Aerobic high-intensity intervals improve V̇O2max more than supramaximal sprint intervals in females, similar to males.

INTRODUCTION: Maximal oxygen uptake (V̇O2max ) is a pivotal factor for aerobic endurance performance. Recently, aerobic high-intensity interval training (HIIT) was documented to be superior to sprint interval training (SIT) in improving V̇O2max in well-trained males. However, as mounting evidence suggests that physiological responses to training are sex-dependent, examining the effects of HIIT versus SIT on V̇O2max , anaerobic capacity, and endurance performance in females is warranted. METHODS: We randomized 81 aerobically well-trained females (22 ± 2 years, 51.8 ± 3.6 mL∙kg-1 ∙min-1 V̇O2max ), training three times weekly for 8 weeks, to well-established protocols: (1) HIIT 4 × 4 min at ~95% of maximal aerobic speed (MAS), with 3 min active recovery (2) SIT 8 × 20 s at ~150% of MAS, with 10 s passive recovery (3) SIT 10 × 30 s at ~175% of MAS, with 3.5 min active recovery. RESULTS: Only HIIT 4 × 4 min increased V̇O2max (7.3 ± 3.1%), different from both SIT groups (all p < 0.001). Anaerobic capacity (maximal accumulated oxygen deficit) increased following SIT 8 × 20 s (6.5 ± 10.5%, p < 0.05), SIT 10 × 30 s (14.4 ± 13.7%, p < 0.05; different from HIIT 4 × 4 min, p < 0.05). SIT 10 × 30 s resulted in eight training-induced injuries, different from no injuries following HIIT 4 × 4 min and SIT 8 × 20 s (p < 0.001). All groups improved long-distance (3000-meter) and sprint (300-meter) running performance (all p < 0.001). SIT protocols improved sprint performance more than HIIT 4 × 4 min (p < 0.05). Compared to previous male results, no increase in V̇O2max following SIT 8 × 20 s (p < 0.01), and a higher injury rate for SIT 10 × 30 s (p < 0.001), were evident. CONCLUSIONS: In aerobically well-trained women, HIIT is superior to SIT in increasing V̇O2max while all-out treadmill running SIT is potentially more harmful.

Aerobic high-intensity intervals are superior to improve V̇O2max compared with sprint intervals in well-trained men.

Maximal oxygen uptake (V̇O2max ) may be the single most important factor for long-distance running performance. Interval training, enabling high intensity, is forwarded as the format that yields the largest increase in V̇O2max . However, it is uncertain if an optimal outcome on V̇O2max , anaerobic capacity, and running performance is provided by training with a high aerobic intensity or high overall intensity. Thus, we randomized 48 aerobically well-trained men (23 ± 3 years) to three commonly applied interval protocols, one with high aerobic intensity (HIIT) and two with high absolute intensity (sprint interval training; SIT), 3× week for 8 weeks: (1) HIIT: 4 × 4 min at ~95% maximal aerobic speed (MAS) with 3 min active breaks. (2) SIT: 8 × 20 s at ~150% MAS with 10 s passive breaks. (3) SIT: 10 × 30 s at ~175% MAS with 3.5 min active breaks. V̇O2max increased more (p < 0.001) following HIIT, 4 × 4 min (6.5 ± 2.4%, p < 0.001) than SIT, 8 × 20 s (3.3 ± 2.4%, p < 0.001) and SIT, 10 × 30 s (n.s.). This was accompanied by a larger (p < 0.05) increase in stroke volume (O2 -pulse) following HIIT, 4 × 4 min (8.1 ± 4.1%, p < 0.001) compared with SIT, 8 × 20 s (3.8 ± 4.2%, p < 0.01) and SIT, 10 × 30 (n.s.). Anaerobic capacity (maximal accumulated oxygen deficit) increased following SIT, 8 × 20 s (p < 0.05), but not after HIIT, 4 × 4 min, nor SIT, 10 × 30 s. Long-distance (3000-m) endurance performance increased (p < 0.05-p < 0.001) in all groups (HIIT, 4 × 4 min: 5.9 ± 3.2%; SIT, 8 × 20 s: 4.1 ± 3.7%; SIT, 10 × 30 s: 2.2 ± 2.2%), with HIIT increasing more than SIT, 10 × 30 s (p < 0.05). Sprint (300-m) performance exhibited within-group increases in SIT, 8 × 20 s (4.4 ± 2.0%) and SIT, 10 × 30 s (3.3 ± 2.8%). In conclusion, HIIT improves V̇O2max more than SIT. Given the importance of V̇O2max for most endurance performance scenarios, HIIT should typically be the chosen interval format.

Maximal strength training in patients with inflammatory rheumatic disease: implications for physical function and quality of life.

PURPOSE: Patients with inflammatory rheumatic disease (IRD) have attenuated muscle strength in the lower extremities, resulting in impaired physical function and quality of life. Although maximal strength training (MST), applying heavy resistance, is documented to be a potent countermeasure for such attenuation, it is uncertain if it is feasible in IRD given the pain, stiffness, and joint swelling that characterize the population. METHODS: 23 patients with IRD (49 ± 13 years; 20 females/3 males), diagnosed with spondyloarthritis, rheumatoid arthritis, or systemic lupus erythematosus, were randomized to MST or a control group (CG). The MST group performed four × four repetitions dynamic leg press two times per week for 10 weeks at ~ 90% of one repetition maximum (1RM). Before and after training 1RM, rate of force development (RFD), and health-related quality of life (HRQoL) were measured. RESULTS: Session attendance in the MST group was 95%, of which 95% conducted according to MST protocol. Furthermore, MST increased 1RM (29 ± 12%, p = 0.001) and early and late phase RFD (33-76%, p < 0.05). All improvements were different from the CG (p < 0.05). MST also resulted in HRQoL improvements in the dimensions; physical functioning, general health, and vitality (p < 0.05). Physical functioning was associated with 1RM (rho = 0.55, p < 0.01) and early phase RFD (rho = 0.53-0.71, p < 0.01; different from CG p < 0.05). CONCLUSIONS: Despite being characterized by pain, stiffness, and joint swelling, patients with IRD appear to tolerate MST well. Given the improvements in 1RM, RFD, and HRQoL MST should be considered as a treatment strategy to counteract attenuated muscle strength, physical function, and HRQoL. TRIAL REGISTRATION: ClinicalTrials.gov, NCT04998955, retrospectively registered.

Determinants of the diminished exercise capacity in patients with chronic obstructive pulmonary disease: looking beyond the lungs.

KEY POINTS: Peak oxygen uptake, a primary determinant of prognosis, mortality and quality of life, is diminished in patients with chronic obstructive pulmonary disease (COPD), with mounting evidence supporting an important role for peripheral dysfunction, particularly within skeletal muscle. In patients with severe COPD and activity-matched controls, muscle oxygen transport and utilization were assessed at peak effort during single-leg knee-extensor exercise (KE), where ventilation is assumed to be submaximal. This strategy removes ventilation as the major constraint to exercise capacity in COPD, allowing maximal muscle function to be attained and evaluated. During maximal KE, both convective arterial oxygen delivery to the skeletal muscle microvasculature and subsequent diffusive oxygen delivery to the mitochondria were diminished in patients with COPD compared to control subjects. These findings emphasize the importance of factors, beyond the lungs, that influence exercise capacity in this patient population and may, ultimately, influence the prognosis, mortality and quality of life for patients with COPD. ABSTRACT: Peak oxygen uptake ( V̇O2peak ), a primary determinant of prognosis, mortality and quality of life, is diminished in patients with chronic obstructive pulmonary disease (COPD). Mounting evidence supports an important role of the periphery, particularly skeletal muscle, in the diminished V̇O2peak with COPD. However, the peripheral determinants of V̇O2peak have not been comprehensively assessed in this cohort. Thus, the hypothesis was tested that both muscle convective and diffusive oxygen (O2 ) transport, and therefore skeletal muscle peak O2 uptake ( V̇MO2peak ), are diminished in patients with COPD compared to matched healthy controls, even when ventilatory limitations (i.e. attainment of maximal ventilation) are minimized by using small muscle mass exercise. Muscle O2 transport and utilization were assessed at peak exercise from femoral arterial and venous blood samples and leg blood flow (by thermodilution) in eight patients with severe COPD (forced expiratory volume in 1s (FEV1 ) ± SEM = 0.9 ± 0.1 l, 30% of predicted) and eight controls during single-leg knee-extensor exercise. Both muscle convective O2 delivery (0.44 ± 0.06 vs. 0.69 ± 0.07 l min-1 , P < 0.05) and muscle diffusive O2 conductance (6.6 ± 0.8 vs. 10.4 ± 0.9 ml min-1  mmHg-1 , P < 0.05) were ∼1/3 lower in patients with COPD than controls, resulting in an attenuated V̇MO2peak in the patients (0.27 ± 0.04 vs. 0.42 ± 0.05 l min-1 , P < 0.05). When cardiopulmonary limitations to exercise are minimized, the convective and diffusive determinants of V̇MO2peak , at the level of the skeletal muscle, are greatly attenuated in patients with COPD. These findings emphasize the importance of factors, beyond the lungs, that may ultimately influence this population's prognosis, mortality and quality of life.

Prediction of upper extremity peak oxygen consumption from heart rate during submaximal arm cycling in young and middle-aged adults.

Based on the strong linear relationship between heart rate (HR) and oxygen consumption, the Åstrand-Ryhming cycle ergometer test (Astrand and Ryhming in J Appl Physiol 7:218-221, 1954) is a widely used submaximal test to predict whole body maximal oxygen consumption ([Formula: see text]). However, a similar test predicting peak oxygen consumption ([Formula: see text]) in the upper extremities is not established, and may be very useful for individuals unable to use their lower extremities or/and if separation of upper extremity aerobic capacity is sought after. Thus, the aim of the current study was to develop a submaximal test predicting [Formula: see text] in arm-cycling. Forty-nine healthy volunteers (25 women: 38 ± 13 years; 24 men: 39 ± 12 years) tested arm-cycle [Formula: see text] on a protocol with 4-min, 21-W increments to exhaustion. The data were contrasted to treadmill [Formula: see text] values. Arm-cycle [Formula: see text] was 66 ± 8% of [Formula: see text] (r = 0.92, p < 0.001; women: 1.9 ± 0.4 L min-1; men: 3.0 ± 0.7 L min-1). Arm-cycle HR and [Formula: see text] exhibited correlations of r = 0.79 and r = 0.78 for women and men, respectively, while corresponding correlations between work rate and [Formula: see text] were r = 0.95 (women) and r = 0.89 (men) (all p < 0.001). Arm-cycle [Formula: see text] prediction revealed a standard error of estimate (SEE) of 11.2% (women) and 10.2% (men), and was primarily due to individual arm-cycle maximal HR (women: 173 ± 13 beats min-1; men: 174 ± 10 beats min-1; correction factor: 5-7%). In conclusion, from a single 4-min stage of submaximal arm cycling, [Formula: see text] can be predicted with a SEE of 10-11%. The arm-cycle test may have important value for individuals who rely on arms in sports and occupations, and for patients with lower extremity disabilities.

Maximal strength training: the impact of eccentric overload.

The search for the most potent strength training intervention is continuous. Maximal strength training (MST) yields large improvements in force-generating capacity (FGC), largely attributed to efferent neural drive enhancement. However, it remains elusive whether eccentric overload, before the concentric phase, may augment training-induced neuromuscular adaptations. A total of 53 23 ± 3 (SD)-yr-old untrained males were randomized to either a nontraining control group (CG) or one of two training groups performing leg press strength training with linear progression, three times per week for 8 wk. The first training group carried out MST with four sets of four repetitions at ~90% one-repetition maximum (1RM) in both action phases. The second group performed MST with an augmented eccentric load of 150% 1RM (eMST). Measurements were taken of 1RM and rate of force development (RFD), countermovement jump (CMJ) performance, and evoked potentials recordings [V-wave (V) and H-reflex (H) normalized to M-wave (M) in musculus soleus]. 1RM increased from 133 ± 16 to 157 ± 23 kg and 123 ± 18 to 149 ± 22 kg and CMJ by 2.3 ± 3.6 and 2.2 ± 3.7cm for MST and eMST, respectively (all P < 0.05). Early, late, and maximal RFD increased in both groups [634-1,501 N/s (MST); 644-2,111 N/s (eMST); P < 0.05]. These functional improvements were accompanied by increased V/M-ratio (MST: 0.34 ± 0.11 to 0.42 ± 14; eMST: .36 ± 0.14 to 0.43 ± 13; P < 0.05). Resting H/M-ratio remained unchanged. Training-induced improvements did not differ. All increases, except for CMJ, were different from the CG. MST is an enterprise for large gains in FGC and functional performance. Eccentric overload did not induce additional improvements, suggesting firing frequency and motor unit recruitment during MST may be maximal. NEW & NOTEWORTHY This is the first study to apply evoked potential recordings to investigate effects on efferent neural drive following high-intensity strength training with and without eccentric overload in a functionally relevant lower extremity exercise. We document that eccentric overload does not augment improvements in efferent neural drive or muscle force-generating capacity, suggesting that high-intensity concentric loads may maximally tax firing frequency and motor unit recruitment.

Increased Blood Lactate Level Deteriorates Running Economy in World Class Endurance Athletes.

Blood lactate accumulation is associated with development of muscle fatigue and negatively correlated to endurance performance. No research has quantified the effects of lactate presence at moderate levels of lactate accumulation. The purpose of this study was to test whether 2 moderate blood lactate concentration levels affect running economy (RE) when running at the individual lactate threshold (LT). Seven male world class endurance athletes with an average V[Combining Dot Above]O2max of 80.7 ± 2.7 ml·kg·min or 5.8 ± 0.5 L·min participated in this study. After the V[Combining Dot Above]O2max test, the subjects were resting or walking and in a random order tested for RE at their LT velocity when the blood lactate level reached either 3 mmol·L or 5 mmol·L. After a new 5-minute exercising period at maximal aerobic velocity, the crossover lactate value RE testing was performed. Running economy was significantly (p ≤ 0.05) deteriorated from 0.668 ± 0.044 to 0.705 ± 0.056 ml·kg·m or 5.5% (p ≤ 0.05) for blood lactate level of 3 mmol·L compared with 5 mmol·L, respectively. Increased lactate level from 3 to 5 mmol·L is thus accompanied by deteriorated RE at LT running velocity. The deteriorated RE at moderate levels of lactate concentration emphasizes the importance of avoiding intensities above LT in the early parts of a dominantly aerobic endurance competition. It also emphasizes the importance of a high V[Combining Dot Above]O2max for aerobic endurance athletes and may partly explain the V[Combining Dot Above]O2 slow component as impaired RE.

Maximal strength training improves bone mineral density and neuromuscular performance in young adult women.

-Exercise guidelines highlight maximizing bone mass early in life as a strategy to prevent osteoporosis. Which intervention is most effective for this purpose remains unclear. This study investigated the musculoskeletal effects of high acceleration, maximal strength training (MST), in young adult women. Thirty healthy women (22 ± 2 years) were randomly assigned to a training group (TG) and a control group (CG). The TG completed 12 weeks of squat MST, executed at 85-90% of maximal strength 1 repetition maximum (1RM), emphasizing progressive loading and high acceleration in the concentric phase. The CG was encouraged to follow the American College of Sports Medicine's exercise guidelines for skeletal health. Measurements included bone mineral density (BMD) and body composition by dual-energy X-ray absorptiometry, dynamic and isometric rate of force development (RFD), and squat 1RM. Serum levels of type 1 collagen amino-terminal propeptide (P1NP), type 1 collagen C breakdown products (CTX), and sclerostin were analyzed by immunoassays. In the TG, lumbar spine and total hip BMD increased by 2.2 and 1.0%, whereas serum P1NP increased by 26.2%. Dynamic RFD and 1RM improved by 81.7 and 97.7%, and isometric RFD improved by 38% at 100 milliseconds. These improvements were significantly greater than those observed in the CG. Within the CG, dynamic RFD and 1RM increased by 27.2 and 12.9% while no other significant changes occurred. These findings suggest that squat MST may serve as a simple, time-efficient strategy to optimize peak bone mass in early adulthood.

Maximal strength training improves work economy, rate of force development and maximal strength more than conventional strength training.

This study compared maximal strength training (MST) with equal training volume (kg × sets × repetitions) of conventional strength training (CON) primarily with regard to work economy, and second one repetition maximum (1RM) and rate of force development (RFD) of single leg knee extension. In an intra-individual design, one leg was randomized to knee-extension MST (4 or 5RM) and the other leg to CON (3 × 10RM) three times per week for 8 weeks. MST was performed with maximal concentric mobilization of force while CON was performed with moderate velocity. Eight untrained or moderately trained men (26 ± 1 years) completed the study. The improvement in gross work economy was -0.10 ± 0.08 L min(-1) larger after MST (P = 0.011, between groups). From pre- to post-test the MST and CON improved net work economy with 31 % (P < 0.001) and 18 % (P = 0.01), respectively. Compared with CON, the improvement in 1RM and dynamic RFD was 13.7 ± 8.4 kg (P = 0.002) and 587 ± 679 N s(-1) (P = 0.044) larger after MST, whereas isometric RFD was of borderline significance 3,028 ± 3,674 N s(-1) (P = 0.053). From pre- to post-test, MST improved 1RM and isometric RFD with 50 % (P < 0.001) and 155 % (P < 0.001), respectively whereas CON improved 1RM and isometric RFD with 35 % (P < 0.001) and 83 % (P = 0.028), respectively. Anthropometric measures of quadriceps femoris muscle mass and peak oxygen uptake did not change. In conclusion, 8 weeks of MST was more effective than CON for improving work economy, 1RM and RFD in untrained and moderately trained men. The advantageous effect of MST to improve work economy could be due to larger improvements in 1RM and RFD.

Maximal strength training in postmenopausal women with osteoporosis or osteopenia.

Current guidelines recommend weight-bearing activities, preferably strength training for improving skeletal health in patients with osteoporosis. What type of strength training that is most beneficial for these patients is not established. Maximal strength training (MST) is known to improve 1-repetition maximum (1RM) and rate of force development (RFD), which are considered as important covariables for skeletal health. Squat exercise MST might serve as an effective intervention for patients with low bone mass. We hypothesized that 12 weeks of squat exercise MST would improve 1RM and RFD in postmenopausal women with osteoporosis or osteopenia and that these changes would coincide with improved bone mineral density (BMD) and bone mineral content (BMC), and serum markers of bone metabolism. The participants were randomized to a training group (TG, n = 10) or control group (CG, n = 11). The TG underwent 12 weeks of supervised squat exercise MST, 3 times a week, with emphasis on rapid initiation of the concentric part of the movement. The CG was encouraged to follow current exercise guidelines. Measurements included 1RM, RFD, BMD, BMC, and serum bone metabolism markers; type 1 collagen amino-terminal propeptide (P1NP) and type 1 collagen C breakdown products (CTX). At posttest, 8 participants remained in each group for statistical analyses. The TG improved the 1RM and RFD by 154 and 52%, respectively. Lumbar spine and femoral neck BMC increased by 2.9 and 4.9%. The ratio of serum P1NP/CTX tended to increase (p = 0.09), indicating stimulation of bone formation. In conclusion, squat exercise MST improved 1RM, RFD, and skeletal properties in postmenopausal women with osteopenia or osteoporosis. The MST can be implemented as a simple and effective training method for patients with reduced bone mass.

Abdominal aerobic endurance exercise reveals spot reduction exists: A randomized controlled trial.

The existence of spot reduction, exercise-induced local body fat reduction, has been debated for half a century. Although the evidence is equivocal, no study has applied aerobic endurance training closely matching interventions for energy expenditure. Sixteen overweight (BMI: 29.8 ± 3.3(SD) kg m-2 ) males (43 ± 9 years) were randomized to: (1) abdominal endurance exercise (AG), combining treadmill running at 70% HRmax (27 min) with 4 × 4 min (30%-40% maximal strength, 1RM) of torso rotation and abdominal crunches (57 min), 4 days⋅week-1 for 10 weeks; or (2) control group (CG) performing only treadmill running (45 min) at 70% HRmax . Local fat mass was measured by dual-energy x-ray absorptiometry (DEXA), along with 1RM, and pulmonary oxygen uptake (to control energy expenditure during training). Trunk fat mass decreased more (697 g, 3%, p < 0.05) in AG (1170 ± 1093 g, 7%; p < 0.05) than in CG (no change). Total fat mass (AG: 1705 ± 1179 g, 6%; CG: 1134 ± 731 g, 5%; both p < 0.01) and body weight (AG: 1.2 ± 1.2 kg, 1%, p < 0.05; CG: 2.3 ± 0.9 kg, 3%, p < 0.01) decreased similarly in AG/CG. Torso rotation (AG: 32 ± 16 kg, 39%, p < 0.01; CG: no change) and abdominal crunch 1RM (AG: 35 ± 16 kg, 36%, p < 0.01; CG: 13 ± 12 kg, 17%, p < 0.05) increased more (p < 0.05/0.01) in AG than CG. Abdominal endurance exercise utilized more local fat than treadmill running, indicating that spot reduction exists in adult males.

Effect of high aerobic intensity interval treadmill walking in people with chronic stroke: a pilot study with one year follow-up.

OBJECTIVE: To determine the physiological and functional responses from high aerobic intensity treadmill walking in 4 x 4-minute intervals in people with chronic stroke and to evaluate the feasibility of this mode of training. METHOD: This was a baseline control trial with 1 year follow-up in an outpatient rehabilitation setting at a university hospital. Eight people with chronic stroke participated in and completed the study. Their mean age was 48.9 (± 10.6) years. We tested uphill treadmill walking in 4 x 4-minute work periods at an intensity between 85% and 95% of peak heart rate from initial maximal treadmill testing. There were 3-minute active breaks between the intervals. The main outcome measures were peak oxygen uptake (VO2peak) and walking economy (Cw). Overall compliance and adverse events determine the feasibility. RESULTS: VO2peak increased from 2.32 (± 0.44) to 2.60 (± 0.55) L • min-1 post training (P = .003). Walking economy (Cw) improved from 1.12 (± 0.15) to 1.04 (± 0.18) L • min-1 (P = .043). At 1 year follow-up, VO2peak was 2.59 (±0.58) L • min -1 and was not significantly different from posttraining measurement (P = 1.00). Cw was 1.19 (± 0.15) L • min-1 at 1 year follow-up and thus was worse than post training (P = .023). Functional improvements were found in the 6-minute walk test (6MWT) (P = .020), 10-meter walk test (10MWT) (P = .032), and Timed Up and Go test (TUG) (P = .002) at post tests. CONCLUSIONS: High aerobic intensity interval treadmill walking significantly increased VO2peak and improved Cw in these subjects. The training was feasible and may have important implications for cardiovascular health and future rehabilitation programs in this population.

Prediction of VO2max From Submaximal Exercise Using the Smartphone Application Myworkout GO: Validation Study of a Digital Health Method.

BACKGROUND: Physical inactivity remains the largest risk factor for the development of cardiovascular disease worldwide. Wearable devices have become a popular method of measuring activity-based outcomes and facilitating behavior change to increase cardiorespiratory fitness (CRF) or maximal oxygen consumption (VO2max) and reduce weight. However, it is critical to determine their accuracy in measuring these variables. OBJECTIVE: This study aimed to determine the accuracy of using a smartphone and the application Myworkout GO for submaximal prediction of VO2max. METHODS: Participants included 162 healthy volunteers: 58 women and 104 men (17-73 years old). The study consisted of 3 experimental tests randomized to 3 separate days. One-day VO2max was assessed with Metamax II, with the participant walking or running on the treadmill. On the 2 other days, the application Myworkout GO used standardized high aerobic intensity interval training (HIIT) on the treadmill to predict VO2max. RESULTS: There were no significant differences between directly measured VO2max (mean 49, SD 14 mL/kg/min) compared with the VO2max predicted by Myworkout GO (mean 50, SD 14 mL/kg/min). The direct and predicted VO2max values were highly correlated, with an R2 of 0.97 (P<.001) and standard error of the estimate (SEE) of 2.2 mL/kg/min, with no sex differences. CONCLUSIONS: Myworkout GO accurately calculated VO2max, with an SEE of 4.5% in the total group. The submaximal HIIT session (4 x 4 minutes) incorporated in the application was tolerated well by the participants. We present health care providers and their patients with a more accurate and practical version of health risk estimation. This might increase physical activity and improve exercise habits in the general population.

Evidence that a higher ATP cost of muscular contraction contributes to the lower mechanical efficiency associated with COPD: preliminary findings.

Impaired metabolism in peripheral skeletal muscles potentially contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). We used (31)P-magnetic resonance spectroscopy ((31)P-MRS) to examine the energy cost and skeletal muscle energetics in six patients with COPD during dynamic plantar flexion exercise compared with six well-matched healthy control subjects. Patients with COPD displayed a higher energy cost of muscle contraction compared with the controls (control: 6.1 ± 3.1% of rest·min(-1)·W(-1), COPD: 13.6 ± 8.3% of rest·min(-1)·W(-1), P = 0.01). Although, the initial phosphocreatine resynthesis rate was also significantly attenuated in patients with COPD compared with controls (control: 74 ± 17% of rest/min, COPD: 52 ± 13% of rest/min, P = 0.04), when scaled to power output, oxidative ATP synthesis was similar between groups (6.5 ± 2.3% of rest·min(-1)·W(-1) in control and 7.8 ± 3.9% of rest·min(-1)·W(-1) in COPD, P = 0.52). Therefore, our results reveal, for the first time that in a small subset of patients with COPD a higher ATP cost of muscle contraction may substantially contribute to the lower mechanical efficiency previously reported in this population. In addition, it appears that some patients with COPD have preserved mitochondrial function and normal energy supply in lower limb skeletal muscle.

Reduced peak oxygen uptake and implications for cardiovascular health and quality of life in patients with schizophrenia.

BACKGROUND: Peak oxygen uptake (VO(2peak)) is a strong predictor of cardiovascular disease (CVD) and all-cause mortality, but is inadequately described in patients with schizophrenia. The aim of this study was to evaluate treadmill VO(2peak), CVD risk factors and quality of life (QOL) in patients with schizophrenia (ICD-10, F20-29). METHODS: 33 patients, 22 men (33.7 ± 10.4 years) and 11 women (35.9 ± 11.5 years), were included. Patients VO(2peak) were compared with normative VO(2peak) in healthy individuals from the Nord-Trøndelag Health Study (HUNT). Risk factors were compared above and below the VO(2peak) thresholds; 44.2 and 35.1 ml·kg⁻¹·min⁻¹ in men and women, respectively. RESULTS: VO(2peak) was 37.1 ± 9.2 ml·kg⁻¹·min⁻¹ in men with schizophrenia; 74 ± 19% of normative healthy men (p < 0.001). VO(2peak) was 35.6 ± 10.7 ml·kg⁻¹·min⁻¹ in women with schizophrenia; 89 ± 25% of normative healthy women (n.s.). Based on odds ratio patients were 28.3 (95% CI = 1.6-505.6) times more likely to have one or more CVD risk factors if they were below the VO(2peak) thresholds. VO(2peak) correlated with the SF-36 physical functioning (r = 0.58), general health (r = 0.53), vitality (r = 0.47), social function (r = 0.41) and physical component score (r = 0.51). CONCLUSION: Men with schizophrenia have lower VO(2peak) than the general population. Patients with the lowest VO(2peak) have higher odds of having one or more risk factors for cardiovascular disease. VO(2peak) should be regarded as least as important as the conventional risk factors for CVD and evaluation of VO(2peak) should be incorporated in clinical practice.

Neuromuscular performance of paretic versus non-paretic plantar flexors after stroke.

The objective of this study was to compare the neuromuscular function of the paretic and non-paretic plantar flexors (i.e. soleus, gastrocnemius medialis, lateralis) in chronic stroke patients. It was hypothesized that the contractile rate of force development (RFD) and neural activation, assessed by electromyogram (EMG) and V-waves normalized to the M-wave, and voluntary activation (twitch interpolation) would be reduced during plantar flexor maximum voluntary isometric contraction and that the evoked muscle twitch properties would be reduced in the paretic limb. Ten chronic stroke survivors completed the study. The main findings were that the paretic side showed deteriorated function compared to the non-paretic leg in terms of (1) RFD in all analyzed time windows from force onset to 250 ms, although relative RFD (i.e. normalized to maximum voluntary force) was similar; (2) fast neural activation (for most analyzed time windows), assessed by EMG activity in time windows from EMG onset to 250 ms; (3) V-wave responses (except for gastrocnemius medialis); (4) voluntary activation; (5) the evoked peak twitch force, although there was no evidence of intrinsic muscle slowing; (6) EMG activity obtained at maximal voluntary force. In conclusion, this study demonstrates considerable neuromuscular asymmetry of the plantar flexors in chronic stroke survivors. Effective rehabilitation regimes should be investigated.

One-arm maximal strength training improves work economy and endurance capacity but not skeletal muscle blood flow.

Maximal strength training with a focus on maximal mobilization of force in the concentric phase improves endurance performance that employs a large muscle mass. However, this has not been studied during work with a small muscle mass, which does not challenge convective oxygen supply. We therefore randomized 23 adult females with no arm-training history to either one-arm maximal strength training or a control group. The training group performed five sets of five repetitions of dynamic arm curls against a near-maximal load, 3 days a week for 8 weeks. This training increased maximal strength by 75% and improved rate of force development during both strength and endurance exercise, suggesting that each arm curl became more efficient. This coincided with a 17-18% reduction in oxygen cost at standardized submaximal workloads (work economy), and a 21% higher peak oxygen uptake and 30% higher peak load during maximal arm endurance exercise. Blood flow assessed by Doppler ultrasound in the axillary artery supplying the working biceps brachii and brachialis muscles could not explain the training-induced adaptations. These data suggest that maximal strength training improved work economy and endurance performance in the skeletal muscle, and that these effects are independent of convective oxygen supply.

Effects of high aerobic intensity training in patients with schizophrenia: a controlled trial.

BACKGROUND: Patients with schizophrenia have a high risk of cardiovascular disease (CVD). High aerobic intensity training (HIT) improve peak oxygen uptake (VO(2peak)), net mechanical efficiency of walking and risk factors for CVD but has not been investigated in patients with schizophrenia. AIMS: To investigate effects from HIT on VO(2peak), net mechanical efficiency of walking and risk factors for CVD in patients with schizophrenia. METHODS: 25 inpatients (F20-29, ICD-10) were allocated to either HIT or playing computer games (CG), 3 days per week for 8 weeks. HIT consisted of 4 × 4-min intervals with 3-min break periods, at 85-95% and 70% of peak heart rate, respectively. RESULTS: 12 and seven patients completed HIT and CG, respectively. The baseline VO(2peak) in both groups combined (n = 19) was 36.8 ± 8.2 ml/kg/min and 3.12 ± 0.55 l/min. The HIT group improved VO(2peak) by 12% from 3.17 ± 0.59 to 3.56 ± 0.68 l/min (P < 0.001), more than the CG group (P = 0.014). Net mechanical efficiency of walking improved by 12% in the HIT group from 19.8 ± 3.0% to 22.2 ± 4.5% (P = 0.005), more than the CG group (P = 0.031). The psychiatric symptoms, expressed as the Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS), did not improve in either group. CONCLUSIONS: VO(2peak) and net mechanical efficiency of walking improved significantly by 8 weeks of HIT. HIT should be included in rehabilitation in order to improve physical capacity and contribute risk reduction of CVD.

Running stride peak forces inversely determine running economy in elite runners.

The present study investigated the relationship between running economy (RE) at 15 km/h(-1) , 3.000-m race time, maximal strength, and a number of physiological, anthropometrical, and mechanical variables. The variables measured included RE, maximal oxygen consumption, heart rate, step length and frequency, contact time, and the peak horizontal and vertical forces of each step. Maximal strength was measured as the 1 repetition maximum (1RM) half-squat using a leg press machine. Eleven male elite endurance athletes with a V(O2)max of 75.8 ± 6.2 mL/kg(-1)/min(-1) participated in this study. After the anthropometric data were collected, they were tested for RE, running characteristics, and force measures on a level treadmill at 15 km/h(-1). The athletes wore contact soles, and the treadmill was placed on a force platform. Maximal oxygen consumption and 1RM were tested after the RE measurements. The sum of horizontal and vertical peak forces revealed a significant inverse correlation (p < 0.05) both with 3,000-m performance (R = 0.71) and RE (R = 0.66). Inverse correlations were also found (p < 0.05) between RE and body height (R = 0.61) and between RE and body fat percentage (R = 0.62). In conclusion, the sum of horizontal and vertical peak forces was found to be negatively correlated to running economy and 3,000-m running performance, indicating that avoiding vertical movements and high horizontal braking force is crucial for a positive development of RE.

Smartphone-Assisted High-Intensity Interval Training in Inflammatory Rheumatic Disease Patients: Randomized Controlled Trial.

BACKGROUND: Patients with inflammatory rheumatic diseases (IRDs) experience disease-related barriers to physical training. Compared with the general population, IRD patients are reported to have reduced maximal oxygen uptake (VO2max) and physical activity levels. Supervised high-intensity interval training (HIIT) is documented to counteract the reduced VO2max and poor cardiovascular health associated with IRDs. However, supervised HIIT is resource demanding. OBJECTIVE: This study sought to investigate if self-administered 4×4-min HIIT guided by a smartphone app (Myworkout GO) could yield similar HIIT-induced effects as standard 4×4-min HIIT performed under the guidance and supervision of health care professionals. The effects studied were on VO2max and health-related quality of life (HRQoL). METHODS: Forty patients (33 female patients, mean age 48 years, SD 12 years; 7 male patients, mean age 52 years, SD 11 years) diagnosed with rheumatoid arthritis, spondyloarthritis, or systemic lupus erythematosus were randomized to a supervised group (SG) or an app group (AG). Both groups were instructed to perform 4×4-min intervals with a rate of perceived exertion of 16 to 17, corresponding to 85% to 95% of the maximal heart rate, twice a week for 10 weeks. Treadmill VO2max and HRQoL measured using RAND-36 were assessed before and after the exercise period. RESULTS: VO2max increased (P<.001) in both groups after 10 weeks of HIIT, with improvements of 3.6 (SD 1.3) mL/kg/min in the SG and 3.7 (SD 1.5) mL/kg/min in the AG. This was accompanied by increases in oxygen pulse in both groups (P<.001), with no between-group differences apparent for either measure. Improvements in the HRQoL dimensions of bodily pain, vitality, and social functioning were observed for both groups (P<.001 to P=.04). Again, no between-group differences were detected. CONCLUSIONS: High-intensity 4×4-min interval training increased VO2max and HRQoL, contributing to patients' reduced cardiovascular disease risk, improved health and performance, and enhanced quality of life. Similar improvements were observed following HIIT when IRD patients were guided using perceived exertion by health care professionals or the training was self-administered and guided by the app Myworkout GO. Utilization of the app may help reduce the cost of HIIT as a treatment strategy in this patient population. TRIAL REGISTRATION: ClinicalTrials.gov NCT04649528; https://clinicaltrials.gov/ct2/show/NCT04649528.