Retrospective Analysis of Training Intensity Distribution Based on Race Pace Versus Physiological Benchmarks in Highly Trained Sprint Kayakers

Background Research results on the training intensity distribution (TID) in endurance athletes are equivocal. This non-uniformity appears to be partially founded in the different quantification methods that are implemented. So far, TID research has solely focused on sports involving the lower-body muscles as prime movers (e.g. running). Sprint kayaking imposes high demands on the upper-body endurance capacity of the athlete. As there are structural and physiological differences between upper- and lower-body musculature, TID in kayaking should be different to lower-body dominant sports. Therefore, we aimed to compare the training intensity distribution during an 8-wk macrocycle in a group of highly trained sprint kayakers employing three different methods of training intensity quantification. Methods Heart rate (HR) and velocity during on-water training of nine highly trained German sprint kayakers were recorded during the final 8 weeks of a competition period leading to the national championships. The fractional analysis of TID was based on three zones (Z) derived from either HR (TIDBla-HR) or velocity (TIDBla-V) based on blood lactate (Bla) concentrations (Z1 ≤ 2.5 mmol L−1 Bla, Z2 = 2.5–4.0 mmol L−1 Bla, Z3 ≥ 4.0 mmol L−1 Bla) of an incremental test or the 1000-m race pace (TIDRace): Z1 ≤ 85% of race pace, Z2 = 86–95% and Z3 ≥ 95%. Results TIDBla-V (Z1: 68%, Z2: 14%, Z3: 18%) differed from TIDBla-HR (Z1: 91%, Z2: 6%, Z3: 3%) in each zone (all p < 0.01). TIDRace (Z1: 73%, Z2: 20%, Z3: 7%) differed to Z3 in TIDBla-V (p < 0.01) and all three TIDBla-HR zones (all p < 0.01). Individual analysis revealed ranges of Z1, Z2, Z3 fractions for TIDBla-HR of 85–98%, 2–11% and 0.1–6%. For TIDBla-V, the individual ranges were 41–82% (Z1), 6–30% (Z2) and 8–30% (Z3) and for TIDRace 64–81% (Z1), 14–29% (Z2) and 4–10% (Z3). Conclusion The results show that the method of training intensity quantification substantially affects the fraction of TID in well-trained sprint kayakers. TIDRace determination shows low interindividual variation compared to the physiologically based TIDBla-HR and TIDBla-V. Depending on the aim of the analysis TIDRace, TIDBla-HR and TIDBla-V have advantages as well as drawbacks and may be implemented in conjunction to maximize adaptation.

The importance of aerobic capacity and nutrition in recreational master mountain runners’ performance and race-induced changes in body composition and biochemical blood indices

This study aimed to explore the importance of aerobic capacity and nutrition on 28-km mountain running performance and race-induced changes in body composition and biochemical blood indices, in recreational master athletes of different performance levels. Twenty male master runners (age: 44.6 ± 7.7 years) were divided into two groups, slower and faster runners, according to their race performance. Maximum oxygen uptake [Formula: see text], velocity at [Formula: see text] [Formula: see text], oxygen consumption [Formula: see text], and velocity [Formula: see text] during the second ventilatory threshold were evaluated. Nutrition was assessed for one week before and during the race. Body composition was evaluated, and blood samples were collected before and 3 h after the race. Slower runners exhibited a greater reduction in lean body mass and greater changes in all muscle damage/inflammation/metabolism blood indices than the faster runners ( η2 = 0.201–0.927; p < 0.05). When all the participants were assessed as one group ( n = 20), significant correlations were found between [Formula: see text], vVO2Thr, race time, energy intake, expenditure, carbohydrate, protein intakes, and post-race changes in body composition and blood markers ( r: −0.825–0.824; p < 0.05). The strongest determinants were [Formula: see text] and vVO2Thr, while energy intake, expenditure, carbohydrate, and protein intakes seemed to be the weakest determinants of race performance and race-induced changes in body composition and blood indices. The results suggest that race-induced changes in body composition and blood indices are determined mainly by master runners’ race performance and endurance capacity and to a lesser extent by nutrition. However, it seems that carbohydrate and protein intakes have equal importance.

Upper- vs. Lower-Body Exercise Performance in Female and Male Cross-Country Skiers

Purpose: To investigate the interaction between exercise modality (i.e., upper- and lower-body exercise) and sex in physiological responses and power output (PO) across the entire intensity spectrum (i.e., from low to maximal intensity).Methods: Ten male and 10 female cross-country (XC) skiers performed a stepwise incremental test to exhaustion consisting of 5 min stages with increasing workload employing upper-body poling (UP) and running (RUN) on two separate days. Mixed measures ANOVA were performed to investigate the interactions between exercise modalities (i.e., UP and RUN) and sex in physiological responses and PO across the entire exercise intensity spectrum.Results: The difference between UP and RUN (ΔUP−RUN), was not different in the female compared with the male XC skiers for peak oxygen uptake (18 ± 6 vs. 18 ± 6 mL·kg−1·min−1, p = 0.843) and peak PO (84 ± 18 vs. 91 ± 22 W, p = 0.207). At most given blood lactate and rating of perceived exertion values, ΔUP−RUN was larger in the male compared with the female skiers for oxygen uptake and PO, but these differences disappeared when the responses were expressed as % of the modality-specific peak.Conclusion: Modality-differences (i.e., ΔUP−RUN) in peak physiological responses and PO did not differ between the female and male XC skiers. This indicates that increased focus on upper-body strength and endurance training in female skiers in recent years may have closed the gap between upper- and lower-body endurance capacity compared with male XC skiers. In addition, no sex-related considerations need to be made when using relative physiological responses for intensity regulation within a specific exercise modality.

Skeletal Muscle Mitochondrial Physiology in Children With Cerebral Palsy: Considerations for Healthy Aging

Skeletal muscle contractile proteins require a constant supply of energy to produce force needed for movement. Energy (ATP) is primarily produced by mitochondrial organelles, located within and around muscle fibers, by oxidative phosphorylation that couples electron flux through the electron transport chain to create a proton gradient across the inner mitochondrial membrane that is in turn used by the ATP synthase. Mitochondrial networks increase in size by biogenesis to increase mitochondrial abundance and activity in response to endurance exercise, while their function and content reduce with constant inactivity, such as during muscle atrophy. During healthy aging, there is an overall decline in mitochondrial activity and abundance, increase in mitochondrial DNA mutations, potential increase in oxidative stress, and reduction in overall muscular capacity. Many of these alterations can be attenuated by consistent endurance exercise. Children with cerebral palsy (CP) have significantly increased energetics of movement, reduced endurance capacity, and increased perceived effort. Recent work in leg muscles in ambulatory children with CP show a marked reduction in mitochondrial function. Arm muscles show that mitochondrial protein content and mitochondria DNA copy number are lower, suggesting a reduction in mitochondrial abundance, along with a reduction in markers for mitochondrial biogenesis. Gene expression networks are reduced for glycolytic and mitochondrial pathways and share similarities with gene networks with aging and chronic inactivity. Given the importance of mitochondria for energy production and changes with aging, future work needs to assess changes in mitochondria across the lifespan in people with CP and the effect of exercise on promoting metabolic health.

The Impact of COVID-19 Lockdown on Agility, Explosive Power, and Speed-Endurance Capacity in Youth Soccer Players

Our goal was to assess agility, explosive power, and speed-endurance capacity by implementing noninvasive procedures and sport-specific tests. We hypothesized that agility, speed, explosive power, and speed-endurance capacity might be maintained or increased by an individualized home-based training program. Eleven adolescent athletes participated in our study; they executed three tests before the coronavirus outbreak and 13 weeks later, after the pandemic curfew. We used the SpeedCourt System to assess the sport-specific speed and agility parameters and monitor speed-endurance capacity. We conducted the first measurement at the end of the preparatory period, on 28 February 2020. The second session consisted of 4 weeks of regular training and 9 weeks of individual, home-based activities. Compared to the first (pre-pandemic) testing session, our participants demonstrated a significantly improved capacity of the lower limbs’ explosive strength after completing the home-based exercise routine, compared to the first (pre-pandemic) testing session. We found that agility, speed, and explosive power might be maintained at the same level under home-based conditions. We found that it was challenging for the participants to increase their “pre-pandemic” endurance capacities.

Effects of Hot and Humid Environments on Thermoregulation and Aerobic Endurance Capacity of Laser Sailors

The purpose was to investigate the effects of hot and humid environments on thermoregulation and aerobic endurance capacity of Laser sailors. A randomized cross-over design was applied to this study, in which nine Laser sailors performed the 6 km rowing test (6 km test) in both a warm (ambient temperature: 23±1.4 °C; relative humidity: 60.5±0.7 %; wind speed: 0 km/h; WARM) and hot environment (ambient temperature: 31.8±1.1 °C; relative humidity: 63.5 ± 4.9 %; wind speed: 3.5±0.7 km/h; HOT). The time for completing 6 km test of HOT group was significantly longer than that of WARM group (P=0.0014). Mean power of 3-4 km, 4-5 km and 5-6 km were significant lower in HOT group (P=0.014, P=0.02, P=0.003). Gastrointestinal temperature and skin temperature were significantly higher in HOT group during the 6 km test (P=0.016, P=0.04). Heat storage at 5 min and 15 min of HOT group were significantly higher than that of WARM group (P=0.0036; P=0.0018). Heart rate and physiological strain index of HOT group were significantly higher than that of WARM group during the 6 km test (P=0.01, P<0.01). The increase magnitude of skin temperature was more obvious than the changes of core temperature during exercise in hot and humid environments. The higher skin temperature narrowed the core to skin temperature gradient and skin to ambient temperature gradient, which may result in greater accumulation of heat storage. The greater heat storage led to the lower muscle power output, which contributed to the reduction of the heat production.

Exercise Prior to Lower Extremity Peripheral Artery Disease Improves Endurance Capacity and Hindlimb Blood Flow by Inhibiting Muscle Inflammation

Lower extremity peripheral artery disease (PAD) is associated with functional decline. Physical exercise has been proven to be an effective therapeutic strategy for PAD; however the effect of exercise initiated before PAD remains unknown. Here, we investigated the preventive effects of exercise on endurance capacity, hindlimb perfusion, and on polarization profile of circulating monocytes and limb muscle macrophages. ApoE−/− mice were subjected to 5-week running wheel exercise or remained sedentary before induction of hindlimb ischemia. The two groups were thereafter kept sedentary. Exercised mice prior to PAD showed higher exhaustive treadmill running distance and time than sedentary mice. Preventive exercise also increased perfusion, arteriole density, and muscle regeneration in the ischemic hindlimb. Moreover, preventive exercise prevented ischemia-induced increased gene expression of pro-inflammatory M1 macrophages markers and cytokines in the ischemic muscle, while no changes were observed for anti-inflammatory M2 macrophage markers. Flow cytometry analysis showed that the proportion of circulating pro-inflammatory monocyte subtype decreased whereas that of anti-inflammatory monocytes increased with preventive exercise. Overall, we show that exercise initiated before PAD improves endurance performance and hindlimb perfusion in mice probably via inhibition of M1 macrophage polarization and inflammation in the ischemic muscle. Our study provides experimental evidence for a role of regular exercise in primary prevention of PAD.

Chronic Sildenafil Therapy in the ZSF1 Obese Rat Model of Metabolic Syndrome and Heart Failure With Preserved Ejection Fraction

Although decreased protein kinase G (PKG) activity was proposed as potential therapeutic target in heart failure with preserved ejection fraction (HFpEF), randomized clinical trials (RCTs) with type-5 phosphodiesterase inhibitors (PDE5i) showed neutral results. Whether specific subgroups of HFpEF patients may benefit from PDE5i remains to be defined. Our aim was to test chronic sildenafil therapy in the young male ZSF1 obese rat model of HFpEF with severe hypertension and metabolic syndrome. Sixteen-week-old ZSF1 obese rats were randomly assigned to receive sildenafil 100 mg·Kg−1·d−1 dissolved in drinking water (ZSF1 Ob SIL, n = 8), or placebo (ZSF1 Ob PL, n = 8). A group of Wistar-Kyoto rats served as control (WKY, n = 8). Four weeks later animals underwent effort tests, glucose metabolism studies, hemodynamic evaluation, and samples were collected for aortic ring preparation, left ventricular (LV) myocardial adenosine triphosphate (ATP) quantification, immunoblotting and histology. ZSF1 Ob PL rats showed systemic hypertension, aortic stiffening, impaired LV relaxation and increased LV stiffness, with preserved ejection fraction and cardiac index. Their endurance capacity was decreased as assessed by maximum workload and peak oxygen consumption (V˙O2) and respiratory quotient were increased, denoting more reliance on anaerobic metabolism. Additionally, ATP levels were decreased. Chronic sildenafil treatment attenuated hypertension and decreased LV stiffness, modestly enhancing effort tolerance with a concomitant increase in peak, ATP levels and VASP phosphorylation. Chronic sildenafil therapy in this model of HFpEF of the young male with extensive and poorly controlled comorbidities has beneficial cardiovascular effects which support RCTs in HFpEF patient subgroups with similar features.