Eric C. Freese

Effects of acute sprint interval cycling and energy replacement on postprandial lipemia

High postprandial blood triglyceride (TG) levels increase cardiovascular disease risk. Exercise interventions may be effective in reducing postprandial blood TG. The purpose of this study was to determine the effects of sprint interval cycling (SIC), with and without replacement of the energy deficit, on postprandial lipemia. In a repeated-measures crossover design, six men and six women participated in three trials, each taking place over 2 days. On the evening of the first day of each trial, the participants either did SIC without replacing the energy deficit (Ex-Def), did SIC and replaced the energy deficit (Ex-Bal), or did not exercise (control). SIC was performed on a cycle ergometer and involved four 30-s all-out sprints with 4-min active recovery. In the morning of day 2, responses to a high-fat meal were measured. Venous blood samples were collected in the fasted state and at 0, 30, 60, 120, and 180 min postprandial. There was a trend toward a reduction with treatment in fasting TG (P = 0.068), but no significant treatment effect for fasting insulin, glucose, nonesterified fatty acids, or betahydroxybutryrate (P > 0.05). The postprandial area under the curve (mmol·l(-1)·3 h(-1)) TG response was significantly lower in Ex-Def (21%, P = 0.006) and Ex-Bal (10%, P = 0.044) than in control, and significantly lower in Ex-Def (12%, P = 0.032) than in Ex-Bal. There was no treatment effect (P > 0.05) observed for area under the curve responses of insulin, glucose, nonesterified fatty acids, or betahydroxybutryrate. SIC reduces postprandial lipemia, but the energy deficit alone does not fully explain the decrease observed.

Effect of prior exercise on postprandial lipemia: an updated quantitative review

Reducing postprandial triglycerides (TG) can lower the risk for cardiovascular disease. The purpose of this study was to perform a meta-analytic review of the literature to estimate the effect of prior exercise on postprandial lipemia. A total of 121 effects were found from 76 studies for the total TG response and 70 effects from 44 studies for the incremental area under the curve (iAUC) TG response. The weighted mean effect was moderate for the total TG response, Cohens d = -0.60 (P < 0.0001), and for the iAUC response, Cohens d = -0.59 (P < 0.0001). Moderator analysis revealed women exhibited a larger reduction (P < .01) in the total TG response following exercise (d = -0.96) than men (d = -0.57); high-intensity interval training induced a larger reduction (P < .05) in the iAUC response (d = -1.49) than aerobic (d = -0.58) or resistance (d = -0.13) exercise, and participants maintaining an energy deficit following exercise exhibited a greater reduction in the iAUC response (d = -0.67) compared with participants in energy balance (d = -0.28). We conclude that prior acute exercise reduces postprandial lipemia, with the magnitude of effect influenced by sex, type of exercise, and energy deficit following exercise.

Effects of six weeks of quercetin supplementation on physical performance in ROTC cadets.

ABSTRACTObjective: To investigate the effects of 6 weeks of quercetin supplementation on physical performance during military physical training. Methods: Using a randomized, double-blind, repeated-measures, placebo-controlled design, 58 healthy, moderately trained men and women were randomly assigned to quercetin (Q) or placebo (P) groups. Peak oxygen uptake (VO2peak) during maximal effort uphill treadmill running and four physical performance measures (Army Physical Fitness Test, [APFT], Baumgartner Modified Pull-Up Test [BMPU], Wingate Anaerobic Test [WanT], and a 36.6-m sprint) were evaluated before and after 42–54 days of supplementation with 1 g/d of quercetin with vitamins and other substances in a soft chew or placebo chew. Results: Pretreatment-to-posttreatment changes in VO2peak and physical performance were not significantly different (p > 0.05) in Q and P. Conclusions: Six weeks of dietary quercetin supplementation in moderately trained individuals conducting military physical training did not ...ABSTRACTObjective: To investigate the effects of 6 weeks of quercetin supplementation on physical performance during military physical training. Methods: Using a randomized, double-blind, repeated-measures, placebo-controlled design, 58 healthy, moderately trained men and women were randomly assigned to quercetin (Q) or placebo (P) groups. Peak oxygen uptake (VO2peak) during maximal effort uphill treadmill running and four physical performance measures (Army Physical Fitness Test, [APFT], Baumgartner Modified Pull-Up Test [BMPU], Wingate Anaerobic Test [WanT], and a 36.6-m sprint) were evaluated before and after 42–54 days of supplementation with 1 g/d of quercetin with vitamins and other substances in a soft chew or placebo chew. Results: Pretreatment-to-posttreatment changes in VO2peak and physical performance were not significantly different (p > 0.05) in Q and P. Conclusions: Six weeks of dietary quercetin supplementation in moderately trained individuals conducting military physical training did not ...

Physiological responses to an acute bout of sprint interval cycling.

Abstract Freese, EC, Gist, NH, and Cureton, KJ. Physiological responses to an acute bout of sprint interval cycling. J Strength Cond Res 27(10): 2768–2773, 2013—Sprint interval training has been shown to improve skeletal muscle oxidative capacity, V[Combining Dot Above]O2max, and health outcomes. However, the acute physiological responses to 4–7 maximal effort intervals have not been determined. To determine the V[Combining Dot Above]O2, cardiorespiratory responses, and energy expenditure during an acute bout of sprint interval cycling (SIC), health, college-aged subjects, 6 men and 6 women, completed 2 SIC sessions with at least 7 days between trials. Sprint interval cycling was performed on a cycle ergometer and involved a 5-minute warm-up followed by four 30-second all-out sprints with 4-minute active recovery. Peak oxygen uptake (ml·kg−1·min−1) during the 4 sprints were 35.3 ± 8.2, 38.8 ± 10.1, 38.8 ± 10.6, and 36.8 ± 9.3, and peak heart rate (b·min−1) were 164 ± 17, 172 ± 10, 177 ± 12, and 175 ± 22. We conclude that an acute bout of SIC elicits submaximal V[Combining Dot Above]O2 and cardiorespiratory responses during each interval that are above 80% of estimated maximal values. Although the duration of exercise in SIC is very short, the high level of V[Combining Dot Above]O2 and cardiorespiratory responses are sufficient to potentially elicit adaptations to training associated with elevated aerobic energy demand.

COMPARISON OF RESPONSES TO TWO HIGH-INTENSITY INTERMITTENT EXERCISE PROTOCOLS

Abstract Gist, NH, Freese, EC, and Cureton, KJ. Comparison of responses to two high-intensity intermittent exercise protocols. J Strength Cond Res 28(11): 3033–3040, 2014—The purpose of this study was to compare peak cardiorespiratory, metabolic, and perceptual responses to acute bouts of sprint interval cycling (SIC) and a high-intensity intermittent calisthenics (HIC) protocol consisting of modified “burpees.” Eleven (8 men and 3 women) moderately trained, college-aged participants (age = 21.9 ± 2.1, body mass index = 24.8 ± 1.9, V[Combining Dot Above]O2peak = 54.1 ± 5.4 ml·kg−1·min−1) completed 4 testing sessions across 9 days with each session separated by 48–72 hours. Using a protocol of 4 repeated bouts of 30-second “all-out” efforts interspersed with 4-minute active recovery periods, responses to SIC and HIC were classified relative to peak values. Mean values for %V[Combining Dot Above]O2peak and %HRpeak for SIC (80.4 ± 5.3% and 86.8 ± 3.9%) and HIC (77.6 ± 6.9% and 84.6 ± 5.3%) were not significantly different (p > 0.05). Effect sizes (95% confidence interval) calculated for mean differences were: %V[Combining Dot Above]O2peak Cohens d = 0.51 (0.48–0.53) and %HRpeak Cohens d = 0.57 (0.55–0.59). A low-volume, high-intensity bout of repeated whole-body calisthenic exercise induced cardiovascular responses that were not significantly different but were ∼1/2SD lower than “all-out” SIC. These results suggest that in addition to the benefit of reduced time commitment, a high-intensity interval protocol of calisthenics elicits vigorous cardiorespiratory and perceptual responses and may confer physiological adaptations and performance improvements similar to those reported for SIC. The potential efficacy of this alternative interval training method provides support for its application by athletes, coaches, and strength and conditioning professionals.

Acute and chronic effects of sprint interval exercise on postprandial lipemia in women at-risk for the metabolic syndrome

Individuals diagnosed with the metabolic syndrome (MetS) exhibit elevated postprandial lipemia (PPL). The aims of this investigation were to determine 1) if an acute bout of sprint interval training (SIT) attenuates PPL; and 2) if the attenuation of PPL following 6 wk of SIT is magnified compared with a single session of SIT prior to training in women at-risk for MetS (n = 45; 30-65 yr). Women were randomized to SIT (n = 22) or a nonexercise control (n = 23; CON) for 6 wk. Postprandial responses to a high-fat meal challenge (HFMC) were assessed in the CON group before (B-HFMC) and after (Post-HFMC) without prior exercise and in the SIT group at baseline (B-HFMC) without prior exercise, after an acute bout of SIT (four 30-s all-out sprints with 4-min recovery) prior to (Pre-HFMC), and after the 6-wk intervention (Post-HFMC). Responses to the HFMC were assessed by collecting venous blood samples in the fasted state and at 0, 30, 60, 120, and 180 min postprandial. Compared with baseline, an acute bout of SIT before (Pre-HFMC) and after the 6-wk intervention (Post-HFMC) significantly attenuated fasted TG (P < 0.05; 16.6% and 12.3%, respectively) and postprandial area under the curve (13.1% and 9.7%, respectively; tAUC) TG responses. There was no difference in fasted or tAUC TG responses between Pre-HFMC and Post-HFMC. SIT is an effective mode of exercise to reduce fasted and postprandial TG concentrations in women at-risk for MetS. Six weeks of SIT does not magnify the attenuation of PPL in response to a single session of SIT.

Effect of Six Weeks of Sprint Interval Training on Mood and Perceived Health in Women at Risk for Metabolic Syndrome

The purpose of this investigation was to determine whether 6 weeks of sprint interval training (SIT) is associated with changes in mood and perceived health in women at risk for developing metabolic syndrome (MetS). Physically inactive women (30-65 years) were randomized to 6 weeks of nutrition meetings and SIT (n = 23; 3 bouts/week of 4-8 30-s cycle sprints with 4-min recovery) or a nonexercise control condition (CON; n = 24). Before and after the 6-week intervention, perceived health status and mood were assessed. Clinically relevant increases in role-physical scores (ES = 0.64) and vitality (ES = 0.52) were found after 6 weeks of SIT compared with a nonexercise control group. For middle-aged women at risk for MetS, it is concluded that high-intensity, low-volume SIT (1) increases feelings of vitality and perceptions of having fewer physical limitations and (2) does not induce mood disturbances as occurs with high-volume, high-intensity training.

Effects of Sprint Interval Cycling on Fatigue, Energy, and Cerebral Oxygenation

INTRODUCTION Feelings of fatigue are reduced after a session of continuous exercise of low-to-moderate intensity lasting 20 min or more, but only when feelings of energy are increased. Feelings of fatigue and energy have not been described after fatiguing, high-intensity interval exercise. Cerebral oxygenation has been implicated as a central correlate of fatigability, but it has not been studied concurrent with perceived fatigue during or after exercise. METHODS Fifteen recreationally active participants (8 women, 7 men) completed bouts of sprint interval cycling (four, 30-s all-out sprints each followed by 4 min of active recovery) and a time- and work-matched bout of constant resistance cycling. Oxygenation (oxygenated hemoglobin [HbO2]) and deoxygenation (deoxygenated hemoglobin [HHb]) in the dorsolateral prefrontal cortex were measured using near-infrared spectroscopy. Fatigue ratings during each sprint and feelings of fatigue and energy during recovery were assessed. RESULTS Increases in HbO2 and HHb in frontal cortex were greater during sprint cycling than during constant resistance cycling (P = 0.001). Fatigability (decreased power output) increased over successive sprints (P = 0.001). About 95% of the increase in fatigue ratings across sprints (P < 0.001) was accounted for by fatigability and cortical HbO2. Feelings of fatigue were decreased (P < 0.001) and feelings of energy were increased (P < 0.05) across sprint recovery periods but were unchanged during constant resistance cycling. About 85% of the changes in feelings of fatigue or energy during recovery were explained by fatigue ratings across sprints and maximum HbO2 in the cortex during recovery. CONCLUSION Repeated, high-intensity sprints were fatiguing, but paradoxical reductions in feelings of fatigue and increases in feelings of energy occurred during recovery that were accounted for by ratings of fatigue during exercise and oxygenation in the dorsolateral prefrontal cortex during recovery.