Acute Effects of Whole-Body Vibration Warm-up on Leg and Vertical Stiffness During Running

ABSTRACT

Paradisis, GP, Pappas, P, Dallas, G, Zacharogiannis, E, Rossi, J, and Lapole, T. Acute effects of whole-body vibration warm-up on leg and vertical stiffness during running. J Strength Cond Res 35(9): 2433-2438, 2021-Although whole-body vibration (WBV) has been suggested as a suitable and efficient alternative to the classic warm-up routines, it is still unknown how this may impact running mechanics. Therefore, the aim of this study was to investigate the effect of a WBV warm-up procedure on lower-limb stiffness and other spatiotemporal variables during running at submaximal speed. Twenty-two males performed 30-second running bouts at 4.44 m·s-1 on a treadmill before and after a WBV and control warm-up protocols. The WBV protocol (vibration frequency: 50 Hz, peak-to-peak displacement: 4 mm) consisted of 10 sets of 30-second dynamic squatting exercises with 30-second rest periods within sets. Leg and vertical stiffness values were calculated using the spring mass model. The results indicated significant increases only after the WBV protocol for leg stiffness (3.4%), maximal ground reaction force (1.9%), and flight time (4.7%). Consequently, the WBV warm-up protocol produced a change in running mechanics, suggesting a shift toward a more aerial pattern. The functional significance of such WBV-induced changes needs further investigation to clearly determine whether it may influence running economy and peak velocity.

The acute effects of different training loads of whole body vibration on flexibility and explosive strength of lower limbs in divers

The purpose of this study was to examine the acute effects of different vibration loads (frequency and amplitude) of whole-body vibration (WBV) on flexibility and explosive strength of lower limbs in springboard divers. Eighteen male and female divers, aged 19 ± 2 years, volunteered to perform 3 different WBV protocols in the present study. To assess the vibration effect, flexibility and explosive strength of lower limbs were measured before (Pre), immediately after (Post 1) and 15 min after the end of vibration exposure (Post 15). Three protocols with different frequencies and amplitudes were used in the present study: a) low vibration frequency and amplitude (30 Hz/2 mm); b) high vibration frequency and amplitude (50 Hz/4 mm); c) a control protocol (no vibration). WBV protocols were performed on a Power Plate platform, whereas the no vibration divers performed the same protocol but with the vibration platform turned off. A two-way ANOVA 3 x 3 (protocol × time) with repeated measures on both factors was used. The level of significance was set at p < 0.05. Univariate analyses with simple contrasts across time were selected as post hoc tests. Intraclass coefficients (ICC) were used to assess the reliability across time. The results indicated that flexibility and explosive strength of lower limbs were significantly higher in both WBV protocols compared to the no vibration group (NVG). The greatest improvement in flexibility and explosive strength, which occurred immediately after vibration treatment, was maintained 15 min later in both WBV protocols, whereas NVG revealed a significant decrease 15 min later, in all examined strength parameters. In conclusion, a bout of WBV significantly increased flexibility and explosive strength in competitive divers compared with the NVG. Therefore, it is recommended to incorporate WBV as a method to increase flexibility and vertical jump height in sports where these parameters play an important role in the success outcome of these sports.

Acute effect of different stretching methods on flexibility and jumping performance in competitive artistic gymnasts

AIM

The purpose of this study was to investigate the acute effects of 3 different warm up methods of stretching (static, proprioceptive neuromuscular facilitation, and stretching exercises on a Vibration platform) on flexibility and legs power-jumping performance in competitive artistic gymnasts.

METHODS

Eighteen competitive artistic gymnasts were recruited to participate in this study. Subjects were exposed to each of 3 experimental stretching conditions: static stretching (SS), proprioceptive neuromuscular facilitation stretching (PNF), and stretching exercises on a Vibration platform (S+V). Flexibility assessed with sit and reach test (S & R) and jumping performance with squat jump (SJ) and counter movement jump (CMJ) and were measured before, immediately after and 15 min after the interventions.

RESULTS

Significant differences were observed for flexibility after all stretching conditions for S+V (+1.1%), SS (+5.7%) and PNF (+6.8%) (P=0.000), which remained higher 15 min after interventions (S+V (1.1%), SS (5.3%) and PNF (5.5%), respectively (P=0.000).

CONCLUSION

PNF stretching increased flexibility in competitive gymnasts, while S+V maintained jumping performance when both methods were used as part of a warm-up procedure.

The acute effect of whole body vibration training on flexibility and explosive strength of young gymnasts

The purpose of this study was to examine the acute effect of a single bout of whole body vibration (WBV) on flexibility and explosive strength of lower limbs in young artistic gymnasts. Thirty-two young competitive gymnasts volunteered to participate in this study, and were allocated to either the vibration group or traditional body weight training according to the vibration protocol. The vibration intervention consisted of a single bout of eccentric and concentric squatting movements on a vibration platform that was turned on (vibration group: VG n = 15), whereas the traditional body weight (no vibration) group performed the same training protocol with the WBV device turned off (NVG: n= 17). Flexibility (sit and reach test) and explosive strength tests [squat jump (SJ), counter movement jump (CMJ), and single leg squat (right leg (RL) and left leg (LL))] were performed initially (pre-test), immediately after the intervention (post-test 1), and 15 minutes after the end of the intervention programme (post-test 15). Four 2x3 ANOVAs were used to examine the interaction between group (VG vs NVG) and time (pre, post 1, and post 15) with respect to examined variables. The results revealed that a significant interaction between group and time was found with respect to SJ (p < 0.05). However, no significant interaction between group and time was found with respect to flexibility, CMJ, RL and LL after the end of the intervention programme (p > 0.05). Further, the percentage improvement of the VG was significantly greater in all examined variables compared to the NVG. This study concluded that WBV training improves flexibility and explosive strength of lower limbs in young trained artistic gymnasts and maintains the initial level of performance for at least 15 minutes after the WBV intervention programme.

Reactions of diphenylcyclopropenone with 1,3-dipoles

Diphenylcyclopropenone reacts with 1,3-diphenylisobenzofuran to give a benzotropone derivative 5, with 3-carboalkoxyaziridines to give trans-3-pyrrolines (e.g. 10), and with a 3-cyanoaziridine to give the pyrrole 20. Possible mechanisms of these reactions are considered and compared with previous 1,3-dipolar additions to cyclopropenones.

Reactions of 4-aroyl-4-oxazolines and 3-aroyI-4,5-dihydrofurans

4-Aroyl-4-oxazolines undergo stereospecific [2 + 3] cycloaddition to olefinic dipolarophiles with the formation of 3-aroyl-4,5-dihydrofurans. The latter are also found to be reactive towards further [2 + 3] cycloaddition reactions. Possible mechanisms for these reactions are discussed and the synthesis of several new furans and dihydrofurans reported.

Reaction of 3-aroylaziridines with diphenylcyclopropenone. Synthesis and properties of novel 4-aroyl-4-oxazolines

3-Aroylaziridines and 3-acylaziridines react with diphenylcyclopropenone with the formation of novel 4-aroyl-4-oxazolines and 4-acyl-4-oxazolines respectively. The unusual physical and chemical properties of these reactive heterocycles are discussed.

Reaction of 3-aroylaziridines with aryl isothiocyanates

3-Aroylaziridines react with a variety of aryl isothiocyanates in refuxing benzene to give either (a) 4-aroyl-5-arylamino-4-thiazolines by a [2 + 3] cycloaddition and/or (b) 2-arylamino-4-aroyl-4-thiazolines. When the N-substituent of the aziridine is cyclohexyl or isopropyl the product type (a) is isolated in greater quantity, but when the N-substituent is methyl, product type (b) is isolated in greater quantity. The reactions provide convenient one-step syntheses of new 4-aroyl-4-thiazolines.