Seasonal Variation in Vitamin D Status Does Not Interfere with Improvements in Aerobic and Muscular Endurance in Conscripts during Basic Military Training

Considering a lack of respective data, the primary objective of this study was to assess whether seasonal variation in vitamin D status (D-status) affects the extent of improvement in physical performance (PP) in conscripts during basic military training (BMT). D-status, PP and several blood parameters were measured repeatedly in conscripts whose 10-week BMT started in July (cohort S-C; n = 96) or in October (cohort A-C; n = 107). D-status during BMT was higher in S-C compared to A-C (overall serum 25(OH)D 61.4 ± 16.1 and 48.5 ± 20.7 nmol/L, respectively; p < 0.0001). Significant (p < 0.05) improvements in both aerobic and muscular endurance occurred in both cohorts during BMT. Pooled data of the two cohorts revealed a highly reliable (p = 0.000) but weak (R2 = 0.038-0.162) positive association between D-status and PP measures both at the beginning and end of BMT. However, further analysis showed that such a relationship occurred only in conscripts with insufficient or deficient D-status, but not in their vitamin D-sufficient companions. Significant (p < 0.05) increases in serum testosterone-to-cortisol ratio and decreases in ferritin levels occurred during BMT. In conclusion, a positive association exists between D-status and PP measures, but seasonal variation in D-status does not influence the extent of improvement in PP in conscripts during BMT.

Muscular Strength and Carotid Intima-Media Thickness in Physically Fit Young Adults: The CHIEF Atherosclerosis Study

Background: Greater muscular strength (MusS) has been found to have an inverse association with subclinical atherosclerosis in children, as well as with mortality from cardiovascular diseases (CVDs) in middle-aged and elderly individuals. However, the association of the degree of MusS with atherosclerosis may differ by sex and has not been clarified in young adults. Methods and Results: A total of 1021 Taiwanese military personnel, aged 18−40 years, participated in annual health examinations in 2018−2020. MusS was separately assessed by 2-min push-up and 2-min sit-up numbers. Subclinical atherosclerosis was measured by the left carotid bulb intima−media thickness (cIMT) using high-resolution ultrasonography. Multiple linear regression with adjustments for age, sex, alcohol intake, cigarette smoking, anthropometric indices, blood pressure, and lipid profiles was utilized to determine the correlation between MusS and cIMT. Both 2-min push-up and 2-min sit-up numbers were inversely correlated with cIMT (standardized β: −0.089 and −0.072, respectively; both p-values < 0.05). In men, both 2-min push-up and 2-min sit-up numbers were inversely correlated with cIMT (standardized β: −0.076 and −0.086, respectively; both p-values < 0.05), while in women, 2-min push-up numbers but not 2-min sit-up numbers were inversely correlated with cIMT (standardized β: −0.204 and −0.01; p = 0.03 and 0.99, respectively). Conclusions: Among young adults, there was an inverse association between MusS and cIMT, emphasizing the beneficial impact of MusS on the regression of atherosclerosis. The study also revealed a sex difference and suggested that training of the upper arm muscles may be an effective preventive measure for young women to reduce the risk of early cardiovascular diseases.

Fit (and Healthy) for Duty: Blood Lipid Profiles and Physical Fitness Test Relationships from Police Officers in a Health and Wellness Program

This research analyzed archival health and wellness program data (2018: 169 males, 39 females; 2019: 194 males, 43 females) to document police officer lipid profiles, and correlate lipids with fitness. Bloodwork included total cholesterol (TC), low-density lipoproteins (LDL-C), high-density lipoproteins (HDL-C), and triglycerides (TG). Fitness data included maximal aerobic capacity (V·O2max); sit-and-reach; push-ups; vertical jump; grip strength; sit-ups; and relative bench press (RBP). Lipid profiles were compared to national standards. Spearman’s correlations derived relationships between lipids and fitness (p < 0.05). Over 2018−2019, 68−76% of officers had desirable TC (<200 mg/dL) and HDL-C (≥60 mg/dL); 67−72% had desirable TG (<150 mg/dL). 54−62% of officers had LDL-C above desirable (≥100 mg/dL); 13−14% had mildly high TG (150−199 mg/dL); 16−18% had high TG (200−499 mg/dL). In 2018, HDL-C correlated with V·O2max, push-ups, grip strength, and RBP in males, and sit-ups in females. TG correlated with V·O2max (both sexes), sit-ups (males), and grip strength (females). In 2019, TG related to V·O2max, push-ups, vertical jump, sit-ups, and RBP in males. TG and LDL-C related to push-ups, and HDL-C to sit-ups and RBP in females. Relationship strengths were trivial-to-small (ρ = ±0.157 − 0.389). Most officers had good lipid profiles relative to cardiovascular disease risk. Nonetheless, the data highlighted the need for comprehensive approaches to decreasing risk.

Are There Differences in Fitness between Recruits from Larger (Hosting) and Smaller (Participating) Law Enforcement Agencies?

Law enforcement agencies often conduct academy training classes that include recruits hired by both the larger hosting agency (HA), and by smaller participating agencies (PA). HAs that need to fill more positions may have recruits with a wide range of fitness levels. Smaller agencies may be more selective in their hiring as they do not have as many available positions. This study compared HA and PA recruit fitness prior to academy. Retrospective analysis was conducted on 11 academy classes, incorporating 742 HA recruits (602 males, 140 females) and 99 PA recruits (82 males, 17 females). The following fitness tests were administered prior to academy: push-ups and sit-ups completed in 60 seconds, vertical jump; 2-kg medicine ball throw, 75-yard pursuit run, and 20-m multistage fitness test. A univariate analysis of variance, with sex as a covariate, analyzed each fitness test to determine any differences between HA and PA recruits. Effect sizes were also calculated. There were significant differences in push-up (p = 0.034, d = 0.22) and situp (p < 0.001, d = 0.47) repetitions between HA and PA recruits. PA recruits completed ~8% and ~12% more repetitions, respectively. There were trivial differences between HA and PA recruits in the other fitness tests, although HA recruits tended to have a wider range of fitness levels. The push-up and sit-up differences may provide some indication that PA were more selective in their hiring. Nonetheless, staff should recognize that individual fitness differences may exist in recruits from different agencies prior to academy training.

Repeated abdominal exercise induces respiratory muscle fatigue

Prolonged bouts of hyperpnea or resisted breathing are known to result in respiratory muscle fatigue, as are primarily non respiratory exercises such as maximal running and cycling. These exercises have a large ventilatory component, though, and can still be argued to be respiratory activities. Sit-up training has been used to increase respiratory muscle strength, but no studies have been done to determine whether this type of non-respiratory activity can lead to respiratory fatigue. The purpose of the study was to test the effect of sit-ups on various respiratory muscle strength and endurance parameters. Eight subjects performed pulmonary function, maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) measurements, and an incremental breathing test before and after completing a one-time fatiguing exercise bout of sit-ups. Each subject acted as their own control performing the same measurements 3-5 days following the exercise bout, substituting rest for exercise. Following sit-up induced fatigue, significant decreases were measured in MIP [121.6 ± 26 to 113.8 ± 23 cmH2O (P <0.025)], and incremental breathing test duration [9.6 ± 1.5 to 8.5 ± 0.7 minutes (P <0.05)]. No significant decreases were observed from control pre-test to control post-test measurements. We conclude that after a one-time fatiguing sit-up exercise bout there is a reduction in respiratory muscle strength (MIP, MEP) and endurance (incremental breathing test duration) but not spirometric pulmonary function. Key pointsExercise that is primarily abdominal in nature can lead to inspiratory muscle fatigue.This exercise also can cause expiratory muscle fatigue, which would be expected.This study shows a link between a predominantly non-respiratory exercise and decreases in both respiratory muscle strength and endurance.

Abdominal Muscle Activity While Performing Trunk-Flexion Exercises Using the Ab Roller, ABslide, FitBall, and Conventionally Performed Trunk Curls

OBJECTIVE: To compare the surface electromyographic activity of the abdominal musculature and rectus femoris (RF) muscle during trunk-flexion exercises using 3 abdominal exercise devices (Ab Roller, ABslide, and FitBall) and the traditional trunk curl. DESIGN AND SETTING: Each subject performed approximately 15 repetitions for each exercise condition. A repeated-measures, one-way multivariate analysis of variance was used to compare the mean integrated electric activity value for each muscle during each exercise condition. SUBJECTS: A total of 10 male and 13 female collegiate undergraduate students. MEASUREMENTS: Surface electromyographic activity was recorded for the upper rectus abdominis (URA), lower rectus abdominis (LRA), external oblique (EO), and RF during 5 consecutive repetitions of each exercise bout. The signal was amplified by a factor of 1000, rectified, and integrated. These integrated values were then divided by the time value for each exercise to give the mean integrated electromyography value. RESULTS: A significant difference existed among exercise conditions for the RF (P <.0001), with the ABslide and the FitBall having greater electric activity than the other exercise conditions. Activity was significantly different (P <.0009) for the URA, with the ABslide having the least electric activity. For the EO, exercising with the ABslide produced significantly greater electric activity (P <.0001) than all other exercise conditions. No significant difference was found across exercise conditions for the LRA (P <.051). CONCLUSIONS: Performing abdominal exercises with the Ab Roller, ABslide, and FitBall did not elicit greater activity of the URA and LRA than performing traditional trunk curls. Use of the ABslide elicited greater EO activity and significantly less URA activity than the other 3 modes. Both the ABslide and FitBall resulted in greater involvement of the hip flexors, an undesirable feature of abdominal exercises.