Ultra-shortened time-domain HRV parameters at rest and following exercise in athletes: an alternative to frequency computation of sympathovagal balance.

PURPOSE: The primary purpose of this study was to determine the accuracy of the standard deviation of normal-to-normal intervals (SDNN) to root mean square of successive normal-to-normal interval differences (RMSSD) ratio from 1-min recordings (SDNN:RMSSD1-min) compared to criterion recordings, as well as its relationship to low-frequency-to-high-frequency ratio (LF:HF) at rest and following maximal exercise in a group of collegiate athletes. METHOD: Twenty athletes participated in the study. Heart rate variability (HRV) data were measured for 5 min before and at 5-10 and 25-30 min following a maximal exercise test. From each 5-min segment, the frequency-domain measures of HF, LF, and LF:HF ratio were analyzed. Time-domain measures of SDNN, RMSSD, and SDNN:RMSSD ratio were also analyzed from each 5-min segment, as well as from randomly selected 1-min recordings. RESULT: The 1-min values of SDNN, RMSSD, and SDNN:RMSSD provided no significant differences and nearly perfect intra-class correlations (ICCs ranged from 0.97 to 1.00, p < 0.001 for all) to the criterion measures from 5-min recordings. In addition, SDNN, RMSSD, and SDNN:RMSSD from the 1-min segments provided very large to nearly perfect correlations (r values ranged from 0.71 to 0.97, p < 0.001 for all) to LF, HF, and LF:HF, respectively, at each time point. CONCLUSION: The findings of the study suggest that ultra-shortened time-domain markers may be useful surrogates of the frequency-domain parameters for tracking changes in sympathovagal activity in athletes.

Validity of Four-Compartment Model Body Fat In Physically Active Men And Women When Using DXA For Body Volume.

The purpose of this study was twofold: 1) compare body volume (BV) estimated from dual energy X-ray absorptiometry (DXA) to BV from a criterion underwater weighing (UWW) with simultaneous residual lung volume (RLV), and 2) compare four-compartment (4C) model body fat percentage (BF%) values when deriving BV via DXA (4CDXA) and UWW (4CUWW) in physically active men and women. One hundred twenty-two adults (62 men and 60 women) who self-reported physical activity levels of at least 1,000 MET·min·wk-1 volunteered to participate (age = 22 ± 5 years). DXA BV was determined with the recent equation from Smith-Ryan et al. while criterion BV was determined from UWW with simultaneous RLV. The mean BV values for DXA were not significant compared with UWW in women (p = .80; constant error [CE] = 0.0L), but were significantly higher in the entire sample and men (both p < .05; CE = 0.3 and 0.7L, respectively). The mean BF% values for 4CDXA were not significant for women (p = .56; CE = -0.3%), but were significantly higher in the entire sample and men (both p < .05; CE = 0.9 and 2.0%, respectively). The standard error of estimate (SEE) ranged from 0.6-1.2L and 3.9-4.2% for BV and BF%, respectively, while the 95% limits of agreement (LOA) ranged from ±1.8-2.5L for BV and ±7.9-8.2% for BF%. 4CDXA can be used for determining group mean BF% in physically active men and women. However, due to the SEEs and 95% LOAs, the current study recommends using UWW with simultaneous RLV for BV in a criterion 4C model when high individual accuracy is desired.

Cross-Validation of Age-Predicted Maximal Heart Rate Equations Among Female Collegiate Athletes.

The purpose of this study was to determine the accuracy of 3 general and 2 female-specific age-predicted maximal heart rate (HRmax) prediction equations in female collegiate athletes. Thirty female collegiate athletes (age = 21.5 ± 1.9 years, height = 164.7 ± 6.6 cm, weight = 61.3 ± 8.2 kg) participated. HRmax was determined with a maximal graded exercise test and predicted with 3 general equations (Fox et al., Astrand, and Tanaka et al.) and 2 female-specific equations (Fairbarn et al. and Gulati et al.). There was no significant difference between observed HRmax (185.9 ± 5.0 b·min) and the Fairbarn (187.5 ± 1.2 b·min) and Gulati (187.1 ± 1.7 b·min) equations (p = 0.11 and 0.23, respectively). The Fox (198.5 ± 1.9 b·min), Astrand (198.1 ± 1.6 b·min), and Tanaka (193.0 ± 1.4 b·min) equations provided significantly higher estimates compared with observed HRmax (p < 0.001 for each). The standard error of the estimate was similar for all the prediction equations (between 5.0 and 5.4 b·min), but the total error was smallest for Fairbarn and Gulati (5.3 b·min for each) and largest for Fox and Astrand (13.9 and 13.3 b·min, respectively). The 95% limits of agreement of the mean error were similar for all of the prediction equations, with values varying between 9.9 and 10.5 b·min. Because of the wide limits of agreement displayed by each equation, the use of age-predicted methods for estimating HRmax in collegiate female athletes should be performed only with caution.

Comparison of total and segmental body composition using DXA and multifrequency bioimpedance in collegiate female athletes.

The purpose of this investigation was to determine the agreement between multifrequency bioelectrical impedance analysis (BIA) and dual-energy x-ray absorptiometry (DXA) for measuring body fat percentage (BF%), fat-free mass (FFM), and total body and segmental lean soft tissue (LST) in collegiate female athletes. Forty-five female athletes (age = 21.2 ± 2.0 years, height = 166.1 ± 7.1 cm, weight = 62.6 ± 9.9 kg) participated in this study. Variables measured through BIA and DXA were as follows: BF%, FFM, and LST of the arms (ARMS(LST)), the legs (LEGS(LST)), the trunk (TRUNK(LST)), and the total body (TOTAL(LST)). Compared with the DXA, the InBody 720 provided significantly lower values for BF% (-3.3%, p < 0.001) and significantly higher values for FFM (2.1 kg, p < 0.001) with limits of agreement (1.96 SD of the mean difference) of ±5.6% for BF% and ±3.7 kg for FFM. No significant differences (p < 0.008) existed between the 2 devices (InBody 720-DXA) for ARMS(LST) (0.05 kg), TRUNK(LST) (0.14 kg), LEGS(LST) (-0.4 kg), and TOTAL(LST) (-0.21 kg). The limits of agreement were ±0.79 kg for ARMS(LST), ±2.62 kg for LEGS(LST), ±3.18 kg for TRUNK(LST), and ±4.23 kg for TOTAL(LST). This study found discrepancies in BF% and FFM between the 2 devices. However, the InBody 720 and DXA appeared to provide excellent agreement for measuring total body and segmental LST. Therefore, the InBody 720 may be a rapid noninvasive method to assess LST in female athletes when DXA is not available.

Crossvalidation of two 20-m shuttle-run tests for predicting VO2max in female collegiate soccer players.

The aim of this study was twofold: (a) to compare the maximal attained speed (MAS) from the 20-m shuttle (MST) and 20-m square-shuttle (SST) tests and (b) to crossvalidate 2 equations for predicting maximal oxygen consumption (VO2max) that were previously developed from MST and SST in a group of female collegiate soccer players. Thirty-nine subjects (age: 20.1 ± 1.5 years) participated in the study. A maximal graded exercise treadmill test was used to measure VO2max. In addition, VO2max was predicted from the MAS obtained during MST ((pred)VO2maxMST) and SST ((pred)VO2maxSST) using previously developed equations. Measured VO2max for the group was 44.2 ± 3.3 ml·kg(-1)·min(-1). The MAS was 12.5 ± 0.6 km·h(-1) for MST and 13.3 ± 0.8 km·h(-1) for SST (p < 0.05). The prediction methods yielded a (pred)VO2maxMST of 49.6 ± 3.9 ml·kg(-1)·min(-1) and predVO2maxSST of 41.8 ± 3.1 ml·kg(-1)·min(-1), which were significantly different from measured VO2max (p < 0.05). The validity statistics revealed the following constant error (CE), correlation coefficient (r), standard error of estimate (SEE), and total error (TE) for (pred)VO2maxMST and (pred)VO2maxSST: CE = 5.35 ± 3.83, r = 0.45 (p < 0.05), SEE = 2.97 ml·kg(-1)·min(-1), TE = 6.39 ml·kg(-1)·min(-1); and CE = -2.43 ± 2.49, r = 0.69 (p < 0.05), SEE = 2.39 ml·kg(-1)·min(-1), TE = 3.43 ml·kg(-1)·min(-1), respectively. Residual plots indicated no proportional bias for either prediction model. The results of this study suggest that female collegiate soccer players had a higher MAS from SST compared with that from MST. In addition, SST appeared to be a more accurate predictor of VO2max than MST in the group of athletes.

Crossvalidation of two heart rate-based equations for predicting VO2max in white and black men.

The purpose of this investigation was to crossvalidate 2 equations that use the ratio of maximal heart rate (HRmax) to resting HR (HRrest) for predicting maximal oxygen consumption (VO2max) in white and black men. One hundred and nine white (n = 51) and black (n = 58) men completed a maximal exercise test on a treadmill to determine VO2max. The HRrest and HRmax were used to predict VO2max via the HRindex and HRratio equations. Validity statistics were done to compare the criterion versus predicted VO2max values across the entire cohort and within each race separately. For the entire group, VO2max was significantly overestimated with the HRindex equation, but the HRratio equation yielded no significant difference compared with the criterion. In addition, there were no significant differences shown between VO2max and either HR-based prediction equation for the white subgroup. However, both equations significantly overestimated VO2max in the black group. Furthermore, large standard error of estimates (ranging from 6.92 to 7.90 ml·kg(-1)·min(-1)), total errors (ranging from 8.30 to 8.62 ml·kg(-1)·min(-1)), and limits of agreement (ranging from upper limits of 16.65 to lower limits of -18.25 ml·kg(-1)·min(-1)) were revealed when comparing the predicted to criterion VO2max for both the groups. Considering the results of this investigation, the HRratio and HRindex methods appear to crossvalidate and prove useful for estimating the mean VO2max in white men as a group but not for an age-matched group of black men. However, because of inflated values for error, caution should be exercised when using these methods to predict individual VO2max.

Skinfold thickness is related to cardiovascular autonomic control as assessed by heart rate variability and heart rate recovery.

The purpose of this study was to determine if heart rate recovery (HRR) and heart rate variability (HRV) are related to maximal aerobic fitness and selected body composition measurements. Fifty men (age = 21.9 ± 3.0 years, height = 180.8 ± 7.2 cm, weight = 80.4 ± 9.1 kg, volunteered to participate in this study. For each subject, body mass index (BMI), waist circumference (WC), and the sum of skinfolds across the chest, abdomen, and thigh regions (SUMSF) were recorded. Heart rate variability (HRV) was assessed during a 5-minute period while the subjects rested in a supine position. The following frequency domain parameters of HRV were recorded: normalized high-frequency power (HFnu), and low-frequency to high-frequency power ratio (LF:HF). To determine maximal aerobic fitness (i.e., VO2max), each subject performed a maximal graded exercise test on a treadmill. Heart rate recovery was recorded 1 (HRR1) and 2 (HRR2) minutes during a cool-down period. Mean VO2max and BMI for all the subjects were 49.5 ± 7.5 ml·kg(-1)·min(-1) and 24.7 ± 2.2 kg·m(-2), respectively. Although VO2max, WC, and SUMSF was each significantly correlated to HRR and HRV, only SUMSF had a significant independent correlation to HRR1, HRR2, HFnu, LF:HF (p < 0.01). The results of the regression procedure showed that SUMSF accounted for the greatest variance in HRR1, HRR2, HFnu, and LF:HF (p < 0.01). The results of this study suggest that cardiovascular autonomic modulation is significantly related to maximal aerobic fitness and body composition. However, SUMSF appears to have the strongest independent relationship with HRR and HRV, compared to other body composition parameters and VO2max.

The accuracy of hand-to-hand bioelectrical impedance analysis in predicting body composition in college-age female athletes.

The purpose of this investigation was to determine the accuracy of hand-to-hand bioelectrical impedance analysis (BIA) for estimating body composition in college-age female athletes using dual-energy X-ray absorptiometry (DEXA) as the criterion measure. Forty National Association for Intercollegiate Athletics college female athletes volunteered to participate in this study. For each participant, total body fat percentage (BF%) and fat-free mass (FFM) were obtained via BIA and DEXA. The mean BF% and FFM values obtained by BIA were compared with the criterion DEXA measure. The DEXA strongly correlated to the BIA for BF% (r = 0.74, R2 = 0.55, SEE = 3.60, and p < 0.01) and FFM (r = 0.84, R2 = 0.71, SEE = 2.45, p < 0.01). However, when compared with the DEXA, the mean values for BIA were significantly lower for BF% (DEXA = 27.6 ± 5.3%, BIA = 22.5 ± 3.5%, p < 0.01) and higher for FFM (DEXA = 47.2 ± 4.5 kg, BIA = 50.6 ± 4.6 kg, p < 0.01). The results of this investigation indicate that hand-to-hand BIA significantly underestimates BF% and overestimated FFM in college-age female athletes when compared with the criterion DEXA. Practitioners should use caution when analyzing body composition with hand-held BIA in a population of athletic women.

The relationship between resting heart rate variability and heart rate recovery.

OBJECTIVE: There is limited research available regarding a possible relationship between resting heart rate variability (HRV) and post-exercise heart rate recovery (HRR). The aim of this study was to examine the relationship between resting HRV and HRR after maximal exercise. METHODS: Sixty-six college age men participated in this study. HRV was measured in a supine position before and for 30 min after a maximal exercise test on a treadmill. HRV was assessed in the time (i.e., SDNN) and frequency (i.e., normalized HF power [HFnu] and normalized LF:HF ratio [LFnu:HFnu]) domains. Heart rate was recorded at maximal exercise (MHR), and at 1- (HR1) and 2- (HR2) min of the cool-down recovery period. HRR was determined from the difference between MHR and HR1 (HRR1) and the difference between MHR and HR2 (HRR2). RESULTS: No significant relationship was found between resting HRV and HRR1 or HRR2. However, SDNN was significantly inversely correlated to MHR (P < 0.05), and HFnu was significantly inversely correlated to MHR (P < 0.01), HR1 (P < 0.01), and HR2 (P < 0.05). Furthermore, MHR accounted for the greatest variation in both SDNN and HFnu (P < 0.05). INTERPRETATION: Therefore, the HRV may not be related to the recovery of HR expressed as a slope (i.e., HRR) within 2 min following a maximal exercise test. This is possibly due to a significant inverse relationship between HRV and MHR, HR1 and HR2 post-maximal exercise.

Sport Locus of Control and Perceived Stress among College Student-Athletes.

The purpose of the study was to analyze athletes' motivation for sport participation as it related to their locus of control. Research was conducted at two Division I universities in the southeastern United States. Participants were given the Sport Locus of Control and Perceived Stress among College Athletes surveys. There were 126 participants with a mean age of 19.69 ± 1.32 years. A Pearson correlation (r) was performed to determine a significant relationship between perceived stress and locus of control. Results indicated a significant negative relationship between the two variables (r = -0.393 and p = 0.001) (a moderate relationship). As perceived stress scores increased, locus of control scores decreased. Correlations related to perceived stress were gender (r = 0.323, p = 0.000), and grade point average (GPA) (r = -0.213, p = 0.01). The only other independent variable that was significantly related to locus of control was being on an academic scholarship (r = -0.203, p = 0.025). Athletes who have an external locus of control feel that they have little control over their circumstances. Findings of this study give coaches another factor to consider in retaining and getting the most from their athletes.

Postexercise heart rate variability following treadmill and cycle exercise: a comparison study.

The purpose of this study was to compare postexercise heart rate variability (HRV) immediately following acute bouts of treadmill (T) and cycle (C) exercise at 65% of mode-specific maximal oxygen consumption reserve (65% VO2 R). Fourteen apparently healthy men participated in this study. On two separate and randomized days, each participant performed 30 min of exercise at 65% VO2 R on T and C. Supine HRV was evaluated as normalized and log-transformed (ln) high-frequency (HF) and low-frequency (LF) spectral power, as well as the LF:HF ratio in 5-min segments immediately before (PRE) and at 10-15 min (POST1) and 25-30 min (POST2) following each exercise bout. There were no significant differences in the HRV values at PRE between the modalities. Following each exercise bout, lnHF was significantly lower at POST2 following C compared to T. In addition, lnLF and LF:HF were significantly higher at POST1 and POST2 following C compared to T. All HRV metrics returned towards baseline 30 min following T but remained significantly different than PRE values after C. These results suggest that following exercise at 65% of mode-specific VO2 R, C is associated with a greater delay of postexercise HRV recovery than T in apparently healthy men.

Effects of Heat Exposure on Body Water Assessed using Single-Frequency Bioelectrical Impedance Analysis and Bioimpedance Spectroscopy.

The purpose of this study was to determine if heat exposure alters the measures of total body water (TBW), extracellular water (ECW), and intracellular water (ICW) in both single-frequency bioelectrical impedance analysis (BIA) and bioimpedance spectroscopy (BIS). Additionally, we sought to determine if any differences exist between the BIA and BIS techniques before and after brief exposure to heat. Body water was evaluated for twenty men (age=24±4 years) in a thermoneutral environment (22°C) before (PRE) and immediately after (POST) 15 min of passive heating (35°C) in an environmental chamber. The mean difference and 95% limits of agreement at PRE demonstrated that BIS yielded significantly higher body water values than BIA (all p<0.05; TBW=1.8kg; ECW=0.6±1.3kg; ICW=1.2±3.7kg). However, the effect size (ES) of the mean differences at PRE were small and the r-values were high (r≥0.97). TBW and ICW remained significantly higher at POST for BIS (both p<0.05; 1.4±3.2kg and 1.1±3.7kg, respectively) whereas ECW was not different (p>0.05; 0.2±1.5kg). Additionally, the ES of the mean differences at POST were trivial to small and the r-values were high (r≥0.96). When analyzing the changes in body water before and after heat exposure, POST values for BIS were significantly higher than PRE (all p<0.001; TBW=0.6±0.8kg; ECW=0.4±0.3kg; ICW=0.3±0.6kg). Similarly, POST values for BIA were significantly higher than PRE (all p<0.001; TBW=1.0±0.6kg; ECW=0.7±0.4kg; ICW=0.4±0.4kg). BIA and BIS provide similar body water estimates. However, the increase in POST body water values indicate more research is needed before either method can be used for estimating body water after heat exposure.

Validity of the body adiposity index in adults with Down syndrome.

The purpose of this investigation was to determine the agreement between the body adiposity index (BAI) and dual energy X-ray absorptiometry (DXA) for measuring BF% in adults with Down syndrome (DS). Twenty adults (male: n=10; female: n=10) with Down syndrome volunteered to participate in this study. Criterion BF% was determined by DXA and predicted BF% was estimated by the BAI method. There was a significant mean difference (p<0.001) between DXA BF% (39.94±10.80%) and the BAI BF% (42.60±8.19%). The correlation between the two BF% variables was large and significant (r=0.73, p<0.001). However, the standard error of the estimate and total error was 7.79% and 7.86%, respectively. Additionally, the 95% limits of agreement ranged from 12.21% below to 17.52% above the constant error of 2.65%. Our findings suggest that on average, the BAI significantly overestimated BF% when compared to DXA values. Though there was a strong correlation between both methods, the wide limits of agreement suggest there is large amount of individual error when estimating BF% via the BAI. Therefore, the use of the BAI for individuals with DS does not appear to be accurate for estimating BF%.

Relationship between post-exercise heart rate variability and skinfold thickness.

This investigation aimed to determine if groupings based upon sum of skinfold thickness (SF) would reflect the differences in heart rate variability (HRV) measured for up to 30-minutes following maximal exercise, and to determine the extent in variation in post-exercise HRV that could be accounted for between the following independent variables: SF, body mass index (BMI) and maximal oxygen consumption (VO2max). SF and BMI measurements were performed on fifty-four men who completed maximal exercise testing to determine VO2max. HRV was evaluated for five-minutes before (Pre), at 0-5 minutes post- (Post1) and 25-30 minutes post-exercise (Post2), and analyzed by frequency domain [high frequency (HF) power, and HF to low frequency power ratio (LF:HF)). Two groups were formed based on being above or below the sample mean value of SF. HF and LF:HF were significantly higher and lower, respectively, at Pre and Post 2 in Group 1 compared to Group 2 (p < 0.05), which remained after controlling for VO2max and BMI. Furthermore, there was a significant trend toward baseline in post-exercise HRV in Group 1 (p < 0.05) but not in Group 2 (p > 0.05). In addition, SF was the only variable to significantly relate to the post-exercise HRV parameters (p < 0.05). The findings of this investigation suggest greater SF is related to a delayed return of HRV toward baseline from maximal exercise. The association between SF and HRV is independent of VO2max and BMI.

The relationship between selected body composition variables and muscular endurance in women.

The primary purpose of this study was to determine if muscular endurance is affected by referenced waist circumference groupings, independent of body mass and subcutaneous abdominal fat, in women. This study also explored whether selected body composition measures were associated with muscular endurance. Eighty-four women were measured for height, weight, body mass index (BMI), waist circumference (WC), and abdominal skinfold thickness (SFAB) and performed 60-s sit-ups (SU) and maximal push-ups (PU) tests. Mean differences in SU and PU scores were tested across three groups based on WC as follows: WCG1 < 70 cm; WCG2 between 70 and 89 cm; WCG3 > or = 90 cm. There were no significant differences in SU and PU scores between WCG1 and WCG2. WCG3 had significantly lower SU and PU scores compared to the other groups. After adjusting for the influence of SFAB, BMI, and weight, the differences disappeared. The regression analysis revealed a two-variable (BMI and SFAB) model that accounted for the variation in SU performance. For PU, only BMI loaded into the regression model. The results of this study suggest that women with a WC > or = 90 cm have decreased muscular endurance compared to their lower WC counterparts. This difference is related to higher body masses.

The effect of experience and gender on cardiovascular and metabolic responses with dynamic Tae Kwon Do exercise.

This study, conducted at the Exercise Physiology Laboratory of Auburn University, AL, addressed and compared the acute cardiovascular and metabolic effects elicited by novice and experienced men and women participants during a single bout of dynamic Tae Kwon Do exercise and investigated whether or not dynamic Tae Kwon Do practice is an exercise modality that provides sufficient cardiorespiratory demand for enhancing aerobic fitness and promoting weight and fat loss. Twenty-eight men and women (aged 19-42) were assigned to 1 of the following 4 groups: Tae Kwon Do experienced and trained men (ME), Tae Kwon Do experienced and trained women (FE), novice Tae Kwon Do men (MN), and novice Tae Kwon Do women (FN). The results of this investigation indicate that this form of exercise can be performed for an extended period of 20 minutes. All 4 groups achieved the recommended stimulus for effective initiation of cardiovascular adaptations and conditioning. The mean exercise heart rate responses (88.3-92.2% of maximal heart rate [HR max]) were similar for all groups. The observed exercise intensity ranged from 67.9 to 72.1% VO2max, and no significant difference based on the experience and gender and exercise oxygen uptake could be established. Data in this study indicate a high caloric expenditure for this mode of exercise. Total caloric cost of 20 minutes of dynamic Tae Kwon Do, 194.8 and 201.6 kcal for novice women and experienced women, respectively, was significantly lower in comparison with that of their men counterparts (316.5 and 286.5 kcal, respectively), but no significant relationship between experience and energy cost was found. The conclusion of this study indicates that dynamic Tae Kwon Do is an exercise modality that can be appropriately prescribed for cardiovascular conditioning, weight control, and fat loss.