The impact of different step rate threshold methods on physical activity intensity in older adults

BackgroundOlder adults benefit most from engaging in higher-intensity physical activity, which is often determined using step rate thresholds. Fixed step rate thresholds that correspond to moderate (MPA) and vigorous-intensity physical activity (VPA) have been developed for heuristic activity promotion. The activPAL monitor uses step rate thresholds to determine activity intensity. Stepping thresholds may also vary based on body mass index (BMI) or aerobic fitness level in older adults. Despite the various thresholds used in the literature, it is unclear whether they produce similar outcomes.Research QuestionHow does time spent in physical activity intensities compare between different step rate thresholds in older adults?MethodsThirty-eight participants (24♀; 67 ± 4 years; BMI: 26.6 ± 4.4 kg/m²) wore an activPAL monitor 24-hr/day for up to 7-d (total: 205-d). Aerobic fitness (V̇O₂max: 23 ± 8 ml/kg/min) was determined via indirect calorimetry during a maximal, graded cycling test. Time spent in each intensity category (light-physical-activity [LPA], MPA, VPA) was determined using the fixed (MPA/VPA) 100/130, 110/130, and activPAL step rate thresholds (74/212), as well as BMI-adjusted absolute (108.5 ± 2.5/134.0 ± 4.8) and BMI-adjusted relative (40%/60% V̇O₂max; 111.4 ± 14.7/132.0 ± 19.0) cut-offs. Times spent in each intensity category were compared between methods.ResultsThe activPAL and 100/130 thresholds yielded less LPA and more MPA than all other methods. The activPAL had no time spent in VPA at all. The BMI-adjusted absolute and relative thresholds produced statistically equivalent time in LPA and MPA (via equivalence testing), but not VPA. No two methods yielded similar time spent in LPA, MPA, or VPA.SignificanceThe choice of step rate threshold has a major impact on physical activity intensity outcomes in older adults. Inherently, strategies that adjust for older adults’ body size and/or aerobic fitness level provide a more individualized data processing strategy than fixed thresholds that assume the same threshold for all older adults     

Racial differences in hemoglobin and plasma volume variation: implications for muscle performance and recovery

Objective: To examine the effect of race differences on sprint performance, Hemoglobin (Hb), Hematocrit (Ht) and plasma volume (PV) variation in response to repeated sprint exercise.

Design: Thirty-six healthy, moderately trained men and women (20.8?±?0.2 year-old) volunteered to participate in this study. They were allocated to one of the four groups according to their gender and race: Black men’s group (BM, n?=?9), White men’s group (WM, n?=?9), Black women’s group (BW, n?=?9) and White women’s group (WW, n?=?9). All participants performed the running-based anaerobic sprint test (RAST), which consists of six?35-m sprints with 10 s of recovery in-between. Six venous blood samples were collected to determine Hb, Ht and PV levels at rest, after warm-up, immediately post- and at 5, 15 and 30 min post-RAST. Blood lactate is also sampled during the 3rd minutes of recovery.

Results: The best running time was significantly shorter (P?=?.002) in BW compared to WW. We have observed significantly higher Hb (P?=?.010) and Ht (P?=?.004) levels in BW compared to WW during the 5th minute of recovery. During RAST, the PV decreased significantly (P?=?.007) in WM only. Black groups had lower (P?<?.05) lactate levels compared to the white subjects. During recovery, PV increase was significantly (P?=?.003) higher in WW compared to BW during the 5th minute of recovery.

Conclusion: This study demonstrated that sprint and repeated sprint performances were different between white and black women. Differences in anaerobic performance between the groups were associated with racial differences in lactate levels and blood count among women’s group during recovery time. Hence, it is important to take into account this race-related difference in hematological parameters in responses to intense efforts.     

Over 55 years of critical power: Fact or artifact?

This report aims to generate an evidence-based debate of the Critical Power (CP), or its analogous Critical Speed (CS), concept. Race times of top Spanish runners were utilized to calculate CS based on three (1500-m to 5000-m; CS_1.5-5km) and four (1500-m to 10000-m; CS_1.5-10km) distance performances. Male running world records from 1000 to 5000-m (CS_1-5km), 1000 to 10,000-m (CS_1-10km), 1000-m to half marathon (CS_{1km-half marathon}), and 1000-m to marathon (CS_1km-marathon) distance races were also utilized for CS calculations. CS_1.5-5km (19.62 km h^?1) and CS_1.5-10km (18.68 km h^?1) were different (p < 0.01), but both approached the average race speed of the longest distance chosen in the model, and were remarkably homogeneous among subjects (97% ±1% and 98% ±1%, respectively). Similar results were obtained using the world records. CS values progressively declined, until reaching a CS_1km-marathon value of 20.77 km h^?1 (10% lower than CS_1-5km). Each CS value approached the average speed of the longest distance chosen in the model (96.4%–99.8%). A power function better fitted the speed-time relationship compared with the standardized hyperbolic function. However, the horizontal asymptote of a power function is zero. This better approaches the classical definition of CP: the power output that can be maintained almost indefinitely without exhaustion. Beyond any sophisticated mathematical calculation, CS corresponds to 95%–99% of the average speed of the longest distance chosen as an exercise trial. CP could be considered a mathematical artifact rather than an important endurance performance marker. In such a case, the consideration of CP as a physiological “gold-standard” should be reevaluated.     

The Acute Effects of Aerobic Dance Exercise with and without Face Mask Use on Attention,Perceived Exertion and Mood States

The present study aimed to determine the effect of wearing a face mask during aerobic dance exercise on cognitive function, more specifically on attention, as well as on perceived exertion and mood states. Thirteen healthy college students (9 males and 4 females: mean age = 17.5 years, height = 1.72 m, weight = 71.00 kg) volunteered to participate in this study. They were randomized to perform aerobic dance exercise while wearing a cloth face mask or no mask or a control condition (sitting on a comfortable chair and reading information about the health benefits of aerobic dance exercise) on three separate occasions (with at least one week of interval). Rate of perceived exertion (RPE), the Brunel Mood Scale (BRUMS) and d2 Attention assessment were assessed before and immediately after each condition. The results demonstrated higher concentration performance for the aerobic dance exercise without face mask than the control condition (p = 0.05). Post RPE and BRUMS fatigue subscale values were significantly higher in the aerobic dance exercise with face mask as compared to the aerobic dance exercise without face mask and control condition (all, p < 0.05). BRUMS vigor subscale value significantly differed across conditions (F = 113.84, p < 0.001, ES = 0.86) and was significantly higher in the aerobic dance exercise group without face mask as compared to the aerobic dance exercise with face mask and the control conditions (both, p < 0.001). This study suggests that face mask use during aerobic dance exercise with moderate intensity did not affect attention. Practitioners, students and athletes should avoid wearing face mask while practicing physical activity or aerobic dance exercise with moderate intensity to improve its acute effect on cognitive function.     

Exercise training reduces oxidative stress in people living with HIV/AIDS: a pilot study

Background: Exercise training has been shown to be an effective strategy to balance oxidative stress status; however, this is underexplored in people living with HIV/AIDS (PLWHA).

Objective: To evaluate the effects of exercise training on oxidative stress in PLWHA receiving antiretroviral therapy.

Methods: Patients performed 24 sessions (3 times per week, 8 weeks) of either aerobic (AT), resistance (RT), or concurrent training (CT). Glutathione disulphide to glutathione ratio (GSSG/GSH) in circulating erythrocytes and thiobarbituric acid–reactive substances (TBARS) in plasma samples were assessed as oxidative stress markers. Eight PLWAH completed the training protocol (AT =3, RT =3, CT =2). The GSSG/GSH and TBARS values were logarithmically transformed to approximate a normal distribution. A paired t-test was used to determine the differences between baseline and post-training values.

Results: Data-pooled analysis showed a decrease in GSSG/GSH and TBARS after the training period: log GSSG/GSH= –1.26?±?0.57 versus –1.54?±?0.65, p?=?.01 and log TBARS =0.73?±?0.35 versus 0.43?±?0.21, p?=?.01. This was paralleled by a rise in peak oxygen uptake (VO_2peak?=?29.14?±?5.34 versus 32.48?±?5.75?ml kg^?1 min^?1, p?=?.04). All the subjects who performed resistance exercises showed an average gain of 37?±?8% in muscle strength with no difference between performing single or multiple sets in terms of muscle strength gain. The results reinforce the clinical importance of exercise as a rehabilitation intervention for PLWHA and emphasizes the safety of exercise at the physiological level with the potential to mediate health outcomes.     

有氧运动对重度单纯性肥胖少儿血载脂蛋白的影响

目的 了解有氧运动对单纯性肥胖少儿血载脂蛋白的影响。方法 对 7 名重度单纯性肥胖少儿进行 10 周有氧运动比较运动前后血载脂蛋白(Apo)的变化。结果 重度单纯性肥胖少儿的ApoB明显高于对照组( P <0.01),但 10 周有氧运动可使肥胖少儿血ApoB降低( P <0.05),且ApoAⅠ有降低趋势( P >0.05)。结论 有氧运动可改善重度肥胖少儿的血脂质代谢紊乱。