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Is high-intensity interval training a time-efficient exercise strategy to improve health and fitness?



Growing research suggests that high-intensity interval training (HIIT) is a time-efficient exercise strategy to improve cardiorespiratory and metabolic health. "All out" HIIT models such as Wingate-type exercise are particularly effective, but this type of training may not be safe, tolerable or practical for many individuals. Recent studies, however, have revealed the potential for other models of HIIT, which may be more feasible but are still time-efficient, to stimulate adaptations similar to more demanding low-volume HIIT models and high-volume endurance-type training. As little as 3 HIIT sessions per week, involving ≤10 min of intense exercise within a time commitment of ≤30 min per session, including warm-up, recovery between intervals and cool down, has been shown to improve aerobic capacity, skeletal muscle oxidative capacity, exercise tolerance and markers of disease risk after only a few weeks in both healthy individuals and people with cardiometabolic disorders. Additional research is warranted, as studies conducted have been relatively short-term, with a limited number of measurements performed on small groups of subjects. However, given that "lack of time" remains one of the most commonly cited barriers to regular exercise participation, low-volume HIIT is a time-efficient exercise strategy that warrants consideration by health practitioners and fitness professionals.
Is high-intensity interval training a time-efficient exercise
strategy to improve health and fitness?
Jenna B. Gillen and Martin J. Gibala
Abstract: Growing research suggests that high-intensity interval training (HIIT) is a time-efficient exercise strategy to improve
cardiorespiratory and metabolic health. “All out” HIIT models such as Wingate-type exercise are particularly effective, but this
type of training may not be safe, tolerable or practical for many individuals. Recent studies, however, have revealed the potential
for other models of HIIT, which may be more feasible but are still time-efficient, to stimulate adaptations similar to more
demanding low-volume HIIT models and high-volume endurance-type training. As little as 3 HIIT sessions per week, involving
≤10 min of intense exercise within a time commitment of ≤30 min per session, including warm-up, recovery between intervals
and cool down, has been shown to improve aerobic capacity, skeletal muscle oxidative capacity, exercise tolerance and markers
of disease risk after only a few weeks in both healthy individuals and people with cardiometabolic disorders. Additional research
is warranted, as studies conducted have been relatively short-term, with a limited number of measurements performed on small
groups of subjects. However, given that “lack of time” remains one of the most commonly cited barriers to regular exercise
participation, low-volume HIIT is a time-efficient exercise strategy that warrants consideration by health practitioners and
fitness professionals.
Key words: interval training, exercise intensity, training adaptations.
Résumé : De plus en plus d’études suggèrent que la méthode d’entraînement par intervalle de haute intensité (« HIIT ») est
économique en matière de temps investi pour l’amélioration de la santé cardiorespiratoire et métabolique. Les approches « a
fond de train » comme les exercices de type Wingate sont particulièrement efficaces, mais ce mode d’entraînement n’est
peut-être pas sécuritaire, facile a
`tolérer et pratique pour bien des individus. Des études récentes révèlent le potentiel d’autres
modèles HIIT Oapparemment plus pratiques et aussi efficaces Opour susciter des adaptations similaires aux plus exigeants
modèles HIIT a
`faible volume et d’entraînement en endurance a
`haut volume. À raison d’aussi peu que trois séances HIIT par
semaine comprenant ≤ 10 min d’exercice intense dans une séance de ≤ 30 min incluant l’échauffement, la récupération entre les
intervalles et le retour au calme, on améliore la capacité aérobie, la capacité oxydative du muscle squelettique, la tolérance a
l’effort et les marqueurs du risque de maladie, et ce, après seulement quelques semaines tant chez des individus en bonne santé
que chez des personnes aux prises avec des troubles cardiométaboliques. Il faut réaliser d’autres études, car celles qui ont été
effectuées présentaient des résultats a
`court terme avec un nombre limité de mesures enregistrées auprès de petits groupes
de sujets. Cependant, « le manque de temps » étant l’argument généralement évoqué comme obstacle a
`la pratique régulière de
l’activité physique, un programme HIIT a
`faible volume constitue une approche efficace que devraient prendre en compte les
praticiens de la santé et les professionnels de la condition physique. [Traduit par la Rédaction]
Mots-clés : entraînement par intervalle, intensité de l’exercice, adaptations a
Current physical activity guidelines including those from the
Canadian Society for Exercise Physiology (CSEP) recommend
that adults should accumulate at least 150 min of moderate- to
vigorous-intensity aerobic physical activity per week to achieve
health benefits (Tremblay et al. 2011). The CSEP guidelines do not
specifically define intensity ranges; however, guidelines from
other agencies, including the American College of Sports Medi-
cine, classify moderate intensity as 64%–76% of maximal heart
rate (HR
) (46%–63% of maximal oxygen uptake (V
)) and
vigorous intensity as 77%–95% of HR
(64%–90% V
et al. 2011). While public health guidelines are based on very
strong scientific evidence, accelerometer data indicate that as
many as 85% of Canadians do not meet the minimum physical
activity recommendations (Colley et al. 2011) with “lack of time”
being one of the most commonly cited barriers to regular partic-
ipation (Trost et al. 2002). Recent evidence from relatively small,
short-term studies suggests that high-intensity interval training
(HIIT) may be as effective as traditional moderate-intensity con-
tinuous training to induce physiological remodelling, which in
turn may be associated with improved health markers, despite a
reduced time commitment.
What is HIIT?
HIIT is characterized by brief, repeated bursts of relatively in-
tense exercise separated by periods of rest or low-intensity exer-
cise. “Low-volume” HIIT refers to exercise training sessions that
are relatively brief Oconsisting of ≤10 min of intense exercise
within a training session lasting ≤30 min including warm-up,
recovery periods between intervals and cool down Osuch that
the total weekly exercise and training time commitment is re-
duced compared with current public health guidelines. One of the
most common models employed in low-volume HIIT studies is the
Wingate Test, which consists of 30 s of “all-out” cycling against a
Received 30 April 2013. Accepted 21 September 2013.
J.B. Gillen and M.J. Gibala.* Department of Kinesiology, McMaster University, 1280 Main St. West, Hamilton, ON L8S 4K1, Canada.
Corresponding author: Martin J. Gibala (e-mail:
*All editorial decisions for this paper were made by Michelle Porter and Terry Graham.
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For personal use only.
high resistance on a specialized cycle ergometer. A typical train-
ing session consists of 4–6 repetitions interspersed by 4 min of
recovery. As little as 6 sessions of this type of training over 2 weeks
robustly increases skeletal muscle oxidative capacity, as reflected
by the maximal activity and (or) protein content of various mito-
chondrial enzymes (Burgomaster et al. 2005,2006;Gibala et al.
2006), in healthy individuals who were previously sedentary or
active on a recreational basis. A 6-week program increased V
and induced cardiovascular and skeletal muscle remodelling sim-
ilar to a traditional endurance training program that was modeled
on current public health guidelines, despite a 90% difference in
training volume (Burgomaster et al. 2007,2008), and markedly
lowered total time commitment (Table 1). Other studies have
shown that short-term Wingate-based HIIT protocols improve in-
sulin sensitivity, measured using oral glucose tolerance tests in
young healthy men (Babraj et al. 2009;Metcalfe et al. 2011) and
overweight/obese individuals (Whyte et al. 2010), as well as using
the gold standard hyperinsulinemic euglycemic clamp method in
recreationally active men and women (Richards et al. 2010). Trapp
and colleagues (2008) also reported significant fat loss in young
women following 15 weeks of low-volume HIIT, which consisted
of 8-s all-out sprints followed by 12 s of recovery for 20 min. The
same HIIT protocol performed for 12 weeks reduced whole-body
fat mass and increased lean mass in the legs and trunk in over-
weight young men (Heydari et al. 2012b).
Modified low-volume HIIT protocols
All-out HIIT protocols are effective; however, considering the
need for specialized equipment and the extremely high level of
subject motivation, this form of training may not be safe, tolera-
ble or practical for many individuals. Recent studies have also
revealed the potential for other models of HIIT, which may be
more feasible but are nonetheless time-efficient compared with
traditional public health guidelines, to stimulate adaptations sim-
ilar to more demanding low-volume HIIT models as well as
relatively high-volume endurance-type training (Table 1). For ex-
ample, a model that we have employed consists of 10 × 1-min
cycling efforts at an intensity eliciting 85%–90% of HR
spersed with 1 min of recovery. The protocol is still relatively
time-efficient in that a single training session consists of only
10 min of vigorous exercise within a 25-min training session in-
cluding warm-up, recovery periods between intervals and cool
down. This model has been applied in studies of young healthy
individuals (Little et al. 2010), as well as overweight/obese individ-
uals (Gillen et al. 2013), older sedentary adults who may be at
higher risk for cardiometabolic disorders (Hood et al. 2011), and
patients with coronary artery disease (CAD) (Currie et al. 2013) and
type 2 diabetes (T2D) (Little et al. 2011).
Short-term studies employing continuous glucose monitoring
have shown that the modified 10 × 1-min model reduced 24-h
blood glucose concentration in people with T2D when measured
immediately after a single bout (Gillen et al. 2012) as well as 72 h
following a 2-week training intervention (Little et al. 2011). Mean
ratings of perceived exertion measured in the latter study were
7 on a 10-point scale, suggesting the stimulus was manageable
for subjects. Another recent study found that 10 × 1-min HIIT
performed 2 times per week for 12 weeks improved arterial endo-
thelial function (assessed by flow mediated dilation) and V
in patients with CAD to the same extent as performing 40 min of
continuous cycling at 60% peak power output per session (Currie
et al. 2013). In addition, Boutcher (2011) recently reviewed poten-
tial mechanisms that may mediate changes in body composition
following HIIT, one of which has been speculated to include re-
peated, transient elevations in postexercise oxygen consumption
over the course of training (Hazell et al. 2012). While the findings
from these small pilot projects are intriguing, large scale investi-
gations with appropriate participant screening and monitoring
are clearly warranted, including randomized clinical trials to
directly compare low-volume HIIT versus traditional endur-
ance training in a comprehensive manner, especially in those
with, or at risk for, cardiometabolic disorders.
How low can you go?
A modified Wingate-based HIIT protocol that consisted of 4 ×
10 s all out sprints induced improvements in aerobic and anaero-
bic performance that were comparable toa4×30-s protocol
(Hazell et al. 2010). Another study by Metcalfe et al. (2011) showed
that a protocol consisting of 2 × 20-s all-out sprints, included
within a 10-min bout of primarily low-intensity cycling, improved
after 6 weeks of training (18 total sessions). Interestingly,
while V
improved in both men and women, insulin sensitiv-
ity measured using oral glucose tolerance tests was only improved
in men (Metcalfe et al. 2011). These findings suggest that provided
exercise is performed using an all-out effort, it may be possible to
confer benefits using protocols that are even more time-efficient
than employed in previous Wingate-based HIIT studies. There is
insufficient evidence at present to make sweeping recommenda-
tions, however, and as alluded to earlier, the effort required with
this type of training and need for specialized equipment may
make it impractical for many individuals. When it comes to low-
volume HIIT protocols, there may be a trade-off between relative
work intensity and the time required to stimulate adaptations,
and this remains a fruitful area of future investigation.
Conclusion and recommendations
While far from definitive, growing evidence suggests that train-
ing using brief repeated bursts of relatively intense exercise can
be an effective strategy to improve fitness and health. Most of the
low-volume HIIT studies have employed a cycling model but other
models of traditional whole-body exercise are also likely to be
effective, e.g., climbing stairs, brisk uphill walking or running.
One recent study found that subjects who trained using 1 set of 8 ×
20 s of a single exercise (burpees, jumping jacks, mountain climb-
ers, or squat thrusts) interspersed by 10 s of rest per session,
4 times per week for 4 weeks increased V
to the same extent
as a group who performed 30 min of traditional endurance train-
ing per session (McRae et al. 2012). It is possible that the very
intense nature of HIIT stimulates rapid changes, whereas adapta-
tions induced by traditional endurance training may occur more
slowly. As with the initiation of any new exercise program, it is
important to undergo proper screening procedures, which in-
cludes completion of an evidence-based screening form such as
the Physical Activity Readiness Questionnaire Plus as well as
medical clearance especially for those who may be at risk for or
afflicted by chronic diseases such as diabetes or cardiovascular
disease (Warburton et al. 2011). It may also be prudent to include a
preconditioning phase of training consisting of more traditional
moderate-intensity aerobic exercise prior to initiating HIIT (e.g.,
20–30 min per session, a few times per week for several weeks), as
it has been shown that a baseline level of fitness is a cardiopro-
tectant and reduces the risks associated with exercise-induced
ischemic events (Thompson et al. 2007). One recent study reported
that HIIT was perceived to be more enjoyable compared with
moderate-intensity continuous exercise training, at least in young
active men (Bartlett et al. 2011), but relatively little is known re-
garding the feasibility of implementing HIIT into individual exer-
cise prescriptions outside of a laboratory setting. It is also
important to note that it may be favourable to include variety in
one’s exercise program in terms of type, intensity and duration
rather than training with only 1 form of exercise. Additional work
is clearly warranted to comprehensively evaluate the long-term
health benefits associated with low-volume HIIT in comparison
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Table 1. Summary of adaptations following 2, 6 and 12–15 weeks of low-volume high-intensity interval training (HIIT).
Protocol Time/session 2 wk 6 wk 12–15 wk
Wingate HIIT (four to six
30-s sprints; 4-min
20 min 1V
(Whyte et al. 2010;Hazell et al. 2010;
Astorino et al. 2012)
(Burgomaster et al. 2007,2008;Astorino
et al. 2012)
1250, 750 kJ and 5 km TT performance
(Burgomaster et al. 2005;Gibala et al. 2006;
Hazell et al. 2010)
1250 kJ TT performance (Burgomaster et al. 2007)
1Wingate PPO and MPO (Burgomaster et al. 2005;
Whyte et al. 2010;Hazell et al. 2010)
1Wingate PPO and MPO (Burgomaster et al. 2008)
1Resting muscle glycogen content (Burgomaster
et al. 2005)
1Resting muscle glycogen content and 2glycogen
utilization during exercise (Burgomaster et al. 2008)
1Maximal activity of CS and COX (Burgomaster et al.
2005,2006;Gibala et al. 2006)
1Maximal activity of CS and -HAD (Burgomaster
et al. 2008)
1COXII and COXIV protein content (Gibala et al.
1GLUT4, PDH and COXIV protein content
(Burgomaster et al. 2007,2008)
1IS (Cederholm Index and GIR) (Babraj et al. 2009;
Richards et al. 2010)
1Whole-body fat oxidation and 2CHO oxidation
during exercise (Burgomaster et al. 2008)
2OGTT glucose and insulin AUC (Babraj et al.
2009;Richards et al. 2010)
1Peripheral arterial compliance (Rakobowchuck
et al. 2008)
1Resting fat oxidation 24 h post-training (Whyte
et al. 2010)
1Endothelial function (Rakobowchuck et al. 2008)
2SBP 24-h post-training (Whyte et al. 2010)
Modified HIIT (10×1min
sprints at 90% HR
1 min recovery)
20 min 150 and 750 kJ TT performance (Little et al. 2010)1V
(Gillen et al. 2013)1V
in CAD patients (Currie et al.
in T2D patients (Little et al. 2011)1W
(Gillen et al. 2013)
1Maximal activity of CS and COX (Little et al.
2010,2011;Hood et al. 2011)
1Maximal activity of CS and -HAD (Gillen et al.
1COXIV and GLUT4 protein content (Little et al.
2010,2011;Hood et al. 2011)
1GLUT4 protein content (Gillen et al. 2013)
2Fasting [insulin] (Hood et al. 2011)2Whole-body and abdominal fat mass (Gillen et al.
1Endothelial function in CAD patients
(Currie et al. 2013)
1IS (HOMA) (Hood et al. 2011)1Leg and gynoid fat-free mass (Gillen et al. 2013)
1Glycemic control in T2D patients (Little et al. 2011)
10×6sall-out sprints;
60 s recovery (2 wk)
10 min 110 km TT performance (Jakeman et al. 2012)1V
(Metcalfe et al. 2011)
10 min at 60 W with two
20 s all out sprints (6 wk)
1IS (Cederholm Index) in males only (Metcalfe
et al. 2011)
8 s sprint at 120 rpm;
12 s recovery at 40 rpm.
Workload 90% HR
20 min 1V
(Trapp et al. 2008;Heydari
et al. 2012b)
2Whole-body abdominal and trunk fat
mass (Trapp et al. 2008;Heydari et al.
1Whole-body leg and trunk fat free
mass (Trapp et al. 2008)
1Resting fat oxidation (Trapp et al. 2008)
2Fasting [insulin] and insulin resistance
(HOMA-IR) (Trapp et al. 2008)
2Arterial stiffness, systolic and
diastolic BP (Heydari et al. 2012a)
Note: Training adaptations were measured ≥72 h following the last training session unless otherwise specified. Most studies were conducted in recreationally active or sedentary healthy men and women, except
for those in overweight men and women (Whyte et al. 2010;Trapp et al. 2008;Heydari et al. 2012a,2012b;Gillen et al. 2012), patients with type 2 diabetes (T2D) (Little et al. 2011), patients with coronary artery disease
(CAD) (Currie et al. 2013) or triathletes (Jakeman et al. 2012). V
, maximal oxygen uptake; TT, time trial; PPO, peak power output; MPO, mean power output; CS, citrate synthase; COX, cytochrome c oxidase; -HAD,
beta hydroxydehydrogenase; GLUT4, glucose transporter 4; PDH, pyruvate dehydrogenase; IS, insulin sensitivity; GIR, glucose infusion rate; CHO, carbohydrate; OGTT, oral glucose tolerance test; AUC, area under the
curve; SBP, systolic blood pressure; HR
, maximal heart rate; W
, maximal workload in watts; HOMA, Homeostasis Model of Assessment; BP, blood pressure.
Gillen and Gibala 411
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... However, despite the well-established health benefits of exercise, a large proportion of adults across the globe [22], in particular obese individuals [23], do not achieve the recommended amounts of weekly physical activity (i.e., at least 150 min of moderate or 75 min of vigorous aerobic physical activity per week plus 2-3 weekly sessions of musclestrengthening exercises [24]), with insufficient time being cited as a major obstacle to regular exercise [25,26]. In this context, various time-efficient exercise modalities, such as low-volume high-intensity interval training (HIIT) [27][28][29], low-volume (single-set) resistance training (RT) [30], or whole-body electromyostimulation (WB-EMS) [31] have gained growing popularity in recent years. The evaluation of the health benefits that can be achieved with these low-volume exercise modalities is an ongoing focus of research. ...
... HIIT is a specific type of cardiovascular training consisting of alternating exercise and recovery periods of various durations [27]. "Low-volume" HIIT (LOW-HIIT) is a very timeefficient subtype of interval training that involves per previous definition a cumulative duration of ≤10 min of vigorous exercise intervals within a session of ≤30 min total duration (including warm-up, recovery periods, and cool-down) [28]. There is increasing evidence that LOW-HIIT protocols can evoke comparable or even greater improvements in several health-related outcomes, including maximal oxygen uptake (VO 2max ) and markers of glycemic control [32,33] as traditional moderate-intensity continuous training (MICT), despite significantly lower time effort. ...
... Several meta-analyses have already revealed the potential of HIIT to reduce markers of inflammation in various populations, including healthy individuals [81,82], overweight and obese cohorts [44], and patients with cardiometabolic disorders [81][82][83][84]. However, currently, data on the effects of low-volume HIIT (i.e., protocols with a maximal session duration of ≤30 min and ≤10 min of intense exercise, respectively, as previously defined [28]) are still very sparse. Kelly et al. [85] investigated the impact of a low-volume HIIT protocol (10 × 1 min intervals at 90% HR max , total session time: 24 min) that was performed for 2 weeks on various physiological parameters, including body composition, glucose control, and inflammatory markers in overweight and obese men. ...
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Exercise is a cornerstone in metabolic syndrome (MetS) treatment. However, the effects of low-volume exercise modalities on MetS-associated low-grade inflammation are unclear. A total of 106 MetS patients (53.7 ± 11.4 years) were randomized to low-volume high-intensity interval training (LOW-HIIT, 14 min/session), single-set resistance training (1-RT, ~15 min/session), whole-body electromyostimulation (WB-EMS, 20 min/session), three-set resistance training (3-RT, ~50 min/session), each performed 2 ×/week for 12 weeks, or a control group (CON). All groups received nutritional counseling for weight loss. Inflammatory and cardiometabolic indices were analyzed pre- and post-intervention. All groups significantly reduced body weight by an average of 3.6%. Only LOW-HIIT reduced C-reactive protein (CRP) (−1.6 mg/L, p = 0.001) and interleukin-6 (−1.1 pg/mL, p = 0.020). High-sensitivity CRP and lipopolysaccharide-binding protein decreased following LOW-HIIT (−1.4 mg/L, p = 0.001 and −2.1 ng/mL, p = 0.004) and 3-RT (−0.6 mg/L, p = 0.044 and −2.0 ng/mL, p < 0.001). MetS severity score improved with LOW-HIIT (−1.8 units, p < 0.001), 1-RT (−1.6 units, p = 0.005), and 3-RT (−2.3 units, p < 0.001). Despite similar effects on body weight, low-volume exercise modalities have different impact on inflammatory and cardiometabolic outcomes in MetS patients. LOW-HIIT has superior efficacy for improving inflammation compared to 1-RT and WB-EMS. Resistance-based exercise appears to require a higher volume to promote beneficial impact on inflammation.
... Steckling et al. (47) in line with our findings, also considered HIIT training as an efficient strategy to improve cardiorespiratory fitness and functional parameters of individuals with obesity. Studies show that HIIT requires less time than conventional moderate-intensity exercise options to obtain health benefits including increased aerobic fitness which corroborates with the present study (48)(49)(50). ...
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Background Intermittent fasting (IF) is a dietary approach that is widely popular due to its effects on weight and body fat loss, but it does not appear to ensure muscle mass preservation. Incorporating high-intensity interval training (HIIT) into an individual’s routine could be an attractive and viable therapeutic option for improving body composition, lifestyle and health promotion. Problematizing the emerging situation of fighting obesity, led us to clarify gaps about IF and hypothesize that IF and HIIT in conjunction may protect against muscle mass decline without impairing nitrogen balance (NB), in addition to improving the physical fitness of women with obesity. Objectives To evaluate the effects of IF alone and combined with HIIT on body composition, NB and strength and physical fitness in women with obesity. Methods Thirty-six women (BMI 34.0 ± 3.2; 32.2 ± 4.4 years) participated and were randomly distributed into three groups: (1) Intermittent fasting combined with exercise group (IF + EX); (2) Exercise group (EX); and (3) Intermittent fasting group (IF). The interventions took place over 8 weeks and all evaluations were performed pre and post-intervention. The HIIT circuit was performed 3x/week, for 25 mins/session, at 70–85% of the maximum heart rate. The intermittent fasting protocol was a 5:2 diet with two meals within 6 h on fasting days, being 25% of total energy intake, plus 18 h of complete fasting. The protocol was performed 2x/week and 5 days of ad libitum ingestion. Resting metabolic rate (RMR) was measured by indirect calorimetry, body composition by BodPod ® , NB from urinary nitrogen, food consumption by food records and physical and strength performance were measured by physical tests. ANOVA two-way repeated measures mixed model was performed followed by Sidak post hoc ( p < 0.05). This project was registered in , NCT05237154. Results There were a reduction in body weight ( P = 0.012) and BMI ( P = 0.031) only in the IF + EX group. There was body fat loss in the IF + EX group (−4%, P < 0.001) and in the EX group (−2.3%, P = 0.043), an increase in fat-free mass in the IF + EX group (+3.3%, P < 0.001) and also in the EX group (+2%, P = 0.043), without differences between groups and the IF group showed no changes. The NB was equilibrium in all groups. All parameters of aerobic capacity and strength improved. Conclusion Combining IF with HIIT can promote increments in fat-free mass, NB equilibrium and improve physical fitness and strength.
... Lower-intensity continuous training can make patients adapt well but may not achieve an ideal exercise rehabilitation effect. Robust clinical interest has emerged in high-intensity interval training (HIIT) for patients with COPD, characterized by brief repeated bursts of relatively intense exercise separated by periods of rest or low-intensity exercise [14]. This type of exercise can produce more cardiac output and myocardial oxygen demand with fewer adverse symptoms [15,16]. ...
... 'Low-volume' HIIT is a rather novel, particularly timeefficient sub-type of interval training, that typically requires < 30 min/session (28). Recently, studies from our group revealed that a highly time-saving low-volume HIIT protocol (14 min/session) effectively improved CRF and cardiometabolic risk profiles in untrained normal-weight individuals (29) and obese MetS patients (30,31). ...
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Non-alcoholic fatty liver disease (NAFLD) and cardiometabolic disorders are highly prevalent in obese individuals. Physical exercise is an important element in obesity and metabolic syndrome (MetS) treatment. However, the vast majority of individuals with obesity do not meet the general physical activity recommendations (i.e. 150 min of moderate activity per week). The present study aimed to investigate the impact of a highly time-saving high-intensity interval training (HIIT) protocol (28 min time requirement per week) on NAFLD fibrosis (NFS) and cardiometabolic risk scores in obese patients with MetS and elevated NFS values. Twenty-nine patients performed HIIT on cycle ergometers (5 x 1 min at an intensity of 80 - 95% maximal heart rate) twice weekly for 12 weeks and were compared to a control group without exercise (CON, n = 17). Nutritional counseling for weight loss was provided to both groups. NFS, cardiometabolic risk indices, MetS z-score, cardiorespiratory fitness (VO2max) and body composition were assessed before and after intervention. The HIIT (-4.3 kg, P < 0.001) and CON (-2.3 kg, P = 0.003) group significantly reduced body weight. There were no significant group differences in relative weight reduction (HIIT: -3.5%, CON: -2.4%). However, only the HIIT group improved NFS (-0.52 units, P = 0.003), MetS z-score (-2.0 units, P < 0.001), glycemic control (HbA1c: -0.20%, P = 0.014) and VO2max (+3.1 mL/kg/min, P < 0.001). Decreases in NFS (-0.50 units, P = 0.025) and MetS z-score (-1.4 units, P = 0.007) and the increment in VO2max (3.3 mL/kg/min, P < 0.001) were significantly larger in the HIIT than in the CON group. In conclusion, only 28 min of HIIT per week can elicit significant improvements in NFS and a several cardiometabolic health indices in obese MetS patients with increased NFS grades. Our results underscore the importance of exercise in NAFLD and MetS treatment and suggest that our low-volume HIIT protocol can be regarded as viable alternative to more time-consuming exercise programs.
... Exercise intensity is proposed as a main determinant of BP reduction following exercise training. A rigorous "working interval" is the drive to promote training adaptations following HIIT protocols 22 and was the central difference between exercise programs in this study. Previous meta-analysis suggests that HIIT generate significant reductions only in SBP in overweight and obese youth, but not in DBP. ...
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Introduction: The prevalence of childhood obesity has increased and is associated with the development of several chronic diseases. Moderate-intensity continuous training is recommended as the main exercise method for treating obesity. However, in overweight and obese individuals, high-intensity interval training models have similar or greater fat reduction potential than moderate-intensity continuous training. Objective: This study aimed to compare the effects of 12 weeks of moderate-intensity continuous training and high-intensity interval training on cardiometabolic parameters, body composition, and cardiorespiratory fitness in obese adolescent boys. Methods: Fifty-six obese boys, aged 10-16 years old, were included. Anthropometric measurements, blood pressure, body composition, oxygen consumption, glucose, insulin, and the lipid profile were assessed. Participants were assigned to moderate-intensity continuous training (n=20), high-intensity interval training (n=20), and control (n=16) groups. The moderate-intensity continuous training sessions consisted of 90 minutes of cycling/walking exercises and the high-intensity interval training sessions consisted of 15 minutes of warm-up, 15-18 minutes of interval exercises, and 15 minutes of cool-down. Both were performed three times a week. A two-way mixed-model factorial analysis of variance (ANOVA) with repeated measures was used. Results: In the high-intensity interval training group, there was an increase in relative and absolute oxygen consumption and a reduction in diastolic blood pressure. However, in the moderate-intensity continuous training group, there were increases in relative oxygen consumption and high-density lipoproteins, as well as reductions in anthropometric measurements, fat mass, and triglycerides. Conclusion: Moderate-intensity continuous training may be a better protocol for the reduction of fat mass, anthropometric measurements, and improvement of the lipid profile, while high-intensity interval training may be more effective in improving blood pressure among obese boys. Both exercises improve cardiorespiratory fitness. Level of evidence II; Therapeutic studies-investigation of treatment results.
... Tabata training works in 20 seconds intervals of high intensity exercise and 10 seconds for rest and repeated 8 times for a total of 4 minutes (Ekström, Ostenberg, Björklund & Alricsson, 2017). Previous studies reported that the Tabata training method had an effect on increasing muscle power (Gillen & Gibala, 2014). A recent study has proven that Tabata training method is effective for improving physical fitness in handball athletes (Setiawan et al., 2020) and martial arts (Patah et al., 2021). ...
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The study purpose. This study aims to evaluate the effect of the Tabata aquatic training method program in increasing the muscle power of beginner level athletes. Materials and methods. The researcher used a mixed method in this study. There were twenty swimming athletes (n = 20, age: 14.40 ± 1.18 years, height: 169.20 ± 3.18 cm, weight: 62.20 ± 2.26 kg) who agreed to participate in this study and were divided into two groups. The treatment group (n = 10) received the Tabata aquatic program and the control group (n = 10) swam every day without participating in any physical activity. The Tabata aquatic program was carried out for 9 weeks with a frequency of 3 times a week. After implementing the Tabata aquatic program, 10 athletes were interviewed. This study applied a quantitative research instrument, including squat jumps, and a qualitative research instrument, including individual in-depth interviews lasting for 30 minutes each. Analysis of quantitative data using IBM SPSS version 25.0 and qualitative data using thematic analysis was applied. Results. Quantitative study results showed that there was a significant increase in the squat jumps test (leg muscle power) in the treatment group and vice versa, there was no increase in the control group. However, in qualitative research results, most participants mentioned that the Tabata aquatic program is a fun training method and has a positive effect. Conclusions. After carrying out the Tabata aquatic program for 9 weeks, we confirmed that this training method has a great impact on improving athletes’ leg muscle power in swimming.
... Low-volume high-intensity interval exercise (HIIE), characterized by brief, repeated bouts of intense exercise separated by periods of rest or low-intensity recovery, improves glycemic control despite a low exercise volume (1,2). For example, a single session of low-volume HIIE involving 8-10 × 1-min cycling intervals at ∼90% maximal heart rate (HRmax) has been demonstrated to reduce mean blood glucose concentrations and postprandial glycemic excursions for up to 24 h following exercise in adults with (3) and without (4,5) type 2 diabetes. ...
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Background Improved glycemic control has been reported for ∼24 h following low-volume high-intensity interval exercise (HIIE), but it is unclear if this is a direct effect of exercise or an indirect effect of the exercise-induced energy deficit. The purpose of this study was to investigate the effect of carbohydrate-energy replacement after low-volume HIIE on 24 h glycemic control in women.Methods Seven untrained women (age: 22 ± 2 yr; BMI: 22 ± 3 kg/m2; VO2peak: 33 ± 7 ml/kg/min) completed three 2-day trials in the mid-follicular phase of the menstrual cycle. Continuous glucose monitoring was used to measure blood glucose concentrations during, and for 24 h following three conditions: (1) HIIE followed by a high-carbohydrate energy replacement drink (EX-HC); (2) HIIE followed by a non-caloric taste-matched placebo drink (EX-NC); and (3) seated control with no drink (CTL). HIIE involved an evening session (1,700 h) of 10 × 1-min cycling efforts at ∼90% maximal heart rate with 1 min recovery. Diet was standardized and identical across all three 2-day trials, apart from the post-exercise carbohydrate drink in EX-HC, which was designed to replenish the exercise-induced energy expenditure. Postprandial glycemic responses to the following days breakfast, snack, lunch, and dinner, as well as 24 h indices of glycemic control, were analyzed.ResultsThe day after HIIE, postprandial glycemia following breakfast and snack were reduced in EX-NC compared to EX-HC, as reflected by lower 3 h glucose mean (breakfast: 5.5 ± 0.5 vs. 6.7 ± 1, p = 0.01, Cohen’s d = 1.4; snack: 4.9 ± 0.3 vs. 5.7 ± 0.8 mmol/L, p = 0.02, d = 1.4) and/or area under the curve (AUC) (breakfast: 994 ± 86 vs. 1,208 ± 190 mmol/L x 3 h, p = 0.01, d = 1.5). Postprandial glycemic responses following lunch and dinner were not different across conditions (p > 0.05). The 24 h glucose mean (EX-NC: 5.2 ± 0.3 vs. EX-HC: 5.7 ± 0.7 mmol/L; p = 0.02, d = 1.1) and AUC (EX-NC: 7,448 ± 425 vs. EX-HC: 8,246 ± 957 mmol/L × 24 h; p = 0.02, d = 1.1) were reduced in EX-NC compared to EX-HC.Conclusion Post-exercise carbohydrate-energy replacement attenuates glycemic control the day following a single session of low-volume HIIE in women.
Introduction Physical exercise provides better body image perception and well-being. However, if practiced compulsively, it may lead to compulsion and psychobiological damage. CrossFit is a method aiming at maximum performance, and it is currently attracting many regular practitioners. Objective Evaluate exercise dependence prevalence, muscle dysmorphia, and trait-state anxiety in CrossFit practitioners. Methods One hundred fifty regular male CrossFit practitioners were evaluated and subdivided into two groups: with and without risk for exercise dependence. Trait-state anxiety and muscle dysmorphia were also assessed. Unpaired t-test compared groups, Fisher's exact test was used for associations between categorical variables (p < 0.05), while correlations were verified using Pearson's correlation coefficient. Results 122 participants were identified with no risk for exercise dependence and 28 with risk for exercise dependence. Participants presented mean age of 30.3 ± 7.05 years and had been practicing physical exercise for 8.02 ± 8.1 years, with training frequency of 5.3 ± 1.09 days per week and 107.9 ± 50.5 minutes per training day. Prevalence risk of exercise dependence was 18.6%, and muscle dysmorphia was significantly different between groups with (10.7%, n = 3) and without risk (6.6%, n = 8) for exercise dependence. Participants with risk for dependence chose CrossFit mainly due to appearance (32%). Conclusion Prevalence risk of exercise dependence was 18.6% and satisfaction with muscle appearance may influence exercise behavior.
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Objective This study compared hematologic, metabolic and antioxidant responses between three high-intensity interval exercise (HIIE) trials of different bout duration and a continuous exercise trial (CON), all with equal average intensity, total work, and duration. Methods Eleven healthy young males performed four trials involving 20 min of cycling, either continuously (49% of power at VO2max, PPO), or intermittently with 48 10-s bouts (HIIE10), 16 30-s bouts (HIIE30) or 8 60-s bouts (HIIE60) at 100% PPO, with a 1:1.5 work-to-recovery ratio at 15% PPO. Venous blood was obtained before, immediately after, and 1 h post-exercise to evaluate hematologic, metabolic and antioxidant responses. Blood lactate concentration was measured in capillary blood during exercise, while urine lactate was measured before and 1 h post-exercise. Results Post-exercise leukocyte count (mean ± SD; 9.7 ± 2.8 kμL⁻¹), uric acid concentration (0.35 ± 0.10 mmolL⁻¹), glucose concentration (6.56 ± 1.44 mmolL⁻¹), and plasma volume change (−13.5 ± 4.4%) were greater in HIIE60 compared to all other trials (p < 0.05). One-hour post-exercise, lymphocytes decreased below pre-exercise values in all HIIE trials, and uric acid increased in the HIIE60 trial (p < 0.05). Urine lactate concentration 1 h post-exercise increased compared to pre-exercise only in HIIE60 (19-fold, p < 0.001), and this was related with the higher blood lactate concentration during exercise in that trial. Conclusions These findings highlight the importance of bout duration, given that shorter bouts of HIIE (30 s or 10 s) induce lower blood cell perturbations, metabolic stress, and antioxidant responses compared to the commonly used 1-min bouts, despite equal total work, duration, and work-to-recovery ratio.
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Purpose: Isocaloric interval exercise training programs have been shown to elicit improvements in numerous physiological indices in patients with CAD. Low-volume high-intensity interval exercise training (HIT) is effective in healthy populations; however, its effectiveness in cardiac rehabilitation has not been established. This study compared the effects of 12-wk of HIT and higher-volume moderate-intensity endurance exercise (END) on brachial artery flow-mediated dilation (FMD) and cardiorespiratory fitness (VO2 peak) in patients with CAD. Methods: Twenty-two patients with documented CAD were randomized into HIT (n = 11) or END (n = 11) based on pretraining FMD. Both groups attended two supervised sessions per week for 12 wk. END performed 30-50 min of continuous cycling at 58% peak power output (PPO), whereas HIT performed ten 1-min intervals at 89% PPO separated by 1-min intervals at 10% PPO per session. Results: Relative FMD was increased posttraining (END, 4.4% ± 2.6% vs 5.9% ± 3.6%; HIT, 4.6% ± 3.6% vs 6.1% ± 3.4%, P ≤ 0.001 pre- vs posttraining) with no differences between groups. A training effect was also observed for relative VO2 peak (END, 18.7 ± 5.7 vs 22.3 ± 6.1 mL · kg(-1) · min(-1); HIT, 19.8 ± 3.7 vs 24.5 ± 4.5 mL · kg(-1) · min(-1), P < 0.001 for pre- vs posttraining), with no group differences. Conclusions: Low-volume HIT provides an alternative to the current, more time-intensive prescription for cardiac rehabilitation. HIT elicited similar improvements in fitness and FMD as END, despite differences in exercise duration and intensity.
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The current study evaluated changes in aerobic fitness and muscular endurance following endurance training and very low volume, whole-body, high-intensity, interval-style aerobic-resistance training. Subjects' enjoyment and implementation intentions were also examined prior to and following training. Subjects (22 recreationally active females (20.3 ± 1.4 years)) completed 4 weeks of exercise training 4 days per week consisting of either 30 min of endurance treadmill training (~85% maximal heart rate; n = 7) or whole-body aerobic-resistance training involving one set of 8 × 20 s of a single exercise (burpees, jumping jacks, mountain climbers, or squat thrusts) separated by 10 s of rest per session (n = 7). A third group was assigned to a nontraining control group (n = 8). Following training, [Formula: see text]O(2peak) was increased in both the endurance (~7%) and interval (~8%) groups (p < 0.05), whereas muscle endurance was improved (p < 0.05) in the interval group (leg extensions, +40%; chest presses, +207%; sit-ups, +64%; push-ups, +135%; and back extensions, +75%). Perceived enjoyment of, and intentions to engage in, very low volume, high-intensity, whole-body interval exercise were both increased following training (p < 0.05). No significant changes were observed for any variable in the control (nontraining) group. These data demonstrate that although improvements in cardiovascular fitness are induced by both endurance and extremely low volume interval-style training, whole-body aerobic-resistance training imparted addition benefit in the form of improved skeletal muscle endurance.
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High-intensity training (HIT) involving 30-s sprints is an effective training regimen to improve aerobic performance. We tested whether 6-s HITs can improve aerobic performance in triathletes. Six subelite triathletes (age, 40 ± 9 years; weight, 86 ± 11 kg; body mass index, 26 ± 3 kg·m⁻²) took part in cycle HIT and 6 endurance-trained subelite athletes (age, 36 ± 9 years; weight, 82 ± 11 kg; BMI, 26 ± 3 kg·m⁻²) maintained their normal training routine. Before and after 2 weeks of HIT, involving 10 × 6-s sprints or normal activity, participants performed a self-paced 10-km time trial and a time to exhaustion test on a cycle ergometer. Finger prick blood samples were taken throughout the time to exhaustion test to determine blood lactate concentration. Two weeks of HIT resulted in a 10% decrease in self-paced 10-km time trial (p = 0.03) but no significant change in time to exhaustion. The time taken to reach onset of blood lactate accumulation (OBLA, defined as the point where blood lactate reaches 4 mmol·L⁻¹) was significantly increased following 2 weeks of HIT (p = 0.003). The change in time trial performance was correlated to the change in time taken to reach OBLA (R² = 0.63; p = 0.001). We concluded that a very short duration HIT is a very effective training regimen to improve aerobic performance in subelite triathletes and this is associated with a delay in blood lactate build-up.
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To determine the effect of a 12-week high intensity intermittent exercise (HIIE) intervention on total body, abdominal, trunk, visceral fat mass, and fat free mass of young overweight males. Participants were randomly assigned to either exercise or control group. The intervention group received HIIE three times per week, 20 min per session, for 12 weeks. Aerobic power improved significantly (P < 0.001) by 15% for the exercising group. Exercisers compared to controls experienced significant weight loss of 1.5 kg (P < 0.005) and a significant reduction in total fat mass of 2 kg (P < 0.001). Abdominal and trunk adiposity was also significantly reduced in the exercising group by 0.1 kg (P < 0.05) and 1.5 kg (P < 0.001). Also the exercise group had a significant (P < 0.01) 17% reduction in visceral fat after 12 weeks of HIIE, whereas waist circumference was significantly decreased by week six (P < 0.001). Fat free mass was significantly increased (P < 0.05) in the exercising group by 0.4 kg for the leg and 0.7 kg for the trunk. No significant change (P > 0.05) occurred in levels of insulin, HOMA-IR, and blood lipids. Twelve weeks of HIIE resulted in significant reductions in total, abdominal, trunk, and visceral fat and significant increases in fat free mass and aerobic power.
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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.
Objective: To investigate the effects of low-volume high-intensity interval training (HIT) performed in the fasted (FAST) versus fed (FED) state on body composition, muscle oxidative capacity, and glycemic control in overweight/obese women. Design and methods: Sixteen women (27 ± 8 years, BMI: 29 ± 6 kg/m(2) , VO2peak : 28 ± 3 ml/kg/min) were assigned to either FAST or FED (n = 8 each) and performed 18 sessions of HIT (10× 60-s cycling efforts at ∼90% maximal heart rate, 60-s recovery) over 6 weeks. Results: There was no significant difference between FAST and FED for any measured variable. Body mass was unchanged following training; however, dual energy X-ray absorptiometry revealed lower percent fat in abdominal and leg regions as well as the whole body level (main effects for time, P ≤ 0.05). Fat-free mass increased in leg and gynoid regions (P ≤ 0.05). Resting muscle biopsies revealed a training-induced increase in mitochondrial capacity as evidenced by increased maximal activities of citrate synthase and β-hydroxyacyl-CoA dehydrogenase (P ≤ 0.05). There was no change in insulin sensitivity, although change in insulin area under the curve was correlated with change in abdominal percent fat (r = 0.54, P ≤ 0.05). Conclusion: Short-term low-volume HIT is a time-efficient strategy to improve body composition and muscle oxidative capacity in overweight/obese women, but fed- versus fasted-state training does not alter this response.
Objective: The effect of 12 weeks of high-intensity intermittent exercise (HIIE) on cardiac, vascular, and autonomic function of young males was examined. Methods: Thirty-eight young men with a BMI of 28.7 ± 3.1 kg m(-2) and age 24.9 ± 4.3 years were randomly assigned to either an HIIE or control group. The exercise group underwent HIIE three times per week, 20 min per session, for 12 weeks. Aerobic power and a range of cardiac, vascular, and autonomic measures were recorded before and after the exercise intervention. Results: The exercise, compared to the control group, recorded a significant reduction in heart rate accompanied by an increase in stroke volume. For the exercise group forearm vasodilatory capacity was significantly enhanced, P < 0.05. Arterial stiffness, determined by pulse wave velocity and augmentation index, was also significantly improved, after the 12-week intervention. For the exercise group, heart period variability (low- and high-frequency power) and baroreceptor sensitivity were significantly increased. Conclusion: High-intensity intermittent exercise induced significant cardiac, vascular, and autonomic improvements after 12 weeks of training.
The Physical Activity Readiness Questionnaire (PAR-Q) and the Physical Activity Readiness Medical Evaluation (PARmed-X) are internationally known preparticipation screening tools developed on the basis of expert opinion. The primary purposes of this consensus document were to seek evidence-based support for the PAR-Q and PARmed-X forms, to identify whether further revisions of these instruments are warranted, to determine how people responding positively to questions on the PAR-Q can be safely cleared without medical referral, and to develop exercise clearance procedures appropriate for various clinical conditions across the human lifespan. Seven systematic reviews were conducted, examining physical-activity-related risks and effective risk-stratification procedures for various prevalent chronic conditions. An additional systematic review assessed the risks associated with exercise testing and training of the general population. Two gap areas were identified and evaluated systematically: the role of the qualified exercise professional and the requisite core competencies required by those working with various chronic conditions; and the risks associated with physical activity during pregnancy. The risks associated with being physically inactive are markedly higher than transient risks during and following an acute bout of exercise in both asymptomatic and symptomatic populations across the lifespan. Further refinements of the PAR-Q and the PARmed-X (including online versions of the forms) are required to address the unique limitations imposed by various chronic health conditions, and to allow the inclusion of individuals across their entire lifespan. A probing decision-tree process is proposed to assist in risk stratification and to reduce barriers to physical activity. Qualified exercise professionals will play an essential role in this revised physical activity clearance process.
High-volume endurance exercise (END) improves glycaemic control in type 2 diabetes (T2D) but many individuals cite 'lack of time' as a barrier to regular participation. High-intensity interval training (HIT) is a time-efficient method to induce physiological adaptations similar to END, but little is known regarding the effect of HIT in T2D. Using continuous glucose monitoring (CGM), we examined the 24-h blood glucose response to one session of HIT consisting of 10 × 60 s cycling efforts at ~90% maximal heart rate, interspersed with 60 s rest. Seven adults with T2D underwent CGM for 24-h on two occasions under standard dietary conditions: following acute HIT and on a non-exercise control day (CTL). HIT reduced hyperglycaemia measured as proportion of time spent above 10 mmol/l (HIT: 4.5 ± 4.4 vs. CTL: 15.2 ± 12.3%, p = 0.04). Postprandial hyperglycaemia, measured as the sum of post-meal areas under the glucose curve, was also lower after HIT vs. CTL (728 ± 331 vs. 1142 ± 556 mmol/l·9 h, p = 0.01). These findings highlight the potential for HIT to improve glycaemic control in T2D.
The purpose of this study was to examine the effects of short-term high-intensity interval training (HIIT) on cardiovascular function, cardiorespiratory fitness, and muscular force. Active, young (age and body fat = 25.3 ± 4.5 years and 14.3 ± 6.4%) men and women (N = 20) of a similar age, physical activity, and maximal oxygen uptake (VO2max) completed 6 sessions of HIIT consisting of repeated Wingate tests over a 2- to 3-week period. Subjects completed 4 Wingate tests on days 1 and 2, 5 on days 3 and 4, and 6 on days 5 and 6. A control group of 9 men and women (age and body fat = 22.8 ± 2.8 years and 15.2 ± 6.9%) completed all testing but did not perform HIIT. Changes in resting blood pressure (BP) and heart rate (HR), VO2max, body composition, oxygen (O2) pulse, peak, mean, and minimum power output, fatigue index, and voluntary force production of the knee flexors and extensors were examined pretraining and posttraining. Results showed significant (p < 0.05) improvements in VO2max, O2 pulse, and Wingate-derived power output with HIIT. The magnitude of improvement in VO2max was related to baseline VO2max (r = -0.44, p = 0.05) and fatigue index (r = 0.50, p < 0.05). No change (p > 0.05) in resting BP, HR, or force production was revealed. Data show that HIIT significantly enhanced VO2max and O2 pulse and power output in active men and women.