Influence of Fatigue on Change of Direction Performance in Soccer Players.

We investigated the acute fatiguing effects of sprint interval training (SIT) on change of direction performance in male and female soccer players. A T-test was performed once before (PRE) and twice following (POST 1 and POST 2) the completion of four sets of 4 s cycle ergometer sprints protocol. The sprint intervals were separated by 25 s active recovery. POST 1 was performed approximately 25 s following the final cycle sprint and POST 2 began two minutes after completing POST 1. Repeated measures ANOVA and Bonferroni post hoc tests were used to determine any significant differences in the time to complete the T-tests. The average power output drop measured during cycle SIT was 30.7 ± 9%. Time to complete the T-test significantly differed among the three tests (PRE: 10.46 ± .17 s; POST 1: 11.67 ± .33 s; POST 2: 10.96 ± .19 s; F (2, 54) = 6.174, p = .003). Post hoc test revealed an increase in time from PRE to POST 1 (p = .002) but no difference between PRE and POST 2 (p = .473). Nine participants (48%) were unable to complete POST 1 without errors; however, ten (52%) participants recovered enough to perform POST 1 without error. These results show that acute fatigue from SIT impairs change of direction performance, but performance can be recovered within a few minutes of rest. Coaches can combine fatigue inducing drills and change of direction training into same sessions with the right rest interval between the training modes.

Sex differences in pelvic and hip flexibility in men and women matched for sit-and-reach score.

The purpose of this study was to test sex differences in sagittal plane thoracic (T), lumbar (L), and pelvic (P) angles measured during the sit-and-reach (SR) test and hip joint angle during a passive straight leg raise (SLR) test in men and women matched for SR scores. Thirty-five men and 35 women performed a standard SR and SLR test. Among the 70 subjects, 25 male and female pairs were identified using <5% difference in the SR score as the pairing criterion. Both SR and SLR tests were videotaped and subsequently analyzed using a computer software angle tool to measure T, L, and P angles during the SR test and hip joint angle during the SLR test. In paired men (M) and women (W), P angle (M: 96.6 ± 9.4° vs. W: 104.7 ± 12.4°) and hip joint angle (M: 87.1 ± 10.5° vs. W: 100.4 ± 12.1°) were lower and L angle (M: 26.3 ± 10.8° vs. W: 21.1 ± 7.6°) was greater in men. There was no difference in the T angle (53.3 ± 11.6° vs. 51.2 ± 11.4°) between men and women. Correlation coefficient indicated that the SR score was moderately associated with the P angle in both men (r = 0.82) and women (r = 0.83), whereas the traditional criterion measure for hip flexibility, SLR hip joint angle, demonstrated a relatively low correlation to SR scores in both men (r = 0.60) and women (r = 0.56). These data indicate that the SR score does not distinguish spine and pelvic flexibility differences in men and women and does not adequately assess hip flexibility.

Reliability of a computer software angle tool for measuring spine and pelvic flexibility during the sit-and-reach test.

The purpose of this study was to determine the reliability of a computer software angle tool that measures thoracic (T), lumbar (L), and pelvic (P) angles as a means of evaluating spine and pelvic flexibility during the sit-and-reach (SR) test. Thirty adults performed the SR twice on separate days. The SR test was captured on video and later analyzed for T, L, and P angles using the computer software angle tool. During the test, 3 markers were placed over T1, T12, and L5 vertebrae to identify T, L, and P angles. Intraclass correlation coefficient (ICC) indicated a very high internal consistency (between trials) for T, L, and P angles (0.95-0.99); thus, the average of trials was used for test-retest (between days) reliability. Mean (±SD) values did not differ between days for T (51.0 ± 14.3 vs. 52.3 ± 16.2°), L (23.9 ± 7.1 vs. 23.0 ± 6.9°), or P (98.4 ± 15.6 vs. 98.3 ± 14.7°) angles. Test-retest reliability (ICC) was high for T (0.96) and P (0.97) angles and moderate for L angle (0.84). Both intrarater and interrater reliabilities were high for T (0.95, 0.94) and P (0.97, 0.97) angles and moderate for L angle (0.87, 0.82). Thus, the computer software angle tool is a highly objective method for assessing spine and pelvic flexibility during a video-captured SR test.

Achievement of VO2max criteria during a continuous graded exercise test and a verification stage performed by college athletes.

The purpose of this study was to determine the incidence of meeting specific VO2max criteria and to test the effectiveness of a VO2max verification stage in college athletes. Thirty-five subjects completed a continuous graded exercise test (GXT) to volitional exhaustion. The frequency of achieving various respiratory exchange ratio (RER) and age-predicted maximum heart rate (HRmax) criteria and a VO2 plateau within 2 and 2.2 ml·kg(-1)·min(-1) (<2SD of the expected increase in VO2) were measured and tested against expected frequencies. After 10 minutes of active recovery, 10 subjects who did not demonstrate a plateau completed a verification stage performed at supramaximal intensity. From the GXT, the number of subjects meeting VO2max plateau was 5 (≤2 ml·kg(-1)·min(-1)) and 7 (≤2.2 ml·kg(-1)·min(-1)), RER criteria 34 (≥1.05), 32 (≥1.10), and 24 (≥1.15), HRmax criteria, 35 (<85%), 29 (<10 b·min(-1)) and 9 (HRmax). The VO2max and HRmax did not differ between GXT and the verification stage (53.6 ± 5.6 vs. 55.5 ± 5.6 ml·kg(-1)·min(-1) and 187 ± 7 vs. 187 ± 6 b·min(-1)); however, the RER was lower during the verification stage (1.15 ± 0.06 vs. 1.07 ± 0.07, p = 0.004). Six subjects achieved a similar VO2 (within 2.2 ml·kg(-1)·min(-1)), whereas 4 achieved a higher VO2 compared with the GXT. These data demonstrate that a continuous GXT limits the college athlete's ability to achieve VO2max plateau and certain RER and HR criteria. The use of a verification stage increases the frequency of VO2max achievement and may be an effective method to improve the accuracy of VO2max measurements in college athletes.

Body-density measurement in children: the BOD POD versus Hydrodensitometry.

OBJECTIVE: To compare estimates of body density (Db) from air-displacement plethysmography (ADP) with measured and predicted thoracic-gas-volume (TGV) measurements and those from hydrodensitometry (HD) in children. METHODS: Seventeen participants (13 male and 4 female; 10.1 ± 2.20 yr, 42.0 ± 15.03 kg, 145.6 ± 17.41 cm, 30.0 ± 8.66 kg/m²) were tested using ADP and HD, with ADP always preceding HD. Db estimates were compared between ADP with measured TGV, ADP with predicted TGV, and the reference measure, HD. Regression analyses were used to assess the accuracy of the ADP methods, and potential bias between the ADP procedures and HD were evaluated using Bland-Altman analyses. The cross-validation criteria described by Lohman for estimating Db relative to HD were used to interpret the results of the study. RESULTS: A significant difference was found between Db estimates from ADP with measured TGV (1.0453 ± 0.01934 g/cm³) and ADP with predicted TGV (1.0415 ± 0.01858 g/cm³); however, neither was significantly different from Db obtained by the reference HD procedure (1.0417 ± 0.02391 g/cm³). For both ADP procedures, regression analyses produced an r = .737-.738, r² = .543-.544, and SEE = 0.02 g/cm³, and the regression lines deviated significantly from the line of identity; however, no significant biases were indicated. CONCLUSIONS: Despite no significant mean differences between Db estimates from the ADP procedures and HD, more cross-validation research is needed before recommending the BOD POD for routine use with children in clinical and research settings.

Repeated Sprint Performance in Male and Female College Athletes Matched for VO2max Relative to Fat Free Mass.

The purpose of this study was to examine gender differences in repeated sprint exercise (RSE) performance among male and female athletes matched for VO2max relative to FFM (VO2max FFM). Thirty nine male and female college athletes performed a graded exercise test for VO2max and hydrostatic weighing to determine FFM. From the results, 11 pairs of males and females matched for VO2max FFM (mean ± SD; 58.3 ± 4.3 and 58.9 ± 4.6 ml·kg FFM-1·min-1; men and women, respectively) were identified. On a separate day, matched participants performed a RSE protocol that consisted of five 6-sec cycle sprints with 30-sec recovery periods, followed by 5-min active recovery and a 30-sec all-out sprint. Repeated 6-sec sprint performance did not differ between men and women; both maintained power output (PO) until sprint 4. POFFM (W·kg-1 FFM) did not differ between men and women during the five sprints. During the 30-sec sprint, men achieved a lower peak POFFM than women (11.7 ± 1.5 vs 13.2 ± 1.2); however, the decline in POFFM over 30 sec was greater in women. VO2 (ml·kg FFM-1·min-1) was lower in men during recovery (24.4 ± 3.8 vs 28.7 ± 5.7) and at the beginning (29.2 ± 4.0 vs 34.7 ± 4.9) and end (49.4 ± 5.0 vs 52.3 ± 4.0). of the 30-sec sprint. These data indicate that men and women with similar aerobic capacities do not respond differently to short repeated sprints but may differ in their ability to recover and perform sprints of longer duration.

Accuracy and feasibility of video analysis for assessing hamstring flexibility and validity of the sit-and-reach test.

The accuracy of video analysis of the passive straight-leg raise test (PSLR) and the validity of the sit-and-reach test (SR) were tested in 60 men and women. Computer software measured static hip-joint flexion accurately. High within-session reliability of the PSLR was demonstrated (R > .97). Test-retest (separate days) reliability for SR was high in men (R = .97) and women R = .98) moderate for PSLR in men (R = .79) and women (R = .89). SR validity (PSLR as criterion) was higher in women (Day 1, r = .69; Day 2, r = .81) than men (Day 1, r = .64; Day 2, r = .66). In conclusion, video analysis is accurate and feasible for assessing static joint angles, PSLR and SR tests are very reliable methods for assessing flexibility, and the SR validity for hamstring flexibility was found to be moderate in women and low in men.

Metabolic cost of stride rate, resistance, and combined use of arms and legs on the elliptical trainer.

We measured the effects of stride rate, resistance, and combined arm-leg use on energy expenditure during elliptical trainer exercise and assessed the accuracy of the manufacturer's energy expenditure calculations. Twenty-six men and women (M age = 29 years, SD = 8; M body weight = 73. 0 kg, SD = 15.2) participated. Twenty-two participants performed two tests, one without the arm poles (leg-only) and the other with arm poles (combined arm-leg). The other 4 participants performed one test without the arm poles. Both tests consisted of six 5-min stages (two stride rates, 110 and 134 stridesmin-1, and three resistance settings: 2, 5, and 8). Steady-state oxygen uptake (VO2), minute ventilation (VE), heart rate (HR) and rating of perceived exertion (RPE) were measured. Repeated measures analysis of variance determined higher (p <. 001) VO2, VE, and RPE, but not HR, during combined arm-leg versus leg-only exercise at any given intensity. Increases in stride rate and resistance increased VO2, VE, RPE, and HR with the greatest effect on VE and HR from Levels 5 to 8. The manufacturer's calculated energy expenditure was overestimated during both tests. Although the oxygen cost for elliptical trainer exercise was calculated to be approximately 0.1 mlxkg(-1) per stride and 0.7 mlxkg(-1) min-1 per resistance level, VO2 varied widely among individuals, possibly due to differences in experience using the elliptical trainer gender, and body composition. The elliptical trainer offers (a) a variety of intensities appropriate for most individuals and (b) both arm and leg exercise. Due to the wide variability in VO2, predicting the metabolic cost during elliptical trainer exercise for an individual is not appropriate.

Evaluation of a treadmill test for predicting the aerobic capacity of firefighters.

BACKGROUND: As part of a comprehensive occupational medical program for fire departments in the USA, the National Fire Protection Association and The Fire Service Joint Labor Management Wellness/Fitness Initiative endorse a standardized submaximal test that uses the Gerkin treadmill protocol for predicting the maximal oxygen uptake (VO(2max)) of firefighters. AIMS: To test the validity of the Gerkin treadmill protocol in healthy men and women. METHODS: Fifty-four healthy men and women (age range 19-58 years) performed the Gerkin test and a treadmill run test to maximal exhaustion. Their heart rates were monitored continuously with an electrocardiogram during each test. During the VO(2max) test, the subjects' VO(2) was measured continuously using indirect calorimetry. RESULTS: Although the predicted and observed VO(2max) values correlated (r = 0.70, P < 0.001 and standard error of estimate = 5.98 ml/kg/min), the mean values differed (49.8 +/- 8.3 and 41.8 +/- 5.8 ml/kg/min, respectively) (P < 0.001). The VO(2max) value was overestimated in 50 (93%) participants. The overestimation was >25% in 18 (33%) participants. Gender, age and VO(2max) did not affect the Gerkin protocol's predictability of VO(2max). CONCLUSIONS: The Gerkin treadmill protocol overpredicts VO(2max) in healthy men and women and, therefore, should not be used for predicting VO(2max) in individual firefighters, particularly if VO(2max) is a criterion for inclusion or exclusion from duty. At this time, a valid treadmill running test is needed for predicting the VO(2max) value of individual firefighters.