Whole body vibration (WBV) has been suggested to improve athletes’ neuromuscular strength and power. This study investigated the effect of single WBV stimulation on volleyball-specific performance. The participants were 20 elite male volleyball players who performed a 1-min warm-up exercise on a vibration platform at a frequency of 30 Hz and peak-to-peak displacement of 2 mm. After the warm-up exercise, the participants performed a blocking agility test (BAT), 10-m sprinting test, agility T-test, and counter movement jump test. We compared the participants’ performance at four time points (Pretest, Post 0, Post 1, and Post 2). The results revealed that the participants’ BAT performance and maximum rate of force development improved significantly 1 min after the vibration stimulation (p < 0.01). The WBV (frequency of 30-Hz, peak-to-peak displacement of 2 mm) intervention significantly improved the volleyball-specific defensive performance and speed strength of the participants. Accordingly, by undergoing WBV as a form of warm-up exercise, the technique and physical fitness of volleyball players can be improved.

Background: Using wearable inertial sensors to accurately estimate energy expenditure (EE) during an athletic training process is important. Due to the characteristics of inertial sensors, however, the positions in which they are worn can produce signals of different natures. To understand and solve this issue, this study used the heart rate reserve (HRR) as a compensation factor to modify the traditional empirical equation of the accelerometer EE sensor and examine the possibility of improving the estimation of energy expenditure for sensors worn in different positions. Methods: Indirect calorimetry was used as the criterion measure (CM) to measure the EE of 90 healthy adults on a treadmill (five speeds: 4.8, 6.4, 8.0, 9.7, and 11.3 km/h). The measurement was simultaneously performed with the ActiGraph GT9X-Link (placed on the wrist and waist) with the Polar H10 Heart Rate Monitor. Results: At the same exercise intensity, the EE measurements of the GT9X on the wrist and waist had significant differences from those of the CM (p < 0.05). By using multiple regression analysis—utilizing values from vector magnitudes (VM), body weight (BW) and HRR parameters—accuracy of EE estimation was greatly improved compared to traditional equation. Modified models explained a greater proportion of variance (R²) (wrist: 0.802; waist: 0.805) and demonstrated a good ICC (wrist: 0.863, waist: 0.889) compared to Freedson’s VM3 Combination equation (R²: wrist: 0.384, waist: 0.783; ICC: wrist: 0.073, waist: 0.868). Conclusions: The EE estimation equation combining the VM of accelerometer measurements, BW and HRR greatly enhanced the accuracy of EE estimation based on data from accelerometers worn in different positions, particularly from those on the wrist.

The purpose of this study was to investigate the receiving ability and efficacy of volleyball players, which can be effectively improved after practicing with volleyballs of different weights. In this study, 36 elite male volleyball players were recruited and participated in a four-week training program in four groups: a lighter-ball training group (LBTG), a heavier-ball training group (HBTG), a normal-ball training group (NBTG), and a control group (CG). All subjects were required to evaluate their receiving ability during the initial training (week-0) and then to reevaluate it after two (week-2) and four (week-4) weeks of training. The statistical analysis revealed that the time factor (F_{2, 64} = 209.346, p < 0.001) and the time × group factor (F_{6, 64} = 17.463, p < 0.001) were significant but the group factor (F_{3, 32} = 0.340, p = 0.797) was not. The results revealed that the LBTG experienced a significant positive effect on the receiving test after four weeks of training, with an 8.6% improvement in skill performance after two weeks and a 16.4% improvement after four weeks. The HBTG, NBTG, and CG improved by 2.6%, 5.3%, and 3.8% after two weeks and by 6.3%, 9.3%, and 4.3% after four weeks, respectively. The main findings were that four weeks of volleyball training with a lighter ball resulted in significant improvements in player performance. In contrast, training with a ball with 70 g of added mass did not effectively enhance motor ability development.