Metabolites of the cytochrome P450 (CYP) pathway may contribute to vasodilation of the vasculature. However, it is not known whether exercise affects their circulating concentrations. The authors determined effects of exercise intensity and duration on plasma concentrations of epoxy and dihydroxy metabolites of arachidonic acid. Their goal was to delineate the threshold workload, optimal workload, and duration required to produce increases in plasma concentrations of these vasoactive substances. Healthy volunteers (N = 14) performed maximal exercise testing on a bicycle ergometer during Visit 1. On separate days, subjects cycled for 20 min at 30%, 60%, and 80% of their maximal exercise intensity. The last day consisted of 40 min of exercise at 60% of maximal exercise intensity. Venous blood was obtained before, during, and after exercise for analysis. Compared with rest, increases were observed during the 80% workload at 20 min postexercise —14,15-DHET (0.77 ± 0.21 vs. 0.93 ± 0.27 nM)—and at 2 min postexercise: 11,12-DHET (0.64 ± 0.22 vs. 0.71 ± 0.24 nM; p < .05). Also compared with rest, 40-min values during the 60% workload were 14,15-DHET 0.79 ± 0.22 vs. 0.91 ± 0.31 nM and at 2 min post 14,15 EET 0.12 ± 0.06 vs. 0.21 ± 0.16 nM (p < .05). Results suggest the CYP metabolites (i.e., DHETs) are released during short-term high-intensity and long-term moderateintensity exercise.
Rose M. Giordano, John W. Newman, Theresa L. Pedersen, Marisa I. Ramos and Charles L. Stebbins
Tatsuhisa Takahashi, Akiyoshi Okada, Jun-ichiro Hayano and Nobuo Takeshima
To determine water immersion’s effect on heart rate (HR) and vagal tone, the authors examined HR and high-frequency R-R-interval variability in 7 healthy older adults at rest and during treadmill walking, starting at 3.0 km/hr and increasing 0.5 km/hr every 3 min at a 5% grade to exhaustion. Participants performed the test on land and then immersed in water to the xiphoid. HR at rest did not differ between water and land. During walking at 3.0 km/min, HR was significantly lower in water than on land, whereas at 4.5 and 5.0 km/min it was significantly higher (each p < .05). Peak HR at exhaustion was not significantly different between water and land. High-frequency amplitudes at rest and during exercise in water were not significantly different from those on land. The results suggest that resting vagus tone and vagal changes in response to walking exercise in elderly adults are not greatly affected by water immersion.
Micailah Brock and Sheri Huckleberry
This paper introduces the concept of dynamic isometrics in training athletes to improve core/postural-related movements while potentially decreasing the occurrence of injury manifested as lower back pain (LBP). Moreover, suggested resistance-training exercises are provided to guide the sport coach. Lower back pain is a common musculoskeletal injury that can be caused by imbalances between anterior and posterior muscle groups. Traditional exercises such as sit-ups and crunches are insufficient as preventatives because very few athletic movements are performed with weighted trunk flexion. Alternatively, sport coaches could implement dynamic isometric training, which closely reflects athletic activities, supports the principle of training specificity, improves balance and strength, and might decrease the occurrence of LBP (Hamlyn, Behm, & Young, 2007).
Avery D. Faigenbaum, Jie Kang, James McFarland, Jason M. Bloom, James Magnatta, Nicholas A. Ratamess and Jay R. Hoffman
Although pre-event static stretching (SS) is an accepted practice in most youth programs, pre-event dynamic exercise (DY) is becoming popular. The purpose of this study was to examine the acute effects of pre-event SS, DY, and combined SS and DY (SDY) on vertical jump (VJ), medicine-ball toss (MB), 10-yard sprint (SP), and pro-agility shuttle run (AG) in teenage athletes (15.5 ± 0.9 years). Thirty athletes participated in three testing sessions in random order on three nonconsecutive days. Before testing, participants performed 5 min of walking/jogging followed by one of the following 10 min warm-up protocols: a) five static stretches (2 × 30 s), b) nine moderate-to-high-intensity dynamic movements (2 × 10 yards), or c) five static stretches (1 × 30 s) followed by the same nine dynamic movements (1 × 10 yards). Statistical analysis of the data revealed that performance on the VJ, MB, and SP were significantly (p < .05) improved after DY and SDY as compared with SS. There were no significant differences in AG after the 3 warm-up treatments. The results of this study indicate that pre-event dynamic exercise or static stretching followed by dynamic exercise might be more beneficial than pre-event static stretching alone in teenage athletes who perform power activities.
Preeti D. Oza, Shauna Dudley-Javoroski and Richard K. Shields
H-reflex depression (diminution of amplitude after a conditioning stimulus) is mediated presynaptically and therefore can help distinguish central versus peripheral mechanisms of fatigue. We examined the effects of a dynamic exercise protocol on H-reflex depression using two conditioning methods: homonymous conditioning (paired-pulse tibial nerve stimulation); and heteronymous conditioning (common peroneal nerve stimulation). Ten subjects performed dynamic contractions of the soleus muscle through 30° ankle range of motion. The concentric phase required a target force of 10% of maximum voluntary isometric contraction (MVIC) and the eccentric phase force target was 80% MVIC. Fatigue persisted for >20 min after cessation of the exercise. Compared with prefatigue values, the dynamic fatigue protocol did not increase presynaptic inhibition after either homonymous or heteronymous conditioning. Peak to peak amplitude of unconditioned H-reflexes was likewise unchanged despite a long term depression of muscle force (long duration fatigue). These results suggest that persistent fatigue after dynamic exercise is attributed to muscle changes and not altered spinal mechanisms.
Ted. A. Kaplan, Gina Moccia and Robert M. McKey Jr.
The purpose of this study was to assess the incidence, degree, pattern, and time course of pulmonary function test (PFT) changes measured after a dynamic exercise challenge. Forced expiratory maneuvers were performed before and serially after a 7-min run-walk in 44 patients with cystic fibrosis (CF). Twenty-four patients met at least one PFT criterion for exercise-induced bronchospasm (EIB) within 21 min after exercise, and 38 patients had >5% increase in a PFT parameter at some point after exercise. The mean time of greatest increase in PFTs occurred sooner than the greatest decrease, which was later than for 22 patients with asthma or allergic rhinitis found to have EIB. Age was inversely related to percentage fall in forced expiratory volume in 1 s (FEV,) after exercise. These results demonstrate a distinct pattern of PFTs measured after exercise in most patients with CF, with an early bronchodilation followed by a significant decrease in PFTs.
Paolo T. Pianosi
This essay expounds on fundamental, quantitative elements of the exercise ventilation in children, which was the subject of the Tom Rowland Lecture given at the NASPEM 2018 Conference. Our knowledge about how much ventilation rises during aerobic exercise is reasonably solid; our understanding of its governance is a work in progress, but our grasp of dyspnea and ventilatory limitation in children (if it occurs) remains embryonic. This manuscript summarizes ventilatory mechanics during dynamic exercise, then proceeds to outline our current understanding of mechanisms of dyspnea, particularly during exercise (exertional dyspnea). Most research in this field has been done in adults, and the vast majority of these studies in patients with chronic obstructive pulmonary disease. To what extent conclusions drawn from this literature apply to children and adolescents—both healthy and those with cardiopulmonary disease—will be discussed. The few, recent, pertinent, pediatric studies will be reviewed in an attempt to provide an empirical basis for proposing a hypothetical model to study exertional dyspnea in youth. Just as somatic growth will have consequences for ventilatory and exercise capacity, so too will neural developmental plasticity and experience affect perception of dyspnea. Our path to understand how these evolving inputs and influences summate during a child’s life will be Columbus’ India.
Kai Roecker, Jule Metzger, Tobias Scholz, Kay Tetzlaff, Stephan Sorichter and Stephan Walterspacher
Specific adjustments to repeated extreme apnea are not fully known and understood. While a blunted ventilatory chemosensitivity to CO2 is described for elite breath-hold divers (BHDs) at rest, it is unclear whether specific adaptations affect their response to dynamic exercise. Eight elite BHDs with a previously validated decrease in CO2 chemosensitivity, 8 scuba divers (SCDs), and 8 matched control subjects were included in a study where markers of ventilatory response, Fowler’s dead space, partial pressure of carbon dioxide (pCO2), and blood lactate concentrations during cycle exercise were measured. Maximal power output did not differ between the groups, but lactate threshold (θL) appeared at a significantly lowered respiratory compensation point (RCP) and at a higher VO2 for the BHDs. End-tidal (petCO2) and estimated arterial pCO2 (paCO2) were significantly higher in BHDs at θL, the RCP, and maximum exhaustion. BHDs showed a significantly (P < .01) slower breathing pattern in relation to a given tidal volume at a specific work rate. In summary, BHDs presented signs of a metabolic shift from aerobic to anaerobic energy supply, decreased chemosensitivity during exercise, and a distinct ventilatory-response pattern during cycle exercise that differs from SCDs and controls.
Cindy Y. Lin, Liang-Ching Tsai, Joel Press, Yupeng Ren, Sun G. Chung and Li-Qun Zhang
Gluteal-muscle strength has been identified as an important component of injury prevention and rehabilitation in several common knee injuries. However, many conventionally prescribed gluteal-strengthening exercises are not performed during dynamic weight-bearing activities, which is when most injuries occur.
To compare lower-limb muscle-activation patterns between conventional gluteal-strengthening exercises and off-axis elliptical exercises with motorized foot-plate perturbations designed to activate gluteal muscles during dynamic exercise.
Twelve healthy volunteers (26.1 ± 4.7 y) participated in the study. They performed 3 conventional exercises (single-leg squat, forward lunge, and clamshell) and 3 elliptical exercises (regular, while resisting an adduction force, and while resisting an internal-rotation torque). Gluteus medius (GMed) and maximus (GMax), quadriceps, hamstrings, and gastrocnemius muscle activations during each exercise were recorded using surface electromyography (EMG) and normalized to maximal voluntary isometric contraction (MVIC).
Normalized GMed EMG was the highest during the adduction-resistance elliptical exercise (22.4% ± 14.8% MVIC), significantly greater than forward lunge (8.2% ± 3.8% MVIC) and regular elliptical (6.4% ± 2.5% MVIC) and similar to clamshell (19.1% ± 8.8% MVIC) and single-leg squat (18.4% ± 7.9% MVIC). Normalized GMax EMG during adduction-resistance (11.1% ± 7.6% MVIC) and internal-rotation-resistance elliptical (7.4% ± 3.8% MVIC) was significantly greater than regular elliptical (4.4% ± 2.4% MVIC) and was similar to conventional exercises. The single-leg squat required more muscle activation from the quadriceps and gastrocnemius than the elliptical exercises.
Off-axis elliptical exercise while resisting an adduction force or internal-rotation torque activates gluteal muscles dynamically while avoiding excessive quadriceps activation during a functional weight-bearing activity compared with conventional gluteal-strengthening exercises.
John Miller and Todd Seidler
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