Intensity Interval Training Research Articles

Effects of Non-Wingate-based High-intensity Interval Training on Cardiorespiratory Fitness and Aerobic-based Exercise Capacity in Sedentary Subjects: A Preliminary Study

This study examined two hypotheses: (1) a non-Wingate-based high-intensity interval training protocol of 20×30-second cycle exercise at 120% of peak aerobic power interspersed with 60-second recovery per session, 3 sessions per week for 6 weeks, can enhance cardiorespiratory fitness and aerobic-based exercise capacity; and (2) proportional-assist ventilation (PAV) can augment interval training intensity, and, in turn, enhance the adaptations to the training in sedentary and mild obese individuals. Sixteen subjects were paired up and assigned into an interval training (IT) group or IT plus PAV (IT + PAV) group. During the 6-week interval training program, the increase in training intensity was not different between the IT and IT + PAV groups (p > 0.05). Nevertheless, significant improvements were found in the peak work rate and peak O2 during the post-training incremental cycling test in both groups. Moreover, the limit of tolerance during the post-training constant-load cycling test (70% of pre-training peak aerobic power) was enhanced, while blood lactate accumulation, heart rate, ratings of breathing discomfort, and perceived exertion at the iso-time point of the pre-training test at exhaustion were reduced (p 0.05). In conclusion, the 6-week non-Wingate-based high-intensity interval training protocol was preliminarily found to enhance cardiorespiratory fitness and aerobic-based exercise capacity in sedentary and mild obese subjects. The provision of PAV during the interval training did not augment training intensity and subsequent aerobic adaptations.

Adaptations to aerobic interval training: interactive effects of exercise intensity and total work duration

To compare the effects of three 7-week interval training programs varying in work period duration but matched for effort in trained recreational cyclists. Thirty-five cyclists (29 male, 6 female, VO(2peak) 52 ± 6 mL kg/min) were randomized to four training groups with equivalent training the previous 2 months (∼6 h/wk, ∼1.5 int. session/wk). Low only (n=8) trained 4-6 sessions/wk at a low-intensity. Three groups (n=9 each) trained 2 sessions/wk × 7 wk: 4 × 4 min, 4 × 8 min, or 4 × 16 min, plus 2-3 weekly low-intensity bouts. Interval sessions were prescribed at the maximal tolerable intensity. Interval training was performed at 88 ± 2, 90 ± 2, and 94 ± 2% of HR(peak) and 4.9, 9.6, and 13.2 mmol/L blood lactate in 4 × 16, 4 × 8, and 4 × 4 min groups, respectively (both P<0.001). 4 × 8 min training induced greater overall gains in VO(2) peak, power@VO(2) peak, and power@4 mM bLa- (Mean ± 95%CI): 11.4 (8.0-14.9), vs 4.2 (0.4-8.0), 5.6 (2.1-9.1), and 5.5% (2.0-9.0) in Low, 4 × 16, and 4 × 4 min groups, respectively (P<0.02 for 4 × 8 min vs all other groups). Interval training intensity and accumulated duration interact to influence the adaptive response. Accumulating 32 min of work at 90% HR max induces greater adaptive gains than accumulating 16 min of work at ∼95% HR max despite lower RPE.

Enhancing recovery from peripheral nerve injury using treadmill training

Full functional recovery after traumatic peripheral nerve injury is rare. We postulate three reasons for the poor functional outcome measures observed. Axon regeneration is slow and not all axons participate. Significant misdirection of regenerating axons to reinnervate inappropriate targets occurs. Seemingly permanent changes in neural circuitry in the central nervous system are found to accompany axotomy of peripheral axons. Exercise in the form of modest daily treadmill training impacts all three of these areas. Compared to untrained controls, regenerating axons elongate considerably farther in treadmill trained animals and do so via an autocrine/paracrine neurotrophin signaling pathway. This enhancement of axon regeneration takes place without an increase in the amount of misdirection of regenerating axons found without training. The enhancement also occurs in a sex-dependent manner. Slow continuous training is effective only in males, while more intense interval training is effective only in females. In treadmill trained, but not untrained mice the extent of coverage of axotomized motoneurons is maintained, thus preserving important elements of the spinal circuitry.

The Effect of Intense Interval Cycle-training on Unloading-Induced Dysfunction and Atrophy in the Human Calf Muscle

We investigated whether intense interval training on a cycle ergometer would prevent loss of muscle strength and atrophy in the human calf during unilateral lower limb suspension (ULLS). The present study involved 11 healthy men. We defined unloading leg and contralateral leg as ULLS-leg and CONT-leg, respectively. The subjects were divided into 2 groups: one with single-leg cycling training (Tr-UL, n=6); the other as a control (UL, n=5). The Tr-UL group performed an intense 25-min interval cycling training up to 80% of peak oxygen uptake on alternate days during 20-d ULLS. It was found that: 1) in maximal voluntary contraction (MVC) and the cross-sectional area of the planter flexor, there was a significant time- (pre-ULLS and post-ULLS) by-leg (ULLS-leg and CONT-leg) interaction; 2) in voluntary activation during MVC evaluated by the twitch interpolation technique, no significant time-by-leg interaction was detected but the trend of change from before to after ULLS tended to be different between ULLS-leg and CONT-leg; and 3) regarding ULLS-leg, the change in any parameters was not significantly different between the Tr-UL and UL groups. These results suggest that unloading induces dysfunction and atrophy in the human calf and that high-intensity interval training on a cycle ergometer cannot significantly prevent unloading-induced deconditioning in the human calf.

Effects of an Acute Sensorimotor and Neurological Training Intervention on Knee Flexor Performance in Females

Sensorimotor failure of the dynamic stabilizers is implicated in anterior cruciate ligament (ACL) injury of the knee. The dose of training required to elicit a biologically meaningful improvement in sensorimotor performance (SMP) is unknown. Novel dynamic SMP assessment tasks have not been previously used to assess the effects of training. PURPOSE: To assess the effects of an intensive functional training intervention on dynamic SMP and neuromuscular performance (NMP) of the knee flexors in females. METHODS: Twelve females (22 ±1.8 yrs) were randomly assigned to a control (CON) [n=5] or experimental (EXP) [n=7] group. The EXP group trained their non-preferred limb (NPL) using six exercises for six sessions a week over two weeks. SMP (constant error (CE) arising from a 'slow' and 'fast' force reproduction task of 50% peak force (PF)) and NMP (PF) were assessed pre and post intervention using a single leg intervention (NPL) contra-lateral control model. The NPL was also assessed pre and post intervention following a single bout of induced fatigue (EXP/CON). Time by limb by group comparisons were made using separate three-way mixed model ANOVA's for PF and CE (expressed as a % of the target force). Three-way mixed model ANOVAs, with repeated measures on time and occasion with group as a between subjects factor were used to evaluate the effects of the intervention on PF and CE during fatigue (NPL only). RESULTS: No significant changes were seen for PF or CE in the CON group across time (p>0.05). In the EXP group, PF was not significantly altered in the NPL from pre to post intervention at rest (196.6 ±43.0 vs. 224.4 ± 74.1 N, p>0.05) or following fatigue (185.9± 39.0 vs. 201.2 ± 67.8 N, p>0.05). CE was not significantly altered in the NPL (EXP group) from pre to post intervention at rest for the slow task (-4.1± 23.6 vs. 2.0 ± 22.2, p>0.05) or the fast task (-9.4 ± 19.1 vs. -5.8 ± 14.2, p>0.05) and was not significantly altered in the NPL from pre to post intervention during fatigue for the slow task (2.0 ± 22.2 vs. 13.3 ± 21.3, p>0.05) or the fast task (-5.8 ± 14.2 vs. -13± 18.5, p>0.05). CONCLUSIONS: No significant alteration to SMP or NMP of the knee flexors was seen at rest or during fatigue following a two-week intensive training intervention in the NPL of females. A greater dose of training may be needed to enhance dynamic stabilization of the knee flexors.

The Effects Of Four Weeks Of High-Intensity Interval Training And Creatine Supplementation On Critical Power And Anaerobic Working Capacity In College-Aged Men

The critical power test provides two measures, critical power (CP) and anaerobic working capacity (AWC). In theory, the CP measurement represents the maximal power output that can be maintained without fatigue, which is regarded as an aerobic measure. AWC is an estimate of work capacity associated with muscle energy reserves adenosine triphosphate (ATP) and phosphocreatine (PCr). High- intensity interval training (HIIT) has been shown to be an effective training method for improving endurance performance, including CP and AWC measures. In addition, creatine (Cr) supplementation has been reported to improve AWC without training; however, Cr had no effect on CP. To date, no one has examined the effect of Cr supplementation during HIIT on CP and AWC. The purpose of this study was to examine the effects of four weeks of HIIT in conjunction with Cr supplementation on CP and AWC in college-aged men. Forty-two recreationally active men (mean ± SD; age 23.62 ± 4.78 yrs; height: 177.48 ± 7.05 cm; weight: 82.23 ± 12.70kg) volunteered to participate in this study. Participants were assigned to one of three groups: Cr (n = 16) 10g Cr + 10g dextrose powder blend; placebo (PL, n = 16) 20g dextrose powder blend; control (CON, n = 10) no treatment. Prior to and following supplementation, each participant performed a continuous maximal oxygen consumption test (o2PEAK) on a cycle ergometer to establish peak power output (PPO). Participants then completed a CP test, consisting of three exercise bouts to exhaustion with the workloads set as a percentage of their PPO to determine CP and AWC. Following initial testing, a 2-week familiarization period of training and supplementing occurred. Baseline values were then measured and all participants in the Cr and PL groups engaged in 4 weeks of HIIT training on a cycle ergometer. Training consisted of either five or six sets of 2-minutes work with 1-minute passive rest, five days per week. Training intensity followed an undulating model starting at 80% PPO and reaching 120%. Significant two-way interactions [time (base- vs. post-) × treatment (Cr vs. PL vs. CON)] were discovered for CP (p = 0.007). Follow-up analyses indicated that the Cr group increased 6.72% ± 2.54%, while PL and CON showed no significant change in CP (3.87% ± 2.30% and -6.27% ± 2.38%, respectively). Furthermore, no changes in AWC were observed in any of the groups following treatment. The current findings suggest that the HIIT and supplementation protocol may be an effective method for improving CP, but had no effect on AWC. It would appear that Cr supplementation may enhance the effect of intense interval endurance training on aerobic performance changes as measure by the CP test. ACKNOWLEGMENTS: This investigation was supported by FSI Nutrition, Omaha, Nebraska.

The effects of low-fat skim chocolate milk on urinary hydration indices in a sample of Division 1-AA cross country runners during off-season training sessions

Methods Urine samples were collected from nine cross country runners twice a week (on the intense interval training days each week) for six weeks pre and post practice sessions. Each week participants consumed one of the three rehydration drinks. Participants served as their own control and drink choice was randomized in a cross over design across the three drinks. Urine was tested at four different times on each of the experimental days; (1) before practice (PRE), (2) immediately after practice (IPE), (3) 60 minutes after practice (RECV), (4) and a midnight sample (PST). Four urine indexes were examined on each of the experimental days to assess the difference in hydration status using the three experimental drinks: 1) Urine osmolality1 (Uosm), 2) specific gravity2 (Usg), 3) volume of urine output3 (Uo), and 4) urine color4 (Ucol).

Effects Of Intensive Interval And Resistance Training On Muscle Size And Function During Unloading

We reported that intensive interval training during 20 days of unloading prevented atrophy of the quadriceps femoris (QF) muscles. However, this training was not effective to attenuate a decrease of maximum muscle strength. PURPOSE: The purpose of this study was to clarify the effects of intensive interval and resistance training on size and function of human skeletal muscle during 20 days of unilateral lower limb unloading. METHODS: Twelve healthy men participated in this study and were divided into two groups: unloading with training (Tr group, n = 6) and unloading only (UL group, n = 6). Both groups underwent lower limb unloading of the left leg for 20 days. Exercise training consisted of an interval exercise protocol of 2- to 3-min intervals alternating between 40% and 80% of peak oxygen uptake and a dynamic leg press protocol of 4 sets of 10 repetitions with 70% one-repetition maximum (1RM) with the unloaded leg on every other days during the experimental period. Maximum voluntary contraction (MVC) during isometric knee extension and 1RM during dynamic leg press was measured. Anatomical magnetic resonance imaging (MRI) of the thighs was taken to calculate volume of the QF muscles. Muscle functional MRI (spin-echo, TR/TE 2000/30, 60 msec) of the QF muscles was obtained during submaximal dynamic knee extension exercise (5 sets of 10 repetitions) at a load of 33%MVC. RESULTS: MVC in the Tr (532 ± 178 N to 453 ± 132 N; -14%, P < 0.05) and UL (495 ± 167 N to 394 ± 114 N; -19%, P < 0.05) groups significantly decreased after unloading. 1 RM during leg press for the Tr group significantly increased (138 ± 33 kg to 152 ± 39 kg; 10%, P < 0.05); while in the UL group significant decreased (141 ± 38 kg to 115 ± 32 kg; -18%, P < 0.05). The volume of the QF muscles in the unloading leg in the Tr group did not change after unloading (2472 ± 279 cm3 to 2470 ± 253 cm3, 0%, N.S.); while, that in the UL group significantly decreased (2252 ± 450 cm3 to 2111 ± 452 cm3, -6%, P < 0.05). There was no significant difference in muscle functional MRI between Tr group and UL groups. CONCLUSIONS: These results suggest that intensive interval and resistance training during 20 days of unloading was effective for prevention of muscle strength and atrophy. Supported by Grants-in-Aid for Scientific Research from the Minister of Education, Culture, Sports, Science and Technology, Grant #17300207.

EXERCÍCIO FÍSICO E REGULAÇÃO DO LACTATO: PAPEL DOS TRANSPORTADORES DE MONOCARBOXILATO (PROTEÍNAS MCT)

Studies demonstrate the existance of de 14 monocarboxylate transporters isoforms (MCTs), proteins of membrane which transport lactate and H+. In contrast, informations concerning the specific function of these several transporters are not specific. On the other hand, others are already well defined. So, the objective of this review was to clarify the effects of exercise on lactate transport and regulation by MCTs. MCT1 and MCT4 are found in muscle, suggesting, thus, distinct functions in the same tissue due to differences of lactate transport and, therefore, may respond differently to modifications in exercise intensities. In addition, its known that endurance training can increase MCT1 muscle content as well as the intense interval training may induce increase in MCT1 and MCT4. These alterations in MCTs contribute to pH control and improve of oxidative capacity.

Cortical Reorganization Following Bimanual Training and Somatosensory Stimulation in Cervical Spinal Cord Injury: A Case Report

Deficits in upper-extremity function in individuals with tetraplegia are primarily due to the loss of motor pathways. Detrimental cortical reorganization, however, may create further loss of function. The purpose of this case report is to describe the cortical changes associated with a combination intervention using bimanual massed practice training with somatosensory stimulation. "BR" was a 22-year-old man with C6 tetraplegia and hand impairment who participated in this training intervention for 3 weeks. BR demonstrated improvements in sensory function, strength (the force-generating capacity of muscle), and performance of functional hand skills. Following the training, the cortical motor map of the biceps brachii muscle shifted anteriorly and increased in area and volume. This is the first documented case in which changes in the size and location of the cortical map were associated with an intervention and improvement in function in an individual with tetraplegia. This case suggests that an intensive training intervention may induce both functional and neurophysiological changes.

Training and testing physical capacities for elite soccer players

Elite soccer players spend a substantial amount of time trying to improve physical capacities, including aerobic endurance and strength and the strength derivatives of speed and power. The average oxygen uptake for international soccer teams ranges from 55 to 68 ml · kg−1 · min−1 and the half-squat maximal strength from 120 to 180 kg. These values are similar to those found in other team sports. Recently, it has been shown that the heart's stroke volume is the element in the oxygen chain that mainly limits aerobic endurance for athletes. These findings have given rise to more intensive training interventions to secure high stroke volumes, which, in turn, have proved positive in changing both maximal oxygen consumption and soccer performance in terms of distance covered, contacts with the ball and number of sprints in a game. The training employed has consisted of 4 × 4-min “intervals” running uphill at 90 – 95% of maximal heart rate interspersed with 3 min jogging at 70% of maximal heart rate to facilitate removal of lactate. Research has revealed that a soccer-specific training routine with the ball might be as effective as plain running. Strength training to produce neural adaptations has been effective in changing not only strength in terms of “one-repetition maximum”, but also sprinting velocity and jumping height, in elite soccer players without any change in body mass. The same training has also improved running economy and thus aerobic endurance performance. The training regimen used for a European Champions League team was 4 × 4 repetitions of half-squats with the emphasis on maximal mobilization of force in the concentric action.

EFFECT OF F1O2 ON PHYSIOLOGICAL RESPONSES AND POWER OUTPUT IN TRAINED CYCLISTS AT MODERATE ALTITUDE.

PURPOSE: To evaluate the effect of different concentrations of inspired oxygen (F1O2) on physiological responses and power output in trained endurance athletes at altitude. METHODS: Subjects (n = 19) were trained male cyclists and triathletes (30 ± 7 yr; 177 ± 5 cm; 69.8 ± 9.8 kg; 9.1 ± 3.2 BF%; VO2max = 4.09 ± 0.52 L min−1, 58.7 ± 3.8 ml kg−1 min−1) who were residents of moderate altitude (1600–1700 m). Testing was conducted at 1860 m where subjects completed three trials in which they performed a standardized interval workout while inspiring a medical grade gas comprised of 21.0% (control), 26.5% or 60.0% O2. The interval workout consisted of 6 x 100 kJ performed on a cycle ergometer (Lode Excalibur™) at a self-selected load and pedaling cadence. Experimental trials were conducted at 7-day intervals in a randomized order and subjects were blinded to F1O2%. An average of the six work intervals was calculated, and a univariate repeated measures ANOVA was used to evaluate mean differences between trials. RESULTS: Major results are reported below as the mean ± SD. CONCLUSION: These data suggest that supplemental O2 (26.5% and/or 60.0% F1O2) produces significant improvements in Hb-O2 saturation and power output during intense interval training at moderate altitude, thereby allowing athletes to “live high-train low”. Supported by the United States Olympic CommitteeTable: No Caption Available

Effect of an increase in volume and intensity of training in elite, female master (>40 yr) cyclists

The purpose of this study was to examine maximal oxygen uptake (VO2 max), lactate threshold (LT), and 13.5 km bicycle time trial performance in elite, female master (>40 yr) cyclists during the course of a 6 month training season. Five elite, female cyclists (mean age = 47 yr), and five age‐matched recreational cyclists served as subjects for the study. VO2 max, LT, and 13.5 km bicycle time were measured at the end of the off‐season (December) and again following 6 months of intensified training. During the off‐season, the master cyclists averaged 160 km a week of moderate (HR < 140 bpm) intensity, steady state exercise. During the 6 month organized training season, both the duration and frequency of training increased, and each cyclist participated in a weekly, one‐hour session of high intensity (HR > 160 bpm) interval training. The results showed that the 13.5 km bicycle time significantly decreased (p < 0.05) from a mean of 1406 sec to 1316 sec in the master cyclists during the course of the competitive training season. Mean VO2 max significantly increased from 51 ml·min−1·kg−1 to 55 ml • min−1 • kg−1 as did LT (150 W to 185 W) following the training period. The same physiological variables were not significantly altered in the recreational cyclists during the course of the study. These results suggest that an improved bicycle time trial performance in elite, female master cyclists following an increase in volume and intensity of training coincides with an improvement in both VO2 max and LT. A dissociation between the relative improvement in LT and VO2 max (23% vs 8%, respectively) after training suggests that a different mechanism is responsible for the respective adaptations.

Monitoring exercise stress by changes in metabolic and hormonal responses over a 24-h period

Metabolic and endocrine responses of 14 subjects of varying levels of fitness to an intensive anaerobic interval training session were assessed before exercise and at 2 h, 4 h, 8 h and 24 h postexercise. The endocrine response of the same subjects to a control day, where they were required not to exercise, was also assessed and compared with the values obtained on the interval training day. Uric acid, urea, and creatine phosphokinase concentrations still remained elevated above pre-exercise values 24 h postexercise. Lactate, creatinine, testosterone and cortisol concentrations were significantly elevated above pre-exercise values immediately postexercise but these had reversed by 2 h postexercise. Over the remainder of the recovery period testosterone concentrations remained significantly lower than values measured at similar times on the control day. This was shown to be due directly to a change in testosterone as sex hormone binding globulin concentration remained constant throughout the recovery period. The data indicate that when comparisons of data were made to control (rest) days, imbalances in homeostasis, due to intensive training, are not totally reversed within the next 24-h. The data also demonstrate that the parameters measured undergo the same variations in subjects with a wide range of physical fitness, indicating that these parameters could be used to monitor exercise stress and recovery in athletes of a wide range of abilities.(ABSTRACT TRUNCATED AT 250 WORDS)