Difference in badminton-specific endurance evaluated by a newly developed on-court test between competitive levels: A pilot study of female players.

We developed a test to evaluate badminton-specific endurance. The study included 10 female badminton players. Five participants were ranked in Japan's top 100 national rankings (ranked), whereas the others were unranked (unranked). Participants reacted quickly with badminton-specific steps from the base center to the four sensors at each corner of a singles badminton court. On each set, they reacted eight times to randomized instructions at stage-specific intervals (1.2, 1.0, and 0.8 s for stages 1, 2, and 3, respectively), which were performed six times with a rest of 20 s in each stage (8 movements × 6 sets × 3 stages). On a different day, participants ran on a treadmill as a comparative test. Blood lactate concentration (BLa) was measured on each test. In the badminton-specific test, ranked participants had lower BLa (4.2 ± 1.7 mM vs. 6.3 ± 3.1 mM), with medium or large effect sizes. The average reach time to sensors was shorter in ranked participants (1.56 ± 0.03 s vs. 1.62 ± 0.07 s), with medium or large effect sizes. BLa was similar between groups, with trivial or small effect sizes in the running test. These results suggest that the newly developed test can evaluate badminton-specific endurance.

Comparison of Morning Heart Rate Variability at the Beginning and End of a Competition Season in Elite Speed Skaters.

The aim of this study was to clarify whether the physiological fatigue status of elite speed skaters is influenced by the approximately five-month international competition season by comparing morning heart rate variability (HRV) at the beginning of the competition season (Japan Single Distances Championships: JSDC) with that at the end of the competition season (World Single Distances Championships: WSDC). Five international-class speed skaters participated in the study. HRV indices and subjective fatigue were measured each morning of the four days prior to the first races of the JSDC and WSDC in the 2007/2008 season. The parasympathetic HRV indices: root mean square of the successive R-R interval differences (RMSSD) (JSDC, 61.0 ms; WSDC, 42.1 ms; p < 0.05), high-frequency component power (HF) (JSDC, 1393 ms2; WSDC, 443 ms2; p < 0.05), and normalized unit of HF (HFnu) (JSDC, 53.2%; WSDC, 25.5%; p < 0.05) were lower for the WSDC than for the JSDC. The decrease in these indices may reflect the skaters' accumulated fatigue during the course of the competition season. Morning measurements of HRV may thus be an efficient way for elite speed skaters and coaches to objectively monitor physiological fatigue throughout the competition season.

Morning Heart Rate Variability as an Indication of Fatigue Status in Badminton Players during a Training Camp.

This study aimed to clarify whether changes in the fatigue status of elite athletes during a precompetition period could be evaluated using morning heart rate variability (HRV) indices. Eight Japanese National Badminton Team players (age, 23.0 ± 2.8 years) participated in this study. HRV and subjective fatigue were measured during the first (days 1-4: Phase 1) and the second half (days 5-8: Phase 2) of an 8-day national team training camp. The global and parasympathetic HRV indices were as follows: standard deviation of all R-R intervals (SDNN) (Phase 1, 87.5 ms; Phase 2, 104.3 ms; p < 0.05), root mean square of the successive R-R interval differences (RMSSD) (Phase 1, 66.6 ms; Phase 2, 103.6 ms; p < 0.05), and high-frequency component power (HF) (Phase 1, 1412.0 ms2; Phase 2, 3318.5 ms2; p < 0.05). All the aforementioned indices increased significantly from Phase 1 to Phase 2. Significant correlations were observed between the change in subjective fatigue and changes in SDNN, RMSSD, and HF (ρ = -0.80, p = 0.017; ρ = -0.77, p = 0.027; and ρ = -0.80, p = 0.017, respectively). Measuring morning HRV indices may be effective for objectively evaluating changes in the fatigue status of elite athletes during a precompetition period.

Threshold Photodetachment Spectroscopy of the Positronium Negative Ion.

Threshold photodetachment spectroscopy of the positronium negative ion has been accomplished for the first time employing an efficient source of the ions and photodetachment techniques combined with a tunable optical parametric oscillator and amplifier laser. The photodetachment threshold, corresponding to the electron affinity of positronium (1^{3}S_{1}), was determined to be 326.88±0.09(stat)±0.10(syst) meV by laser photodetachment threshold measurements. This result is consistent with a variational calculation corrected for leading relativistic and quantum electrodynamical effects.

Changes in Duration and Intensity of the World's Top-Level Badminton Matches: A Consideration of the Increased Acute Injuries among Elite Women's Singles Players.

The purpose of this study was to clarify whether there have been any specific changes in the characteristics of the world's top-level women's singles badminton matches compared to men's singles matches after the current badminton scoring system was implemented in 2006. We compared the characteristics of the matches between the Super Series tournaments in 2007 and 2017. Match duration increased as the rally and rest times increased in both men's and women's singles matches. Specifically, in women's singles, it was suggested that a further increase in physical demands because of the increased number of shots per second may have resulted in longer rest time in proportion to rally time. Moreover, increases in match duration (final eight, 53.3 ± 6.6 min; early rounds, 42.1 ± 3.6 min; P < 0.05) and number of shots per rally (final eight, 10.4 ± 1.2; early rounds, 8.7 ± 1.1; P < 0.05) in women's singles were more prominent in the final eight rounds (quarterfinals, semifinals, and finals) than in the early rounds (rounds 1 and 2). The recent changes in characteristics of the world's top-level badminton matches may account for the increased acute injuries that are frequently observed in elite women's singles players. Thus, appropriate training programs are crucial to effectively improve performance and prevent injuries among elite badminton players.

Salivary secretory immunoglobulin a response of elite speed skaters during a competition period.

We aimed to determine the responses of salivary secretory immunoglobulin A (SIgA) and the incidence of upper respiratory tract infections (URTI) symptoms among elite speed skaters during an actual competition period. The subjects were 8 international-class elite speed skaters. Saliva samples were obtained 3, 2, and 1 days before the race, the day of the race, and 1 day after the race. Salivary secretory immunoglobulin A concentration was measured by enzyme immunoassay, and SIgA secretion rate was calculated. A visual analogue scale was used to subjectively assess fatigue and tension. Daily URTI symptoms were recorded by using a questionnaire. There was no statistically significant difference in the saliva flow rate (p = 0.69), SIgA concentration (p = 0.07), and subjective fatigue (p = 0.07) during the competition period. The SIgA secretion rate recorded for the day of the race was significantly high compared with that of 3 and 2 days before and 1 day after the race (p < 0.05). The subjective tension recorded on the race day was significantly high compared with that for 3, 2, and 1 days before the race (p < 0.05). Two subjects exhibited URTI symptoms after the race. These findings suggest that salivary SIgA in elite speed skaters increased after a tapering period and that an actual high-intensity speed skating race decreased salivary SIgA in elite speed skaters. These data also suggest that the incidence of URTI symptoms might be related to the SIgA level. Coaches may need to take precautions after competitions to minimize their athletes' contact with cold viruses and adjust training load for a few days after competition to improve the decreased mucosal immune function.