Cardiovascular Demand Differences Between Male and Female US Marine Recruits During Progressive Loaded Hikes

Schram, B, Orr, R, Niederberger, B, Givens, A, Bernards, J, and Kelly, KR. Cardiovascular demand differences between male and female US Marine recruits during progressive loaded hikes. J Strength Cond Res XX(X): 000-000, 2024-Despite having to carry the same occupational load, female soldiers tend to be lighter than male soldiers. The aim of this study was to determine the differences in cardiovascular load between female and male US Marine recruits during progressive load carriage hikes. United States Marine Corps recruits (565 male recruits; 364 female recruits) completed 6 loaded hikes over 6 weeks (1: 10 kg, 30 minutes; 2: 10 kg, 45 minutes; 3: 15 kg, 30 minutes, 4: 15 kg, 45 minutes; 5: 20 kg, 30 minutes; 6: 20 kg, 45 minutes) during which cardiovascular response was measured. Average heart rate (HRavg), HR maximum (HRmax), and pace were measured via a wrist-worn physiological monitor. Independent sample t-tests were conducted to compare between sexes, with significance set at 0.008 after adjusting for multiple comparisons. The average female recruit had significantly lower body mass (BM) compared with the average male recruit (p &lt; 0.001) and thus carried a significantly heavier relative load. (10 kg ∼17%, 15 kg ∼25%, 20 kg ∼33%, p &lt; 0.001). There were no significant differences in pace in any hike, and no significant differences were found in HRavg or HRmax when comparing female and male Marines during Hike 1. For female Marines, HRavg was significantly higher compared with male Marines during Hike 2 (+6.5 b·min-1, p &lt; 0.001) and Hike 3 (+7.4 b·min-1, p &lt; 0.001), and both HRavg and HRmax were significantly higher in Hike 4 (+11.9 b·min-1, +8.4 b·min-1, p &lt; 0.001), Hike 5 (+7.7 b·min-1, +7.9 b·min-1, p &lt; 0.001), and Hike 6 (+6.9 b·min-1, +7.1 b·min-1, p &lt; 0.001), respectively. Female Marines endured greater cardiovascular demand compared with male Marines during load carriage events when carrying loads greater than 15 kg (∼25% BM).</p

Elastic behaviour of the carotid artery in intact spontaneously hypertensive rats

Intact spontaneously hypertensive rats (SHR) were studied to assess the effect of prolonged antihypertensive treatment on the elastic behaviour of the external carotid artery. Thirty-week-old SHR received the ACE inhibitor captopril, the ateriolar dilator hydralazine or their vehicle for 6 weeks. These rats were compared to normotensive, vehicle treated WKY rats. The internal diameter of the carotid artery was measured continuously in halothane-anaesthetized rats using an echo-tracking device, and intra-arterial pressure was also monitored continuously, on the controlateral side. Captopril- and hydralazinetreated SHR as well as normotensive controls had similar blood pressure values. No significant shift in the distensibility-pressure curves was observed among vehicle-treated SHR and WKY rats or the SHR which had received captopril or hydralazine. Histological examination of the carotid artery fixed ex vivo with paraformaldehyde showed a significant increase in cross-sectional area in vehicle-treated SHR as compared to their normotensive counterparts. These results therefore suggest that the elastic behaviour of elastic arteries is not necessarily altered by the structural changes developing in response to hypertensio

Microsatellite instability and defects in mismatch repair proteins: a new aetiology for Sertoli cell‐only syndrome

Microsatellite instability is characteristic of certain types of cancer, and is present in rodents lacking specific DNA mismatch repair proteins. These azoospermic mice exhibit spermatogenic defects similar to some human testicular failure patients. Therefore, we hypothesized that microsatellite instability due to deficiencies in mismatch repair genes might be an unrecognized aetiology of human testicular failure. Because these azoospermic patients are candidates for testicular sperm extraction and ICSI, transmission of mismatch repair defects to the offspring is possible. Seven microsatellite loci were analysed for instability in specimens from 41 testicular failure patients and 20 controls. Blood and testicular DNA were extracted from patient and control specimens, and amplified by PCR targeting seven microsatellite loci. DNA fragment length was analysed with an ABI Prism 310 Genotyping Machine and GeneScan software. Immunohistochemistry was performed on paraffinized testis biopsy sections and cultured testicular fibroblasts from each patient to determine if expression of the mismatch repair proteins hMSH2 and hMLH1 was normal in both somatic and germline cells. Results demonstrate that microsatellite instability and DNA mismatch repair protein defects are present in some azoospermic men, predominantly in Sertoli cell‐only patients (P < 0.01 and P < 0.05 respectively). This provides evidence of a previously unrecognized aetiology of testicular failure that may be associated with cancer predispositio

Gender differences in injuries sustained during United States Marine Corps training

Aim: To investigate gender-specific differences in injuries in United States Marine Corps (USMC) trainees.Design: Retrospective cohort study.Method: Point-of-care injury data for USMC recruits (females=94; males=681) completing training were drawn from the Marine Corps Recruit Depot San Diego sports medicine injury database and analysed descriptively. The male: female incidence rate ratio (IRR) was calculated.Results: Male trainees suffered more injuries (male=268; 39%; female n=22; 23%; IRR=1.68 (95% CI 1.33 to 2.1)). Sprains and strains were the leading nature of injury (female=41%; male=25%) followed by pain(female=23%; male=22%). The leading type of injury was ‘new overuse injuries’ for both genders (54% each). Female trainees experienced more acute injuries (36% versus 26%). While female (55%) and male (58%)rates of ‘moderate’ injuries were similar, female trainees experienced more ‘mild’ injuries (36% versus 25%). The knee (female=27%: male=23%) and lower leg (female=23%: male=21%) were the leading injury sites. All injuries were to the lower limbs in female trainees; male trainees also reported injuries to the upper limb (12%) and trunk (8%).Conclusion: Female trainees experienced fewer injuries than male trainees, with more being mild. Both genders had similar natures of injuries in similar body sites except that male trainees reported some upper body and trunk injuries.</div

A graph-based modelling methodology for high-pressure networks applied on waterjet machining

This paper proposes a graph-based methodology that models high-pressure networks of varioustopologies. Therefore, a mathematical modelling of a supply network for waterjet machining will be introduced. High-pressure components are assigned to homogeneous segments, each representing a local pressure state as a differential equation. Segments are subsequently interconnected along the fluid flow path as an algebraic equation that allocates a fluid flow to the interconnections, resulting in a lumped parameter model. For this purpose, a graph network description has been used to approximate the spatially distributed high-pressure system. In this way, the proposed methodology offers a flexible modelling to cope with different network topologies. Moreover, a variable fluid compressibility has also been introduced so that a wide operating range can be included. This modelling methodology has been applied to a supply network for waterjet machining. The resulting mathematical model has been verified by measurements from a test bench with a pressure range of 100 to 400 MPa. It was shown that a variable fluid compressibility improves the model’s accuracy and that modelling errors can be reduced in comparison to other existing methodologies