Trine Karlsen

Age‐predicted maximal heart rate in healthy subjects: The HUNT Fitness Study

Maximal heart rate (HRmax) declines substantially with age, but the magnitude and possible modifying effect of gender, body composition, and physical activity are not fully established. The present study examined the relationship between HRmax and age in 3320 healthy men and women within a wide age range using data from the HUNT Fitness Study (2007–2008). Subjects were included if a maximal effort could be verified during a maximal exercise test. General linear modeling was used to determine the effect of age on HRmax. Subsequently, the effects of gender, body mass index (BMI), physical activity status, and maximal oxygen uptake were examined. Mean predicted HRmax by three former prediction formulas were compared with measured HRmax within 10‐year age groups. HRmax was univariately explained by the formula 211 − 0.64·age (SEE, 10.8), and we found no evidence of interaction with gender, physical activity, VO2max level, or BMI groups. There were only minor age‐adjusted differences in HRmax between these groups. Previously suggested prediction equations underestimated measured HRmax in subjects older than 30 years. HRmax predicted by age alone may be practically convenient for various groups, although a standard error of 10.8 beats/min must be taken into account. HRmax in healthy, older subjects and women were higher than previously reported.

High-Intensity Interval Training in Patients with Heart Failure with Reduced Ejection Fraction

Background: Small studies have suggested that high-intensity interval training (HIIT) is superior to moderate continuous training (MCT) in reversing cardiac remodeling and increasing aerobic capacity in patients with heart failure with reduced ejection fraction. The present multicenter trial compared 12 weeks of supervised interventions of HIIT, MCT, or a recommendation of regular exercise (RRE). Methods: Two hundred sixty-one patients with left ventricular ejection fraction ⩽35% and New York Heart Association class II to III were randomly assigned to HIIT at 90% to 95% of maximal heart rate, MCT at 60% to 70% of maximal heart rate, or RRE. Thereafter, patients were encouraged to continue exercising on their own. Clinical assessments were performed at baseline, after the intervention, and at follow-up after 52 weeks. Primary end point was a between-group comparison of change in left ventricular end-diastolic diameter from baseline to 12 weeks. Results: Groups did not differ in age (median, 60 years), sex (19% women), ischemic pathogenesis (59%), or medication. Change in left ventricular end-diastolic diameter from baseline to 12 weeks was not different between HIIT and MCT (P=0.45); left ventricular end-diastolic diameter changes compared with RRE were −2.8 mm (−5.2 to −0.4 mm; P=0.02) in HIIT and −1.2 mm (−3.6 to 1.2 mm; P=0.34) in MCT. There was also no difference between HIIT and MCT in peak oxygen uptake (P=0.70), but both were superior to RRE. However, none of these changes was maintained at follow-up after 52 weeks. Serious adverse events were not statistically different during supervised intervention or at follow-up at 52 weeks (HIIT, 39%; MCT, 25%; RRE, 34%; P=0.16). Training records showed that 51% of patients exercised below prescribed target during supervised HIIT and 80% above target in MCT. Conclusions: HIIT was not superior to MCT in changing left ventricular remodeling or aerobic capacity, and its feasibility remains unresolved in patients with heart failure. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00917046.

High Intensity Interval Training in Heart Failure Patients with Reduced Ejection Fraction

Background: Small studies have suggested that high-intensity interval training (HIIT) is superior to moderate continuous training (MCT) in reversing cardiac remodeling and increasing aerobic capacity in patients with heart failure with reduced ejection fraction. The present multicenter trial compared 12 weeks of supervised interventions of HIIT, MCT, or a recommendation of regular exercise (RRE). Methods: Two hundred sixty-one patients with left ventricular ejection fraction ⩽35% and New York Heart Association class II to III were randomly assigned to HIIT at 90% to 95% of maximal heart rate, MCT at 60% to 70% of maximal heart rate, or RRE. Thereafter, patients were encouraged to continue exercising on their own. Clinical assessments were performed at baseline, after the intervention, and at follow-up after 52 weeks. Primary end point was a between-group comparison of change in left ventricular end-diastolic diameter from baseline to 12 weeks. Results: Groups did not differ in age (median, 60 years), sex (19% women), ischemic pathogenesis (59%), or medication. Change in left ventricular end-diastolic diameter from baseline to 12 weeks was not different between HIIT and MCT (P=0.45); left ventricular end-diastolic diameter changes compared with RRE were −2.8 mm (−5.2 to −0.4 mm; P=0.02) in HIIT and −1.2 mm (−3.6 to 1.2 mm; P=0.34) in MCT. There was also no difference between HIIT and MCT in peak oxygen uptake (P=0.70), but both were superior to RRE. However, none of these changes was maintained at follow-up after 52 weeks. Serious adverse events were not statistically different during supervised intervention or at follow-up at 52 weeks (HIIT, 39%; MCT, 25%; RRE, 34%; P=0.16). Training records showed that 51% of patients exercised below prescribed target during supervised HIIT and 80% above target in MCT. Conclusions: HIIT was not superior to MCT in changing left ventricular remodeling or aerobic capacity, and its feasibility remains unresolved in patients with heart failure. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00917046.

Exercise-Training Intervention Studies in Competitive Swimming

Competitive swimming has a long history and is currently one of the largest Olympic sports, with 16 pool events. Several aspects separate swimming from most other sports such as (i) the prone position; (ii) simultaneous use of arms and legs for propulsion; (iii) water immersion (i.e. hydrostatic pressure on thorax and controlled respiration); (iv) propulsive forces that are applied against a fluctuant element; and (v) minimal influence of equipment on performance. Competitive swimmers are suggested to have specific anthropometrical features compared with other athletes, but are nevertheless dependent on physiological adaptations to enhance their performance. Swimmers thus engage in large volumes of training in the pool and on dry land. Strength training of various forms is widely used, and the energetic systems are addressed by aerobic and anaerobic swimming training. The aim of the current review was to report results from controlled exercise training trials within competitive swimming. From a structured literature search we found 17 controlled intervention studies that covered strength or resistance training, assisted sprint swimming, arms-only training, leg-kick training, respiratory muscle training, training the energy delivery systems and combined interventions across the aforementioned categories. Nine of the included studies were randomized controlled trials. Among the included studies we found indications that heavy strength training on dry land (one to five repetitions maximum with pull-downs for three sets with maximal effort in the concentric phase) or sprint swimming with resistance towards propulsion (maximal pushing with the arms against fixed points or pulling a perforated bowl) may be efficient for enhanced performance, and may also possibly have positive effects on stroke mechanics. The largest effect size (ES) on swimming performance was found in 50 m freestyle after a dry-land strength training regimen of maximum six repetitions across three sets in relevant muscle-groups (ES 1.05), and after a regimen of resisted- and assisted-sprint training with elastic surgical tubes (ES 1.21). Secondly, several studies suggest that high training volumes do not pose any immediate advantage over lower volumes (with higher intensity) for swim performance. Overall, very few studies were eligible for the current review although the search strategy was broad and fairly liberal. The included studies predominantly involved freestyle swimming and, overall, there seems to be more questions than answers within intervention-based competitive swimming research. We believe that this review may encourage other researchers to pursue the interesting topics within the physiology of competitive swimming.

Home-based versus hospital-based high-intensity interval training in cardiac rehabilitation: a randomized study

Background High-intensity interval training (HIT) as exercise therapy is gradually implemented in cardiac rehabilitation as the cardiovascular benefits from exercise is intensity dependent. However, in previous studies, HIT has been performed with strict supervision. The aim of the study was to assess the feasibility and effectiveness of different modes of HIT in cardiac rehabilitation. Design a randomized clinical study. Methods Ninety participants with coronary artery disease (80 men/10 women, mean age 57 ± 8 years) were randomly assigned to one of three exercise modes: group exercise (GE), treadmill exercise (TE), or home-based exercise (HE). HIT was performed twice a week for 12 weeks with an exercise intensity of 85–95% of peak heart rate. The primary outcome measure was change in peak oxygen uptake (peak VO2). Results Eighty-three participants (92%) completed the intervention without any severe adverse events. Peak VO2 increased from 34.7 ± 7.3 to 39.0 ± 8.0 ml/kg/min, 32.7 ± 6.5 to 36.0 ± 6.2 ml/kg/min, and 34.4 ± 4.8 to 37.2 ± 5.2 ml/kg/min in TE, GE, and HE, respectively. Mean group difference for TE vs. HE was 1.6 ml/kg/min (95% confidence interval, CI, 0.7 to 3.1, p = 0.02), TE vs. GE 1.1 ml/kg/min (95% CI−0.5 to 2.5, p = 0.27), and GE vs. HE 0.6 ml/kg/min (95% CI −1.0 to 2.1, p = 1). However, on-treatment analysis showed no significant difference between groups. Conclusion HIT was efficiently performed in three settings of cardiac rehabilitation, with respect to target exercise intensity, exercise attendance, and increase in peak VO2. Exercise mode was not essential for exercise capacity.

High Intensity Interval Training for Maximizing Health Outcomes

Regular physical activity and exercise training are important actions to improve cardiorespiratory fitness and maintain health throughout life. There is solid evidence that exercise is an effective preventative strategy against at least 25 medical conditions, including cardiovascular disease, stroke, hypertension, colon and breast cancer, and type 2 diabetes. Traditionally, endurance exercise training (ET) to improve health related outcomes has consisted of low- to moderate ET intensity. However, a growing body of evidence suggests that higher exercise intensities may be superior to moderate intensity for maximizing health outcomes. The primary objective of this review is to discuss how aerobic high-intensity interval training (HIIT) as compared to moderate continuous training may maximize outcomes, and to provide practical advices for successful clinical and home-based HIIT.

Maximal Strength Training Restores Walking Mechanical Effeciency in Heart Patients

The purpose of this study was to investigate whether maximal strength leg press training improves walking mechanical efficiency in coronary artery disease patients. Ten coronary artery disease patients trained 24 sessions of horizontal leg press. Each training session consisted of 4 sets with 4 repetitions of maximal mobilization of concentric force to exhaustion. Seven healthy age matched subjects served as time controls. Maximal strength training improved walking mechanical efficiency (i.e. the oxygen cost to generate a given work load) by 35% (p=0.007) in coronary artery disease patients (from 18+/-4% at pre test to 25+/-6% at post test), and restored walking efficiency to the level of the healthy age matched controls ( approximately 25%). Strength training further improved one repetition maximum from 138+/-24 to 198+/-24 kg (44%) (p=0.000) and rate of force development by 85% (p=0.001), with no change in the control group. Maximal strength leg press training restores walking mechanical efficiency and significantly improves one repetition maximum and rate of force development in coronary artery disease patients after 24 training sessions each lasting only 20 min.

Interval and strength training in CAD patients.

This study sought to study the effect of high intensity aerobic interval endurance training on peak stroke volume and maximal strength training on mechanical efficiency in coronary artery disease (CAD) patients. 8 CAD patients (age 61.4 ± 3.7 years) trained 30 interval training sessions with 4 × 4 min intervals at 85-95% of peak heart rate while 10 CAD patients (age 66.5 ± 5.5 years) trained 24 sessions of maximal horizontal leg press. In the interval training group peak stroke volume increased significantly by 23% from 94.1 ± 23.0 mL · beat (-1) to 115.8 ± 22.4 mL · beat (-1) (p<0.05). Peak oxygen uptake increased significantly by 17% from 27.2 ± 4.5 mL · kg (-1) · min (-1) to 31.8 ± 5.0 mL · kg (-1) min (-1) (p<0.05) in the same group. In contrast, there was no such exercise training-induced change in peak stroke volume or peak oxygen uptake in the maximal strength training group, despite a 35% improvement in sub maximal walking performance.

Effect of aerobic high-intensity hybrid training on stroke volume and peak oxygen consumption in men with spinal cord injury.

Objective:The aim of this study was to determine the effect of high-intensity interval training during combined arm cycling exercise (ACE) and functional electrical stimulation leg cycling (hybrid exercise), on peak stroke volume and peak oxygen consumption in individuals with spinal cord injury (SCI). Design:A baseline control trial at an outpatient SCI clinic (St. Olavs University Hospital, Norway) was conducted. Participants included six men with SCI in stable neurologic recovery (ASIA Impairment Scale grade A). The study intervention included aerobic high-intensity hybrid exercise training three times a week for 8 wks preceded by a 7-wk control period of regular daily activity. Main outcome measures were peak stroke volume during hybrid cycling and peak oxygen consumption during hybrid cycling, ACE, and functional electrical stimulation leg cycling. The tests were conducted at three time points: 1, baseline; 2, control; and 3, post-training. Results:Data are presented as mean (SD). From control to post-training tests, a significant increase in peak stroke volume by 33% (P = 0.004), from 77.7 (9.9) to 103.4 (17.1) ml/beat, was found. Furthermore, between control and post-training tests, hybrid peak oxygen consumption increased by 24.4%, from 24.6 (3.9) to 30.6 (5.2) ml kg−1 min−1 (P = 0.003), and peak oxygen consumption during isolated ACE and functional electrical stimulation cycling increased by 25.9% (P = 0.001) and 23.5% (P = 0.007), respectively. Conclusions:Training aerobic high-intensity hybrid intervals at 85%-95% of peak Watt was feasible for this group of SCI men and significantly increased peak stroke volume and peak oxygen uptake. Because aerobic capacity is directly linked to mortality and morbidity, the present study may be useful for designing training programs sufficient to reverse the risk of cardiovascular disease in SCI.

Long-term Exercise Adherence After High-intensity Interval Training in Cardiac Rehabilitation: A Randomized Study.

BACKGROUND AND PURPOSE Exercise adherence in general is reported to be problematic after cardiac rehabilitation. Additionally, vigorous exercise is associated with impaired exercise adherence. As high-intensity interval training (HIT) is frequently used as a therapy to patients with coronary artery disease in cardiac rehabilitation, the objective was to assess long-term exercise adherence following an HIT cardiac rehabilitation programme. METHODS A multicentre randomized study was carried out. Eligible participants were adults who had previously attended a 12-week HIT cardiac rehabilitation programme, as either a home-based or hospital-based HIT (treadmill exercise or group exercise). The primary outcome was change in peak oxygen uptake; secondary outcomes were self-reported and objectively measured physical activity. RESULTS Out of 83 eligible participants, 76 were available for assessment (68 men/8 women, mean age 59 (8) years) at a one-year follow-up. Peak oxygen uptake was significantly elevated above baseline values, (treadmill exercise: 35.8 (6.4) vs. 37.4 (7.4) ml kg(-1)  min(-1) , group exercise: 32.7 (6.5) vs. 34.1 (5.8) ml kg(-1)  min(-1) and home-based exercise: 34.5 (4.9) vs. 36.7 (5.8) ml kg(-1)  min(-1) at baseline and follow-up, respectively), with no significant differences between groups. The majority of the participants (>90%) met the recommended daily level of 30 minutes of moderate physical activity. The home-based group showed a strong trend towards increased physical activity compared with the hospital-based groups. DISCUSSION The results from this study have shown that both home-based and hospital-based HIT in cardiac rehabilitation induce promising long-term exercise adherence, with maintenance of peak oxygen uptake significantly above baseline values at a one-year follow-up. The implication for physiotherapy practice is that HIT in cardiac rehabilitation induces satisfactory long-term exercise adherence.