Handgrip Peak Force and Rate of Force Development Measurements: Are They Reliable and Do They Correlate with Vertical Jump Power?

Handgrip peak force and rate of force development (RFD) measurements have been shown to be effective parameters at characterizing the strength capacities of numerous muscle groups, including those of the lower extremities. However, the reliability of these measurements and their relationship with vertical jump (VJ) peak power remains uncertain. PURPOSE: The purpose of this study was to examine the reliability of handgrip peak force and RFD measurements. A secondary aim was to determine if these measurements are correlated with the peak power produced during a VJ test. METHODS: Twenty young, healthy women (age = 21 ± 3 years) volunteered for this study. Participants reported for testing on two different occasions, separated by 2-7 days at approximately the same time of day (± 2 hours). For each testing session, participants completed three VJs followed by three handgrip maximal voluntary contraction (MVC) assessments with the dominant hand. VJs were performed using a linear velocity transducer that was attached to the posterior portion of a belt fastened around the participants’ waistline. For all VJs, participants were instructed to jump up as explosively as possible with both feet at the same time and land on the floor in the starting position. Prior to the VJ assessments, each participant\u27s body mass was entered into the linear velocity transducer microcomputer. Estimated peak power output was calculated in watts (W) and displayed by the microcomputer at the conclusion of each jump. Handgrip MVCs were performed using a novel strength testing device. This device consisted of a microcomputer and a load cell that was equipped with two semi-cylindrical handles for gripping. For each MVC, participants sat in an upright position and were instructed to squeeze the handles of the load cell “as hard and fast as possible” for 3-4 seconds. Handgrip peak force, peak RFD, and RFD at 0-100 (RFD100) and 0-200 (RFD200) milliseconds from contraction onset were calculated and displayed by the device at the conclusion of each assessment. The intraclass correlation coefficient (ICC) and coefficient of variation (CV) were calculated between sessions to assess the reliability of handgrip peak force and RFD variables. The relationships between these variables and VJ peak power were determined by Pearson correlation coefficients (r). RESULTS: Handgrip peak force, peak RFD, RFD100, and RFD200 were highly consistent between sessions, with ICCs ranging between 0.89 and 0.92 and CV values between 4.9 and 6.4%. There were significant correlations between VJ peak power and handgrip peak force (r = 0.612, P = 0.004), peak RFD (r = 0.731, P \u3c 0.001), RFD100 (r = 0.671, P = 0.001), and RFD200 (r = 0.701, P = 0.001). CONCLUSION: The results of this study showed that peak force, peak RFD, RFD100, and RFD200 were reliable measures for assessing handgrip strength in young, healthy adults. These measurements were significantly correlated with VJ peak power and thus, could be effective parameters at predicting lower-body explosiveness. The predictive capacity of such parameters to determine a person’s peak power may be important in the early stages of rehabilitation, especially if that person is unable to perform a VJ test

Age-related Differences in Handgrip Strength Characteristics and Vertical Jump Performance

Handgrip strength characteristics, such as peak force and rate of force development (RFD), have been shown to be significantly associated with the performance capacities of the lower-body musculature. Declines in lower-body performance are commonly reported as a consequence of aging. However, few studies have investigated the influence of age on handgrip peak force and RFD. PURPOSE: The purpose of this study was to examine age-related differences in handgrip peak force and RFD between young and older women and the relationships of these characteristics with lower-body performance during a vertical jump (VJ) test. METHODS: Twenty young (age = 21 ± 3 years) and twenty older (67 ± 5 years) healthy women completed three VJs followed by three handgrip maximal voluntary contraction (MVC) assessments with the dominant hand. All VJs were performed on a jump mat. The jump mat assessed lower-body performance by measuring VJ height (cm). Handgrip MVCs were performed using a novel strength testing device. This device consisted of a microcomputer and a load cell that was equipped with two semi-cylindrical handles for gripping. For each MVC, participants sat in an upright position and were instructed to squeeze the handles of the load cell “as hard and fast as possible” for 3-4 seconds. Handgrip peak force, peak RFD, and RFD at 0-100 (RFD100) and 0-200 (RFD200) milliseconds from contraction onset were calculated and displayed by the device at the conclusion of each MVC and were normalized to body mass. Independent samples t-tests were used to compare VJ height and handgrip peak force and RFD characteristics between the young and older women. Pearson correlation coefficients (r) were calculated separately for the young and older women to examine the relationships between VJ height and handgrip peak force and RFD. RESULTS: The older women exhibited significantly lower VJ height (older = 20.3 ± 3.8 cm; young = 34.4 ± 5.9 cm; P \u3c 0.001), peak force (older = 2.4 ± 0.4 N·kg-1; young = 2.7 ± 0.5 N·kg-1; P = 0.028), peak RFD (older = 13.6 ± 2.6 N·s-1·kg-1; young = 16.4 ± 2.9 N·s-1·kg-1; P = 0.003), RFD100 (older = 13.2 ± 3.0 N·s-1·kg-1; young = 15.7 ± 3.3 N·s-1·kg-1; P = 0.016), and RFD200 (older = 9.3 ± 1.6 N·s-1·kg-1; young = 10.8 ± 1.6 N·s-1·kg-1; P = 0.003) than the younger women. Positive correlations were observed between VJ height and handgrip RFD200 (r = 0.502, P = 0.024) and peak RFD (r = 0.453, P = 0.045) for the younger women. Positive correlations were also observed between VJ height and handgrip RFD200 (r = 0.446, P = 0.049) and peak RFD (r = 0.408, P = 0.074) for the older women, although the latter correlation did not reach statistical significance. There were no significant correlations between VJ height and handgrip peak force (young: r = 0.389, P = 0.090; older: r = 0.311, P = 0.183) or RFD100 (young: r = 0.366, P = 0.113; older: r = 0.382, P = 0.096) for either age group. CONCLUSION: These findings demonstrated that VJ height and handgrip peak force and RFD characteristics decrease in old age. The significant correlations observed between VJ height and RFD200 in the young and older women suggest that handgrip rapid strength (0-200 milliseconds) may be an effective predictor of one’s jumping ability

Reliability and Relationships between Supine Medicine Ball Throw Kinetics and Vertical Jump Height

Supine medicine ball throw (SMBT) assessments have been used previously to evaluate upper-body explosive strength in young adults. Kinetic variables, such as peak force and rate of force development (RFD), can be measured during a SMBT. These variables have been suggested to be important predictors of athletic performance capacities. However, limited data exist regarding the reliability of SMBT peak force and RFD measurements and how they associate with performance during a vertical jump (VJ) test. PURPOSE: The purpose of this study was to examine the reliability of SMBT variables and their relationship with VJ height. METHODS: Twenty young, healthy women (age = 21 ± 3 years) volunteered for this study. Participants reported for testing on two different occasions, separated by 2-7 days at approximately the same time of day (± 2 hours). For each testing session, participants completed three VJs followed by three SMBT assessments. All VJs were performed on a jump mat. The jump mat measured VJ height (cm) based on flight time. For the SMBTs, participants laid on a force plate in the supine position with their hands on the ball (2.7 kg) and knees and hips flexed at 90º. Participants were instructed to throw the ball explosively upward with as much force as possible, using a motion similar to a basketball chest pass. The vertical force signal (N) from the force plate was recorded during each throw and used to measure peak force and RFD variables. Peak force was calculated as the highest force value. RFDmax was calculated as the highest slope for any 20 ms epoch that occurred over the rising portion of the force signal. RFD30% and RFD40-80% were calculated as the linear slope of the force signal from the onset of the throw to 30% peak force and from 40% to 80% peak force, respectively. The intraclass correlation coefficient (ICC) and coefficient of variation (CV) were calculated between sessions to assess the reliability of SMBT peak force and RFD variables. The relationships between these variables and VJ height were assessed by Pearson correlation coefficients (r). RESULTS: The ICC for SMBT RFD30% was 0.55. This ICC was considerably lower than the ICCs for the other SMBT variables (0.82-0.88). The CV value for SMBT RFD30% was 27.2%, whereas the CV values for SMBT peak force, RFDmax, and RFD40-80% were all less than or equal to 14.0%. There were significant relationships between VJ height and SMBT peak force (r = 0.483, P = 0.031), RFDmax (r = 0.484, P = 0.031), and RFD40-80% (r = 0.491, P = 0.028); however, there was no significant relationship between VJ height and RFD30% (r = 0.359, P = 0.120). CONCLUSION: The results of this study demonstrated that SMBT peak force, RFDmax, and RFD40-80% were reliable measures for assessing upper-body explosive strength in young, healthy adults. These measurements were significantly associated with VJ height and therefore, may be effective parameters at predicting a person’s jumping ability and overall athletic performance potential. RFD30% was unreliable and not significantly correlated with VJ height. As a result, this variable should not be used as a performance measure when conducting SMBT assessments

Receptor Determinant Analogues for All 9-O-Ac-Sialoglycan-Recognizing Corona Viruses

In present study, analogues of receptor determinants were identified, which can mimic 9-O-Acsialoglycan-recognition by viruses and its usage in antiviral. It is well known that receptor determinants are part of host cell surface receptors which are recognized by virus surface glycoprotein as the first interaction of the target cell. This recognition governs the further processes of viral infection. Similar to other influenza viruses, Corona virus also processes through mechanisms of host interaction. This hostvirus interaction involves a conserved domain at interaction component of virus, which is known to be a key component during the process of virus infection. Therefore in the present study profile of possible Pharmacophore of conserved domain was used as a filter to identify analogues of receptor determinant from database ZINC database. The identified molecules were re-observed among the applicability domain defined by existing antiviral drugs as well as natural existing receptor determinant with sialic acid. The identified molecule needs to be further evaluated through in-vitro experiments. </p

Evolutions in Gaseous and Liquid Fuel Cook-Stove Technologies

The rapidly growing global demand for pollutant-free cooking energy has proliferated the research and development of energy efficient and clean cook-stoves. This paper presents a comprehensive review on the gradual improvements in cook-stove designs, focusing on gaseous and liquid fuel-operated cook-stoves around the world. Various literatures concerning the technical aspects such as design and testing, are brought together to provide an insight into the present status of developments in cook-stoves. This review of cook-stove performance covers topics such as stable operating conditions, flame propagation aspects, heat transfer and temperature distribution within the burner, fuel consumption, thermal efficiency, and emissions. Covering both laboratory-scale and field studies, the various cook-stove technologies reported so far are summarized with relevant comments regarding their commercial viabilities. The numerical modeling of combustion in cook-stoves; human health and the environmental impacts of unclean cooking technologies; and various schemes, strategies, and governmental initiatives for the promotion of cleaner cooking practices are also presented, with suggestions for future work