Simon Higgins

Moderate, but not vigorous, intensity exercise training reduces C-reactive protein

Abstract Background: Sprint interval cycle training is a contemporary popular mode of training but its relative efficacy, under conditions of matched energy expenditure, to reduce risk factors for cardiometabolic disease is incompletely characterised, especially in young women. The purpose of this investigation was to determine the relative efficacy of six weeks of moderate-intensity cycling (MOD-C) and vigorous sprint-interval cycling (VIG-SIC) on lipid profile, insulin (INS) and insulin resistance using the homeostatic model assessment (HOMA-IR) and C-reactive protein (CRP) in inactive, overweight/obese (OW/OB) young women. Methods: Participants (BMI ≥25 kg/m2, waist circumference ≥88 cm) were randomly assigned to MOD-C (20–30 min at 60–70% of heart rate reserve(HRR)) or VIG-SIC (5–7 repeated bouts 30-second maximal effort sprints, followed by four minutes of active recovery) supervised training three days/week for six weeks, with each group matched on energy expenditure. Adiposity (%Fat) was measured using dual x-ray absorptiometry. Results: Forty-four participants (20.4 ± 1.6 years, 65.9% Caucasian, 29.8 ± 4.1 kg/m2) were included in the analysis. The improvement in CRP observed in the MOD-C group was larger than the VIG-C group (p = .034). Overall, high-density lipoprotein (HDL-C) and low-density lipoprotein (LDL-C) levels improved following training (p < .05); however, total cholesterol, triglyceride, INS and HOMA-IR did not improve (p > .05). Conclusion: These results indicate MOD-C training may be more effective in reducing CRP than VIG-SIC.

Sedentary Behaviors in Children and Adolescents: What Is the Influence on Bone Strength?

Whether driving to work, sitting in the classroom or office, or watching TV, sedentary behavior is commonplace in modern society. This is especially true for children and adolescents who, behind older adults, spend the largest proportion of their day being sedentary. Evidence linking excess sedentary behavior to increased adiposity and cardiometabolic risk in youth has contributed to the adoption of guidelines advising the restriction of behaviors such as TV viewing in several countries. However, evidence is limited concerning the effects of sedentary behaviors on bone strength, especially during adolescent growth, the period of peak bone mineral accrual. A recent review concluded that a negative association exists between sedentary behavior and bone mineral accrual in the lower extremities. In contrast, longitudinal data in adolescents highlighted positive relationships between sedentary behaviors and some aspects of bone microarchitecture. Regardless of the direction of the relationship, findings appear to be independent of time spent in moderate-to-vigorous physical activity (MVPA). While it is premature to generate public health recommendations with respect to sedentary behaviors and bone, it is clear that MVPA remains the most influential activity-related behavior for optimal bone accrual. Future guidelines should continue to promote activity while examining its interaction with sedentary behaviors.

Interactive associations of physical activity, adiposity, and oral contraceptive use on C-reactive protein levels in young women

ABSTRACT Oral contraceptives (OCs) are the most frequently used type of birth control among young women. OC-users have higher C-reactive protein (CRP) values, an indicator of systemic inflammation, than do non-OC-users. In addition, adiposity (percent fat) is positively associated with CRP, and physical activity (PA) is inversely associated with CRP. The present study determined the interactive associations of PA, percent fat, and OC-use with CRP. Data were collected during 2012–2015 at the University of Georgia. Objective PA was measured via pedometers. Percent fat was measured via dual X-ray absorptiometry. The current OC-use was self-reported. High-sensitivity (hs) CRP was determined using venipuncture. Multivariate linear regression determined the interactive associations of percent fat, OC-use, and PA with hs-CRP. Participants (n = 247; mean age 18.9 ± 1.4 years, 60.7 percent white) accumulated a mean of 10,075.7 ± 3,593.4 steps/day. One-third of participants were categorized as overweight/obese by BMI (mean = 24.5 ± 4.8 kg/m2, mean percent fat = 35.2 ± 6.8). The current OC-use was reported by 26.2 percent of the sample (n = 61). A significant three-way interaction (β = 0.01, p = .03) indicated that higher PA was associated with lower hs-CRP in non-OC-users with higher percent fat, but not among OC-users with higher percent fat. These results highlight the need to measure and account for the current OC-use in studies examining the relationship between PA and CRP.