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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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... High-intensity interval training (HIIT) is a training protocol that involves short periods of intense exertion followed by brief recovery periods or low-intensity activity (Billat, 2001;Buchheit & Laursen, 2013;Gibala et al., 2012;Gillen & Gibala, 2014;Ross et al., 2016;Bishop et al., 2019). When compared to sedentary (non-exercising) or moderate-intensity groups, HIIT is effective in strengthening cardiorespiratory fitness, aerobic capacity, and body composition (Buchan et al., 2011;Costigan et al., 2015;Kessler et al., 2012;Laursen & Jenkins, 2002;Logan et al., 2014;Sawyer et al., 2020;Sperlich et al., 2011). ...
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The purpose of this systematic review was to overview the physiological and performance effects of high-intensity interval training (HIIT) in tennis players. Searches for this review were performed by using four electronic databases: Web of Science, Scopus, SPORTDiscus with Full-Text, and PubMed. Intervention studies investigating the effects of HIIT on tennis players were searched from inception to December 29th, 2021. Seven studies met all of the inclusion criteria and were included in the study. The findings revealed that tennis players who participated in HIIT interventions had improved their aerobic capacity and tennis performance. Fluctuating results were reported for agility, sprint, and jump performances. In conclusion, the results of the review may suggest that HIIT is more beneficial for tennis players to achieve improvement in cardiorespiratory fitness and technical abilities regardless of age, gender, and competitive level.
... HIIT is a time-effective way to increase aerobic capacity, insulin sensitivity, blood pressure, and body composition compared to MICT according to evidence from laboratory research, however there is a lack of studies conducted in real world settings without the use of expensive equipment (i.e. cycle ergometers and treadmills), performed in small spaces and easy to implement in outdoor environment (Gillen & Gibala, 2014). ...
... Given the high proportion of sedentary behavior in the general population and the perceived barriers such as "lack of time", "lack of motivation", or "other responsibilities" for not engaging in regular exercise [6][7][8], efficient and enjoyable exercise programs are needed. In this regard, different forms of high-intensity interval training (HIIT), i.e., the alternation between high-intensity efforts and recovery periods could serve as useful alternatives to higher-volume low-intensity continuous endurance training (LIT) [9]. ...
Background: A sedentary lifestyle with low energy expenditure (EE) is associated with chronic diseases and mortality. Barriers such as "lack of time" or "lack of motivation" are common reasons why physical exercise is neglected in the general population. To optimize EE in the time available, time-efficient but also enjoyable types of exercise are required. We therefore used an isocaloric approach to systematically investigate the effects of six different endurance exercise modalities on metabolic, mechanical, cardiorespiratory, and subjective variables in relation to biological sex and physical fitness. Methods: Out of 104, 92 healthy participants (21 recreationally trained and 18 trained females, 25 recreationally trained and 28 trained males) were subjected to physiological exercise testing to determine the exercise intensities for six exercise modalities, i.e., three different high-intensity interval training (HIIT) protocols (5 × 4 min, 15 × 1 min, 30 × 30 sec intervals), threshold (THR), speed endurance production (SEP), and low-intensity training (LIT). One of three HIIT sessions served as the reference for the subsequent isocaloric exercise modalities which were completed in randomized order. Metabolic and mechanical variables, i.e., EE during exercise, time to isocaloric EE (Tiso), relative and absolute fat contribution, post-exercise oxygen consumption (EPOC), mechanical energy, as well as cardiorespiratory and subjective variables, i.e., heart rate, oxygen uptake response, rating of perceived exertion, and enjoyment were assessed. Data were analyzed using a 6 × 2 × 2 repeated-measures ANOVA. Results: All three versions of HIIT and THR achieved the same EE during exercise for the same training duration. We found that LIT had a 1.6-fold (p < 0.001) and SEP a 1.3-fold (p < 0.001) longer Tiso compared to HIIT with no effects of biological sex (p = 0.42, pη2 = 0.01) or physical fitness (p = 0.09, pη2 = 0.04). There was a main effect of exercise modality on EPOC (p < 0.001, pη2 = 0.76) with highest values for HIIT 30 × 30 (p = 0.032) and lowest for LIT (p < 0.001). The highest relative and absolute amounts of fatty acids were measured during LIT (p < 0.001), and the lowest values were obtained during HIIT modalities. HIIT 30 × 30 was the most enjoyable version of HIIT (p = 0.007), while THR was the least enjoyable exercise modality (p = 0.008). Conclusion: HIIT modalities are time-saving and enjoyable, regardless of sex and physical fitness. The results illustrate the relationship between exercise modality and metabolic, physiological, and subjective responses, and are thus of great interest to healthy individuals seeking time-saving and enjoyable exercise options.
... One of such regimens is the highintensity interval training (HIIT) which can most simply be described as bouts of exercise with short rest periods in between. It has been shown that musculoskeletal system could be better regulated with interval training versus the conventional exercises in young healthy individuals [1]. In terms of endurance, shortperiod, highintensity physical exercise provided significant benefits in a 40km race trial simulation [2]. ...
Aim. To explore effects of additional mind exercises on physical fitness and sport performance in athletes undergoing interval training. Material and Methods. Thirty athletes were assigned into two equal groups. They either received only interval training or a combination of interval training and mind exercises 6 days/week for 24 weeks. Data was collected at baseline and after 5, 10, 15, 20, and 24 weeks. Interval training comprised speed, endurance, strength, plyometrics, and flexibility components. Data collection comprised demographics, time required to complete 600-meter run, number of push-ups in 1 minute, Illinois agility run test time, Broad jump distance, and number of sit-ups in 1 minute. Results. Interval training with (P < 0.001) or without (P < 0.01) mind exercises resulted in significant reduction in body mass. Body mass index and 600m runtime reduced while number of push-ups and sit-ups in 1 minute, and agility run time improved in both groups (P < 0.001). After 24 weeks, mind exercises group ran significantly faster (P < 0.001). Mind exercises resulted in longer Broad jump (P < 0.001) compared to interval training alone (P < 0.01). Conclusions. Interval training caused significant reduction in body mass and lead to significantly improved physical fitness and sport performance. Addition of mind exercises resulted in significantly faster 600m run and longer Broad jump.
... High intensity interval training (HIIT) is an alternative to traditional training programmes, causing important physiological adaptations and eliciting improvements in fitness, and health [1]. HIIT is distinguished from other training programmes because sessions consist of relatively brief bursts of vigorous activity (i.e. ...
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Introduction: The force–velocity profile has been analysed previously in different sports modalities; nevertheless, it has not been analysed in CrossFit. Objective: The aim of this study was to report neuromuscular characteristics of CrossFit athletes using their individual force-velocity profile, investigating differences according to sex, age, and training frequency. Materials and Methods: 72 males (33.17 ± 6.86 years; BMI: 25.93 ± 3.64 kg/m2) and 18 females (30.11 ± 6.92 years; BMI: 23.53 ± 3.98 kg/m2) participated in this study. The force-velocity profile was calculated using Samozino’s method. Furthermore, neuromuscular characterization was completed with a squat jump and three drop jumps (20, 30, and 40 cm). Results: Regarding sex, significant differences in all analysed mechanical variables (p < 0.001) were found except for the theoretical maximal force (p = 0.944). No significant differences were found between age groups. Considering training frequency, athletes who train more than 5 days per week showed higher performance in all analysed mechanical variables (p < 0.05). Conclusion: CrossFit athletes have a force-velocity profile more oriented towards velocity than force. Males and females have different neuromuscular characteristics, also neuromuscular improvements can be achieved at any age. Moreover, higher neuromuscular performance is developed with a training frequency of 5 days or more per week.
... In line with this, it is evident that the intensification of aerobic training through interval stimuli is the fastest and most efficient way to develop aerobic performance and VO2max (8)(9)(10) . With this strategy, gradual increases in inclination were inversely associated with a proportional reduction in eccentric loads during running (11) , which result in less muscle damage to intra and extrafusal fibers (12) . ...
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Background: Physical exercise programs are typically composed of activities directed to the development of different physical abilities, usually stimulated in the same session. Objective: The aim of the study was to determine the effect of one session of aerobic exercise at high intensity to 1% and 10% gradient on the height (HJump) and kinematics of the depth jump (PExc - eccentric, concentric phase PCon, and contact time – CT). Methods: Twenty-five moderately trained men (VO2Max 53.2 ± 4.3 attended five visits in the laboratory. Familiarity with the procedures in depth jump, VO2Max measures and their velocity associated (VVO2Max), and time to exhaustion performance (TLim) were performed at two initial visits. Results: On the three subsequent visits, the volunteers were subjected to three maximum depth jumps before and 10 min after the following conditions: (1) running intervals at high intensity of 10% gradient (R10%), (2) at 1% gradient (R1%), and control condition (CON). The order of conditions was determined randomly. A running condition did not induce significant changes from HJump (R1% 1.1% vs 1.0% R10%) when expressed as percentage difference from the CON condition. The PExc, PCon, and CT also did not change after running sessions (P> 0.05). None of the intervals running strategies were able to generate significant change in height and kinematics of the vertical depth jump. Conclusion: The prescription of the running at VVO2Max in 1% or 10% gradient does not seem to lead to concurrent effect, is suggested to ensure the concomitant development of maximal aerobic power and explosive strength.
... Reviews have shown that HIIT improves cardiorespiratory fitness [2,3], cardiac function [4], and even reduces abdominal fat [5]. Both HIIT and moderate-intensity continuous exercise have been shown to improve maximum oxygen capacity in young to middle-aged adults, with HIIT being slightly more effective [3] and more time efficient [6]. However, with numerous protocols studied to date, choosing the right HIIT protocol may involve understanding the biomarkers that are produced by high-intensity exercise. ...
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Background Some health benefits from high-intensity interval training (HIIT) are facilitated by peripheral blood lactate levels. However, the lactate response from HIIT is variable and dependent on protocol parameters. Objectives We aimed to determine the HIIT protocol parameters that elicited peak lactate levels, and how these levels are associated with post-HIIT cognitive performance. Study Design We conducted a systematic review with meta-regression. Methods MEDLINE, Embase, CENTRAL, SPORTDiscus, and CINAHL + were searched from database inception to 8 April, 2022. Peer-reviewed primary research in healthy adults that determined lactate (mmol/L) and cognitive performance after one HIIT session was included. Mixed-effects meta-regressions determined the protocol parameters that elicited peak lactate levels, and linear regressions modelled the relationship between lactate levels and cognitive performance. Results Study entries (n = 226) involving 2560 participants (mean age 24.1 ± 4.7 years) were included in the meta-regression. A low total work-interval volume (~ 5 min), recovery intervals that are about five times longer than work intervals, and a medium session volume (~ 15 min), elicited peak lactate levels, even when controlling for intensity, fitness (peak oxygen consumption) and blood measurement methods. Lactate levels immediately post-HIIT explained 14–17% of variance in Stroop interference condition at 30 min post-HIIT. Conclusions A HIIT protocol that uses the above parameters (e.g., 8 × 30-s maximal intensity with 90-s recovery) can elicit peak lactate, a molecule that is known to benefit the central nervous system and be involved in exercise training adaptations. This review reports the state of the science in regard to the lactate response following HIIT, which is relevant to those in the sports medicine field designing HIIT training programs. Trial Registry Clinical Trial Registration: PROSPERO (CRD42020204400).
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We investigated the effects of performing a period of resistance training (RT) on the performance and molecular adaptations to a subsequent period of endurance training (ET). Twenty-five young adults were divided into RT+ET (n=13), which underwent seven weeks of RT followed by seven weeks of ET, and ET-only (n=12), which performed seven weeks of ET. Body composition, endurance performance, and muscle biopsies were collected before RT (T1, baseline for RT+ET), before ET (T2, post RT for RT+ET and baseline for ET), and after ET (T3). Immunohistochemistry was performed to determine fiber cross-sectional area (fCSA), myonuclear content, myonuclear domain size, satellite cell number, and mitochondrial content. Western blots were used to quantify markers of mitochondrial remodeling. Citrate synthase activity and markers of ribosome content were also investigated. Resistance training improved body composition and strength, increased vastus lateralis thickness, mixed and type II fCSA, myonuclear number, markers of ribosome content, and satellite cell content (p<0.050). In response to ET, both groups similarly decreased body fat percentage and improved endurance performance (e.g., VO2max, and speed at which the onset of blood lactate accumulation occurred during the VO2max test). Levels of mitochondrial complexes I-IV in the ET-only group increased 32–66%, while the RT+ET group increased 1–11%. Additionally, mixed fiber relative mitochondrial content increased 15% in the ET-only group but decreased 13% in the RT+ET group. In conclusion, RT performed prior to ET had no additional benefits to ET adaptations. Moreover, prior RT seemed to impair mitochondrial adaptations to ET.
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El presente trabajo académico tuvo como objetivo revisar en las bases de datos los efectos producidos por el entrenamiento intermitente de alta intensidad o HIIT sobre la composición corporal de adultos sedentarios, se realizó una técnica de búsqueda booleana y se definieron los criterios de inclusión y exclusión en dependencia de los objetivos y con el fin de dar respuesta a la pregunta de investigación, se identificaron 2925 artículos, en un proceso de selección se pudieron rescatar 12 artículos que cumplían con todos los criterios de inclusión, los principales resultados muestran que el 100% de trabajos analizados presenta una mejora en lo que respecta a composición corporal, también se obtuvo resultados diversos en los métodos de entrenamiento HIIT, siendo los más utilizados los trabajos en cicloergómetro, cinta para correr, y entrenamiento en circuitos de resistencia muscular, los que por lo general tienen una duración de 10 a 12 semanas. En conclusión, los programas de entrenamiento HIIT resulta ser una opción apropiada al momento de mejorar la composición corporal de adultos sedentarios, siempre y cuando haya una correcta administración de las cargas y una progresión optima del entrenamiento.
Recent studies have concluded that high-intensity interval training should be seen as a “viable alternative” to, and may be more enjoyable than, moderate-intensity continuous exercise. If true, these claims have the potential to revolutionize the science and practice of exercise, establishing high-intensity interval training as not only a physiologically effective exercise modality but also a potentially sustainable one. However, these claims stand in contrast to voluminous evidence according to which high levels of exercise intensity are typically experienced as less pleasant than moderate levels. To help researchers, peer reviewers, editors, and critical readers appreciate possible reasons for the apparently conflicting results, we present a checklist that identifies crucial methodological elements in studies investigating the effects of high-intensity interval training on affect and enjoyment. This second installment covers how “high-intensity” and “moderate-intensity” experimental conditions are defined, the timing of assessments of affect, the modeling of affective responses, and data interpretation.
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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.