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Neil Armstrong

Purpose:

The presence of a maturational threshold that modulates children’s physiological responses to exercise training continues to be debated, not least due to a lack of longitudinal evidence to address the question. The purpose of this study was to investigate the interaction between swim-training status and maturity in nineteen trained (T, 10 ± 1 years, −2.4 ± 1.9 years prepeak height velocity, 8 boys) and fifteen untrained (UT, 10 ± 1 years, −2.3 ± 0.9 years prepeak height velocity, 5 boys) children, at three annual measurements.

Methods:

In addition to pulmonary gas exchange measurements, stroke volume (SV) and cardiac output (Q) were estimated by thoracic bioelectrical impedance during incremental ramp exercise.

Results:

At baseline and both subsequent measurement points, trained children had significantly (p < .05) higher peak oxygen uptake (year1 T 1.75 ± 0.34 vs. UT 1.49 ± 0.22; year 2 T 2.01 ± 0.31 vs. UT 1.65 ± 0.08; year 3 T 2.07 ± 0.30 vs. UT 1.77 ± 0.16 l min−1) and Q (year 1 T 15.0 ± 2.9 vs. UT 13.2 ± 2.2; year 2 T 16.1 ± 2.8 vs. UT 13.8 ± 2.9; year 3 T 19.3 ± 4.4 vs. UT 16.0 ± 2.7 l min−1). Furthermore, the SV response pattern differed significantly with training status, demonstrating the conventional plateau in UT but a progressive increase in T. Multilevel modeling revealed that none of the measured pulmonary or cardiovascular parameters interacted with maturational status, and the magnitude of the difference between T and UT was similar, irrespective of maturational status.

Conclusion:

The results of this novel longitudinal study challenge the notion that differences in training status in young people are only evident once a maturational threshold has been exceeded.

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Hervé Assadi and Romuald Lepers

Purposes:

To compare the physiological responses and maximal aerobic running velocity (MAV) during an incremental intermittent (45-s run/15-s rest) field test (45-15FIT) vs an incremental continuous treadmill test (TR) and to demonstrate that the MAV obtained during 45-15FIT (MAV45-15) was relevant to elicit a high percentage of maximal oxygen uptake (VO2max) during a 30-s/30-s intermittent training session.

Methods:

Oxygen uptake (VO2), heart rate (HR), and lactate concentration ([La]) were measured in 20 subjects during 2 maximal incremental tests and four 15-min intermittent tests. The time spent above 90% and 95% VO2max (t90% and t95% VO2max, respectively) was determined.

Results:

Maximal physiological parameters were similar during the 45-15FIT and TR tests (VO2max 58.6 ± 5.9 mL · kg−1 · min−1 for TR vs 58.5 ± 7.0 mL · kg−1 · min−1 for 45-15FIT; HRmax 200 ± 8 beats/min for TR vs 201 ± 7 beats/min for 45-15FIT). MAV45-15 was significantly (P < .001) greater than MAVTR (17.7 ± 1.1 vs 15.6 ± 1.4 km/h). t90% and t95% VO2max during the 30-s/30-s performed at MAVTR were significantly (P < .01) lower than during the 30-s/30-s performed at MAV45-15. Similar VO2 during intermittent tests performed at MAV45-15 and at MAVTR can be obtained by reducing the recovery time or using active recovery.

Conclusions:

The results suggested that the 45-15FIT is an accurate field test to determine VO2max and that MAV45-15 can be used during high-intensity intermittent training such as 30-s runs interspersed with 30-s rests (30-s/30-s) to elicit a high percentage of VO2max.

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Laura Capranica and Mindy L. Millard-Stafford

A prevailing theory (and practical application) is that elite performance requires early childhood skill development and training across various domains, including sport. Debate continues whether children specializing early (ie, training/competition in a single sport) have true advantage compared with those who sample various sports early and specialize in a single sport later (adolescence). Retrospective data and case studies suggest either model yields elite status depending upon the sport category (ie, situational: ball games, martial arts, fencing; quantitative: track and feld, swimming, skiing; or qualitative: gymnastics, diving, figure skating). However, potential risks of early specialization include greater attrition and adverse physical/emotional health outcomes. With the advent of the IOC Youth Olympic Games, increased emphasis on global youth competition has unknown implications but also represents a potential platform for investigation. Modification of youth competition formats should be based upon multidisciplinary research on psycho-physiological responses, and technical-tactical behaviors during competition. The assumption that a simple scaled-down approach of adult competitions facilitates the development of technical/tactical skills of youth athletes is not necessarily substantiated with field-based research. Relatively little evidence exists regarding the long-term effects of rigorous training and competitive schedules on children in specific sports. It is clear that more prospective studies are needed to understand the training dose that optimally develops adaptations in youth without inducing dropout, overtraining syndrome, and/or injury. Such an approach should be sport specific as well as gender based. Until such evidence exists, coaches and sport administrators will continue to rely upon their sport-specific dogma to influence programmatic development of our most vulnerable population.

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Maria Konstantaki, Edward Winter and Ian Swaine

Context:

Forward propulsion in freestyle swimming is predominantly achieved through arm action. Few studies have assessed the effects of arm training on arm power and swimming performance, yet there have not been any investigations on the effects of arms-only swimming training on swimming performance and physiological responses to arm exercise.

Purpose:

To investigate the changes in arms-only and full-stroke swimming performance, movement economy and aerobic power after an arms-only swimming training program.

Methods:

Fifteen male county level swimmers were assigned either to an experimental (ES, n = 8) or control group (CS, n = 7). For six weeks ES performed arms-only freestyle swimming exercises for 20% of their weekly training distance three times per week, whereas CS performed their usual swimming training. Before and after the training program, both groups performed a) two time trials, 186 m using arms-only (186ARMS) and 372 m using full-stroke (372FULL) freestyle swimming, and b) an incremental arm-pulling exercise test. The time to complete the trials was recorded. Peak oxygen uptake (VO2peak), peak exercise intensity (EIpeak) submaximal oxygen uptake at 60 W (VO2−60) and exercise intensity at ventilatory threshold (VTW) were determined from the exercise test.

Results:

After training, ES had improved in 186ARMS (−14.2 ± 3.6%, P = .03), VO2−60 (−22.5 ± 2.3%, P = .04), EIpeak (+17.8 ± 4.2%, P = .03), and VTW (+18.9 ± 2.3%, P = .02), but not in VO2peak (P = .09) or in 372FULL (P = .07). None of the measures changed in CS (P > .05).

Conclusion:

Arms-only swimming training at 20% of the weekly training distance is an effective method to improve arm conditioning during the preparatory phase of the annual training cycle.

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Carlo Castagna, Lorenzo Francini, Susana C.A. Póvoas and Stefano D’Ottavio

Purpose:

To examine the acute effects of generic drills (running drills [RDs]) and specific (small-sided-games [SSGs]) long-sprint-ability (LSA) drills on internal and external load of male soccer players.

Methods:

Fourteen academy-level soccer players (mean ± SD age 17.6 ± 0.61 y, height 1.81 ± 0.63 m, body mass 69.53 ± 4.65 kg) performed four 30-s LSA bouts for maintenance (work:rest 1:2) and production (1:5) with RDs and SSGs. Players’ external load was tracked with GPS technology (20-Hz), and heart rate (HR), blood lactate concentration (BLc), and rating of perceived exertion (RPE) were used to characterize players’ internal load. Individual peak BLc was assessed with a 30-s all-out test on a nonmotorized treadmill (NMT).

Results:

Compared with SSGs, the RDs had a greater effect on external load and BLc (large and small, respectively). During SSGs players covered more distance with high-intensity decelerations (moderate to small). Muscular RPE was higher (small to large) in RDs than in SSGs. The production mode exerted a moderate effect on BLc while the maintenance condition elicited higher cardiovascular effects (small to large).

Conclusion:

The results of this study showed the superiority of generic over specific drills in inducing LSA-related physiological responses. In this regard production RDs showed the higher postexercise BLc. Individual peak blood lactate responses were found after the NMT 30-s all-out test, suggesting this drill as a valid option to RDs. The practical physiological diversity among the generic and specific LSA drills here considered enable fitness trainers to modulate prescription of RD and SSG drills for LSA according to training schedule.

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Matt B. Brearley and James P. Finn

Background:

Despite the thermal challenge of demanding workloads performed in high cabin temperatures while wearing heavy heat-retardant clothing, information on physiological responses to racing V8 Supercars in hot conditions is not readily available.

Purpose:

To describe the thermal, cardiovascular, and perceptual strain on V8 Supercar drivers competing in hot conditions.

Methods:

Thermal strain was indicated by body-core temperature using an ingested thermosensitive pill. Cardiovascular strain was assessed from heart rate, hydration status, and sweat rate. Perceptual strain was estimated from self-rated thermal sensation, thermal discomfort (modified Gagge scales), perceived exertion (Borg scale), and perceptual strain index.

Results:

Prerace body-core temperatures were (mean ± SD) 37.7°C ± 0.4°C (range 37.0°C to 38.2°C), rising to 39.0°C ± 0.4°C (range 38.4°C to 39.7°C) postrace. Driver heart rates were >160 and >170 beats/min for 85.3% and 46.7% of racing, respectively. Sweat rates were 1.06 ± 0.12 L/h or 13.4 ± 1.2 mL · kg−1 · h−1, and postrace dehydration was 0.6% ± 0.6% of prerace body mass. Drivers rated thermal sensation as hot (10.3 ± 0.9), thermal discomfort as uncomfortable (3.1 ± 1.0), and perceived exertion as very hard to very, very hard (8.7 ± 1.7) after the races. Overall physiological and perceptual strain were 7.4 ± 1.0 and 7.1 ± 1.2, respectively.

Conclusions:

Despite the use of cooling, V8 Supercar drivers endure thermal, cardiovascular, and perceptual strain during brief driving bouts in hot conditions.

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Michael J. Hartman, Brandon Clark, Debra A. Bemben, J. Lon Kilgore and Michael G. Bemben

Context:

Many elite athletes use increased daily training frequencies as a means to increase training load without substantial published literature to support this practice.

Purpose:

To compare the physiological responses to twice- and once-daily training sessions with similar training volumes.

Methods:

Ten nationally competitive male weightlifters (age 20.5 ± 1.2 y, body mass 92.9 ± 23.6 kg, training history 5.5 ± 1.5 y) were matched on body mass and training experience, then randomly assigned to train either once or twice daily for 3 wk. Isometric knee-extension strength (ISO), muscle cross-sectional area, vertical-jump peak power, resting hormone concentrations, neuromuscular activation (EMG), and weightlifting performance were obtained before and after the experimental training period.

Results:

All dependent measures before the training intervention were similar for both groups. A 2-way repeated-measures ANOVA did not reveal any significant main effects (group or trial) or interaction effects (group × trial) for any of the dependent variables. There were also no significant group differences when parameters were expressed as percentage change, but the twice-daily training group had a greater percentage change in ISO (+5.1% vs +3.2%), EMG (+20.3% vs +9.1%), testosterone (+10.5% vs +6.4%), and testosterone:cortisol ratio (−10.5% vs +1.3%) than did the once-daily training group.

Conclusions:

There were no additional benefits from increased daily training frequency in national-level male weightlifters, but the increase in ISO and EMG activity for the twice-daily group might provide some rationale for dividing training load in an attempt to reduce the risk of overtraining.

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Martin Buchheit, Bachar Haydar, Karim Hader, Pierre Ufland and Said Ahmaidi

Purpose:

To examine physiological responses to submaximal feld running with changes of direction (COD), and to compare two approaches to assess running economy (RE) with COD, ie, during square-wave (SW) and incremental (INC) exercises.

Methods:

Ten male team-sport athletes performed, in straight-line or over 20 m shuttles, one maximal INC and four submaximal SW (45, 60, 75 and 90% of the velocity associated with maximal pulmonary O2 uptake [vVO2pmax]). Pulmonary (VO2p) and gastrocnemius (VO2m) O2 uptake were computed for all tests. For both running mode, RE was estimated as the O2 cost per kilogram of bodyweight, per meter of running during all SW and INC.

Results:

Compared with straight-line runs, shuttle runs were associated with higher VO2p (eg, 33 ± 6 vs 37 ± 5 mL O2·min–1·kg–1 at 60%, P < .01) and VO2m (eg, 1.1 ± 0.5 vs 1.3 ± 0.8 mL O2·min–1·100 g–1 at 60%, P = .18, Cohen’s d = 0.32). With COD, RE was impaired during SW (0.26 ± 0.02 vs 0.24 ± 0.03 mL O2·kg–1·m–1, P < .01) and INC (0.23 ± 0.04 vs 0.16 ± 0.03 mL O2·kg–1·m–1, P < .001). For both SW and INC tests, the changes in RE with COD were related to height (eg, r = .56 [90%CL, 0.01;0.85] for SW) and weekly training/competitive volume (eg, r = –0.58 [–0.86;–0.04] for SW). For both running modes, RE calculated from INC was better than that from SW (both P < .001).

Conclusion:

Although RE is impaired during feld running with COD, team-sport players of shorter stature and/or presenting greater training/competitive volumes may present a lower RE deterioration with COD. Present results do not support the use of INC to assess RE in the feld, irrespective of running mode.

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Stephen Seiler and Øystein Sylta

The purpose of this study was to compare physiological responses and perceived exertion among well-trained cyclists (n = 63) performing 3 different high-intensity interval-training (HIIT) prescriptions differing in work-bout duration and accumulated duration but all prescribed with maximal session effort. Subjects (male, mean ± SD 38 ± 8 y, VO2peak 62 ± 6 mL · kg–1 · min–1) completed up to 24 HIIT sessions over 12 wk as part of a training-intervention study. Sessions were prescribed as 4 × 16, 4 × 8, or 4 × 4 min with 2-min recovery periods (8 sessions of each prescription, balanced over time). Power output, HR, and RPE were collected during and after each work bout. Session RPE was reported after each session. Blood lactate samples were collected throughout the 12 wk. Physiological and perceptual responses during >1400 training sessions were analyzed. HIIT sessions were performed at 95% ± 5%, 106% ± 5%, and 117% ± 6% of 40-min time-trial power during 4 × 16-, 4 × 8-, and 4 × 4-min sessions, respectively, with peak HR in each work bout averaging 89% ± 2%, 91% ± 2%, and 94% ± 2% HRpeak. Blood lactate concentrations were 4.7 ± 1.6, 9.2 ± 2.4, and 12.7 ± 2.7 mmol/L. Despite the common prescription of maximal session effort, RPE and sRPE increased with decreasing accumulated work duration (AWD), tracking relative HR. Only 8% of 4 × 16-min sessions reached RPE 19–20, vs 61% of 4 × 4-min sessions. The authors conclude that within the HIIT duration range, performing at “maximal session effort” over a reduced AWD is associated with higher perceived exertion both acutely and postexercise. This may have important implications for HIIT prescription choices.

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Sonya L. Cameron, Rebecca T. McLay-Cooke, Rachel C. Brown, Andrew R. Gray and Kirsty A. Fairbairn

Purpose:

This study investigated the effect of ingesting 0.3 g/kg body weight (BW) of sodium bicarbonate (NaHCO3) on physiological responses, gastrointestinal (GI) tolerability, and sprint performance in elite rugby union players.

Methods:

Twenty-five male rugby players, age 21.6 (2.6) yr, participated in a randomized, double-blind, placebo-controlled crossover trial. Sixty-five minutes after consuming 0.3 g/kg BW of either NaHCO3 or placebo, participants completed a 25-min warm-up followed by 9 min of high-intensity rugby-specific training followed by a rugby-specific repeated-sprint test (RSRST). Whole-blood samples were collected to determine lactate and bicarbonate concentrations and pH at baseline, after supplement ingestion, and immediately after the RSRST. Acute GI discomfort was assessed by questionnaire throughout the trials, and chronic GI discomfort was assessed during the 24 hr postingestion.

Results:

After supplement ingestion and immediately after the RSRST, blood HCO3 concentration and pH were higher for the NaHCO3 condition than for the placebo condition (p < .001). After the RSRST, blood lactate concentrations were significantly higher for the NaHCO3 than for the placebo condition (p < .001). There was no difference in performance on the RSRST between the 2 conditions. The incidence of belching, stomachache, diarrhea, stomach bloating, and nausea was higher after ingestion of NaHCO3 than with placebo (all p < .050). The severity of stomach cramps, belching, stomachache, bowel urgency, diarrhea, vomiting, stomach bloating, and flatulence was rated worse after ingestion of NaHCO3 than with placebo (p < .050).

Conclusions:

NaHCO3 supplementation increased blood HCO3 concentration and attenuated the decline in blood pH compared with placebo during high-intensity exercise in well-trained rugby players but did not significantly improve exercise performance. The higher incidence and greater severity of GI symptoms after ingestion of NaHCO3 may negatively affect physical performance, and the authors strongly recommend testing this supplement during training before use in competitive situations.