determined using 34 subjects by way of intraclass correlation coefficients with a value of 0.73 for peak power and SEM of 105.4 W, indicating an acceptable level of reliability. Subjects were divided into 3 groups by position: linemen (Line), skill, and linebackers (LB). Alpha level was p < 0.05. Peak power was 1674.5 +/- 300.8, 1712.6 +/- 251.5, and 1388.6 +/- 210.4 W for the LB, Line, and Skill groups, respectively. Groups were significantly different (p < 0.0001), with the LB and Line found to be more powerful than the Skill group. Peak power continued to increase throughout the 25 trials in the Skill and LB group but plateaued after approximately 17 trials in the Line group. It was concluded that the FST was a reliable test for measuring peak anaerobic power in collegiate football players, which, theoretically, should provide more accurate measures of peak power caused by increased vertical displacement and longer duration, resulting in a decreased influence of cheating strategies during test administration. To achieve maximal power in stair climbing tasks, coaches may need to incorporate a greater number of trials or a more intense warm-up than has been previously reported.

Anthropometry increases 1 repetition maximum predictive ability of NFL-225 test for Division IA college football players.

The purpose of this study was to compare existing 1 repetition maximum (1RM) bench press prediction equations in National Collegiate Athletic Association (NCAA) Division IA college football players and determine if the error associated with the prediction of 1RM bench press from the National Football League (NFL)-225 test could be reduced through the addition of anthropometric measurements. Anthropometric measures, 1RM bench press, NFL-225 test repetitions to fatigue, and body composition data were collected on 87 Division IA football players (mean+/-SD age 19.9+/-1.3 years; height 182.3+/-7.3 cm; body mass 102.3+/-21.1 kg; % fat 13.9+/-6.7; 1RM bench press 140.5+/-2 6.6 kg; and NFL-225 reps to fatigue 14.1+/-8.0). Hierarchical regression revealed an R=0.87 when predicting 1RM from the NFL-225 test alone, which improved to R=0.90 with the addition of the anthropometric variables: arm circumference and arm length. The following equation was the best performing model to predict 1RM bench press: 1RM (lb)=299.08+2.47 arm circumference (cm)--4.60 arm length (cm)+5.84 reps @ 225; SEE=18.3 lb). This equation predicted 43.7% of subjects' within +/-10 lb of their actual 1RM bench press. Using a crossvalidation group, the equation resulted in estimates of 1RM which were not significantly different than the actual 1RM. Because of the variability that has been shown to be associated with 1RM prediction equations, the use of actual 1RM testing is recommended when this is a critical variable. However, coaches, scouts, and athletes, who choose to estimate 1RM bench press using repetitions to failure from the NFL-225 test, may benefit from the use of the equations developed in this study to estimate 1RM bench press with the inclusion of simple anthropometric measurements.

The effect of Kinesio-tape® on pain and vertical jump performance in active individuals with patellar tendinopathy.

BACKGROUND: Patellar tendinopathy is a common inflammatory condition in athletes who undergo large volumes of running and jumping. Kinesio-tape® (KT) is proposed to provide pain relief; however, its effect has not been examined on patellar tendinopathy. OBJECTIVE: To examine the effects of KT on pain modulation for active individuals with patellar tendinopathy during functional activities. METHODS: Thirteen symptomatic knees from seven college-aged females (6 bilateral; 1 unilateral) were included. Participants underwent three data collection sessions with KT, sham, and no tape (NT) in a randomized order. During the session, participants performed a maximum vertical jump, single-leg squats and isometric knee extension. The KT intervention was applied according to the KT manual and the sham utilized the same pattern without tension. Pain level was evaluated using the numeric pain scale before, during and after each activity. Function was assessed as maximum vertical jump height and maximum isometric strength. A separate repeated measures ANOVA was used to compare each dependent variable (pain level, vertical jump height, and isometric strength) among the conditions. RESULTS: Reported pain scores were significantly lower (p = 0.05) during the maximal vertical jump test for KT (3.38 ± 1.26) compared to NT (4.54 ± 2.22). Significantly lower jump heights were found under KT (17.73 ± 3.06in) during the maximum vertical jump test compared to sham (18.65 ± 2.17in, p = 0.000) and NT (18.18 ± 2.93in, p = 0.008). CONCLUSIONS: The use of the KT tape with a tendon corrective strip and muscle facilitative strip was effective for decreasing pain associated with patellar tendinopathy during jump landing but led to decreased maximum jump height. CLINICAL TRIAL IDENTIFIER: NCT04153877.

Validation of the human activity profile in HIV-positive individuals on HAART.

OBJECTIVES: This study tested the validity of the Human Activity Profile (HAP) in an HIV-positive population receiving highly active antiretroviral therapy (HAART). The HAP is a 94-item questionnaire for estimating functional capacity based on estimated metabolic equivalents for activities of daily living. METHODS: Twenty-six HIV-positive participants (24 male, 2 female; age 46.0 +/- 9.3 years) receiving HAART completed the HAP and an exercise protocol (Balke treadmill test). The HAP yields a maximal activity score (MAS) and adjusted activity score (AAS; MAS minus activities no longer performed). Twelve participants also completed another nonexercise questionnaire (NEx). RESULTS: Mean maximal oxygen uptake values (VO(2max)) were normally distributed, similar to non-HIV-positive normative data (37.73 +/- 6.95 mL O2*kg-1*min-1) and poorly correlated with MAS and AAS (r = 0.27 and rho = 0.32, respectively), possibly due to a ceiling effect. Estimated VO(2max) from the NEx was not significantly different than measured VO2max and was highly correlated (r = 0.82). CONCLUSIONS: The HAP is not a valid indicator of functional capacity for HIV-positive patients on HAART. The lack of functional impairment suggests that, in the absence of other clinically relevant limitations, HIV-positive individuals on HAART may benefit from exercise prescriptions developed similarly for non-HIV-positive individuals, based on the NEx or submaximal testing protocols, without requiring adaptive strategies.

Prediction of anaerobic power values from an abbreviated WAnT protocol.

The traditional 30-second Wingate anaerobic test (WAnT) is a widely used anaerobic power assessment protocol. An abbreviated protocol has been shown to decrease the mild to severe physical discomfort often associated with the WAnT. Therefore, the purpose of this study was to determine whether a 20-second WAnT protocol could be used to accurately predict power values of a standard 30-second WAnT. In 96 college females, anaerobic power variables were assessed using a standard 30-second WAnT protocol. Maximum power values as well as instantaneous power at 10, 15, and 20 seconds were recorded. Based on these results, stepwise regression analysis was performed to determine the accuracy with which mean power, minimum power, 30-second power, and percentage of fatigue for a standard 30-second WAnT could be predicted from values obtained during the first 20 seconds of testing. Mean power values showed the highest level of predictability (R2 = 0.99) from the 20-second values. Minimum power, 30-second power, and percentage of fatigue also showed high levels of predictability (R2 = 0.91, 0.84, and 0.84, respectively) using only values obtained during the first 20 seconds of the protocol. An abbreviated (20-second) WAnT protocol appears to effectively predict results of a standard 30-second WAnT in college-age females, allowing for comparison of data to published norms. A shortened test may allow for a decrease in unwanted side effects associated with the traditional WAnT protocol.

Reliability and accuracy of handheld stopwatches compared with electronic timing in measuring sprint performance.

This study assessed reliability of split times obtained by handheld stopwatches (HHSs) compared with electronic timing (ET) during a 200-m sprint. Two HHS timing methods were compared with ET: single-split timers (SST) and multiple-split timers (MST). Twenty-six timers without previous experience were given instruction and completed practice trials until good agreement was achieved between ET and HHS. Trained runners (8 males, 10 females) were timed for each 25-m interval on a standard 200-m course. Repeated-measures analysis of variance and intraclass correlation models were used to determine reliability. A total of 248 split times were analyzed. No significant differences were found between the three timing methods (p > 0.99), and calculated intraclass correlation values were high (0.988). Mean error between SST, MST, and ET (-0.04 +/- 0.24 and -0.05 +/- 0.24 seconds, respectively) indicated faster HHS times, though not significantly. However, absolute errors were considerably larger (0.15 +/- 0.20 and 0.16 +/- 0.19 between SST, MST, and ET, respectively). The HHS-recorded splits were faster than ET in 67.3% of splits and slower in 29.4%. The distribution of errors made the development of a reliable correction factor to convert HHS to ET impossible. It was concluded that on the basis of the small mean error and high intraclass correlations, the use of HHSs may be a viable alternative to ET in collecting group data. However, on the basis of the absolute error between HHS and ET, when high degrees of precision are required, ET should be used, and reliable correction of HHS to ET values is not possible. It was further concluded that HHS times should be reported without attempting correction and interpreted in light of the shortcomings of the HHS method.

Effects of combination oral contraceptives on strength development in women athletes.

This study was designed to investigate the effects of combination oral contraceptive agents (OCAs) on strength and torque production in collegiate women softball and water polo athletes who participated in a 12-week strength development program. A double-blind research design was used to mask subjects to the main outcome of interest. Thirty-one women collegiate softball and water polo players were divided into experimental (OCA users, n = 13), and control (non-OCA users, n = 18) groups. All subjects participated in the same supervised 12-week preseason strength development program. One-repetition maximum bench press (1RMBP), 10-repetition maximum leg extension (10RMLE), isokinetic peak torque bench press (IKBP), and isokinetic peak torque leg extension (IKLE) data were collected at weeks 0 (pre-test), 4, 8, and 12 (post-test). Significant increases in strength and torque production over time were identified regardless of group for 1RMBP, 10RMLE, and IKLE. No significant differences in IKBP torque production occurred during the 12-week strength training program. No significant differences in 1RMBP, 10RMLE, IKBP, or IKLE occurred between the OCA users and the non-OCA users groups. It was concluded that, within the limitations of the study, the use of combination OCAs did not provide sufficient androgenic effect to increase strength gains beyond the stimulus of the training protocol.

The effectiveness of scaling procedures for comparing ground reaction forces.

Various scaling methods are used when attempting to remove the influence of anthropometric differences on ground reaction forces (GRF) when comparing groups. Though commonly used, ratio scaling often results in an over-correction. Allometric scaling has previously been suggested for kinetic variables but its effectiveness in partialing out the effect of anthropometrics is unknown due to a lack of consistent application. This study examined the effectiveness of allometric scaling vertical, braking and propulsive GRF and loading rate for 84 males and 47 females while running at 4.0 m/s. Raw, unfiltered data were ratio scaled by body mass (BM), height (HT), and BM multiplied by HT (BM∗HT). Gender specific exponents for allometric scaling were determined by performing a log-linear (for BM and HT individually) or log-multilinear regression (BMHT). Pearson productmoment correlations were used to assess the effectiveness of each scaling method. Ratio scaling by BM, HT, or BM∗HT resulted in an over-correction of the data for most variables and left a considerable portion of the variance still attributable to anthropometrics. Allometric scaling by BM successfully removed the effect of BM and HT for all variables except for braking GRF in males and vertical GRF in females. However, allometric scaling for BMHT successfully removed the effect of BM and HT for all reactionary forces in both genders. Based on these results, allometric scaling for BMHT was the most appropriate scaling method for partialing out the effect of BM and HT on kinetic variables to allow for effective comparisons between groups or individuals.

Dynamic Varus and the Development of Iliotibial Band Syndrome.

CONTEXT: Although the risk of osteoarthritis development after acute knee injury has been widely studied, the long-term consequences of knee overuse injury are not well understood. OBJECTIVE: To identify the relationship between gait-related risk factors associated with osteoarthritis and the development of iliotibial band syndrome (ITBS) in members of a single University Army Reserve Officers' Training Corps unit. DESIGN: Prospective cohort study. SETTING: Biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: Sixty-eight cadets undergoing standardized physical fitness training. INTERVENTION(S): Three-dimensional lower extremity kinematics (240 Hz) and kinetics (960 Hz) were collected for 3 bilateral trials during shod running at 4.0 m/s ± 10%. Injury tracking was conducted for 7 months of training. MAIN OUTCOME MEASURE(S): Biomechanical variables, including varus thrust and knee-adduction moment, were compared between the injured and control groups. RESULTS: Twenty-six cadets with no history of overuse injury served as the control group, whereas 6 cadets (7 limbs) who developed ITBS that required them to modify their training program or seek medical care (or both) served as the injured group. Maximum varus velocity was higher ( P = .006) and occurred sooner during stance ( P = .04) in the injured group than in the control group, indicating greater varus thrust. Maximum knee-varus angle and maximum knee-adduction moment were higher ( P = .02 and P = .002, respectively) and vertical stiffness was lower ( P = .03) in the injured group. CONCLUSIONS: Measures of dynamic varus stability appeared to be altered in individuals who developed ITBS. Biomechanical knee variables previously identified as increasing the risk for knee osteoarthritis were also associated with the development of ITBS in healthy adults.

Asymmetry between lower limbs during rested and fatigued state running gait in healthy individuals.

Although normal gait is often considered symmetrical in healthy populations, differences between limbs during walking suggest that limbs may be used preferentially for braking or propulsion. The purpose of this study was to evaluate kinematic and kinetic variables, at both rested state and following a two-stage treadmill fatiguing run, for asymmetry between limbs. Kinematic (240Hz) and kinetic (960Hz) running data were collected bilaterally for 20 physically active individuals at both rested and fatigued states. Symmetry angles were calculated to quantify asymmetry magnitude at rested and fatigued states. Paired t-tests were used to evaluate differences between right and left limbs at rested and fatigued states, as well as rested and fatigued states symmetry angles. Variables that have been previously associated with the development of overuse injuries, such as knee internal rotation, knee stiffness, loading rate, and adduction free moment, were found to be significantly different between limbs at both rested and fatigued states. Significant differences in vertical stiffness were found, potentially indicating functional asymmetry during running. Symmetry angle was used to investigate changes in percentage of asymmetry at rested and fatigued states. Small (1-6%), but significant decreases in vertical stiffness, loading rate, and free moment symmetry angles indicate that these variables may become more symmetrical with fatigue. Knee internal rotation and knee stiffness became more asymmetrical with fatigue, increasing by 14% and 5.3%, respectively. The findings of the current study indicate that fatigue induced changes in gait may progress knee movement pattern asymmetry.

Short Communication: HIV Patient Systemic Mitochondrial Respiration Improves with Exercise.

In HIV-infected individuals, impaired mitochondrial function may contribute to cardiometabolic disease as well as to fatigue and frailty. Aerobic exercise improves total body energy reserves; however, its impact at the cellular level is unknown. We assessed alterations in cellular bioenergetics in peripheral blood mononuclear cells (PBMC) before and after a 12-week aerobic exercise study in sedentary HIV-infected subjects on stable antiretroviral therapy who successfully completed a 12-week aerobic exercise program. In this prospective study, participants underwent supervised 20-40 min of light aerobic exercise (walking or jogging) performed three times per week for 12 weeks, gradually increasing to maintain an intensity of 50%-80% of heart rate reserve. Maximal aerobic capacity (VO2MAX) was assessed by a graded exercise test on a cycle ergometer before and after completion of the study. PBMC from compliant subjects (attended at least 70% of exercise sessions) were assessed for mitochondrial respiration using the Seahorse XF24 Bio-Analyzer. Seven of 24 enrolled subjects were compliant with the exercise regimen. In these individuals, a significant increase (p = .04) in VO2MAX over 12 weeks was found with a median increase of 14%. During the same interval, a 2.45-fold increase in PBMC mitochondrial respiratory capacity (p = .04), a 5.65-fold increase in spare respiratory capacity (p = .01), and a 3.15-fold (p = .04) increase in nonmitochondrial respiration was observed. Aerobic exercise improves respiration at the cellular level. The diagnostic and prognostic value of such improved cellular respiration in the setting of chronic HIV warrants further investigation.