Jan Helgerud’s research while affiliated with Norwegian University of Science and Technology and other places

We appreciate that our recent article is read with great interest and inspires discussion and new insights into the complex challenges of people experiencing long-term symptoms following SARS-CoV-2 infection, as expressed in the letter from Garbsch and colleagues. It is clear that some patients experience persisting symptoms for a long time after the acute phase, and that this condition is not yet fully understood. However, of importance, the severity of the acute phase, the types of persisting symptoms, and impairments may vary widely. Yet, the diagnosis and our understanding of it still do not reflect this complexity well. These are likely factors that contribute to different observations in several studies.

Purpose To explore the relationships between performance variables and physiological variables in a short-time (2–3 min) cycling time trial (TT) on a cycle ergometer. Methods Fifteen young elite cyclists (age: 17.3 ± 0.7 years, maximal oxygen uptake (VO2max): 76.6 ± 5.2 mL⋅kg⁻¹⋅min⁻¹) participated in this study. Maximal aerobic power (MAP), maximal anaerobic power (MANP), time to exhaustion at 130% of maximal aerobic power (TTE), maximal accumulated oxygen deficit (MAOD) in the TT, anaerobic power reserve (APR) and lactate threshold (LT) was tested. MAP was calculated as VO2max/oxygen cost of cycling (CC), MANP was determined as mean power output (W) during a 10 s maximal cycling sprint test, and MAOD was calculated as (VO2 demand - VO2 measured) ∙ time. APR was calculated as the relative difference between MAP and MANP. Results There was a strong correlation between MAP and TT time (r = −0.91, p < 0.01) with a standard error of estimate (SEE) of 4.4%, and a moderate association between MANP and TT time (r = −0.47, p = 0.04). Neither MAOD, TTE, LT nor APR correlated with TT. Conclusion MAP was highly correlated with TT with a SEE of 4.4%. Since neither TTE nor MAOD correlated with TT, this indicates that these two variables do not play a significant role in differentiating short-time endurance cycling performance. We suggest training for improving MAP and, or MANP to improve short-time endurance cycling performance.

Aim We examined bench press adaptations to three widely used strength training methods; maximal strength training (MST), hypertrophy training (HT) and explosive strength training (EST). To reflect how these methods are typically applied by practitioners, MST and EST were volume matched, whereas HT were performed at higher volume. Methods Sixty-three moderately trained subjects (32 males; 31 females) were randomized into 8 weeks of MST, HT, EST or control (CON), 3 sessions/week. MST performed 4 x 4 repetitions bench press at ≥85% of 1RM. HT performed 3 x 8-12 repetitions at ∼70-80% of 1RM. EST performed 4 x 6-7 repetitions bench press throws at 40% of 1RM. Maximal-, explosive- and endurance strength characteristics were assessed, as well as muscle hypertrophy. Results 1RM increased more after MST (+21.5%) and HT (+17.9%) compared to EST (+5.9%) and CON (all p ≤ 0.001). Rate of force development (RFD) at 50% of 1RM increased more after MST (+58.4%) than EST (+27.1%, p ≤ 0.01) and CON ( p ≤ 0.01), and more after HT (+38.9%) than CON ( p ≤ 0.01). Mean propulsive velocity (MPV) increased more after MST compared to CON across all loads (20-80% of 1RM), and more than EST at 80% ( p ≤ 0.001), 60% ( p ≤ 0.01), with a strong tendency at 40% of 1RM ( p = 0.053). Δ1RM correlated with ΔMPV at all loads of the L-v profile ( r = 0.40-0.56, p ≤ 0.001). Conclusions MST and HT were more effective than EST for improving maximal and explosive strength performance against moderate and high loads. At low loads, EST was not more effective than MST and HT, despite high degree of velocity specificity. Changes in muscle strength appear to be more important than velocity specificity to increase performance across the L-v profile.

Introduction SARS-CoV-2 may result in the development of new symptoms, known as long COVID, a few months after the original infection. Purpose It is elusive to what extent physical capacity in patients diagnosed with long COVID is impacted. Methods We compared maximal oxygen uptake (V̇O2max), one of the single most important factors for cardiovascular health and mortality, expired lung volumes and air flow, oxygen cost of walking and 6-min-walking-test (6MWT), in 20 patients diagnosed with long COVID (11 males and 9 females; 44 ± 16 years (SD); 26.7 ± 3.8BMI, duration of acute phase 1.7 ± 1.2 weeks, tested 4 ± 3 months after long COVID diagnosis) with 20 healthy age and sex matched controls (11 males and 9 females; 44 ± 16 years; 25.9 ± 4.0BMI). Results Long COVID patients had a V̇O2max of 41.4 ± 16.2 mL∙kg⁻¹∙min⁻¹(men) and 38.2 ± 7.5 (women) and this was not different from controls. Similarly, mean spirometry measures in the patient group (VC; FVC; FEV1; FEV1/FVC) were also not different (85–106%) from predicted healthy values. Finally, inclined treadmill (5%, 4 km∙h⁻¹) walking economy was not different between the groups (long COVID: 15.2 ± 1.1 mL∙kg⁻¹∙min⁻¹; controls: 15.2 ± 1.2 mL∙kg⁻¹∙min⁻¹), while the 6MWT revealed a difference (long COVID: 606 ± 118 m; controls: 685 ± 85 m; p = 0.036). Conclusion V̇O2max, oxygen cost of walking, and spirometry measurements did not appear to be impaired in patients diagnosed with long COVID with a prior mild to moderate SARS-CoV-2 infection. The typical outcomes in these essential factors for health and longevity implies that while long COVID can present with a range of symptoms, caution should be made when attributing these symptoms directly to compromised pulmonary function or V̇O2max.

Improving peak oxygen uptake (V̇O2peak) and maximal strength are key objectives of rehabilitation for patients with unspecific musculoskeletal disorders (MSDs). Although high‐intensity training yield superior outcomes for these factors, patients with MSDs may not tolerate high‐intensity due to pain and fear. Therefore, we examined the effect and feasibility of incorporating aerobic high‐intensity intervals (HIITs) and maximal strength training (MST) in a standard clinical rehabilitation program for patients with unspecific MSDs. 73 patients (45 ± 10 years) with MSDs partaking in a standard, public, and 4‐week rehabilitation program were randomized to high‐intensity training (HG: 4 × 4 minutes intervals at ∼90% of maximal heart rate; HRmax, and 4 × 4 repetitions leg press at ∼90% of 1 repetition maximum; 1RM, with maximal intended velocity) or keep todays treatment of low‐to moderate‐intensity training (MG: various cycling, walking, and/or running activities at ∼70%–80% of HRmax and 3 × 8 − 10 repetitions leg press at ∼75% of 1RM without maximal intended velocity). HG improved V̇O2peak (12 ± 7%) and leg press 1RM (43 ± 34%) more than moderate‐intensity group (V̇O2peak; 5 ± 6%, 1RM; 19 ± 18%, both p < 0.001). We observed that no adverse events and no between‐group differences in dropout rate or self‐reported quality of life (both p > 0.05). There were positive correlations between improved V̇O2peak and improved physical (p = 0.024) and emotional (0.016) role functioning. We conclude that both high‐intensity interval training and MST are feasible and improve V̇O2peak and maximal strength more than standard low‐to moderate‐intensity treatment of patients with unspecific MSDs. Our findings suggest that high‐intensity training should be implemented as a part of standard clinical care of this patient population.

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% HR max (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% HR max . 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.

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.

Prolonged moderate intensity exercise leads to a progressive upward drift in heart rate (HR) that may compromise stroke volume (SV). Alternatively, the HR drift may be related to abated SV due to impaired ventricular function. The aim of this study was to examine the effects of cardiovascular drift on left ventricular volumes and in turn SV. Thirteen healthy young males completed two 60-minute cycling bouts on a semi-recumbent cycle ergometer at 57%VO2max either under placebo condition (CON) or after ingesting a small dose of β1-blockers (BB). Measurements of HR, end-diastolic volume (EDV), and end-systolic volume were obtained by echocardiography and used to calculate SV. Other variables such as ear temperature, skin temperature, blood pressure, and blood volume were measured to assess potential changes in thermoregulatory needs and loading conditions. HR drift was successfully prevented when using BB from min10 to min60 (128±9 to 126±8bpm, p=0.29) but not in CON (134±10 to 148±10bpm, p<0.01). Conversely, during the same time, SV increased by 13% when using BB (103±9 to 116±7mL, p<0.01) while it was unchanged in CON (99±7 to 101±9mL, p=0.37). The SV behavior was mediated by a 4% increase in EDV in the BB condition (164±18 to 170±18mL, p<0.01), while no change was observed in the CON condition (162±18 to 160±18mL, p=0.23). In conclusion, blocking HR drift enhances EDV and SV during prolonged exercise. These findings suggest that SV behavior is tightly related to filling time and loading conditions of the left ventricle.

The purpose of this study was to investigate to what extent aerobic power (MAP), maximal anaerobic power (MANP), anaerobic capacity measured as time to exhaustion at 130% MAP (TTE), and maximal accumulated oxygen deficit (MAOD) correlated with 800 m double poling time trial performance (800TT) in a ski ergometer. A second aim was to investigate the relationship between TTE and MAOD, and to what extent TTE and MAOD would relate to anaerobic power reserve (APR). Eighteen cross-country skiers were tested for peak oxygen uptake (VO2peak) and oxygen cost of double poling to assess MAP. Peak power measurements during a 100 m TT were performed to assess MANP. TTE and an 800TT with continuous VO2 measurements were performed to assess time performance and MAOD. All tests were performed on a ski ergometer. Both MAP and MANP correlated strongly (r = − 0.936 and − 0.922, respectively, p < 0.01) with 800TT. Neither TTE nor MAOD correlated with 800TT. TTE correlated moderately with MAOD, both in mL kg−1 and in %VO2peak (r = 0.559, p < 0.05 and 0.621, p < 0.01, respectively). Both TTE and MAOD seemed to be a product of APR. These results suggest focusing on MAP and MANP, but not anaerobic capacity to explain time performance in an event with approximately 3 min duration.