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Genevieve Fridlund Dunton, Donna Spruijt-Metz, Jennifer Wolch, Chih-Ping Chou, Michael Jerrett, Jason Byrne, Susan Weaver and Kim D. Reynolds

Background:

Efforts to increase community levels of physical activity through the development of multiuse urban trails could be strengthened by information about factors predicting trail use. This study examined whether reasons for trail use predict levels of physical activity on urban trails.

Methods:

Adults (N = 335) living within a 1-mile buffer zone of urban trails in Chicago, Dallas, and Los Angeles completed a self-report measure assessing demographics, reason for trail use, and physical activity on the trail. Accelerometers measured total daily moderate-to-vigorous physical activity (MVPA). Environmental features of the urban trail were assessed with the Systematic Pedestrian and Cyclist Environmental Scan for trails measure. Multivariate regression analyses were conducted that accounted for clustering of individuals within trail segments.

Results:

After controlling for demographic and environmental factors and total daily MVPA, reasons for trail use significantly predicted recreational but not transportation activity. Recreational trail activity was greater for participants who reported exercise and health reasons for trail use as compared with other reasons (ie, social interaction, enjoying nature, walking pets) for recreational trail use.

Conclusions:

To increase the use of urban trails, it may be useful to promote the health and exercise benefits of recreational trail use.

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W. Jack Rejeski, Edward Gregg, Amy Thompson and Michael Berry

In this investigation, we examined the role of acute aerobic exercise (AE) in buffering physiological responses to mental stress. Twelve trained cyclists participated in three counterbalanced treatment conditions on separate days: attention control, light exercise (50% of VO2max for 30 min), and heavy exercise (80% of VO2max for 60 min). After a 30-min rest period following each condition, subjects completed a modified Stroop task. Blood pressure (BP) and heart rate (HR) were monitored for (a) baseline responses, (b) task reactivity, and (c), 5 min of recovery following the stressor. Mean arterial pressure (MAP) revealed that reactivity was attenuated by both heavy- and light-exercise conditions as compared to responses in the control condition. Moreover, heavy exercise was more effective in reducing MAP reactivity than light exercise. Systolic BP during the task was significantly higher in the control and light-exercise conditions than following heavy exercise; diastolic BP was significantly higher in the control condition than in either exercise condition. There were no significant effects for HR. These results suggest that there is a dose-response relationship between acute AE and the attenuation of psychophysiological reactivity during stress.

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Karin Pfeiffer, Natalie Colabianchi, Marsha Dowda, Dwayne Porter, James Hibbert and Russell R. Pate

Background:

In adults, associations between church attendance and positive health behaviors exist; however, similar evidence among children and youth is lacking. The purposes of this investigation were to examine the associations between physical activity (PA) and church attendance, PA and use of church as a PA facility, and PA and proximity to churches among those who use church as a PA facility (while addressing racial and geographical differences).

Methods:

High school girls (N = 915, age = 17.7 ± 0.6 years, 56% African American) completed the 3-Day Physical Activity Recall and surveys including demographics and use of PA facilities. Geographic Information Systems data were used to spatially examine the number of churches within a 0.75-mile street network buffer around girls’ homes. Associations were examined using mixed model analyses controlling for demographic factors.

Results:

For the overall sample, total METs (56 versus 52) and proportion of girls meeting PA guidelines (62% vs. 52%) were significantly higher in church attendees versus nonattendees. Among participants who used facilities, having more churches close to home was associated with more PA.

Conclusions:

Church attendance and use are correlates of physical activity that should be further explored and addressed in future intervention research with adolescent girls.

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Geoff Minett, Rob Duffield and Stephen P. Bird

Purpose:

To investigate the effects of an acute multinutrient supplement on game-based running performance, peak power output, anaerobic by-products, hormonal profiles, markers of muscle damage, and perceived muscular soreness before, immediately after, and 24 h following competitive rugby union games.

Methods:

Twelve male rugby union players ingested either a comprehensive multinutrient supplement (SUPP), [RE-ACTIVATE:01], or a placebo (PL) for 5 d. Participants then performed a competitive rugby union game (with global positioning system tracking), with associated blood draws and vertical jump assessments pre, immediately post and 24 h following competition.

Results:

SUPP ingestion resulted in moderate to large effects for augmented 1st half very high intensity running (VHIR) mean speed (5.9 ± 0.4 vs 4.8 ± 2.3 m·min−1; d = 0.93). Further, moderate increases in 2nd half VHIR distance (137 ± 119 vs 83 ± 89 m; d = 0.73) and VHIR mean speed (5.9 ± 0.6 v 5.3 ± 1.7 m·min−1; d = 0.56) in SUPP condition were also apparent. Postgame aspartate aminotransferase (AST; 44.1 ± 11.8 vs 37.0 ± 3.2 UL; d = 1.16) and creatine kinase (CK; 882 ± 472 vs. 645 ± 123 UL; d = 0.97) measures demonstrated increased values in the SUPP condition, while AST and CK values correlated with 2nd half VHIR distance (r = −0.71 and r = −0.76 respectively). Elevated C-reactive protein (CRP) was observed postgame in both conditions; however, it was significantly blunted with SUPP (P = .05).

Conclusions:

These findings suggest SUPP may assist in the maintenance of VHIR during rugby union games, possibly via the buffering qualities of SUPP ingredients. However, correlations between increased work completed at very high intensities and muscular degradation in SUPP conditions, may mask any anticatabolic properties of the supplement.

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Ruth M. Hobson, Roger C. Harris, Dan Martin, Perry Smith, Ben Macklin, Kirsty J. Elliott-Sale and Craig Sale

The ability to buffer H+ could be vital to exercise performance, as high concentrations of H+ contribute to the development of fatigue.

Purpose:

The authors examined the effect of sodium bicarbonate (SB) supplementation on 2000-m rowing-ergometer performance.

Methods:

Twenty male rowers (age 23 ± 4 y, height 1.85 ± 0.08 m, mass 82.5 ± 8.9 kg, 2000-m personal-best time 409 ± 16 s) completed two 2000-m rowing-ergometer time trials, separated by 48 h. Participants were supplemented before exercise with 0.3 g/kg body mass of SB or a placebo (maltodextrin; PLA). The trials were conducted using a double-blinded, randomized, counterbalanced crossover study design. Time to complete the 2000-m and time taken for each 500-m split were recorded. Blood lactate, bicarbonate, pH, and base excess were determined preexercise, immediately postexercise, and 5 min postexercise. Performance data were analyzed using paired t tests, as well as magnitude-based inferences; hematological data were analyzed using a repeated-measures ANOVA.

Results:

Using paired t tests, there was no benefit of SB over PLA (P = .095). However, using magnitude-based inferences there was a likely beneficial effect of SB compared with PLA (PLA 412.0 ± 15.1 s, SB 410.7 ± 14.9 s). Furthermore, SB was 0.5 ± 1.2 s faster than PLA in the third 500 m (P = .035; possibly beneficial) and 1.1 ± 1.7 s faster in the fourth 500 m (P = .004; very likely beneficial). All hematological data were different between SB and PLA and were different from preexercise to postexercise.

Conclusion:

SB supplementation is likely to be beneficial to the performance of those competing in 2000-m rowing events, particularly in the second half of the event.

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Gabriel Motta Pinheiro Brisola, Fabio Milioni, Marcelo Papoti and Alessandro Moura Zagatto

In water polo, several high-intensity efforts are performed, leading to the fatigue process due to accumulation of hydrogen ions, and thus β-alanine supplementation could be an efficient strategy to increase the intramuscular acid buffer.

Purpose

To investigate whether 4 wk of β-alanine supplementation enhances parameters related to water polo performance.

Methods

Twenty-two highly trained male water polo players of national level were randomly assigned to receive 28 d of either β-alanine or a placebo (4.8 g/d of the supplement in the first 10 d and 6.4 g/d in the final 18 d). The participants performed 30-s maximal tethered swimming (30TS), 200-m swimming (P200m), and 30-s crossbar jumps (30CJ) before and after the supplementation period.

Results

The β-alanine group presented significant increases in 30TS for mean force (P = .04; Δ = 30.5% ± 40.4%) and integral of force (P = .05; Δ = 28.0% ± 38.0%), as well as P200m (P = .05; Δ = –2.2% ± 2.6%), while the placebo group did not significantly differ for mean force (P = .13; Δ = 24.1% ± 33.7%), integral of force (P = .12; Δ = 24.3% ± 35.1%), or P200m (P = .10; Δ = –1.6% ± 3.8%). However, there was no significant group effect for any variable, and the magnitude-based-inference analysis showed unclear outcomes between groups (Cohen d ± 95%CL mean force = 0.16 ± 0.83, integral of force = 0.12 ± 0.84, and P200m = 0.05 ± 0.30). For 30CJ the results were similar, with improvements in both groups (placebo, Δ = 14.9% ± 14.1%; β-alanine, Δ = 16.9% ± 18.5%) but with no significant interaction effect between groups and an unclear effect (0.14 ± 0.75).

Conclusion

Four weeks of β-alanine supplementation does not substantially improve performance of 30TS, P200m, or 30CJ in highly trained water polo athletes compared with a control group.

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James R. Debenham, William I. Gibson, Mervyn J. Travers, Amity C. Campbell and Garry T. Allison

Context:

Eccentric exercises are increasingly being used to treat lower-limb musculoskeletal conditions such as Achilles tendinopathy. Despite widespread clinical application and documented efficacy, mechanisms underpinning clinical benefit remain unclear. Positive adaptations in motor performance are a potential mechanism.

Objective:

To investigate how an eccentric loading intervention influences measures of stretch-shortening-cycle (SSC) behavior during a hopping task.

Design:

Within-subjects repeated-measures observational study.

Setting:

University motion-analysis laboratory.

Participants:

Healthy adults.

Interventions:

A single intervention of 5 sets of 10 eccentric plantar-flexion contractions at 6 repetitions maximum using a commercial seated calf-raise machine.

Main Outcome Measures:

Lower-limb stiffness, sagittal-plane ankle kinematics, and temporal muscle activity of the agonist (soleus) and antagonist (tibialis anterior) muscles, measured during submaximal hopping on a custom-built sledge-jump system.

Results:

Eccentric loading altered ankle kinematics during submaximal hopping; peak angle shifted to a less dorsiflexed position by 2.9° and ankle angle precontact shifted by 4.4° (P < .001). Lower-limb stiffness increased from 5.9 to 6.8 N/m (P < .001), while surface EMG measures of soleus occurred 14–44% earlier (P < .001) after the loading intervention.

Conclusions:

These findings suggest that eccentric loading alters SSC behavior in a manner reflective of improved motor performance. Decreased ankle excursion, increased lower-limb stiffness, and alterations in motor control may represent a positive adaptive response to eccentric loading. These findings support the theory that mechanisms underpinning eccentric loading for tendinopathy may in part be due to improved “buffering” of the tendon by the neuromuscular system.

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Marissa A. Kobayashi, Tae Kyoung Lee, Rafael O. Leite, Blanca Noriega Esquives, Guillermo Prado, Sarah E. Messiah and Sara M. St. George

Family Communication on Physical Activity The stress-buffering hypothesis refers to the idea that social support can buffer the harmful effects of stress on a number of youth outcomes including stress and depression. 18 , 19 Social support operates through the assistance obtained from positive

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Anne Delextrat, Sinead Mackessy, Luis Arceo-Rendon, Aaron Scanlan, Roger Ramsbottom and Julio Calleja-Gonzalez

the blood by 4–8 mmol/L, which in turn buffers hydrogen (H + ) ions and increases blood alkalosis ( Jones et al., 2016 ). Kemp et al. ( 2006 ) suggested that this alkaline environment in the extracellular fluid increased the efflux of H + out of the working muscles, hence reducing intracellular

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Gary J. Slater, Jennifer Sygo and Majke Jorgensen

sprint performance ( Hargreaves et al., 1997 ). Taken together, this provides potential opportunities for nutritional interventions that could impact on training and performance, including buffering against acidosis for longer sprints (i.e., 400 m) and optimization of the phosphagen energy systems for