Inactivity, PhysicalNCT07328568
Effect of Low Volume Sprint Interval Training on Cardiorespiratory Fitness
A study testing High intensity interval training in people with Inactivity, Physical and Overweight (BMI > 25), run by California State University, San Marcos at 1 site in United States.
Trial summary
Low levels of physical activity (PA) are related to poor health and greater risk of premature death in adults. Lack of time is cited as a primary barrier to partaking in PA. In the last 20 years, a lot of attention has been directed towards the efficacy of high intensity interval training (HIIT), which consists of… Read more about this study
- Who is it for?
- Ages 18 to 55 years
- Conditions the study is for
- Inactivity, Physical, Overweight (BMI > 25), Healthy Participants
- What is being tested?
- High intensity interval training
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 60 participants
- Where
- 1 siteUnited States
- Study dates
- 5 Nov 2025to 1 Sep 2028
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 55 years
- All sexes
- No healthy volunteers
- Adult
Who may be able to join
- Healthy
- BMI < 35 kg/m2
- younger than 56 yr old
- no joint issues
Who cannot join
- Those adults who are currently active and not weight stable
- Adults with BMI > 35 kg/m2
- Use of medications which may alter study outcomes
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
California State University--San Marcos Human Performance Laboratory
San Marcos, California, 92096
Todd A Astorino, Ph.D, astorino@csusm.edu
Todd Anthony Astorino, Ph.D
About this study
Official title: The Effect of Low Volume Sprint Interval Training on Cardiorespiratory Fitness--a Randomized Controlled Trial
Low levels of physical activity (PA) are related to poor health and greater risk of premature death in adults. Lack of time is cited as a primary barrier to partaking in PA. In the last 20 years, a lot of attention has been directed towards the efficacy of high intensity interval training (HIIT), which consists of brief, intense bursts of PA separated by recovery. One primary benefit of HIIT is a sizable increase in cardiorespiratory fitness (CRF), which enables adults to exercise better and reduce health risks due to the strong link between health status and CRF.
Completion of cardiovascular exercise is typically recommended for all adults to increase CRF, yet it takes a lot of time and may be perceived as boring. Alternatively, HIIT requires less time and tends to cause greater feelings of enjoyment in many adults. Hundreds of studies report an increase in CRF in response to HIIT in various groups of adults ranging from athletes and those with obesity, diabetes, cancer, stroke, and even spinal cord injury, which emphasizes the potency of this vigorous form of PA. Yet, many studies are weakened by a small sample size which questions the feasibility of these findings.
Read more
This randomized controlled trial will test the efficacy and feasibility of a very small amount of HIIT, referred to as reduced exertion high intensity interval training (REHIT), in inactive adults. In the proposed study, REHIT will consist of 2 days per week of 1 to two 10 - 20 second sprints on a stationary bike. The proposed sample will include 60 adults who complete 18 sessions of REHIT over a 9 week period, and their responses will be compared to a non exercising control group. During the study, changes in CRF, fuel metabolism, and psychological responses will be monitored, with the latter outcome shedding light on the overall feasibility of HIIT in inactive adults.
Overall, this novel study has profound public health applications as it will assess fitness and health related changes to a small dose of PA in the largest sample to date. If substantial changes in CRF are shown, these data have the potential to modify public health guidelines for implementing PA in inactive adults.
Read the detailed description
Low levels of physical activity (PA) and cardiorespiratory fitness (CRF) are significant issues for societal health. Public health guidelines for adults recommend > 150 min of moderate-intensity continuous training (MICT) or 75 min of vigorous exercise per week, and strength training on > 2 days per week. However, in 2020, 75% of adult Americans did not meet these PA recommendations. Physical inactivity is the fourth leading cause of death worldwide, as it increases the risk of 40 chronic conditions. Low maximal oxygen uptake (V̇O2max; the gold standard index of CRF) is strongly associated with increased risk of future morbidity and all-cause mortality. In fact, many large-scale studies have reported V̇O2max to be a more powerful predictor of risk for future morbidity and all-cause mortality than more traditional risk factors such as smoking, hypertension, obesity, high cholesterol, and insulin resistance. For population-level health, the largest benefits from improved PA and CRF are gained by the least fit individuals, with even small increases in fitness shown to improve health. Despite exercise being the only viable means to improve V̇O2max, it remains underutilized for primary disease prevention. Nevertheless, adults do not engage in PA due to a perceived lack of time. High intensity interval training (HIIT) is a time-efficient form of PA requiring brief intense bursts of activity separated by rest periods. Empirical data show that HIIT elicits similar and in some cases superior benefits versus MICT, often with less time. A special type of HIIT is reduced exertion high intensity interval training (REHIT) requiring only two 20 second sprints within a 10 minute session. A few studies show that REHIT increases CRF and other health-related outcomes, yet these studies have been criticized due to their small sample size, which serves to question the broad application of REHIT in adults. The proposed randomized controlled trial will recruit 60 inactive adults to complete 24 sessions of REHIT and compare resultant changes in CRF, substrate metabolism, and psychological responses to a non-exercising control group. This sample size is threefold higher than used in prior work and provides adequate statistical power to detect meaningful increases in V̇O2max. The proposed study will advance further research in the area of HIIT and if successful, may promote inclusion of REHIT in PA recommendations as a feasible alternative or adjunct to moderate or vigorous-intensity exercise as promoted in current PA recommendations.
- Being tested
- High intensity interval training
- Keywords
- high intensity interval training, maximal oxygen uptake, fat metabolism, affective valence, body composition, exercise adherence
- Medical subject headings
- Sedentary Behavior, Overweight
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
High intensity interval trainingOther
Participants will complete 24 sessions of REHIT and their responses will be compared to a non exercising control group.
| Study group | Role | What they receive |
|---|---|---|
| Intervention group | Experimental | This group will perform long term REHIT. Receives: Other: High intensity interval training |
| Non exercising control group | Placebo comparator | This group will not complete REHIT, and will be given the option to complete the training once post testing is performed. Receives: Other: High intensity interval training |
What is being measured
The primary outcome is the main question the study is designed to answer.
Cardiorespiratory fitness
Cardiorespiratory fitness (CRF) is determined by oxygen transport from cardiovascular system to mitochondria and is strongly related to health status and premature mortality. It will be assessed using VO2max testing on a cycle ergometer and expressed in mL/kg/min.
Measured: CRF will be assessed at baseline 48 - 72 hours before the start of training, and at 6 and 12 weeks of training, which represent halfway and end of training. The assessments will be performed at least 24 hours after sessions of exercise training.
Secondary outcomes (5)
Fat and Carbohydrate Oxidation
Substrate metabolism represents the breakdown of fat and carbohydrate for energy expenditure and is related to metabolic health. It is measured during submaximal exercise during which time, participants' expired air is collected continuously. In this study, participants will complete 10 min of low intensity exercise before the VO2max test, and gas exchange data will be acquired to estimate the respiratory exchange ratio (RER) which is used to assess the percent contribution of fat and carbohydrate use. Moreover, fat and CHO oxidation will be calculated from standard equations and expressed in g/min.
Measured: Fat and carbohydrate oxidation will be measured at baseline before the start of training and at 6 and 12 weeks of training, representing halfway and end of training, and at baseline and at 12 weeks in the non exercising control group.
Cardiac output
Cardiac output (CO in L/min) refers to the amount of blood delivered by the heart each minute and is the product of stroke volume and HR. Its assessment can shed light on the factors explaining the increase in VO2max with exercise training. In this study, it will be measured noninvasively using thoracic impedance cardiography.
Measured: CO will be measured at baseline and at 6 and 12 weeks of training, representing halfway and the end of training, and at baseline and at 12 weeks in the non exercising control group.
Enjoyment of REHIT
The real-world feasibility and efficacy of REHIT has been challenged, as it is thought that this type of vigorous exercise is not enjoyable for adults. One measure related to this is enjoyment, which can be assessed with the 18-item Physical Activity Enjoyment scale. This validated survey is frequently used in similar studies to gauge psychological responses to exercise training. The Physical Activity Enjoyment scale will be completed 5 minutes after sessions of exercise training.
Measured: This outcome will be assessed during session #2 of each week of training in the exercise training group. So, this outcome will be assessed weekly during all 12 weeks of training.
Perceived exertion responses to REHIT
The real-world feasibility and efficacy of REHIT has been challenged, as it is thought that this type of vigorous exercise is not enjoyable for adults. One measure related to this is perceived exertion, which can be assessed with the 6 - 20 Borg scale of Rating of Perceived Exertion. This validated survey is frequently used in similar studies to gauge psychological responses to exercise training. This RPE scale will be administered throughout sessions of exercise training, including at baseline, during the warm-up, after sprint 1, midway during recovery, after sprint 2, and then at the end of the exercise session.
Measured: This outcome will be assessed during session #2 of each week of training in the exercise training group. So, this outcome will be assessed weekly during all 12 weeks of training
Pleasure responses to REHIT
The real-world feasibility and efficacy of REHIT has been challenged, as it is thought that this type of vigorous exercise is not pleasing for adults which may cause poor adherence to training. One measure related to this is pleasure:displeasure, which can be assessed with the +5 to -5 Feeling Scale, where +5 = very good, 0 = neutral, and -5 is very bad. This validated survey is frequently used in similar studies to gauge psychological responses to exercise training. This Feeling Scale will be administered throughout sessions of exercise training, including at baseline, during the warm-up, after sprint 1, midway during recovery, after sprint 2, and then at the end of the exercise session.
Measured: This outcome will be assessed during session #2 of each week of training in the exercise training group. So, this outcome will be assessed weekly during all 12 weeks of training
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted9 Jan 2026
- Study start5 Nov 2025
- Primary completion1 Jun 2028 (estimated)
- Study completion1 Sep 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for Inactivity, PhysicalStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- This is a randomized controlled trial.
- Masking
- None (open label)
- Enrolment
- 60 participants (estimated)
Sponsor and investigators
- Lead sponsor
- California State University, San Marcos
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Todd A Astorino, Ph.D, Principal investigator, California State University, San Marcos
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07328568
- Sponsor's protocol ID
- R15AG093525
- Status last verified
- Aug 2026
- First submitted
- 31 Oct 2025
- Last updated
- 24 Aug 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: All participant data will be reported in articles published related to this project.
Publications
Astorino TA, Metcalfe RS, Vollaard NBJ. The effect of low volume sprint interval training on cardiorespiratory fitness: study protocol for a definitive randomized controlled trial. Trials. 2026 Mar 23;27(1):340. doi: 10.1186/s13063-026-09647-x.
PubMed 41872855
Study at a glance
From the registry record, last updated by the sponsor on 24 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Effect of Low Volume Sprint Interval Training on Cardiorespiratory Fitness--a Randomized Controlled Trial
- ClinicalTrials.gov ID
- NCT07328568
- Acronym / sponsor ID
- R15AG093525
- Keywords
- high intensity interval training, maximal oxygen uptake, fat metabolism, affective valence, body composition, exercise adherence
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 60 participants (estimated)
- Lead sponsor
- California State University, San MarcosUniversity, hospital or other
- Study start
- 5 Nov 2025 (actual)
- Primary completion
- 1 Jun 2028 (estimated)
- Study completion
- 1 Sep 2028 (estimated)
- First posted
- 9 Jan 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Low levels of physical activity (PA) are related to poor health and greater risk of premature death in adults. Lack of time is cited as a primary barrier to partaking in PA. In the last 20 years, a lot of attention has been directed towards the efficacy of high intensity interval training (HIIT), which consists of brief, intense bursts of PA separated by recovery. One primary benefit of HIIT is a sizable increase in cardiorespiratory fitness (CRF), which enables adults to exercise better and reduce health risks due to the strong link between health status and CRF.
Completion of cardiovascular exercise is typically recommended for all adults to increase CRF, yet it takes a lot of time and may be perceived as boring. Alternatively, HIIT requires less time and tends to cause greater feelings of enjoyment in many adults. Hundreds of studies report an increase in CRF in response to HIIT in various groups of adults ranging from athletes and those with obesity, diabetes, cancer, stroke, and even spinal cord injury, which emphasizes the potency of this vigorous form of PA. Yet, many studies are weakened by a small sample size which questions the feasibility of these findings.
This randomized controlled trial will test the efficacy and feasibility of a very small amount of HIIT, referred to as reduced exertion high intensity interval training (REHIT), in inactive adults. In the proposed study, REHIT will consist of 2 days per week of 1 to two 10 - 20 second sprints on a stationary bike. The proposed sample will include 60 adults who complete 18 sessions of REHIT over a 9 week period, and their responses will be compared to a non exercising control group. During the study, changes in CRF, fuel metabolism, and psychological responses will be monitored, with the latter outcome shedding light on the overall feasibility of HIIT in inactive adults.
Overall, this novel study has profound public health applications as it will assess fitness and health related changes to a small dose of PA in the largest sample to date. If substantial changes in CRF are shown, these data have the potential to modify public health guidelines for implementing PA in inactive adults.
Detailed description
Low levels of physical activity (PA) and cardiorespiratory fitness (CRF) are significant issues for societal health. Public health guidelines for adults recommend > 150 min of moderate-intensity continuous training (MICT) or 75 min of vigorous exercise per week, and strength training on > 2 days per week. However, in 2020, 75% of adult Americans did not meet these PA recommendations. Physical inactivity is the fourth leading cause of death worldwide, as it increases the risk of 40 chronic conditions. Low maximal oxygen uptake (V̇O2max; the gold standard index of CRF) is strongly associated with increased risk of future morbidity and all-cause mortality. In fact, many large-scale studies have reported V̇O2max to be a more powerful predictor of risk for future morbidity and all-cause mortality than more traditional risk factors such as smoking, hypertension, obesity, high cholesterol, and insulin resistance. For population-level health, the largest benefits from improved PA and CRF are gained by the least fit individuals, with even small increases in fitness shown to improve health. Despite exercise being the only viable means to improve V̇O2max, it remains underutilized for primary disease prevention. Nevertheless, adults do not engage in PA due to a perceived lack of time. High intensity interval training (HIIT) is a time-efficient form of PA requiring brief intense bursts of activity separated by rest periods. Empirical data show that HIIT elicits similar and in some cases superior benefits versus MICT, often with less time. A special type of HIIT is reduced exertion high intensity interval training (REHIT) requiring only two 20 second sprints within a 10 minute session. A few studies show that REHIT increases CRF and other health-related outcomes, yet these studies have been criticized due to their small sample size, which serves to question the broad application of REHIT in adults. The proposed randomized controlled trial will recruit 60 inactive adults to complete 24 sessions of REHIT and compare resultant changes in CRF, substrate metabolism, and psychological responses to a non-exercising control group. This sample size is threefold higher than used in prior work and provides adequate statistical power to detect meaningful increases in V̇O2max. The proposed study will advance further research in the area of HIIT and if successful, may promote inclusion of REHIT in PA recommendations as a feasible alternative or adjunct to moderate or vigorous-intensity exercise as promoted in current PA recommendations.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- This is a randomized controlled trial.
| Arm | Type | Receives |
|---|---|---|
| Intervention group | Experimental | Other: High intensity interval trainingThis group will perform long term REHIT. |
| Non exercising control group | Placebo comparator | Other: High intensity interval trainingThis group will not complete REHIT, and will be given the option to complete the training once post testing is performed. |
Who may qualify
- Ages
- 18 to 55 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult
Key inclusion criteria (4 listed)
- Healthy
- BMI < 35 kg/m2
- younger than 56 yr old
- no joint issues
Key exclusion criteria (3 listed)
- Those adults who are currently active and not weight stable
- Adults with BMI > 35 kg/m2
- Use of medications which may alter study outcomes
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| High intensity interval trainingParticipants will complete 24 sessions of REHIT and their responses will be compared to a non exercising control group. | Other | Intervention group, Non exercising control group |
Primary outcome
Cardiorespiratory fitness
Time frame: CRF will be assessed at baseline 48 - 72 hours before the start of training, and at 6 and 12 weeks of training, which represent halfway and end of training. The assessments will be performed at least 24 hours after sessions of exercise training.
Cardiorespiratory fitness (CRF) is determined by oxygen transport from cardiovascular system to mitochondria and is strongly related to health status and premature mortality. It will be assessed using VO2max testing on a cycle ergometer and expressed in mL/kg/min.
5 secondary outcomes
Fat and Carbohydrate Oxidation
Time frame: Fat and carbohydrate oxidation will be measured at baseline before the start of training and at 6 and 12 weeks of training, representing halfway and end of training, and at baseline and at 12 weeks in the non exercising control group.
Cardiac output
Time frame: CO will be measured at baseline and at 6 and 12 weeks of training, representing halfway and the end of training, and at baseline and at 12 weeks in the non exercising control group.
Enjoyment of REHIT
Time frame: This outcome will be assessed during session #2 of each week of training in the exercise training group. So, this outcome will be assessed weekly during all 12 weeks of training.
Perceived exertion responses to REHIT
Time frame: This outcome will be assessed during session #2 of each week of training in the exercise training group. So, this outcome will be assessed weekly during all 12 weeks of training
Pleasure responses to REHIT
Time frame: This outcome will be assessed during session #2 of each week of training in the exercise training group. So, this outcome will be assessed weekly during all 12 weeks of training
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Aug 2026.
- Derived from this study: PubMed 41872855Astorino TA, Metcalfe RS, Vollaard NBJ. The effect of low volume sprint interval training on cardiorespiratory fitness: study protocol for a definitive randomized controlled trial. Trials. 2026 Mar 23;27(1):340. doi: 10.1186/s13063-026-09647-x.
- Individual participant dataSharing planned: No. All participant data will be reported in articles published related to this project.
Related trials for Inactivity, Physical
Active, not recruiting
Promoting Physical Activity in Older Hispanic/Latino(a) Adults
Sedentary Behavior, Physical Inactivity
Not yet recruiting
Effects of Different Amounts of Plyometric Exercise Without Jumping in Physically Inactive Older Adults
Sedentary Behavior / Physical Inactivity, Aging
Not yet recruiting
Individual Variability in Energy Compensation After a 12-Week Supervised Exercise Intervention
Physical Inactivity, Overweight
Active, not recruiting
E-Bike Commuting and Health in Overweight College Students
Obesity &Amp; Overweight, Sedentary Behaviors
Enrolling by invitation
Effects of a School-Based Physical Activity Intervention on 24-Hour Movement Behaviours and Motor Development in Preschool Children - Study Protocol
Physical Inactivity, Sedentariness
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Todd A Astorino, Ph.D principal investigator
California State University, San Marcos
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing High intensity interval training in people with Inactivity, Physical and Overweight (BMI > 25), run by California State University, San Marcos at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 24 Aug 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Todd A Astorino, Ph.D (760750-7351, astorino@csusm.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Cardiorespiratory fitness (time frame: CRF will be assessed at baseline 48 - 72 hours before the start of training, and at 6 and 12 weeks of training, which represent halfway and end of training. The assessments will be performed at least 24 hours after sessions of exercise training.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07328568, which also lists 1 linked publication.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 24 Aug 2026; AzTrials last refreshed its copy on 26 Oct 2026.