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

The Acute Effects of Carrying a Heavy Grocery Bag on Handgrip Rapid Strength in Young and Older Women

Declines in handgrip rapid strength characteristics, which include rate of force development (RFD), are commonly reported as a consequence of aging. These declines have been shown to have a detrimental effect on the functional performance abilities of older adults. Such an effect may be amplified by a further decrease in handgrip RFD as a result of fatigue. Evidence suggests that carrying a heavy grocery bag can elicit fatigue-induced changes in muscle activity and cardiovascular parameters. It is unclear if carrying a heavy grocery bag will elicit fatigue-induced changes in handgrip RFD. PURPOSE: The purpose of this study was to examine the acute effects of carrying a heavy grocery bag on handgrip RFD in young and older women. METHODS: Ten young (age = 22 ± 3 years) and ten older (71 ± 10 years) healthy women performed a control condition and an experimental condition of grocery bag carrying for 3 minutes. The control condition consisted of quiet resting for 3 minutes in a seated position. This condition was performed first to avoid any potential carry-over effects. After completing the control condition, the participants rested for 20 minutes before completing the experimental condition, which consisted of walking at 3.5 km·h-1 on a treadmill for 3 minutes while carrying a heavy grocery bag (5.3 kg) in the dominant hand. Three handgrip maximal voluntary contraction (MVC) assessments were completed immediately before (pretest) and after (posttest) the control and grocery bag carry conditions to determine the acute effects of each condition on RFD. All handgrip MVCs were performed with the dominant hand 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 RFD at 0-100 milliseconds from contraction onset was calculated and displayed by the device at the conclusion of each MVC and was normalized to body mass. A three-way mixed factorial analysis of variance was used to analyze the RFD data. RESULTS: The grocery bag carry condition elicited a significant decrease in RFD for the older women (pretest = 13.7 ± 3.6 N·s-1·kg-1; posttest = 12.7 ± 3.3 N·s-1·kg-1; P \u3c 0.001) but not for the younger women (pretest = 16.8 ± 2.9 N·s-1·kg-1; posttest = 16.8 ± 2.7 N·s-1·kg-1; P = 0.830). No changes in RFD were observed for either age group from pre- (young = 16.9 ± 3.2 N·s-1·kg-1; older = 13.4 ± 3.3 N·s-1·kg-1) to posttest (young = 16.9 ± 2.7 N·s-1·kg-1; older = 13.5 ± 2.9 N·s-1·kg-1) for the control condition (P = 0.721-0.830). CONCLUSION: We found no significant changes in RFD for the younger women; however, for the older women, a significant decrease in RFD was observed as a result of the grocery bag carry condition. These findings suggest that carrying a heavy grocery bag for 3 minutes may impair the handgrip rapid strength capacities of older women