Sports medicine international open最新文献

Ischemic preconditioning (IP) has a small benefit on exercise performance, but differences in the IP method, performance tasks and exercise modality have made providing practical coach guidelines difficult. We investigated the performance-enhancing effects of IP on cyclists by comparing the frequency of IP application over a 7-day period. Using a randomized, sham-controlled, single-blinded experiment, 24 competitive age-group track cyclists (38±12 years) were assigned to one of three twice-daily (sham: 20 and 20 mmHg; once-a-day: 20 and 220 mmHg; twice-a-day: 220 and 220 mmHg) IP leg protocols (4 × 5 min ischemia/5 min reperfusion alternating between legs) over seven consecutive days. A 4000-m cycling-ergometer time trial was completed before, immediately following and one week after the protocols. Neither mean power, nor 4000-m performance time nor VO ₂ were significantly affected by either of the IP protocols compared to the sham at any time point following treatment. Repeated application of IP over seven days did not enhance the performance of trained cyclists in a 4000-m laboratory time trial. More research is required to understand how changes to methodological variables can improve the chances of IP successfully enhancing athlete performance.

This study evaluates the effects of the use of backpack load and trekking poles on field track walking energy expenditure. Twenty male volunteer pole walkers (age: 22.70±2.89 years; body mass: 77.90±11.19 kg; height: 1.77±0.06 m; percentage of body fat: 14.6±6.0%) walked at a self-selected pace on a pedestrian field track over a period of more than six months. Each subject was examined at random based on four walking conditions: non-poles and non-load, with poles and non-load, non-poles and with load, with poles and with load. Heart rate, oxygen uptake and energy expenditure were continuously recorded by a portable telemetric system. Non-load walking speed was lower during walking with poles when compared with no poles ( p ≤0.05). Oxygen uptake, energy expenditure and heart rate varied significantly across different conditions. Our results suggest that the use of trekking poles does not influence energy expenditure when walking without an additional load, but it can have an effect during backpack load walking. Moreover, our results indicate that the use of trekking poles may not be helpful to lower the exertion perceived by the subjects when walking with an additional load.

Hemoglobin mass (tHb) is a key determinant of maximal oxygen uptake (VO ₂ max). We examined whether oxyhemoglobin desaturation (ΔS _a O ₂ ) at VO ₂ max modifies the relationship between tHb and VO ₂ max at moderate altitude (1,625 m). Seventeen female and 16 male competitive, endurance-trained moderate-altitude residents performed two tHb assessments and two graded exercise tests on a cycle ergometer to determine VO ₂ max and ΔS _a O ₂ . In males and females respectively, VO ₂ max (ml·kg ^-1 ·min ^-1 ) ranged from 62.5-83.0 and 44.5-67.3; tHb (g·kg ^-1 ) ranged from 12.1-17.5 and 9.1-13.0; and S _a O ₂ at VO ₂ max (%) ranged from 81.7-94.0 and 85.7-95.0. tHb was related to VO ₂ max when expressed in absolute terms and after correcting for body mass (r=0.94 and 0.86, respectively); correcting by ΔS _a O ₂ did not improve these relationships (r=0.93 and 0.83). Additionally, there was a negative relationship between tHb and S _a O ₂ at VO ₂ max (r=-0.57). In conclusion, across a range of endurance athletes at moderate altitude, the relationship between tHb and VO ₂ max was found to be similar to that observed at sea level. However, correcting tHb by ΔS _a O ₂ did not explain additional variability in VO ₂ max despite significant variability in ΔS _a O ₂ ; this raises the possibility that tHb and exercise-induced ΔS _a O ₂ are not independent in endurance athletes.

The purpose of this study was to determine if tuck jumps can be used as a dynamic movement assessment to ascertain a previous history of upper extremity injury in an overhead throwing sport. Seventy-one youth baseball and softball athletes (28 baseball/43 softball; 12.41±2.22 yrs.; 161.98±13.65 cm; 59.17 ± 14.90 kg) were recruited to participate and were placed in either the previous injury (N=18) or no previous injury (N=53) groups. Kinematic data were collected from jumps 4 through 8 during a trial of 10 tuck jumps performed at 100 Hz using an electromagnetic tracking system (trakSTAR ^TM , Ascension Technologies, Inc., Burlington, VT, USA) synced with the MotionMonitor ^® (Innovative Sports Training, Chicago, IL, USA). A logistic regression showed no significance in trunk flexion or upper leg elevation in the ability to determine upper extremity injury ( χ ² (1, N =71)=3.55, p =0.315). In conclusion, examining only trunk flexion and upper leg elevation during the tuck jump assessment (TJA) is not enough for clinicians to recognize previous upper extremity injury. Even though the body behaves as a kinetic chain, simplifying the dynamic movement assessment while not specifying the type of upper extremity injury is not favorable for the clinician to identify previous injury.

While many older adults are immobile and frail, others still participate in competitive sports. World records of javelin throw decrease with increasing age. It is, however, unknown 1) whether the decline is linear or, as in sprint performance, accelerates beyond the age of 69; and 2) to what extent frailty-related changes in throwing technique contribute to decreasing performance. We plotted current world records against age and assessed the performance of 27 male javelin throwers 69 years and older during three master athletics championships. Three to six throws were filmed, and the best throw of each athlete selected. A step-wise linear regression was applied to assess contributions of age, angle of release, angle of attitude, angle of attack and elbow angle just before the pull to performance. The ageing-related decline in javelin-throw performance accelerated after age 69. Age was the main predictor of performance (adjusted R ² =0.68), with a small contribution of elbow angle (adjusted R ² increased to 0.76) and angle of attack (R ² =0.82; all P<0.001) in the older athletes. None of the technique-related parameters correlated with age. Although the technique had some influence on javelin-throwing performance, the accelerated decline was not associated with a characteristic ageing-related change in technique.

The aim of the present study was to assess prospectively the effect of pre-season fitness on injury rate during the competitive season among professional soccer players. Thirty-one players participated in the study during two consecutive competitive seasons (2015-16 and 2016-17; a squad of 22 players in each season). During the 6-week pre-season training period (8 training sessions and a friendly match every week, 14-18 training hours/week) there was a significant improvement in VO ₂ max, a significant increase in ideal and total sprint time and no change in vertical jump, flexibility and repeated sprint-test performance decrement. During the two consecutive seasons, 28 injuries were recorded. Ten injuries were classified as mild (missing 3-7 days of practice/match), 8 as moderate (missing 8-28 days) and 10 as severe (missing >28 days). The rate of match injuries was higher (9.4 per 1000 match hours) compared to practice injuries (4.7 per 1000 training hours). Most injuries were overuse injuries (72%) of the lower limbs (71%). Most of match injuries occurred during the last 15 min of each half. There were no differences in fitness characteristics in the beginning of pre-season training between injured and non-injured players. However, improvements in VO ₂ max during the pre-season training period were significantly lower among injured players (0.9±5.5%) compared to non-injured players (10.4±6.5%, p<0.05). Our results emphasize the importance of pre-season training in professional soccer players not only for improvement in fitness but also for injury prevention during the following competitive season.

The present study determined metabolic and performance responses to repeated sprint exercise under hypoxia among female team-sport athletes. Fifteen female athletes (age, 20.7±0.2 years; height, 159.6±1.7 cm; body weight, 55.3±1.4 kg) performed two exercise trials under either a hypoxic [HYPO; fraction of inspired oxygen (F _i O ₂ ), 14.5%] or normoxic (NOR; F _i O ₂ , 20.9%) condition. The exercise consisted of two sets of 8×6-s maximal sprint (pedaling). The average power output was not significantly different between trials for set 1 ( P =0.89), but tended to be higher in the NOR trial for set 2 ( P =0.05). The post-exercise blood lactate concentrations were significantly higher in the HYPO trial than that in the NOR trial ( P <0.05). Exercise significantly increased serum growth hormone (GH) and cortisol concentrations ( P <0.01 for both hormones), with no difference between the trials. In conclusion, repeated short-duration sprints interspaced with 30-s recovery periods in moderate hypoxia caused further increase in blood lactate compared with the same exercise under normoxic conditions among female team-sport athletes. However, exercise-induced GH and cortisol elevations or power output during exercise were not markedly different regardless of the different levels of inspired oxygen.

Purpose: Traditional heart-rate monitoring through the use of electrocardiograms or chest-worn heart rate sensors can be challenging in certain sports or in field settings. New technologies, such as photoplethysmography (PPG), have enabled heart-rate monitoring at alternate sites. However, to date, the accuracy and validity of various PPG sensors has not been examined in detail. The purpose of the present investigation was to determine the validity of an arm-worn PPG sensor during yoga sequences.

Methods: Fifteen college-aged men and women participated in a ~45 min power vinyasa yoga class. During the class, participants wore Polar ^® H7 chest straps and RCX3 receivers (criterion) and Polar ^® OH1 arm bands on their upper right arm (practical). Mean differences were compared via a paired t -test, heart rate during yoga using a time*device repeated measures ANOVA, and agreement assessed with Bland-Altman analysis.

Results: Mean heart rates during yoga were not different (mean difference=0.76, 95% CI: -0.54 to 2.06; p =0.229). Yoga created a main effect of time on heart rate ( p <0.0001), but there was no difference between devices ( p =0.86) or interaction ( p =0.90). Mean bias±95% limits of agreement was 0.76±1.30 bpm, with a typical error of 2.42±1.49 bpm and a coefficient of variation of 1.8±1.5%.

Conclusions: Results of the present investigation revealed that the Polar ^® OH1 is a valid measure of heart rate during moderate-vigorous exercise. Future validation studies should consider other exercise modes and participant characteristics.

Motives for physical activity were compared between adults who either successfully or unsuccessfully maintained regular physical activity over the last 10 years. Adults age 28-45 (N=721) completed an online survey, reporting their current physical activity levels and self-determination theory (SDT) motives, as well as their physical activity levels at least 10 years prior. With participants' current and retrospective reports of their physical activity, four sample subgroups were created, including maintainers, improvers, decliners, and sedentary. ANOVA analyses were used to examine differences in motives between physical activity maintenance groups. Those who successfully maintained regular physical activity (maintainers) reported higher intrinsic and extrinsic motives compared to those who were not regularly active ( P <0.05). Interestingly, maintainers reported similar physical activity motives compared to those who reported increased physical activity over time. Among the current sample and consistent with theory, motives for physical activity significantly influenced participants' long-term maintenance of regular physical activity. Future interventions should consider these constructs to promote sustained physical activity.

Perception of red color is associated with higher testosterone concentration and better human performance. Thus, we evaluated the acute effects of wearing colored-lens glasses on the YoYo intermittent endurance exercise test 2 (YoYoIE2) performance indicators and testosterone concentration. Ten soccer players performed three YoYoIE2 (counterbalanced crossover) wearing colorless (control), blue- or red-lensed glasses (2-4 days of rest in between). YoYoIE2 performance did not differ among the trials ( p >0.05), but blood testosterone increased post-exercise in red compared to red baseline (red=14%, effect size=0.75). Analysis showed faster heart rate recovery ( p <0.05) at 1 min post-test for blue compared to red lenses. Rating of perceived exertion and blood lactate concentration did not differ ( p >0.05) among the trials. Wearing red-colored lenses during high-intensity intermittent exercise increased testosterone concentration, but do not influence performance.