High-intensity Training versus Traditional Exercise Interventions for Promoting Health

Lars Nybo; Emil Sundstrup; Markus D. Jakobsen; Magni Mohr; Therese Hornstrup; Lene Simonsen; Jens Bülow; Morten B. Randers; Jens J. Nielsen; Per Aagaard; Peter Krustrup

Disclosures

Med Sci Sports Exerc. 2010;42(10):1951-1958. 

In This Article

Methods

Thirty-six untrained men that had not participated in any type of regular physical training for at least 2 yr were recruited for the study. The participants had a mean age of 31 yr (range = 20–43 yr; for anthropometric details, see Table 1), and they were all nonsmokers, without diagnosed metabolic or cardiovascular diseases. The study was carried out in accordance with the guidelines contained in the Declaration of Helsinki and approved by the local ethical committee of Copenhagen (14606; H-C-2007-0012), and informed written consent was obtained from all subjects.

Design

The subjects were divided into four groups: 1) a group that performed intense interval running (INT; n = 8); 2) a strength-training group (STR; n = 8); 3) a group that performed prolonged moderate intense continuous running (MOD; n = 9); and 4) a control group performing no physical training (CON; n = 11). The participant in the three training groups completed three different 12-wk training programs as described below, whereas the participants in CON continued their daily life activities during the period. Before and after the 12-wk intervention period, the subjects completed a series of tests that consisted of an exercise test, an oral glucose tolerance test (OGTT), measurements of resting blood pressure, a plasma lipoprotein profile, and obtainment of a muscle biopsy for determination of capillarization and metabolic enzyme levels.

Except for the training regimens and for the days before the testing days, the subjects were instructed to continue their habitual lifestyle and to maintain their normal dietary practices throughout the 12-wk period. However, before the experimental days, the subjects were required to refrain from alcohol and exercise for 48 h before the resting measurement and the experimental exercise trials.

Measurements and Test Procedures

Subjects were familiarized with the exercise test and with the blood pressure measurements at least one time before the experiment. Fasting blood glucose, lipoproteins, resting HR, and blood pressure were determined in the morning under standardized conditions and after an overnight fast. Blood pressure was measured at least six times, with the subjects in a supine position, by an automatic upper arm blood pressure monitor (M-7 or HEM-709; OMRON, Schaumburg, IL), and an average of the six values for diastolic and systolic blood pressure was recorded. Mean arterial pressure (MAP) was calculated as 1/3 × systolic pressure + 2/3 × diastolic pressure. With this procedure, the coefficient of variation (CV) for repeated measures on the same day was less than 2%, and the day-to-day variation (CV for the control group) was 2.6%.

Exercise Test

Pulmonary gas exchange (CPX MedGraphics, St. Paul, MN), HR (Polar Team System; Polar Electro Oy, Kempele, Finland), and venous blood sampling were performed during a standardized treadmill test consisting of 6 min of walking at 6.5 km·h−1 and 6 min of submaximal running at 9.5 km·h−1, followed by a 15-min rest period and thereafter an incremental test to exhaustion. Pulmonary oxygen uptake (V̇O2) and RER were measured during the last 3 min of walking at 6.5 km·h−1 and similarly during the last 3 min of running at 9.5 km·h−1. V̇O2max and HRmax were determined as the peak value reached in a 30-s period during the incremental test. Fat oxidation during walking was calculated from the RER and the steady state V̇O2 measured at 6.5 km·h−1 and similarly for submaximal running at 9.5 km·h−1.

Oral Glucose Tolerance Test

Subjects refrained from performing any strenuous physical activity for 2 d before the OGTT and attended the laboratory having fasted overnight. Venous blood samples were collected from an antecubital venous catheter before and 15, 30, 60, 90, and 120 min after ingestion of 75 g of glucose.

Furthermore, before the OGTT, while the subject was still fasting, 2 mL of blood was drawn into heparinized syringes for determination of fasting insulin and glucose levels (ABL 615; Radiometer Medical, Copenhagen, Denmark). Furthermore, 10 mL was drawn into dry syringes for determination of plasma fatty acid, HDL cholesterol, and plasma triacylglycerol concentrations measured by commercial kits (Wako Chemicals, Neuss, Germany) on a Hitachi autoanalyzer (Roche Diagnostic, Basel, Switzerland). The analytical variations (CV) for these measures are reported to be less than 1.5%. LDL cholesterol was calculated in accordance with the Friedewald-Levy-Fredrickson equation (27b) as total cholesterol minus HDL cholesterol and one-fifth of total plasma triacylglycerol. Plasma concentrations of insulin were determined using a RIA kit (Pharmacia Insulin Radioimmunoassay 100; Pharmacia & Upjohn Diagnostics, Uppsala, Sweden; intra-assay CV 3%).

Body weight was measured in the morning after an overnight fast on a platform scale (Ohaus, Germany). Body composition was determined by dual-energy x-ray absorptiometry (DEXA scan, DPX-IQ version 4.6.6; Lunar Corp., Madison, WI).

Muscle biopsies were obtained at rest from musculus vastus lateralis under local anesthesia using the Bergstrom technique. The posttraining biopsy was obtained between 48 and 72 h after the final training session, and the pretraining biopsies were also obtained with no physical activity for 48 h before the biopsy. All biopsies were frozen in liquid nitrogen within 15 s and stored at −80°C for subsequent analysis. Muscle tissue was subsequently freeze dried and dissected free of all visible exogenous adipose tissue, connective tissue, and blood under a stereo microscope (Stemi 2000-C; Zeiss, Oberkochen, Germany).

Approximately 30 mg of wet weight muscle tissue was mounted in an embedding medium (OCT Tissue-Tek; Sakura Finetek, Zoeterwoude, The Netherlands), frozen in precooled isopentane, and analyzed histochemically for capillaries. Maximal citrate synthase (CS) and beta-hydroxyacyl-CoA-dehydrogenase (HAD) activities were determined fluorimetrically on a separate piece of muscle from the biopsy. The muscle fibers were mixed, and pooled fibers were used for the determination of maximal enzyme activity as expressed in micromole per gram (dry weight muscle) per minute.[22]

Training

The high-intensity training consisted of a brief 5-min warm-up with light jogging followed by five intervals of 2 min of near-maximal running (HR above 95% of their HRmax at the end of the 2-min period; total exercise time per session = 20 min, including warm-up). For all training groups, there were three scheduled training sessions per week. However, because of injuries or absence for other reasons, the participants in the INT group completed 2.0 ± 0.1 sessions per week corresponding to a total training time during the 12 wk of approximately 480 min, including warm-up. Three of the subjects in INT missed between one and four training sessions because of overuse injuries (shin splints-periostitis tibialis medialis and/or lateralis); however, no acute injuries were registered. Furthermore, one of the subjects suffered from inflammation of the hollow foot tendon (fasciitis plantaris), and another had bilateral unspecific knee pain. The prolonged running sessions consisted of 1 h of continuous running at 80% of individual HRmax approximately 65% of V̇O2max (as evaluated from the correlation between V̇O2 and HR during the treadmill test). The average number of completed training sessions was 2.5 ± 0.2 per week for the participants in MOD corresponding to a total training time of approximately 1800 min. In the MOD group, two subjects missed training sessions because of overuse injuries similar to those reported for the INT group. The strength-training program consisted of 12 wk of progressive heavy-resistance strength training (2.0 ± 0.1 times a week; total time, ~1500 min). The training consisted of three to four sets of the following exercises: squat, hack squat, incline leg pres, isolated knee extension, hamstring curls, and calf raises. The loads corresponded to 12–16 repetition maximum (RM) during the first 4 wk and 6–10 RM during the remaining 8 wk of the training period, with the absolute loads gradually adjusted to match the individual progressions in muscle strength. The total exercise time was 60 min per session, and the subjects completed training with 1-min breaks between sets (average HR during training, ~50% of HRmax).

Statistics

Between- and within-group data were evaluated both by two-factor mixed ANOVA design and with one-way ANOVA on repeated measurement. When a significant interaction was detected, data were subsequently analyzed using a Newman-Keuls post hoc test. The significance level was set at P < 0.05. Data are presented as means ± SE unless otherwise indicated.

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