Six weeks (3 times/wk) of sprint-interval training (SIT) or continuous endurance training (CET) promote body-fat losses despite a substantially lower training volume with SIT. In an attempt to explain these findings, the authors quantified VO2 during and after (24 h) sprint-interval exercise (SIE; 2 min exercise) vs. continuous endurance exercise (CEE; 30 min exercise). VO2 was measured in male students (n = 8) 8 times over 24 hr under 3 treatments (SIE, CEE, and control [CTRL, no exercise]). Diet was controlled. VO2 was 150% greater (p < .01) during CEE vs. SIE (87.6 ± 13.1 vs. 35.1 ± 4.4 L O2; M ± SD). The observed small difference between average exercise heart rates with CEE (157 ± 10 beats/min) and SIE (149 ± 6 beats/min) approached significance (p = .06), as did the difference in peak heart rates during CEE (166 ± 10 beats/min) and SIE (173 ± 6 beats/min; p = .14). Total O2 consumed over 8 hr with CEE (263.3 ± 30.2 L) was greater (p < .01) than both SIE (224.2 ± 15.3 L; p < .001) and CTRL (163.5 ± 16.1 L; p < .001). Total O2 with SIE was also increased over CTRL (p < .001). At 24 hr, both exercise treatments were increased (p < .001) vs. CTRL (CEE = 500.2 ± 49.2; SIE = 498.0 ± 29.4; CTRL = 400.2 ± 44.6), but there was no difference between CEE and SIE (p = .99). Despite large differences in exercise VO2, the protracted effects of SIE result in a similar total VO2 over 24 hr vs. CEE, indicating that the significant body-fat losses observed previously with SIT are partially due to increases in metabolism postexercise.
Tom J. Hazell, T. Dylan Olver, Craig D. Hamilton and Peter W. R. Lemon
Jeffrey E. Herrick, Judith A. Flohr, Davis L. Wenos and Michael J. Saunders
This study compared the metabolic and performance effects of riding front-only suspension (FS) and front-and-rear suspension (FRS) mountain bicycles on an off-road course that simulated competitive cross-country race conditions (>105 min in duration, with ∼70% of time spent riding uphill).
Seven competitive mountain bikers (73.8 ± 7.6 kg; 61.0 ± 4.3 mL·kg–1·min–1) completed two randomized FS and FRS trials. Bikes were similar, excluding rear wheel suspension on the FRS, which increased bike weight by ∼2 kg. Each trial consisted of four laps of rugged 8 km trail with 154 m of elevation gain per lap. The first three laps were performed at ∼70% of VO2max; VO2, HR, and RPE were collected during the first and third laps. The final lap was performed as a maximal time-trial effort.
During the first and third laps, VO2, HR, and RPE were similar between FS and FRS. However, FS was significantly faster than FRS during the ascending segment of the course (17.6 ± 2.9 vs 18.9 ± 3.4 min, P = .035), despite similar VO2 (P = .651). Although not statistically significant, FRS tended to be faster than FS during the descending portion of the course (8.1 ± 2.0 vs 9.1 ± 2.1, P = .067) at similar VO2. Performance during the final time-trial lap was significantly faster for FS than FRS (24.9 ± 3.9 min, 27.5 ± 4.9 min, P = .008).
FS was faster than FRS over a course that simulated competitive cross-country race conditions. The faster times were likely the result of improved cycling economy during ascending, which were at least partially influenced by the lighter weight of the FS.
Matthew W. Driller, James W. Fell, John R. Gregory, Cecilia M. Shing and Andrew D. Williams
Several recent studies have reported substantial performance and physiological gains in well-trained endurance runners, swimmers, and cyclists following a period of high-intensity interval training (HIT). The aim of the current study was to compare traditional rowing training (CT) to HIT in well-trained rowers.
Subjects included 5 male and 5 female rowers (mean ± SD; age = 19 ± 2 y; height = 176 ± 8 cm; mass = 73.7 ± 9.8 kg; Vo2peak = 4.37 ± 1.08 L·min−1). Baseline testing included a 2000-m time trial and a maximal exercise test to determine Vo2peak, 4-min all-out power, and 4 mmol·L−1 blood lactate threshold. Following baseline testing, rowers were randomly allocated to HIT or CT, which they performed seven times over a 4-wk period. The HIT involved 8 × 2.5-min intervals at 90% of the velocity maintained at Vo2peak, with individual recoveries returning to 70% of the subjects’ maximal heart rate between intervals. The CT intensity consisted of workloads corresponding to 2 and 3 mmol·L−1 blood lactate concentrations. On completion of HIT or CT, rowers repeated the testing performed at baseline and were then allocated to the alternative training program and completed a crossover trial.
HIT produced greater improvements in 2000-m time (1.9 ± 0.9%; mean ± SD), 2000-m power (5.8 ± 3.0%), and relative Vo2peak (7.0 ± 6.4%) than CT.
Four weeks of HIT improves 2000-m time-trial performance and relative Vo2peak in competitive rowers, more than a traditional approach.
Louise Croft, Suzanne Dybrus, John Lenton and Victoria Goosey-Tolfrey
To examine the physiological profiles of wheelchair basketball and tennis and specifically to: (a) identify if there are differences in the physiological profiles of wheelchair basketball and tennis players of a similar playing standard, (b) to determine whether the competitive physiological demands of these sports differed (c) and to explore the relationship between the blood lactate [Bla−] response to exercise and to identify the sport specific heart rate (HR) training zones.
Six elite athletes (4 male, 2 female) from each sport performed a submaximal and VO2 peak test in their sport specific wheelchair. Heart rate, VO2, and [Bla−] were measured. Heart rate was monitored during international competitions and VO2 was calculated from this using linear regression equations. Individual HR training zones were identified from the [Bla–] profile and time spent within these zones was calculated for each match.
Despite no differences in the laboratory assessment of HRpeak, the VO2peak was higher for the basketball players when compared with the tennis players (2.98 ± 0.91 vs 2.06 ± 0.71; P = .08). Average match HR (163 ± 11 vs 146 ± 16 beats-min–1; P = .06) and average VO2 (2.26 ± 0.06 vs 1.36 ± 0.42 L-min-1; P = .02) were higher during actual playing time of basketball when compared with whole tennis play. Consequently, differences in the time spent in the different training zones within and between the two sports existed (P < .05).
Wheelchair basketball requires predominately high-intensity training, whereas tennis training requires training across the exercise intensity spectrum.
Gregory B. Dwyer and Anthony D. Mahon
Little is known about the responses to graded exercise in athletes with cerebral palsy (CP). This study compared the ventilatory threshold (VT) and peak VO2 among athletes with CP during treadmill and cycle ergometry exercise. Six (4 men, 2 women) track athletes with CP volunteered to participate in the study. Graded exercise tests on a treadmill and cycle ergometer were performed on separate days to assess VT and peak VO2. Paired t tests were used to compare the two exercise modes. The VT, expressed as a percentage of peak VO2, was significantly higher on the cycle ergometer than on the treadmill. The absolute VO2 at the VT was similar during both testing modes, and peak VO2 was significantly higher on the treadmill than on the cycle ergometer. Similar to responses seen in able-bodied individuals, the VO2 at VT was similar during both modes of exercise, while the peak VO2 was 10% lower on the cycle than on the treadmill. Cycle ergometer peak VO2 in these athletes was higher than previous reports of individuals with CP for the cycle ergometer.
Thomas J. O’Connor, Rick N. Robertson and Rory A. Cooper
Three-dimensional kinematic variables and their relationship to the physiology of racing wheelchair propulsion were studied. Six male wheelchair athletes performed two trials (medium and maximum speed) of 3 min each. VO2, VO2/kg, VE, and HR were measured. Results showed that at medium speed, wrist velocity on hand contact was significantly correlated with VO2/kg. At maximum speed, elbow velocity during preparatory phase was significantly correlated with VO2. Stepwise regression showed wrist trajectory angle and elbow velocity during preparatory phase were significantly correlated with VO2/kg. Results indicate that kinematic variables recorded prior to and on hand contact with the pushrim are significant variables in developing a more efficient racing wheelchair propulsion technique. Results of this study indicate a need to educate coaches of wheelchair track athletes concerning the best racing wheelchair propulsion technique.
Espen Tønnessen, Thomas A. Haugen, Erlend Hem, Svein Leirstein and Stephen Seiler
To generate updated Olympic-medal benchmarks for V̇O2max in winter endurance disciplines, examine possible differences in V̇O2max between medalists and nonmedalists, and calculate gender difference in V̇O2max based on a homogeneous subset of world-leading endurance athletes.
The authors identified 111 athletes who participated in winter Olympic Games/World Championships in the period 1990 to 2013. All identified athletes tested V̇O2max at the Norwegian Olympic Training Center within ±1 y of their championship performance. Testing procedures were consistent throughout the entire period.
For medal-winning athletes, the following relative V̇O2max values (mean:95% confidence intervals) for men/women were observed (mL · min–1 · kg–1): 84:87-81/72:77-68 for cross-country distance skiing, 78:81-75/68:73-64 for cross-country sprint skiing, 81:84-78/67:73-61 for biathlon, and 77:80-75 for Nordic combined (men only). Similar benchmarks for absolute V̇O2max (L/min) in male/female athletes are 6.4:6.1-6.7/4.3:4.1-4.5 for cross-country distance skiers, 6.3:5.8-6.8/4.0:3.7-4.3 for cross-country sprint skiers, 6.2:5.7-6.4/4.0:3.7-4.3 for biathletes, and 5.3:5.0-5.5 for Nordic combined (men only). The difference in relative V̇O2max between medalists and nonmedalists was large for Nordic combined, moderate for cross-country distance and biathlon, and small/trivial for the other disciplines. Corresponding differences in absolute V̇O2max were small/trivial for all disciplines. Male cross-country medalists achieve 15% higher relative V̇O2max than corresponding women.
This study provides updated benchmark V̇O2max values for Olympic-medal-level performance in winter endurance disciplines and can serve as a guideline of the requirements for future elite athletes.
Jennifer Rogers, Robert W. Summers and G. Patrick Lambert
The purpose of this study was to determine if lowering carbohydrate (CHO) concentration in a sport drink influences gastric emptying, intestinal absorption, or performance during cycle ergometry (85 min, 60% VO2peak). Five subjects (25 ± 1 y, 61.5 ± 2.1 mL · kg−1 · min−1 VO2peak) ingested a 3% CHO, 6% CHO, or a water placebo (WP) beverage during exercise. Gastric emptying was determined by repeated double sampling and intestinal absorption by segmental perfusion. Total solute absorption and plasma glucose was greater for 6% CHO; however, neither gastric emptying, intestinal water absorption, or 3-mi time trial performance (7:58 ± 0:33 min, 8:13 ± 0:25 min, and 8:25 ± 0:29 min, respectively, for 6% CHO, 3% CHO, and WP) differed among solutions. These results indicate lowering the CHO concentration of a sport drink from 6% CHO does not enhance gastric emptying, intestinal water absorption, or time trial performance, but reduces CHO and total solute absorption.
Neil M. Johannsen and Rick L. Sharp
The purpose of this study was to investigate differences in substrate oxidation between dextrose (DEX) and unmodified (UAMS) and acid/alcohol-modified (MAMS) cornstarches. Seven endurance-trained men (VO2peak = 59.1 ± 5.4 mL·kg−1·min−1) participated in 2 h of exercise (66.4% ± 3.3% VO2peak) 30 min after ingesting 1 g/kg body weight of the experimental carbohydrate or placebo (PLA). Plasma glucose and insulin were elevated after DEX (P < 0.05) compared with UAMS, MAMS, and PLA. Although MAMS and DEX raised carbohydrate oxidation rate through 90 min of exercise, only MAMS persisted throughout 120 min (P < 0.05 compared with all trials). Exogenous-carbohydrate oxidation rate was higher in DEX than in MAMS and UAMS until 90 min of exercise. Acid/alcohol modification resulted in augmented carbohydrate oxidation with a small, sustained increase in exogenous-carbohydrate oxidation rate. MAMS appears to be metabolizable and available for oxidation during exercise.
Brooke R. Stephens, Andrew S. Cole and Anthony D. Mahon
This study examined substrate use during exercise in early-pubertal (EP), mid-pubertal (MP), late-pubertal (LP), and young-adult (YA) males. Fuel use was calculated using the RER and VO2 response during cycling exercise at 30 to 70% of VO2peak. Significant group by intensity interactions were found for lactate, RER, percent CHO, and fat use, in addition to fat and CHO oxidation rates, which suggest a maturation effect on substrate use during exercise. While significance was not achieved at all intensities, post hoc analyses revealed greater fat use, lower CHO use, and lower lactate concentrations in EP and MP compared to LP or YA. No differences were noted between EP and MP or LP and YA at any intensity, suggesting the development of an adult-like metabolic profile occurs between mid- to late-puberty and is complete by the end of puberty.