Anthropometrics Impact Army Combat Fitness Test Performance in Reserve Officer Training Corps Cadets

INTRODUCTION

Fitness is a vital component in military success. The Army is in the process of implementing a new assessment for soldier fitness, the Army Combat Fitness Test (ACFT). Success on the assessment is a major factor in job assignments and promotional opportunities. This generates questions related to modifiable (i.e., fitness and body composition) and non-modifiable (i.e., limb length and testing equipment) factors impacting performance. Currently, anthropometrics differences in ACFT performance have not been investigated. Thus, this study aimed to assess the impact of anthropometrics on ACFT performance in Reserve Officer Training Corps Cadets.

MATERIALS AND METHODS

Anthropometric measures and ACFT scores were collected from Reserve Officer Training Corps cadets (n = 105, age: 20.4 ± 2.4 years, body mass index: 25.0 ± 2.8 kg/m2, and M/F = 84/21). All ACFT events were evaluated by certified graders. Measurement locations were based on established anthropometric assessment standards and previous research (hand, lower arm, upper arm, upper leg, lower leg, and torso lengths). The study was approved by the Auburn University Institutional Review Board (protocol code #21-410).

RESULTS

There were weak correlations between hand length and three-repetition maximum deadlift [0.393; P ≤ .001], standing power throw [0.399; P ≤ .001], sprint-drag-carry [-0.315; P = .002], and ACFT score [0.212; P = .035]. The lower leg had weak correlations with standing power throw [0.249; P = .013], sprint-drag-carry [-0.215; P = .033], and ACFT score [0.213; P = .034]. Hand and lower leg length impacted individual event performances when comparing shortest and longest limb lengths [all P values <.05].

CONCLUSIONS

Hand and lower leg length significantly impact ACFT performance. These results present practical information to individuals responsible for developing protocols and scoring for the ACFT. Reassessment of events and the equipment utilized are warranted to assure that event performance is not hindered by a non-modifiable factor that is not representative of fitness or occupational demands. Future work should investigate how different trap-bar and kettlebell handle sizes, as well as medicine ball sizes, impact performance on the ACFT.

Acute high-dose MitoQ does not increase urinary kidney injury markers in healthy adults: a randomized crossover trial

Several human studies have used the mitochondrial antioxidant MitoQ. Recent in vitro data indicating that MitoQ may induce nephrotoxicity caused concern regarding the safety of MitoQ on the kidneys, but the doses were supraphysiological. Therefore, we sought to determine whether acute MitoQ elicits changes in urinary biomarkers associated with tubular injury in healthy adults with our hypothesis being there would be no changes. Using a randomized crossover design, 32 healthy adults (16 females and 16 males, 29 ± 11 yr old) consumed MitoQ (100-160 mg based on body mass) or placebo capsules. We obtained serum samples and a 4- to 6-h postcapsule consumption urine sample. We assessed creatinine clearance and urine kidney injury biomarkers including the chitinase 3-like-1 gene product YKL-40, kidney-injury marker-1, monocyte chemoattractant protein-1, epidermal growth factor, neutrophil gelatinase-associated lipocalin, interleukin-18, and uromodulin using multiplex assays. We used t tests, Wilcoxon tests, and Hotelling's T2 to assess global differences in urinary kidney injury markers between conditions. Acute MitoQ supplementation did not influence urine flow rate (P = 0.086, rrb = 0.39), creatinine clearance (P = 0.085, rrb = 0.42), or urinary kidney injury markers (T22,8 = 30.6, P = 0.121, univariate ps > 0.064). Using exploratory univariate analysis, MitoQ did not alter individual injury markers compared with placebo (e.g., placebo vs. MitoQ: YKL-40, 507 ± 241 vs. 442 ± 236 pg/min, P = 0.241; kidney injury molecule-1, 84.1 ± 43.2 vs. 76.2 ± 51.2 pg/min, P = 0.890; and neutrophil gelatinase-associated lipocalin, 10.8 ± 10.1 vs. 9.83 ± 8.06 ng/min, P = 0.609). In conclusion, although longer-term surveillance and data are needed in clinical populations, our findings suggest that acute high-dose MitoQ had no effect on urinary kidney injury markers in healthy adults.NEW & NOTEWORTHY We found acute high-dose mitochondria-targeted antioxidant (MitoQ) supplementation was not nephrotoxic and had no effect on markers of acute kidney injury in healthy adults. These findings can help bolster further confidence in the safety of MitoQ, particularly for future investigations seeking to examine the role of mitochondrial oxidative stress, via acute MitoQ supplementation, on various physiological outcomes.

Validity of heart rate derived core temperature estimation during simulated firefighting tasks

Rectal core temperature monitoring can help fire services mitigate heat injury but can be invasive and impractical. EQ02 + LifeMonitor provides a non-invasive estimation of core temperature. Therefore, the primary purpose of this study was to determine the validity of the EQ02 + LifeMonitor compared to the gold standard rectal thermometer core temperature assessment, as well as the potential influence of turnout gear on the estimated and physiological strain experienced during these activities. Thirteen participants completed simulated firefighting tasks with and without turnout gear, involving four rounds of a 5-min walk on a treadmill at 2.8 mph/2.5% grade and 20 deadlifts over 5 min in an environmental chamber set to 40.6 °C; 50% humidity. During each trial participants wore both an EQ02 + LifeMonitor and DataTherm II rectal thermometer. The results from the devices were statistically equivalent (p < 0.001), yet there was a statistically significant difference in the value (~ 0.1 °C; p < 0.001). There was a significant effect of devices [p < 0.001] and time [p < 0.001], but no interaction effect [p = 0.70] on core temperature drift. Estimated core temperature was marginally different from that measured via the DataTherm II. The EQ02 on average overestimated core temperature. Heart rate, rating of perceived exertion, and area under the curve of core temperature were significantly elevated due to turnout gear [ps < 0.025], but not core temperature skin temperature, or ventilatory rate [ps > 0.372]. These results suggest the EQ02 + LifeMonitor may be a viable, non-invasive alternative for assessing core temperature compared to rectal temperature monitoring, especially during rigorous, intermittent activities. Turnout gear does however increase heart rate, cumulative core temperature, and perceived exertion. Additionally, the validity of the estimated core temperature is not impacted by the use turnout gear. This is likely due to significant changes in heart rate, which allowed the heart-rate derived estimate of core temperature to remain consistent with changes in DataTherm II rectal temperatures.

Adjusting for muscle strength and body size attenuates sex differences in the exercise pressor reflex in young adults

Females typically exhibit lower blood pressure (BP) during exercise than males. However, recent findings indicate that adjusting for maximal strength attenuates sex differences in BP during isometric handgrip (HG) exercise and postexercise ischemia (PEI; metaboreflex isolation). In addition, body size is associated with HG strength but its contribution to sex differences in exercising BP is less appreciated. Therefore, the purpose of this study was to determine whether adjusting for strength and body size would attenuate sex differences in BP during HG and PEI. We obtained beat-to-beat BP in 110 participants (36 females, 74 males) who completed 2 min of isometric HG exercise at 40% of their maximal voluntary contraction followed by 3 min of PEI. In a subset (11 females, 17 males), we collected muscle sympathetic nerve activity (MSNA). Statistical analyses included independent t tests and mixed models (sex × time) with covariate adjustment for 40% HG force, height2, and body surface area. Females exhibited a lower absolute 40% HG force than male participants (Ps < 0.001). Females exhibited lower Δsystolic, Δdiastolic, and Δmean BPs during HG and PEI than males (e.g., PEI, Δsystolic BP, 15 ± 11 vs. 23 ± 14 mmHg; P = 0.004). After covariate adjustment, sex differences in BP responses were attenuated. There were no sex differences in MSNA. In a smaller strength-matched cohort, there was no sex × time interactions for BP responses (e.g., PEI systolic BP, P = 0.539; diastolic BP, P = 0.758). Our data indicate that sex differences in exercising BP responses are attenuated after adjusting for muscle strength and body size.NEW & NOTEWORTHY When compared with young males, females typically exhibit lower blood pressure (BP) during exercise. Adjusting for maximal strength attenuates sex differences in BP during isometric handgrip (HG) exercise and postexercise ischemia (PEI), but the contribution of body size is unknown. Novel findings include adjustments for muscle strength and body size attenuate sex differences in BP reactivity during exercise and PEI, and sex differences in body size contribute to HG strength differences.

Cross-sectional analysis of racial differences in hydration and neighborhood deprivation in young adults

BACKGROUND

Inadequate hydration is associated with cardiovascular and kidney disease morbidity and all-cause mortality. Compared with White individuals, Black individuals exhibit a higher prevalence of inadequate hydration, which may contribute to racial health disparities. However, the underlying reasons for these differences in hydration remain unclear.

OBJECTIVE

This cross-sectional study aimed to investigate whether neighborhood deprivation contributes to racial differences in hydration status.

METHODS

We assessed 24 Black and 30 White college students, measuring 24-hour urine osmolality, urine flow rate, urine specific gravity, and plasma copeptin concentration. Participants recorded their food and fluid intake for 3 d to assess total water intake from food and beverages. Neighborhood socioeconomic deprivation was measured using a tract-level Area Deprivation Index.

RESULTS

Black participants exhibited higher urine osmolality (640 [314] compared with 440 [283] mOsm/kg H2O, respectively, P = 0.006) and lower urine flow rate (1.06 [0.65] compared with 1.71 [0.89] ml/min, respectively, P = 0.009) compared with White participants, indicating greater hypohydration among Black participants. Black participants reported lower total water intake from food and beverages than White participants (2.3 ± 0.7 compared with 3.5 ± 1.1 L/day, respectively, P < 0.01). Black participants exhibited higher copeptin than White participants (6.3 [3.1] compared with 4.5 [2.3] pmol/L, P = 0.046), and urine osmolality mediated 67% of the difference (P = 0.027). Black participants reported greater cumulative exposure to neighborhood deprivation during childhood (ages 0-18 y). Furthermore, neighborhood deprivation during childhood was associated with urine specific gravity (P = 0.031) and total water intake from food and beverages (P = 0.042) but did not mediate the racial differences in these measures.

CONCLUSION

Our data suggest that compared with White young adults, Black young adults are hypohydrated and exhibit higher plasma copeptin concentration, and that greater neighborhood deprivation is associated with chronic underhydration irrespective of race. This trial was registered at clinicaltrials.gov as NCT04576338.

Interplay of Race and Neighborhood Deprivation on Ambulatory Blood Pressure in Young Adults

Background

Ambulatory blood pressure (BP) monitoring measures nighttime BP and BP dipping, which are superior to in-clinic BP for predicting cardiovascular disease (CVD), the leading cause of death in America. Compared with other racial/ethnic groups, Black Americans exhibit elevated nighttime BP and attenuated BP dipping, including in young adulthood. Social determinants of health contribute to disparities in CVD risk, but the contribution of neighborhood deprivation on nighttime BP is unclear. Therefore, we examined associations between neighborhood deprivation with nighttime BP and BP dipping in young Black and White adults.

Methods

We recruited 21 Black and 26 White participants (20 M/27 F, mean age: 21 years, body mass index: 25±4 kg/m2) for 24-hour ambulatory BP monitoring. We assessed nighttime BP and BP dipping (nighttime:daytime BP ratio). The area deprivation index (ADI) was used to measure neighborhood deprivation. Associations between ADI and ambulatory BP were examined.

Results

Black participants exhibited higher nighttime diastolic BP compared with White participants (63±8 mmHg vs 58±7 mmHg, p=0.003), and attenuated BP dipping ratios for both systolic (0.92±0.06 vs 0.86±0.05, p=0.001) and diastolic BP (0.86±0.09 vs 0.78±0.08, p=0.007). Black participants experienced greater neighborhood deprivation compared with White participants (ADI scores: 110±8 vs 97±21, p<0.001), and ADI was associated with attenuated systolic BP dipping (ρ=0.342, p=0.019).

Conclusions

Our findings suggest neighborhood deprivation may contribute to higher nighttime BP and attenuated BP dipping, which are prognostic of CVD, and more prevalent in Black adults. Targeted interventions to mitigate the effects of neighborhood deprivation may help to improve nighttime BP.

Clinical Trial Registry

URL: https://www.clinicaltrials.gov; Unique identifier: NCT04576338.

Acute beetroot juice reduces blood pressure in young Black and White males but not females

A complex interplay of social, lifestyle, and physiological factors contribute to Black Americans having the highest blood pressure (BP) in America. One potential contributor to Black adult's higher BP may be reduced nitric oxide (NO) bioavailability. Therefore, we sought to determine whether augmenting NO bioavailability with acute beetroot juice (BRJ) supplementation would reduce resting BP and cardiovascular reactivity in Black and White adults, but to a greater extent in Black adults. A total of 18 Black and 20 White (∼equal split by biological sex) young adults completed this randomized, placebo-controlled (nitrate (NO3-)-depleted BRJ), crossover design study. We measured heart rate, brachial and central BP, and arterial stiffness (via pulse wave velocity) at rest, during handgrip exercise, and during post-exercise circulatory occlusion. Compared with White adults, Black adults exhibited higher pre-supplementation resting brachial and central BP (Ps ≤0.035; e.g., brachial systolic BP: 116(11) vs. 121(7) mmHg, P = 0.023). Compared with placebo, BRJ (∼12.8 mmol NO3-) reduced resting brachial systolic BP similarly in Black (Δ-4±10 mmHg) and White (Δ-4±7 mmHg) adults (P = 0.029). However, BRJ supplementation reduced BP in males (Ps ≤ 0.020) but not females (Ps ≥ 0.299). Irrespective of race or sex, increases in plasma NO3- were associated with reduced brachial systolic BP (ρ = -0.237, P = 0.042). No other treatment effects were observed for BP or arterial stiffness at rest or during physical stress (i.e., reactivity); Ps ≥ 0.075. Despite young Black adults having higher resting BP, acute BRJ supplementation reduced systolic BP in young Black and White adults by a similar magnitude, an effect that was driven by males.

Short-term high-salt consumption does not influence resting or exercising heart rate variability but increases MCP-1 concentration in healthy young adults

High salt consumption increases blood pressure (BP) and cardiovascular disease risk by altering autonomic function and increasing inflammation. However, it is unclear whether salt manipulation alters resting and exercising heart rate variability (HRV), a noninvasive measure of autonomic function, in healthy young adults. The purpose of this investigation was to determine whether short-term high-salt intake 1) alters HRV at rest, during exercise, or exercise recovery and 2) increases the circulating concentration of the inflammatory biomarker monocyte chemoattractant protein 1 (MCP-1). With the use of a randomized, placebo-controlled, crossover study, 20 participants (8 females; 24 ± 4 yr old, 110 ± 10/64 ± 8 mmHg) consumed salt (3,900 mg sodium) or placebo capsules for 10 days each separated by ≥2 wk. We assessed HRV during 10 min of baseline rest, 50 min of cycling (60% V̇o2peak), and recovery. We quantified HRV using the standard deviation of normal-to-normal RR intervals, the root mean square of successive differences (RMSSD), and additional time and frequency domain metrics of HRV. Plasma samples were collected to assess MCP-1 concentration. No main effect of high salt or condition × time interaction was observed for HRV metrics. However, acute exercise reduced HRV (e.g., RMSSD time: P < 0.001, condition: P = 0.877, interaction: P = 0.422). High salt elevated plasma MCP-1 (72.4 ± 12.5 vs. 78.14 ± 14.7 pg/mL; P = 0.010). Irrespective of condition, MCP-1 was moderately associated (P values < 0.05) with systolic (r = 0.32) and mean BP (r = 0.33). Short-term high-salt consumption does not affect HRV; however, it increases circulating MCP-1, which may influence BP in young adults.

The janus face of ketone bodies in hypertension

Hypertension is the most important risk factor for the development of terminal cardiovascular diseases, such as heart failure, chronic kidney disease, and atherosclerosis. Lifestyle interventions to lower blood pressure are generally desirable prior to initiating pharmaceutical drug treatments, which may have undesirable side effects. Ketogenic interventions are popular but the scientific literature supporting their efficacy is specific to certain interventions and outcomes in animal models and patient populations. For example, although caloric restriction has its own inherent difficulties (e.g. it requires high levels of motivation and adherence is difficult), it has unequivocally been associated with lowering blood pressure in hypertensive patients. On the other hand, the antihypertensive efficacy of ketogenic diets is inconclusive, and this is surprising, given that these diets have been largely helpful in mitigating metabolic syndrome and promoting longevity. It is possible that side effects associated with ketogenic diets (e.g. dyslipidemia) aggravate the hypertensive phenotype. However, given the recent data from our group, and others, reporting that the most abundant ketone body, β-hydroxybutyrate, can have positive effects on endothelial and vascular health, there is hope that ketone bodies can be harnessed as a therapeutic strategy to combat hypertension. Therefore, we conclude this review with a summary of the type and efficacy of ketone supplements. We propose that ketone supplements warrant investigation as low-dose antihypertensive therapy that decreases total peripheral resistance with minimal adverse side effects.

Effects of Three Modest Levels of Proximal Loading on Marathon Pace Running Economy

This study examined the effect of modest increases in proximal body mass on running economy expressed as metabolic cost (MC). External loads of 1.6 (L), 2.4 (M), and 3.2 kg (H) were added to the anterior and posterior torso region of male (n = 18) and female (n = 18) runners using a double-layered compression garment with gel inserts. MC was evaluated using stoichiometry equations of data collected via indirect calorimetry. Data was collected during four, 5-min running bouts at marathon pace for the 3 load levels and an unloaded state (CON). When data from both sexes were combined, MC for CON (13.2 ± 2.7) was lower (p < 0.05) versus L (13.5 ± 2.6), M (13.6 ± 2.6), and H (13.7 ± 2.6 kcal/min), but L did not differ from CON when data was analyzed for each sex. Male runners exhibited stepped increases in MC across loads and a weak-moderate relationship (r = 0.37; p < 0.01) between percentage change in absolute MC and increased percent body mass. A prediction model for MC (Δ% kcal/min = 0.98(Δ% body mass) - 0.91; SEE = ± 2.5%) was developed. For female runners, L increased MC by ~3.5% above CON, but no differentiation was found among L, M, and H, limiting the development of a prediction equation for females. Modest increases in body mass can produce detectable and potentially important levels of running economy impairment, but the relationship between changes in body mass and RE are complex, particularly in regards to sex.