Validity Study of a Jump Mat Compared to the Reference Standard Force Plate

Acute effects of voluntary isometric contractions at maximal shortening vs. ballistic stretching on flexibility, strength and jump

Background

Isometric training is used in sport, conventional physical activity and rehabilitation. Understandably, there is a great deal of research related to its effect on performance. It is known that the length of the muscle at the moment of contraction is a determinant of strength levels. In the literature we find research on isometric training in short muscle lengths, although it has not been studied in maximally shortened positions or the acute effects that occur after its application. Ballistic stretching (BS) is also popular in sport. Their execution involves actively reaching maximally shortened muscle positions. So far, isometric training has not been compared with protocols involving ballistic stretching. Considering the above, the aim of the present study was to investigate the effects of BS and voluntary isometric contraction at maximal shortening (VICAMS) on range of motion, strength and vertical jump.

Methods

The study involved 60 healthy, physically active individuals (40 and 52 years old) who were randomly assigned to three groups: BS, VICAMS and a control group (CG). To assess acute effects, before and after the intervention, active range of motion (AROM), maximal voluntary isometric force (MVIF) and countermovement jump height (CMJ) were determined.

Results

Time main effects and time*group interactions were found for all variables (p < 0.001). Between-group differences were shown for the VICAMS group after the intervention, with statistically significant higher AROM values compared to the other groups. MVIF values were also higher in the VICAMS group. Intra-group differences were observed for the VICAMS and Ballistic groups, as values on all variables increased from baseline. For the CMJ, intra-group differences showed that both the VICAMS and BS groups improved values compared to baseline values.

Conclusions

The application of VICAMS induced acute improvements over BS in AROM, MVIF and CMJ. These results are important for coaches seeking immediate performance improvement and offer an optimal solution to the warm-up protocol.

Single-Leg Vertical Hop Test Detects Greater Limb Asymmetries Than Horizontal Hop Tests After Anterior Cruciate Ligament Reconstruction in NCAA Division 1 Collegiate Athletes

BACKGROUND

Knee function deficits may persist after anterior cruciate ligament reconstruction (ACLR). Return to sport (RTS) testing batteries assess recovery after ACLR and can guide RTS progression, but the ideal test components are debatable. The single leg vertical hop for height (SLVH) test using a commercially available jump mat may provide a valuable assessment of knee function.

HYPOTHESIS/PURPOSE

The purpose of this study was to compare the limb symmetry index (LSI) of SLVH to horizontal hop testing in a cohort of National Collegiate Athletic Association (NCAA) Division 1 collegiate athletes after ACLR. The hypothesis was the SLVH would elicit significantly lower LSI than horizontal hop tests.

STUDY DESIGN

Cross-Sectional Study.

METHODS

Eighteen National Collegiate Athletic Association (NCAA) Division 1 collegiate athletes (7 males, 11 females) at 7.33 ± 2.05 months after ACLR were included in this retrospective study. LSI was calculated for single hop for distance (SHD), triple hop for distance (THD), cross-over hop for distance (CHD), timed 6-meter hop (T6H), and SLVH. A repeated measures ANOVA was performed to identify differences in LSI for each test. Spearman's Rho correlation coefficient was calculated to examine the relationship between LSIs for each test.

RESULTS

The LSI for SLVH (84.48% ± 11.41%) was significantly lower than LSI for SHD (95.48 ± 8.02%, p = 0.003), THD (94.40 ± 3.70%, p = 0.002), CHD (95.85 ± 7.00, p = 0.007), and T6H (97.69 ± 6.60%, p = 0.001). The correlation of LSI between SLVH and the horizontal hop tests was weak and non-significant for SHD (rs = 0.166, p = 0.509), CHD (rs = 0.199, p = 0.428), and T6H (rs = 0.211, p = 0.401) and moderate and non-significant for THD (rs = 0.405, p = 0.096).

CONCLUSIONS

Individuals after ACLR had lower LSI on the SLVH than on horizontal hop tests and weak to moderate correlations between the tests suggest SLVH detects performance deficits not identified by the horizontal hop tests.

LEVEL OF EVIDENCE

3.

The Effects of Soft Tissue Flossing on Hamstring Range of Motion and Lower Extremity Power

BACKGROUND

Flossing includes wrapping a specialized latex band around a muscle group providing compression, partially occluding blood flow, followed by performing exercises. This is hypothesized to improve flexibility by dissipating myofascial adhesions; however, research is lacking.

OBJECTIVE

To determine the effect of the application of a floss band to the thigh on hamstring flexibility and lower extremity power.

DESIGN

Crossover Study.

SETTING

Exercise Physiology Laboratory.

PARTICIPANTS

Twenty-one recreationally active individuals (8 male, 13 female; age = 22.62±2.99 years; height = 171.52±9.08 cm; mass = 73.57±11.37 kg).

METHODS

Three counterbalanced interventions were studied during body weight squats, lunges, and hamstring curls (without resistance): floss, sham, and control. The floss treatment included wrapping the Rogue Wide Voodoo Floss Band™ from the proximal knee to the gluteal fold at a pressure of 140 to 200 mmHg. The sham treatment included wrapping the same band in the same location with less pressure (10 to 40 mmHg) while the control treatment did not include floss band application. Hip flexion range of motion, via the straight leg raise, and power (single-leg vertical jump) were compared from pre-test to post-test using a 3x2 repeated measures ANOVA.

RESULTS

There was a significant interaction between time and session for hamstring flexibility (F(2,40)=17.54, p<0.001, η2=0.47). Post hoc tests showed significant differences between pre- (86.14±8.06 degrees) and post-test (90.81±7.69 degrees) for the floss session (p<0.001, Mean Difference=4.67, CI95=3.35-5.98) and between pre- (87.67±7.51 degrees) and post-test (89.86±7.88 degrees) for the sham session (p=0.001, Mean Difference=2.19, CI95=0.98-3.40). There were no significant interactions for jump power (F(2,40)=1.82, P=0.18, η2=0.08, 1-β=0.36).

CONCLUSIONS

Flossing treatment increased hamstring flexibility more than the sham session without affecting lower body power. Flossing could be beneficial when treatment or performance preparation goals are increased flexibility without decreased power. Future studies should continue to examine the clinical effectiveness of flossing on an injured population.

Validity and Reliability of an Electronic Contact Mat for Drop Jump Assessment in Physically Active Adults

The aim of the present study was to investigate the concurrent validity and the test–retest reliability of an electronic contact mat for drop jump assessment in physically active adults. Seventy-nine young, physically active adults participated in the validity study, and 49 subjects were recruited for the reliability study. The motor task required subjects to perform two-legged drop jumps using drop heights of 24, 43, and 62 cm as well as one-legged drop jumps with the left and right leg using a drop height of 24 cm. Ground contact times were simultaneously quantified with an electronic contact mat, a force plate (i.e., gold standard), and a light-barrier system (another criterion device). Concurrent validity was assessed using intraclass correlation coefficient (ICC), systematic bias, limits of agreement, and linear regression analysis. Test–retest reliability (one week apart) was determined by calculating the ICC, the standard error of measurement (SEM), the coefficient of variation (CV), and Lin´s concordance correlation coefficient (р_c). Further, we determined the minimal detectable change (MDC_95%). Irrespective of drop height and jump condition, good agreements between testing devices (ICC ≥ 0.95) were shown. Compared to the force plate (−0.6 to 3.1 ms) but not to the light-barrier system (31.4 to 41.7 ms), the contact mat showed low systematic bias values. In terms of test–retest reliability, our analyses showed that the measuring devices are in agreement (ICC: 0.70–0.92; SEM: 8.5–18.4 ms; CV: 3.6–6.4%). Depending on the measurement device, drop height, and jump condition, a MDC_95% value ranging from 23.6 to 50.9 ms represents the minimum amount of change needed to identify practical relevant effects in repeated measurements of drop jump performance. Our findings indicate that the electronic contact mat is a valid and reliable testing device for drop jump assessment from different drop heights in young physically active adults.

Validity and intra-rater reliability of MyJump app on iPhone 6s in jump performance

OBJECTIVES

Smartphone applications are increasingly used by researchers, coaches, athletes and clinicians. The aim of this study was to examine the concurrent validity and intra-rater reliability of the smartphone-based application, MyJump, against laboratory-based force plate measurements.

DESIGN

Cross sectional study.

METHODS

Participants completed counter-movement jumps (CMJ) (n=29) and 30cm drop jumps (DJ) (n=27) on a force plate which were simultaneously recorded using MyJump. To assess concurrent validity, jump height, derived from flight time acquired from each device, was compared for each jump type. Intra-rater reliability was determined by replicating data analysis of MyJump recordings on two occasions separated by seven days.

RESULTS

CMJ and DJ heights derived from MyJump showed excellent agreement with the force plate (ICC values range from 0.991 for CMJ to 0.993) However mean DJ height from the force plate was significantly higher than MyJump (mean difference: 0.87cm, 95% CI: 0.69-1.04cm). Intra-rater reliability of MyJump for both CMJ and DJ was almost perfect (ICC values range from 0.997 for CMJ to 0.998 for DJ); however, mean CMJ and DJ jump height for Day 1 was significantly higher than Day 2 (CMJ: 0.43cm, 95% CI: 0.23-0.62cm); (DJ: 0.38cm, 95% CI: 0.23-0.53cm).

CONCLUSION

The present study finds MyJump to be a valid and highly reliable tool for researchers, coaches, athletes and clinicians; however, systematic bias should be considered when comparing MyJump outputs to other testing devices.