Jump Power Research Articles

Changes in real-world walking speed following 60-day bed-rest

The aim of this work was to explore whether real-world walking speed (RWS) would change as a consequence of 60-day bed-rest. The main hypothesis was that daily RWS would decrease after the bed-rest, with a subsequent recovery during the first days of re-ambulation. Moreover, an exploratory analysis was done in order to understand whether there is an agreement between the loss in RWS after bed-rest and the loss in the maximum oxygen uptake capacity (VO2max), or the loss in maximal vertical jump power (JUMP) respectively. Twenty-four subjects were randomly assigned to one of three groups: a continuous artificial gravity group, an intermittent artificial gravity group, or a control group. The fitted linear mixed effects model showed a significant decrease (p < 0.001) of RWS after the 60-day bed-rest and a subsequent increase (p < 0.001) of RWS during the 14-day recovery period in the study facility. No or little agreement was found between the loss in RWS and the loss in VO2max capacity or the loss in maximal vertical jumping power (RWS vs. VO2max: p = 0.81, RWS vs. JUMP: p = 0.173). Decreased RWS after bed-rest, with a follow-up recovery was observed for all three groups, regardless of the training intervention. This suggests that RWS, also in these settings, was able to reflect a de-conditioning and follow-up recovery process.

Jump Power Predicts Fracture Risk in Older Adults Independent of Sarcopenia and FRAX.

Low countermovement jump power is associated with prevalent fracture, osteoporosis, and sarcopenia in older adults. However, whether jump power predicts incident fracture risk remains uninvestigated. Data of 1366 older adults in a prospective community cohort were analyzed. Jump power was measured using a computerized ground force plate system. Fracture events were ascertained by follow-up interview and linkage to the national claim database (median follow-up 6.4 years). Participants were divided into normal and low jump power groups using a predetermined threshold (women <19.0 W/kg; men <23.8 W/kg; or unable to jump). Among the study participants (mean age 71.6 years, women 66.3%), low jump power was associated with a higher risk of fracture (hazard ratio [HR] = 2.16 versus normal jump power, p < 0.001), which remained robust (adjusted HR = 1.45, p = 0.035) after adjustment for fracture risk assessment tool (FRAX) major osteoporotic fracture (MOF) probability with bone mineral density (BMD) and Asian Working Group for Sarcopenia (AWGS) 2019 sarcopenia definition. In the AWGS no sarcopenia group, participants with low jump power had a significantly higher risk of fracture than those with normal jump power (12.5% versus 6.7%; HR = 1.93, p = 0.013), comparable to that of possible sarcopenia without low jump power (12.0%). Possible sarcopenia group with low jump power had a similar risk of fracture (19.3%) to sarcopenia group (20.8%). When the definition of sarcopenia was modified with jump power measurement (step-up approach: no sarcopenia to possible sarcopenia; possible sarcopenia to sarcopenia when low jump power present), jump power-modified sarcopenia improved sensitivity (18%-39.3%) to classify individuals who sustained MOF during follow-up to high risk compared with AWGS 2019 sarcopenia, while maintaining positive predictive value (22.3%-20.6%). In summary, jump power predicted fracture risk in community-dwelling older adults independently of sarcopenia and FRAX MOF probabilities, suggesting potential contribution of complex motor function measurement in fracture risk assessment. © 2023 American Society for Bone and Mineral Research (ASBMR).

Adaptive Fuzzy Asynchronous Control for Nonhomogeneous Markov Jump Power Systems Under Hybrid Attacks

This article investigates the adaptive fuzzy asynchronous control problem for discrete-time nonhomogeneous Markov jump power systems under hybrid attacks. A nonhomogeneous Markov process is used to describe the phenomenon of transient failures occurring in power lines and subsequent switching of associated circuit breakers. The corresponding nonhomogeneous hidden Markov model is utilized to detect the jump modes of power systems. Both deception attack and denial-of-service attack are analyzed simultaneously owing to the vulnerability of power systems. With detected modes and fuzzy logic systems, an adaptive fuzzy asynchronous control strategy is proposed. Using the mode-dependent Lyapunov function, the existence conditions of the desired controller law are obtained such that the closed-loop power systems are bounded stable in the mean-square sense. Finally, the usefulness of the developed control strategy is demonstrated by a numerical example.

The Relationship Between Muscular Strength, Jump Power, and Bone Health in Collegiate Distance Runners

The Relationship Between Muscular Strength, Jump Power, and Bone Health in Collegiate Distance Runners

Ellipsoidal Design of Robust Stabilization for Markov Jump Power Systems under Normal and Contingency Conditions

The essential prerequisites for secure customer service are power system stability and reliability. This work shows how to construct a robust switching control for studying power system load changes using an invariant ellipsoid method. Furthermore, the suggested control ensures stability when the system is subjected to random stochastic external disturbances, and functions randomly in two conditions: normal and contingency. The extreme (least) reliability state is chosen as the most severe scenario (corresponding to a transmission line outage). As a two-state Markov random chain, the transition probabilities are utilized to simulate the switching between normal and contingency modes (or processes). To characterize the dynamics of the studied system, a stochastic mathematical model is developed. The effect of stochastic disturbances and random normal/contingency operations is taken into account during the design stage. For a stochastic power system, a novel excitation control is designed. The attractive ellipsoid approach and linear matrix inequalities (LMIs) optimization are used to build the best two-controller gains. Therefore, the proposed modeling/design technique can be employed for the power system under load changes, stochastic topological changes, and random disturbances. Finally, the system’s random dynamics simulation indicates the effectiveness of the designed control law.

Elevated serum γ-glutamyl transferase is associated with low muscle function in adults independent of muscle mass

ObjectiveElevated serum γ-glutamyl transferase (GGT), a hepatic cholestasis or liver damage marker, has been associated with low lean mass and adiposity. However, whether serum GGT can predict muscle function in adults remains unclear. The aim of this study was to determine whether an elevated serum GGT is associated with low peak weight-corrected jump power (JP) and low handgrip strength (HGS). MethodsThis study included 662 individuals aged ≥50 y in the final cohort (women, 86%; mean age, 64.8 y). The primary outcome was low peak weight-corrected JP defined as <23.8 W/kg and <19W/kg in men and women, respectively, and the secondary outcome was low HGS (<28 kg in men; <18 kg in women). ResultsParticipants with low JP had a higher GGT level, older age, lower HGS, and higher body fat than those without low JP. Serum GGT showed a negative association with JP (adjusted β = –1.16, P = 0.005) and HGS (adjusted β = –0.92, P = 0.018). One log-unit increment in GGT was associated with elevated odds of low JP (adjusted odds ratio [aOR] 2.13, P = 0.002) after adjustment for age, sex, lean mass, and body fat percentage, particularly in individuals without hepatic steatosis (aOR, 2.30) versus those with hepatic steatosis (aOR, 0.80; Pinteraction = 0.020). ConclusionElevated serum GGT was associated with low muscle function in adults independent of age, muscle mass, and adiposity, indicating that serum GGT may play a role as an independent marker of muscle function. <END ABSTRACT>

Validity and Reliability of Integrated Digital-Based Jump Power Meter Test Instrument for Measuring Limb Muscle Power

Exercise evaluations and measurements are critical. Tests to measure leg muscle power have generated subpar results, prompting the development of an integrated digital-based jump power meter (JPM) instrument. Before using this method, it must be field-tested. The goal of this study was to assess the validity and reliability of the JPM test-retest procedure. The descriptive quantitative research method was used, while data was collected based on the test method. Volleyball players aged 17-20 with weights ranging from 50 kg to 75 kg and heights ranging from 160 cm to 177 cm took part in the study. Pearson's product-moment analysis was used to test the validity of the data, while Cronbach's alpha analysis was used to test the reliability. Each of the male and female players' validity and reliability test results showed a coefficient value greater than 0.9. Based on these findings, the JPM test instrument has nearly perfect validity and reliability. Therefore, the creation of the JPM can facilitate the activities of testing, measuring, and evaluating sports for athletes and coaches, resulting in improved athlete performance.

Innovation for Development of Integrated Digital-Based Jump Power Meter Test for Measuring Limb Muscle Power in Athletes: Aiken Validity and Inter-rater Reliability

Technological advancements create favorable conditions for the world of sports, demonstrating the strength and management of sports through technology. In the 4.0 era, the sports evaluation process is digital already. The test instrument to measure leg muscle power is still done manually today, so a digitally based conceptual design of the leg muscle power instrument is required. Jump power meter (JPM) based on integrated digital technology is an innovative test instrument for limb muscle power with modern technology and the practicality of inputting data. However, for further development, a design assessment by an expert should be carried out. This study aimed to develop a digital-based integrated JPM conceptual design to measure leg muscle power, then tested for content validity and inter-rater reliability. A qualitative and quantitative research method was used with documents and five experts. The first stage of this study was document analysis and field observations, followed by data collection using the Delphi technique in the second stage. The rating scale used was 1-5. The content validity formula for this research was Aiken. Reliability was tested using Cronbach Alpha, while interclass coefficient correlation was used to test the conceptual design of JPM. The study found that the conceptual design of the test instrument to measure jump power could be used to measure an athlete's leg muscle power. Based on the findings of this study, the Aiken coefficient was in the range of 0.85-1.00, with Cronbach Alpha reliability of 0.587&gt;0.6. Meanwhile, the ICC agreements of one rater and between raters are 0.221 and 0.586, respectively. As a result, it can be concluded that the instrument has a high level of content validity and reliability in all aspects.

Physical function and physical activity in adults with X-linked hypophosphatemia.

There is a dearth of literature on physical function and physical activity in adults with X-linked hypophosphatemia (XLH). We described muscle strength and power, functional capacity, mobility and physical activity level and explored the relationships among these variables in adults with XLH. Participants were recruited as part of a UK-based prospective cohort study, the RUDY Study. They underwent a clinical visit and physical examination, including assessment of handgrip strength, jump power (mechanography), six-minute walk test (6MWT) and short physical performance battery (SPPB), and completed the International Physical Activity Questionnaire (IPAQ). Performance data were analysed using parametric and non-parametric tests, whereas correlations were assessed by univariate analysis. Twenty-six adults with XLH (50% males) with a mean age of 44 ± 16.1years were recruited. Jump power and 6MWT distances (p < 0.0001) were 54.4% and 38.6% lower respectively in individuals with XLH compared with normative values. These deficits were not associated with age or sex. Handgrip strength values were similar to expected values. Deficits in muscle power were more pronounced than those reported at 6MWT (p < 0.0001). Univariate analysis revealed only a correlation between total physical activity and muscle power (r = 0.545, p = 0.019). Adults with XLH have a marked deficit in lower limb muscle power and a reduced functional capacity, with a high incidence of impaired mobility and inactivity. In addition to metabolic effects of XLH, low physical activity may contribute to deficits in lower limb power. Further studies are required to develop novel treatment approaches to improve physical function and mobility.

The implementation of plyometrics circuit model to increase jump power

The purpose of this study was to determine the difference in the effect of plyometrics circuit model based on the analysis of vertical jump movement on the increasing of jump power. This study used an experimental method consisting of two variables, namely the manipulative independent variable (exercise model) and the dependent variable (jump power). The research design was one group pre-test and post-test design. The sample used in this study was 10 students of the third semester of sports majoring in Health, Physical Education, and Recreation (HPER). The sample was taken by using purposive random sampling. Jump power data was measured by vertical jump test. The data analysis technique used Paired Samples Test. The prerequisite test used the sample normality test (Kolmogorov-Smirnov Test with α = 0.05) and the homogeneity of variance test (Levene Test with α = 0.05). Based on the results of the study, it showed that there was a significant difference between the pre-test and post-test of plyometrics circuit training model to increase jump power, Tscore = 12.31 > Ttable = 1.83 (p<0.05).

Long Jump, Vertical Jump, and Vertical Jump Power Reference Curves for 10-18 Year Olds

ABSTRACT We developed age- and sex-specific smoothed percentiles for vertical and long jump, as well as vertical jump power, in healthy 10–18 year olds (n = 529, 47.1% female). Jump height and distance were measured and vertical jump power was assessed via mechanography. LMS regression was used to create smoothed age-specific reference curves, separated by sex. Pearson correlations between the jumps ranged from r = 0.22 to 0.64, varying by age and sex. Comparing medians, younger males had slightly higher values for vertical and long jump compared to females. Vertical jump power was more comparable between the sexes. For all measures, differences between the sexes become more pronounced at ages associated with the transition into adolescence. Growth model coefficients are reported for calculation of Z-scores. The growth curves can be used to compare samples, track lower body power, and link tests of fitness to athletic performance or health-related outcomes.

Vertical Jump Power Is Associated with Healthy Bone Outcomes in Youth: ROC Analyses and Diagnostic Performance

ABSTRACT Using a sample of healthy youth (n = 466, 10 to 18 yr), we report the predictive utility of vertical jump power (VJ Power, W) for predicting bone strength. We measured VJ Power using mechanography and an indicator of bone strength, i.e., height-adjusted total bone mineral content less head (TBLH BMC, g), using DXA. Growth curve models were used to convert VJ Power to age- and sex-specific percentiles/Z-scores. Associations were examined using receiver operator characteristic curve analysis, i.e., area-under-the-curve (AUC), as well as sensitivity (Se) and specificity (Sp) for Desirable, Marginal, and Low groups based on VJ Power percentiles. The AUC was 0.84 for TBLH BMC ≤ −2.0 Z-score from VJ Power percentiles. Se for Marginal and Low groups were 71.4% and 42.9%, respectively. Sp for Marginal and Low groups were 85.2% and 95.1%, respectively. The results suggest the utility of using VJ Power percentiles for assessing bone strength.

Predictive Validity of Handgrip Strength, Vertical Jump Power, and Plank Time in the Identification of Pediatric Sarcopenia

ABSTRACT This study examined the predictive validity of musculoskeletal fitness tests for identifying sarcopenia in youth. The sample was 529 participants age 10 to 18 years. Indices included: total lean body mass (LBM) normalized for height (LBM index, LBMI, kg/m2), appendicular LBMI (aLBMI, kg/m2), and LBM to fat body mass (FBM) ratio (LBM/FBM). Lean and fat tissue were measured via DXA. The cutoff value for sarcopenia was – 2.0 standard deviations ≤ mean for age and sex. Fitness was assessed using handgrip, plank, and vertical jump tests. Variables were standardized using the lambda-mu-sigma (LMS) method. By sex, analysis included the area under the curve (AUC), sensitivity (Se), and specificity (Sp). The ROC curves for aLBMI was highly accurate (AUCs ≥ 0.90, Se and Sp = 86–88%) for vertical jump and moderately accurate for handgrip (AUCs = 0.87–0.88, Se and Sp = 71–75%). Fitness tests can be used to identify pediatric sarcopenia.

Combination of DXA and BIS Predicts Jump Power Better Than Traditional Measures of Sarcopenia.

ABSTRACTTraditional diagnostic criteria for sarcopenia use dual‐energy X‐ray absorptiometry (DXA)‐measured appendicular lean mass (ALM), normalized to height (ALM/ht2) or body mass index (ALM/BMI) to define low muscle mass. However, muscle function declines with aging before the loss of muscle mass is detected by ALM. This is likely due, in part, to qualitative muscle changes such as extracellular and intracellular fluid compartment shifts uncaptured by DXA. We propose combining bioimpedance spectroscopy (BIS), which estimates extracellular and intracellular compartment volume, with DXA to more accurately predict muscle function. This combination may help incorporate muscle quality, thereby improving sarcopenia diagnosis. We cross‐sectionally analyzed data from 248 Black and White participants aged 25 to 75 years from the Midlife in the United States Refresher Cohort. We proposed two novel muscle measures: ALM corrected by the BIS‐derived whole‐body extracellular to intracellular fluid ratio (E/I) and leg lean mass (LLM) corrected by leg‐specific E/I, creating (ALM/(E/I)W) and (LLM/(E/I)L), respectively. We compared the associations of traditional muscle measures, ALM/(E/I)W, and LLM/(E/I)L, with grip strength and lower limb power using jumping mechanography. LLM/(E/I)L explained jump power best at R 2 = 0.803 compared with ALM/(E/I)W (p < 0.0001) and all other measures. ALM/(E/I)W explained jump power second best (R 2 = 0.759) but not significantly better than traditional muscle measures. No muscle measure performed better than covariates when predicting handgrip strength. LLM/(E/I)L outperformed ALM/ht2 and ALM/BMI when predicting jump power. We propose LLM/(E/I)L is a powerful and clinically relevant method that accounts for muscle quality. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Muscle Function is Associated With Presence, New-onset, or Worsening of Hepatic Steatosis Assessed by Biochemical Parameters, Independent of Muscle Mass

Non-alcoholic fatty liver disease (NAFLD) becomes a major health problem leading to metabolic complications and end-stage liver disease, lacking effective therapeutic interventions. Skeletal muscle deficit, or sarcopenia, is related to accelerated accumulation of ectopic fat at liver. Skeletal muscle can be a novel intervention target of NAFLD. However, previous studies focused on the association between muscle mass and NAFLD, whereas the association of muscle function with NAFLD, a more clinically relevant assessment regarding skeletal muscle, remains unclear. Among participants enrolled between 2013 to 2014 in cardiovascular and Metabolic Diseases Etiology Research Center (CMERC) study (n=807), a cohort of community-dwelling Korean adults to study cardiovascular risk factors, a total of 500 individuals were recruited for 5-year follow-up. Hepatic steatosis was defined by hepatic steatosis index 36 or higher (HSI=8X(AST/ALT)+BMI+2 [if diabetes]+2 [if female]). New-onset of hepatic steatosis was defined as newly developed hepatic steatosis at current follow-up compared to baseline and worsening of HSI was defined as the highest quartile of HSI changes (2 or higher HSI increase). Muscle function was assessed by peak countermovement jump power relative weight (W/kg), 5 times chair rise test (CRT; in seconds), and grip strength (GS; in kg). Appendicular lean mass (ALM) was measured using bioimpedance analysis (InBody770, Biospace, Seoul, Korea). A total of 439 subjects (women 74%; mean age 57 ± 8 year) were analyzed after excluding those with excessive alcohol intake (n=51) and any missing values (n=10). Hepatic steatosis was present in 40% of subjects, which was increased from baseline period (33%, p<0.001). Low peak jump power (adjusted odds ratio [aOR] 1.14 per 1 W/kg decrease), GS (aOR 1.08 per 1kg decrease), and CRT performance (aOR 1.09 per 1 second increase; p<0.05 for all) were all associated with elevated odds of hepatic steatosis, after adjustment for age, gender, height, ALM, and metabolic syndrome components. Compared to those without hepatic steatosis at baseline and follow-up, those with persistent hepatic steatosis had significantly lower jump power in both men and women (33 vs. 40 W/kg in men, p=0.027; 26 vs. 29 W/kg in women, p<0.001). Jump power remained as robust predictor for new-onset hepatic steatosis or worsening of HSI (aOR 1.05 per 1W/kg decrease, p=0.044), whereas GS, CRT, and ALM were not. Muscle function measured by jump power was associated with presence or worsening of hepatic steatosis assessed by biochemical parameters, independent of muscle mass. Acknowledgement: We thank CMERC participants and all research staffs for this work. Funding: This study was supported by research grants from Hanmi Pharmaceutical Co.,Ltd. (4-2018-0845).

Computed Tomography-Derived Skeletal Muscle Radiodensity Predicts Peak Weight-Corrected Jump Power in Older Adults: The Korean Urban Rural Elderly (KURE) Study.

Computed tomography (CT)-derived skeletal muscle area (SMA) and skeletal muscle radiodensity (SMD) reflect distinctive quantitative and qualitative characteristics of skeletal muscles. However, data on whether CT-based muscle parameters, especially SMD, can predict muscle function is limited. In a prospective cohort, 1523 community-dwelling older adults who underwent abdominal CT scans and the countermovement two-legged jumping test on a ground reaction force platform were analyzed (mean age 74.7years, 65.1% women). SMA and SMD were measured at third lumbar vertebra level (L3). Individuals with low jump power (peak weight-corrected jump power < 23.8W/kg in men and < 19.0W/kg in women using clinically validated threshold) were older; had lower SMA, SMD, and maximal grip strength values; and had lower chair rise test and timed up and go test performance than those without low jump power. SMD was positively associated with peak weight-corrected jump power (adjusted β = 0.33 and 0.23 per 1 HU increase in men and women, respectively, p < 0.001). One HU decrement in SMD was associated with 10% elevated odds of low jump power (adjusted OR [aOR] 1.10, p < 0.001) after adjusting for age, sex, height, inflammation, and insulin resistance markers, whereas the association of SMA with low jump power was attenuated (aOR 1.00, p = 0.721). SMD showed better discrimination for low jump power than SMA (AUC 0.699 vs. 0.617, p < 0.001), with additional improvement when added to SMA and conventional risk factors (AUC 0.745 to 0.773, p < 0.001). Therefore, CT-measured L3 SMD can be a sensitive surrogate marker for muscle function along with SMA in older adults, which merits further investigation.

The Effect of Potentialization afterElectro-Stimulation Activation on VerticalHeel Performance

Introduction: Post Activation Potentiation (PAP) is the effect caused by a conditioning exercise with maximum or submaximal loads that promotes increased explosive strength in the subsequent activity. This phenomenon is due to the phosphorylation of light chain regulatory myosin manifesting in fast-twitch type II fibers. Electro-stimulation is a method that uses electric currents to promote involuntary muscle contraction, and its higher incidence in type II fibers because they have thicker and more superficial nerve endings. Objective: To compare the effects of an electro-stimulation protocol with a plyometric protocol to induce PAP on vertical jump performance. Methods: Plyometric Protocol (PP) - 2 sets of 10 ankle hops, 3 sets of 5 hundle hops, and 5 cold jumps. Electro-stimulation Protocol (EP) - Protocol 32 Neurodyn device 4 channels, Russian current, 90% of pain threshold with 3 rise, 12 on, 3 decay and 18 off with 70Hz frequency burst during 5 'and control condition (CC). 5 'after each protocol the Jump Power Test (JPT) was performed and 3' after the jump resistance test (RS). Results: Only the PP produced a significant effect when compared to the other protocols (p ≤ 0.05) PP+EP (290,49 ± 14,28 e 280,36 ± 10,26) (p=0.016) and PP+CC (290,49 ± 14,28 e 280,18 ± 12,07) (p=0.006). Regarding the% fatigue, the PP protocol had indices higher than the EP protocol (p=0.054) and CC (p=0.050). Conclusion: It was concluded that the electro-stimulation did not produce PAP effect nor in greater magnitude than the Plyometric protocol, but had the highest jump resistance compared to the control condition and plyometrics.

Jump power, leg press power, leg strength and grip strength differentially associated with physical performance: The Developmental Epidemiologic Cohort Study (DECOS).

Weight-bearing jump tests that measure lower-extremity muscle power may be more strongly related to physical performance measures vs. non-weight-bearing leg press power, leg press strength and grip strength. We investigated if multiple muscle function measures differentially related to standard physical performance measures. In the Developmental Epidemiologic Cohort Study (DECOS; N=68; age 78.5±5.5years; 57% women; 7% minorities), muscle function measures included power in Watts/kg (functional, weight-bearing: jump; mechanical: Nottingham power rig; Keiser pneumatic leg press) and strength in kg/kg body weight (Keiser pneumatic leg press; hand-held dynamometry). Physical performance outcomes included 6m usual gait speed (m/s), usual-paced 400m walk time (seconds), and 5-repeated chair stands speed (stands/s). Women (N=31; 79.8±5.0years) had lower muscle function and slower gait speed compared to men (N=25; 78.7±6.6years), though similar 400m walk time and chair stands speed. In partial Pearson correlations adjusted for age, sex, race and height, muscle function measures were moderately to strongly correlated with each other (all p<0.05), though the individual correlations varied. In multiple regression analyses, each muscle function measure was statistically associated with all physical performance outcomes in models adjusted for age, sex, race, height, self-reported diabetes, self-reported peripheral vascular disease and self-reported pain in legs/feet (all p<0.05). Jump power (β=0.75) and grip strength (β=0.71) had higher magnitudes of association with faster gait speed than lower-extremity power and strength measures (β range: 0.32 to 0.58). Jump power (β=0.56) had a slightly lower magnitude of association with faster 400m walk time vs. Keiser power70% 1-RM (β=0.61), and a higher magnitude of association vs. Nottingham power, Keiser strength and grip strength (β range: 0.41 to 0.47). Jump power (β=0.38) had a lower magnitude of association with chair stands speed than any other power or strength measures (β range: 0.50 to 0.65). Jump power/kg and grip strength/kg may be more strongly related to faster gait speed, a standard measure of physical function and vital sign related to disability and mortality in older adults, compared to leg press power/strength. However, jump power/kg had a similar magnitude of association with 400m walk time as Keiser power70% 1-RM/kg and a lower magnitude of association with faster chair stands speed than the other muscle function measures. Importantly, choice of muscle function measures should carefully reflect the study focus and methodologic considerations, including population.

Defining an international cut-off of two-legged countermovement jump power for sarcopenia and dysmobility syndrome

SummaryWe aimed to establish jump power cut-offs for the composite outcome of either sarcopenia (EWGSOP2) or dysmobility syndrome using Asian and Caucasian cohorts. Estimated cut-offs were sex specific (women: < 19.0 W/kg; men: < 23.8 W/kg) but not ethnicity specific. Jump power has potential to be used in definitions of poor musculoskeletal health.PurposeWeight-corrected jump power measured during a countermovement jump may be a useful tool to identify individuals with poor musculoskeletal health, but no cut-off values exist. We aimed to establish jump power cut-offs for detecting individuals with either sarcopenia or dysmobility syndrome.MethodsAge- and sex-matched community-dwelling older adults from two cohorts (University of Wisconsin-Madison [UW], Korean Urban Rural Elderly cohort [KURE], 1:2) were analyzed. Jump power cut-offs for the composite outcome of either sarcopenia defined by EWGSOP2 or dysmobility syndrome were determined.ResultsThe UW (n = 95) and KURE (n = 190) cohorts were similar in age (mean 75 years) and sex distribution (68% women). Jump power was similar between KURE and UW women (19.7 vs. 18.6 W/kg, p = 0.096) and slightly higher in KURE than UW in men (26.9 vs. 24.8 W/kg, p = 0.050). In UW and KURE, the prevalence of sarcopenia (7.4% in both), dysmobility syndrome (31.6% and 27.9%), or composite of either sarcopenia or dysmobility syndrome (32.6% and 28.4%) were comparable. Low jump power cut-offs for the composite outcome differed by sex but not by ethnicity (< 19.0 W/kg in women; < 23.8 W/kg in men). Low jump power was associated with elevated odds of sarcopenia (adjusted odds ratio [aOR] 4.07), dysmobility syndrome (aOR 4.32), or the composite of sarcopenia or dysmobility syndrome (aOR 4.67, p < 0.01 for all) independent of age, sex, height, and ethnicity.ConclusionSex-specific jump power cut-offs were found to detect the presence of either sarcopenia or dysmobility syndrome in older adults independent of Asian or Caucasian ethnicity.

Biometric And Performance Data In American Junior Nordic Combined And Ski Jumping Athletes

Nordic Combined (NC) and Ski Jumping (SJ) require particular athletic abilities and physical attributes for optimal performance. For instance, SJ requires particular focus on jumping technique and explosiveness, whereas the cross country ski portion of NC involves aerobic energy delivery, skiing efficiency, and power generation. Coaches and athletes monitor various performance metrics throughout the year to determine response to training and, hopefully, predict future performance. Normative data for these metrics has been analyzed in elite SJ and NC athletes but there is limited information regarding junior athletes. PURPOSE: Present normative biometric and performance testing data of American junior NC and SJ athletes and compare differences between age and sex. METHODS: A retrospective cohort study was completed evaluating data collected on 299 NC and SJ athletes ages 7-19 tested as part of USA Nordic's normal preseason evaluations between 2012-2018. Body mass index, static standing jump and countermovement jump height, various broad jump distances, timed agility testing, and 20 meter sprint times were collected and analyzed for differences between age and sex. RESULTS: Body mass index was greater in females than males. The interaction between age and sex was significant for static jump height, all broad jump metrics, time agility testing, and 20 meter sprint time. Jump power was greater in females than males. No difference was found between sex or across age in countermovement jump height. CONCLUSIONS: This was the first study to report biometric and performance data in junior American NC and SJ athletes. Our findings provide valuable normative information and identified several age and sex related differences in these athletes. These findings can be used by other junior athletes and their coaches for comparison purposes and when developing training programs.