Acquisition of peak bone mass in a Norwegian youth cohort: longitudinal findings from the Fit Futures study 2010-2022.

In a Norwegian youth cohort followed from adolescence to young adulthood, bone mineral density (BMD) levels declined at the femoral neck and total hip from 16 to 27 years but continued to increase at the total body indicating a site-specific attainment of peak bone mass. PURPOSE: To examine longitudinal trends in bone mineral density (BMD) levels in Norwegian adolescents into young adulthood. METHOD: In a prospective cohort design, we followed 980 adolescents (473 (48%) females) aged 16-19 years into adulthood (age of 26-29) on three occasions: 2010-2011 (Fit Futures 1 (FF1)), 2012-2013 (FF2), and 2021-2022 (FF3), measuring BMD (g/cm2) at the femoral neck, total hip, and total body with dual x-ray absorptiometry (DXA). We used linear mixed models to examine longitudinal BMD changes from FF1 to FF3. RESULTS: From the median age of 16 years (FF1), femoral neck BMD (mean g/cm2 (95% CI)) slightly increased in females from 1.070 (1.059-1.082) to 1.076 (1.065-1.088, p = 0.015) at the median age of 18 years (FF2) but declined to 1.041 (1.029-1.053, p < 0.001) at the median age of 27 years (FF3). Similar patterns were observed in males: 16 years, 1.104 (1.091-1.116); 27 years, 1.063 (1.050-1.077, p < 0.001); and for the total hip in both sexes (both p < 0.001). Total body BMD increased from age 16 to 27 years in both sexes (females: 16 years, 1.141 (1.133-1.148); 27 years, 1.204 (1.196-1.212), p < 0.001; males: 16 years, 1.179 (1.170-1.188); 27 years, 1.310 (1.296-1.315), p < 0.001). CONCLUSION: BMD levels increased from 16 to 18 years at the femoral and total hip sites in young Norwegian females and males, and a small decline was observed at the femoral sites when the participants were followed up to 27 years. Total body BMD continued to increase from adolescence to young adulthood.

Comparison of resistance training using barbell half squats and trap bar deadlifts on maximal strength, power performance, and lean mass in recreationally active females: an eight-week randomised trial.

BACKGROUND: The aim of this study was to investigate the effect of high load resistance training using barbell half squats compared with trap bar deadlifts on maximal strength, power performance, and lean mass in recreationally active females. METHODS: Twenty-two recreationally active female participants (age: 26.9 ± 7.7 yrs.; height: 166.0 ± 5.1 cm; weight: 68.6 ± 9.9 kg) were randomly assigned to either a barbell half squat group (SG: n = 10) or trap bar deadlift group (DG: n = 12). Training consisted of twice-weekly sessions for eight weeks. Both groups completed one-repetition maximum (1RM) testing for both barbell half squat and trap bar deadlift groups. Countermovement jump (CMJ) and sprint performance were also assessed. Total body (TBLM) and leg lean mass (LLM) were measured with dual-energy x-ray absorptiometry. Between-group differences were analysed using analysis of covariance. RESULTS: SG tended to improve 1RM half squat (21.0 ± 11.5 kg vs. 13.1 ± 7.5 kg) more than DG (mean difference (MD): 8.0 kg, 95% CI: -0.36 - 16.3 kg). A similar pattern in favour of DG (18.4 ± 11.2 vs. 11.7 ± 8.1 kg) compared to SG was observed (MD: 6.5 kg, 95% CI: -2.5 - 15.6 kg). No between-group differences for sprint, jump or lean body mass changes was observed. For groups combined, the following changes in CMJ (2.0 ± 2.4 cm), 5-m sprint (-0.020 ± 0.039 s), 15-m sprint (-0.055 ± 0.230 s), TBLM (0.84 ± 1.12 kg), and LLM (0.27 ± 0.59 kg) was observed. CONCLUSIONS: An exercise intervention consisting of half squats or trap bar deadlift were associated with improved muscle strength, power, and lean mass. Our findings suggests that in recreationally active females, exercise selection is less of a concern provided that heavy loads are applied, and relevant muscle groups are targeted.

Females Display Lower Risk of Myocardial Infarction From Higher Estimated Cardiorespiratory Fitness Than Males: The Tromsø Study 1994-2014.

Objective: To examine the dose-response association between estimated cardiorespiratory fitness (eCRF) and risk of myocardial infarction (MI). Patients and Methods: Adults who attended Tromsø Study surveys 4-6 (Janurary 1,1994-December 20, 2008) with no previous cardiovascular disease were followed up through December 31, 2014 for incident MI. Associations were examined using restricted cubic splines Fine and Gray regressions, adjusted for education, smoking, alcohol, diet, sex, adiposity, physical activity, study survey, and age (timescale) in the total cohort and subsamples with hyperlipidemia (n=2956), hypertension (n=8290), obesity (n=5784), metabolic syndrome (n=1410), smokers (n=3823), and poor diet (n=3463) and in those who were physically inactive (n=6255). Results: Of 14,285 participants (mean age ± SD, 53.7±11.4 years), 979 (6.9%) experienced MI during follow-up (median, 7.2 years; 25th-75th, 5.3-14.6 years). Females with median eCRF (32 mL/kg/min) had 43% lower MI risk (subdistributed hazard ratio [SHR], 0.57; 95% CI, 0.48-0.68) than those at the 10th percentile (25 mL/kg/min) as reference. The lowest MI risk was observed at 47 mL/kg/min (SHR, 0.02; 95% CI, 0.01-0.11). Males had 26% lower MI risk at median eCRF (40 mL/kg/min; SHR, 0.74; 95% CI, 0.63-0.86) than those at the 10th percentile (32 mL/kg/min), and the lowest risk was 69% (SHR, 0.31; 95% CI, 0.14-0.71) at 60 mL/kg/min. The associations were similar in subsamples with cardiovascular disease risk factors. Conclusion: Higher eCRF associated with lower MI risk in females and males, but associations were more pronounced among females than those in males. This suggest eCRF as a vital estimate to implement in medical care to identify individuals at high risk of future MI, especially for females.

Occupational physical activity and risk of mortality in women and men: the Tromsø Study 1986-2021.

OBJECTIVE: Associations between occupational physical activity (OPA) and mortality risks are inconclusive. We aimed to examine associations between (1) OPA separately and (2) jointly with leisure time physical activity (LTPA), and risk of all-cause, cardiovascular disease (CVD) and cancer mortality, over four decades with updated exposure and covariates every 6-8 years. METHODS: Adults aged 20-65 years from the Tromsø Study surveys Tromsø3-Tromsø7 (1986-2016) were included. We categorised OPA as low (sedentary), moderate (walking work), high (walking+lifting work) or very high (heavy manual labour) and LTPA as inactive, moderate and vigorous. We used Cox/Fine and Gray regressions to examine associations, adjusted for age, body mass index, smoking, education, diet, alcohol and LTPA (aim 1 only). RESULTS: Of 29 605 participants with 44 140 total observations, 4131 (14.0%) died, 1057 (25.6%) from CVD and 1660 (40.4%) from cancer, during follow-up (median: 29.1 years, 25th-75th: 16.5.1-35.3). In men, compared with low OPA, high OPA was associated with lower all-cause (HR 0.83, 95% CI 0.74 to 0.92) and CVD (subdistributed HR (SHR) 0.68, 95% CI 0.54 to 0.84) but not cancer mortality (SHR 0.99, 95% CI 0.84 to 1.19), while no association was observed for moderate or very high OPA. In joint analyses using inactive LTPA and low OPA as reference, vigorous LTPA was associated with lower all-cause mortality combined with low (HR 0.75, 95% CI 0.64 to 0.89), high (HR 0.67, 95% CI 0.54 to 0.82) and very high OPA (HR 0.74, 95% CI 0.58 to 0.94), but not with moderate OPA. In women, there were no associations between OPA, or combined OPA and LTPA, with mortality. CONCLUSION: High OPA, but not moderate and very high OPA, was associated with lower all-cause and CVD mortality risk in men but not in women. Vigorous LTPA was associated with lower mortality risk in men with low, high and very high OPA, but not moderate OPA.

Device-measured physical activity, sedentary time, and risk of all-cause mortality: an individual participant data analysis of four prospective cohort studies.

OBJECTIVES: To examine whether moderate-to-vigorous physical activity (MVPA) modifies the association between sedentary time and mortality and vice versa, and estimate the joint associations of MVPA and sedentary time on mortality risk. METHODS: This study involved individual participant data analysis of four prospective cohort studies (Norway, Sweden, USA, baseline: 2003-2016, 11 989 participants ≥50 years, 50.5% women) with hip-accelerometry-measured physical activity and sedentary time. Associations were examined using restricted cubic splines and fractional polynomials in Cox regressions adjusted for sex, education, body mass index, smoking, alcohol, study cohort, cardiovascular disease, cancer, and/or diabetes, accelerometry wear time and age. RESULTS: 6.7% (n=805) died during follow-up (median 5.2 years, IQR 4.2 years). More than 12 daily sedentary hours (reference 8 hours) was associated with mortality risk only among those accumulating <22 min of MVPA per day (HR 1.38, 95% CI 1.10 to 1.74). Higher MVPA levels were associated with lower mortality risk irrespective of sedentary time, for example, HR for 10 versus 0 daily min of MVPA was 0.85 (95% CI 0.74 to 0.96) in those accumulating <10.5 daily sedentary hours and 0.65 (95% CI 0.53 to 0.79) in those accumulating ≥10.5 daily sedentary hours. Joint association analyses confirmed that higher MVPA was superior to lower sedentary time in lowering mortality risk, for example, 10 versus 0 daily min of MVPA was associated with 28-55% lower mortality risk across the sedentary time spectrum (lowest risk, 10 daily sedentary hours: HR 0.45, 95% CI 0.31 to 0.65). CONCLUSIONS: Sedentary time was associated with higher mortality risk but only in individuals accumulating less than 22 min of MVPA per day. Higher MVPA levels were associated with lower mortality risk irrespective of the amount of sedentary time.

Vertebral Fractures Assessed by Dual-Energy X-Ray Absorptiometry and All-Cause Mortality: The Tromsø Study, 2007-2020.

Vertebral fractures have been associated with increased mortality, but findings are inconclusive, and many vertebral fractures avoid clinical attention. We investigated this association in a general population of 2,476 older adults aged ≥55 years from Tromsø, Norway, who were followed over 2007-2020, using dual-energy x-ray absorptiometry (DXA) at baseline to evaluate vertebral fractures (mild, moderate, or severe). We used multiple Cox regression models to estimate hazard ratios (HRs) for all-cause mortality, adjusted for age, sex, body mass index, education, smoking, alcohol intake, cardiovascular disease, and respiratory disease. Mean follow-up in the cohort was 11.2 (standard deviation, 2.7) years; 341 participants (13.8%) had ≥1 vertebral fracture at baseline, and 636 participants (25.7%) died between baseline and follow-up. Full-adjustment models showed a nonsignificant association between vertebral fracture status (yes/no) and mortality. Participants with ≥3 vertebral fractures (HR = 2.43, 95% confidence interval: 1.57, 3.78) or ≥1 severe vertebral fracture (HR = 1.65, 95% confidence interval: 1.26, 2.15) had increased mortality compared with those with no vertebral fractures. Dual-energy x-ray absorptiometry-based screening could be a potent and feasible tool in detecting vertebral fractures that are often clinically silent yet independently associated with premature death. Our data indicated that detailed vertebral assessment could be warranted for a more accurate survival estimation.

Adoption, acceptability and sustained use of digital interventions to promote physical activity among inactive adults: a mixed-method study.

Introduction: Despite the positive effects of physical activity (PA) to prevent lifestyle diseases and improve health and well-being, only one-third of Norwegian adults meet the minimum recommendations on PA. Digital interventions to promote PA in inactive adults may improve health and well-being by being available, personalized and adequate. Knowledge on users' adoption, acceptability and sustainability of digital interventions to promote PA is still limited. Objective: To investigate the adoption, acceptability and sustained use of three digital interventions for promoting PA among inactive adults. Design: A randomized control trial (ONWARDS) with 183 participants assigned to 3 groups and followed up for 18 months. All participants received a wearable activity tracker with the personalized metric Personal Activity Intelligence (PAI) on a mobile app, two groups received additional access to online training and one group had also access to online social support. Methods: A mixed-methods approach was used to address the study objective. Acceptability was evaluated through the System Usability Scale (SUS) (n = 134) at 6 months. Adoption and sustained use were evaluated through a set of questions administered at 12 months (n = 109). Individual interviews were performed at 6 months with a sample of participants (n = 18). Quantitative data were analyzed with descriptive statistics, whereas qualitative data were analyzed using the Framework approach. Results: PAI was the most successful intervention, with satisfactory usability and positive effects on motivation and behavior change, contributing to high adoption and sustained use. Online social support had a high acceptability and sustained use, but the intervention was not perceived as motivational to increase PA. Online training had low adoption, usability and sustained use. The qualitative interviews identified five main themes: (1) overall approach to physical activity, (2) motivation, (3) barriers to perform PA, (4) effects of PA, and (5) usability and acceptability of the digital interventions. Conclusion: Personalized digital interventions integrating behavior change techniques such as individual feedback and goal setting are more likely to increase acceptability, adoption and sustained use. Future studies should investigate which digital interventions or combinations of different interventions are more successful in promoting PA among inactive adults according to the characteristics and preferences of the users. Trial registration: Clinical trial registered at ClinicalTrials.gov: NCT04526444.

Digital interventions to promote physical activity among inactive adults: A study protocol for a hybrid type I effectiveness-implementation randomized controlled trial.

Introduction: Physical inactivity is the fourth leading risk factor for global mortality, and inactive adults have a higher risk to develop lifestyle diseases. To date, there is preliminary evidence of the efficacy of fitness technologies and other digital interventions for physical activity (PA) promotion. Intervention studies are needed to test the effectiveness and implementation of innovative PA promotion strategies. Methods and analysis: The ONWARDS study is a hybrid type I effectiveness-implementation randomized control trial aiming at an inactive and presumably high-risk population living in Northern Norway. One hundred and eighty participants will be assigned to 3 groups in a 1:1:1 ratio and participate for 18 months. Participants in group A will be provided an activity tracker with the personalized metric Personal Activity Intelligence (PAI). Participants in group B will be provided with both an activity tracker with the personalized metric PAI and access to online training videos (Les Mills+) to perform home-based training. Participants in group C will be provided an activity tracker with the personalized metric PAI, home-based online training and additional peer support via social media. The primary objective is to test which combination of interventions is more effective in increasing PA levels and sustaining long-term exercise adherence. Secondary objectives include: proportion of participants reaching PA recommendations; exercise adherence; physical fitness; cardiovascular risk; quality of life; perceived competence for exercise; self-efficacy; social support; usability; users' perspectives on implementation outcomes (adoption, acceptability, adherence, sustainability). The study design will allow testing the effectiveness of the interventions while gathering information on implementation in a real-world situation. Discussion: This study can contribute to reduce disparities in PA levels among inactive adults by promoting PA and long-term adherence. Increased PA might, in turn, result in better prevention of lifestyle diseases. Digital interventions delivered at home can become an alternative to training facilities, making PA accessible and feasible for inactive populations and overcoming known barriers to PA. If effective, such interventions could potentially be offered through national health portals to citizens who do not meet the minimum recommendations on PA or prescribed by general practitioners or specialists. Trial registration: https://clinicaltrials.gov/ct2/show/NCT04526444, Registered 23 April 2021, identifier: NCT04526444.

Criterion validity of the Saltin-Grimby Physical Activity Level Scale in adolescents. The Fit Futures Study.

BACKGROUND: The Saltin-Grimby Physical Activity Level Scale (SGPALS) is commonly used to measure physical activity (PA) in population studies, but its validity in adolescents is unknown. This study aimed to assess the criterion validity of the SGPALS against accelerometry in a large sample of adolescents. A secondary aim was to examine the validity across strata of sex, body mass index (BMI), parental educational level, study program and self-reported health. METHODS: The study is based on data from 572 adolescents aged 15-17 years who participated in the Fit Futures Study 2010-11 in Northern Norway. The participants were invited to wear an accelerometer (GT3X) attached to their hip for seven consecutive days. We used Spearman's rho and linear regression models to assess the validity of the SGPALS against the following accelerometry estimates of PA; mean counts/minute (CPM), steps/day, and minutes/day of moderate-to-vigorous physical activity (MVPA). RESULTS: The SGPALS correlated with mean CPM (ρ = 0.40, p<0.01), steps/day (ρ = 0.35, p<0.01) and MVPA min/day (ρ = 0.35, p<0.01). We observed no differences between correlations within demographic strata (all p>0.001). Higher scores on SGPALS were associated with a higher CPM, higher number of steps per day and more minutes of MVPA per day, with the following mean differences in PA measurements between the SGPALS ranks: CPM increased by 53 counts (95% CI: 44 to 62), steps/day increased by 925 steps (95% CI: 731 to 1118), and MVPA by 8.4 min/day (95% CI: 6.7 to 10.0). Mean difference between the highest and lowest SGPALS category was 2947 steps/day (6509 vs. 9456 steps/day) and 26.4 min/day MVPA (35.2 minutes vs 61.6 minutes). CONCLUSION: We found satisfactory ranking validity of SGPALS measured against accelerometry in adolescents, which was fairly stable across strata of sex, BMI, and education. However, the validity of SGPALS in providing information on absolute physical activity levels seem limited.

Affective Valence and Enjoyment in High- and Moderate-High Intensity Interval Exercise. The Tromsø Exercise Enjoyment Study.

Introduction: Exercise at high intensity may cause lower affective responses toward exercise compared with moderate intensity exercise. We aimed to elucidate affective valence and enjoyment in high- and moderate-high interval exercise. Methods: Twenty recreationally active participants (9 females, 11 males, age range: 20-51 years) underwent three different treadmill running exercise sessions per week over a 3-week period, in randomized order; (1) CE70: 45 min continuous exercise at 70% of heart rate maximum (HRmax), (2) INT80: 4 × 4 min intervals at 80% of HRmax, (3) INT90: 4 × 4 min intervals at 90% of HRmax. Pre-tests included graded submaximal steady state intensities and a test to exhaustion for determining peak oxygen uptake and HRmax. Affective valence (pleasure/displeasure) was measured before, during and after the sessions using the Feeling Scale (FS). Enjoyment was assessed before and after the sessions applying the Physical Activity Enjoyment Scale (PACES) and during the sessions using the Exercise Enjoyment Scale (EES). Results: The participants felt lower pleasure (between-sessions effect: p = 0.02, p η2: 0.13) during INT90 sessions (FS: 1.08, 95% CI: 0.35-1.92) compared with INT80 (FS: 2.35, 95% CI: 1.62-3.08, p = 0.052) and CE70 sessions (FS: 2.45, 95% CI: 1.72-3.18, p = 0.03), with no differences between INT80 and CE70 sessions (p = 1.00). There were higher enjoyment after INT80 sessions (PACES: 101.5, 95% CI: 95.7-107.3) versus CE70 sessions (PACES: 91.3 95% CI: 85.5-97.1, p = 0.046), and no differences between INT90 (PACES: 98.2, 95% CI: 92.4-103.4) and CE70 (p = 0.29) or INT80 (p = 1.00). For enjoyment during exercise, CE70 were perceived more enjoyable, and INT80 and INT90 less enjoyable in week 2 (EES: week x session: p = 0.01, p η2: 0.11; CE70: 4.3, 95% CI: 3.6-4.9, INT80: 4.6, 95% CI: 3.9-5.2, INT90: 4.0, 95% CI: 3.4-4.7) and 3 (EES: CE70: 4.2, 95% CI: 3.7-4.8, INT80: 4.8, 95% CI: 4.2-5.3, INT90: 4.3, 95% CI: 3.8-4.9) than in week 1 (EES: CE70: 3.5, 95% CI: 3.0-4.0, INT80: 5.0, 95% CI: 4.5-5.5, INT90: 4.5, 95% CI: 4.0-5.0). Conclusion: The negative affective consequences associated with high intensity interval exercise can be alleviated by keeping the intensity at or around 80% of HRmax while preserving the beneficial enjoyment responses associated with interval exercise.

Seasonal variations in physical activity among Norwegian elementary school children in Arctic regions.

The aim of this study was to measure seasonal variations in physical activity (PA) during Polar Nights (PN) and Polar Days (PD) among elementary school children in the Arctic regions of Norway. One hundred and seventy-eight schoolchildren from 1st, 3rd, 5thand 7th grade participated in the study. Physical activity was measured for seven consecutive days with an ActiGraph GT3X-BT accelerometer and is expressed as total PA incounts per minute (cpm) and moderate-to-vigorous activity (MVPA) (min∙day-1). During PN, 51% of boys and 33% of girls met the PA recommendations, whereas 36% of boys and 34% of girls met the recommendations during PD. Time spent doing MVPA did not differ between the two seasons (all p ≥ 0.073). Overall, the children accumulated 613 ±154 cpm during PN, which was lower than during PD 704 ± 269 cpm, p < 0.001). A larger proportion of boys than girls met the PA recommendations during PN compared with PD. Our findings did not show any clear seasonal variation for MVPA or total PA among children,except for some differences within sexes in different grades. This study indicates that interventions aimed at increasing PA should be implemented throughout the year in the Arctic regions. .

Complex lifestyle intervention among inactive older adults with elevated cardiovascular disease risk and obesity: a mixed-method, single-arm feasibility study for RESTART-a randomized controlled trial.

BACKGROUND: Physical inactivity and obesity are global public health challenges. Older adults are important to target for prevention and management of disease and chronic conditions. However, many individuals struggle with maintaining increased physical activity (PA) and improved diet. This feasibility study provides the foundation for the RESTART trial, a randomized controlled trial (RCT) to test a complex intervention to facilitate favourable lifestyle changes older adults can sustain. The primary objective of this study was to investigate study feasibility (recruitment, adherence, side-effects, and logistics) using an interdisciplinary approach. METHODS: This 1-year prospective mixed-method single-arm feasibility study was conducted in Tromsø, Norway, from September 2017. We invited by mail randomly selected participants from the seventh survey of the Tromsø Study (2015-2016) aged 55-75 years with sedentary lifestyle, obesity, and elevated cardiovascular risk. Participants attended a 6-month complex lifestyle intervention program, comprising instructor-led high-intensive exercise and nutritionist- and psychologist-led counselling, followed by a 6-month follow-up. All participants used a Polar activity tracker for daily activity monitoring during the intervention. Participants were interviewed three times throughout the study. Primary outcome was study feasibility measures. RESULTS: We invited potential participants (n=75) by mail of which 27 % (n=20) agreed to participate. Telephone screening excluded four participants, and altogether 16 participants completed baseline screening. The intervention and test procedures of primary and secondary outcomes were feasible and acceptable for the participants. There were no exercise-induced injuries, indicating that the intervention program is safe. Participants experienced that the dietary and psychological counselling were delivered too early in the intervention and in too close proximity to the start of the exercise program. Minor logistic improvements were implemented throughout the intervention period. CONCLUSION: This study indicates that it is feasible to conduct a full-scale RCT of a multi-component randomized intervention trial, based on the model of the present study. No dropouts due to exercise-induced injury indicates that the exercises were safe. While minor improvements in logistics were implemented during the intervention, we will improve recruitment and adherence strategies, rearrange schedule of intervention contents (exercise, diet, and psychology), as well as improve the content of the dietary and behavioural counselling to maximize outcome effects in the RESTART protocol. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03807323 Registered 16 January 2019 - retrospectively registered.

The bidirectional associations between leisure time physical activity change and body mass index gain. The Tromsø Study 1974-2016.

OBJECTIVES: To examine whether leisure time physical activity changes predict subsequent body mass index (BMI) changes, and conversely, whether BMI changes predict subsequent leisure time physical activity changes. METHODS: This prospective cohort study included adults attending ≥3 consecutive Tromsø Study surveys (time: T1, T2, T3) during 1974-2016 (n = 10779). If participants attended >3 surveys, we used the three most recent surveys. We computed physical activity change (assessed by the Saltin-Grimby Physical Activity Level Scale) from T1 to T2, categorized as Persistently Inactive (n = 992), Persistently Active (n = 7314), Active to Inactive (n = 1167) and Inactive to Active (n = 1306). We computed BMI change from T2 to T3, which regressed on preceding physical activity changes using analyses of covariance. The reverse association (BMI change from T1 to T2 and physical activity change from T2 to T3; n = 4385) was assessed using multinomial regression. RESULTS: Average BMI increase was 0.86 kg/m2 (95% CI: 0.82-0.90) from T2 to T3. With adjustment for sex, birth year, education, smoking and BMI at T2, there was no association between physical activity change from T1 to T2 and BMI change from T2 to T3 (Persistently Inactive: 0.89 kg/m2 (95% CI: 0.77-1.00), Persistently Active: 0.85 kg/m2 (95% CI: 0.81-0.89), Active to Inactive: 0.90 kg/m2 (95% CI: 0.79-1.00), Inactive to Active 0.85 kg/m2 (95% CI: 0.75-0.95), p = 0.84). Conversely, increasing BMI was associated with Persistently Inactive (odds ratio (OR): 1.17, 95% CI: 1.08-1.27, p < 0.001) and changing from Active to Inactive (OR: 1.16, 95% CI: 1.07-1.25, p < 0.001) compared with being Persistently Active. CONCLUSIONS: We found no association between leisure time physical activity changes and subsequent BMI changes, whereas BMI change predicted subsequent physical activity change. These findings indicate that BMI change predicts subsequent physical activity change at population level and not vice versa.

Maximal Strength, Sprint, and Jump Performance in High-Level Female Football Players Are Maintained With a Customized Training Program During the COVID-19 Lockdown.

INTRODUCTION: The COVID-19 outbreak with partial lockdown has inevitably led to an alteration in training routines for football players worldwide. Thus, coaches had to face with the novel challenge of minimizing the potential decline in fitness during this period of training disruption. METHODS: In this observational pre- to posttest study involving Norwegian female football players (18.8 ± 1.9 years, height 1.68 ± 0.4 m, mass 61.3 ± 3.7 kg), we investigated the effects of a prescribed home-based and group-based intervention, implemented during the COVID-19 lockdown, on maximal muscular force production and high velocity variables. Specifically, maximal partial squat strength one repetition maximum (1RM), counter movement jump (CMJ) and 15 m sprint time were assessed 1 week prior to the lockdown and 12 weeks after the onset of lockdown. We also collected training content and volume from the prescribed training program and self-reported perceived training quality and motivation toward training. RESULTS: We observed no change in 1RM [pretest: 104 ± 12 kg, posttest: 101 ± 11 kg (P = 0.28)], CMJ height [pretest: 28.1 ± 2.3 cm, posttest: 26.8 ± 1.9 (P = 0.09)], and 15 m sprint time [pretest: 2.60 ± 0.08 s, posttest: 2.61 ± 0.07 s (P = 0.52)]. CONCLUSION: Our findings suggest that a prescribed home-based and group-based intervention with increased training time devoted to strength, jump, and sprint ability, and regulated to obtain a sufficient infection control level is feasible and effective to preserve strength, jumping, and sprinting abilities of high-level female football players during a ∼ 3-month period of a pandemic-induced lockdown.

Ski Skating Race Technique-Effect of Long Distance Cross-Country Ski Racing on Choice of Skating Technique in Moderate Uphill Terrain.

The aim of this study was to investigate the effect of prolonged ski racing using skating style on technique choice in a transition section among female and male high-level skiers. Fifty three national-to-elite level skiers (20 females: 26.7 ± 4.8 years, 167.0 ± 6.5 m, 61.0 ± 5.1 kg, and 75.5 ± 68.8 FIS points; 33 males: 25.2 ± 3.5 years, 179.0 ± 5.2 cm, 73.1 ± 5.7 kg, and 73.7 ± 63.2 FIS points) were video recorded along a flat-to-uphill transition section of a course during the 30-km (females) and 50-km (males) races at the 2018 Norwegian National Championships. Across laps, section speeds decreased (P < 0.001) in all skiers, with the best-ranked skiers faster than the lowest-ranked (P < 0.001), and males faster than females in the first and middle laps. Section speed within each lap was associated with race performance (r = 0.76-0.86, P < 0.001 in females and r = 0.87-0.89, P < 0.001 in males). The prevalence of Gear 2 (G2) increased, while Gear 3 (G3) use decreased (both P < 0.001) across the subsequent laps, with females preferring G2 more than males in lap one (P = 0.027). In long-distance skate-style skiing, transition performance is representative of race performance and skiers decrease the use of the often-faster G3 technique while increasing the use of the slower G2 technique due to prolonged exercise. Especially female skiers should consider adding some flat-to-uphill G3 practice into established training, specifically early in the session before fatigue may occur.

Do declines in occupational physical activity contribute to population gains in body mass index? Tromsø Study 1974-2016.

OBJECTIVE: To examine whether occupational physical activity changes predict future body mass index (BMI) changes. METHODS: This longitudinal cohort study included adult participants attending ≥3 consecutive Tromsø Study surveys (examinations 1, 2 and 3) from 1974 to 2016 (N=11 308). If a participant attended >3 surveys, the three most recent surveys were included. Occupational physical activity change (assessed by the Saltin-Grimby Physical Activity Level Scale) was computed from the first to the second examination, categorised into persistently inactive (n=3692), persistently active (n=5560), active to inactive (n=741) and inactive to active (n=1315). BMI change was calculated from the second to the third examination (height being fixed at the second examination) and regressed on preceding occupational physical activity changes using analysis of covariance adjusted for sex, birth year, smoking, education and BMI at examination 2. RESULTS: Overall, BMI increased by 0.84 kg/m2 (95% CI 0.82 to 0.89). Following adjustments as described previously, we observed no differences in BMI increase between the occupational physical activity change groups (Persistently Inactive: 0.81 kg/m2, 95% CI 0.75 to 0.87; Persistently Active: 0.87 kg/m2, 95% CI 0.82 to 0.92; Active to Inactive: 0.81 kg/m2, 95% CI 0.67 to 0.94; Inactive to Active: 0.91 kg/m2, 95% CI 0.81 to 1.01; p=0.25). CONCLUSION: We observed no prospective association between occupational physical activity changes and subsequent BMI changes. Our findings do not support the hypothesis that occupational physical activity declines contributed to population BMI gains over the past decades. Public health initiatives aimed at weight gain prevention may have greater success if focusing on other aspects than occupational physical activity.

Flywheel squats versus free weight high load squats for improving high velocity movements in football. A randomized controlled trial.

BACKGROUND: High load (HL: > 85% of one repetition maximum (1RM)) squats with maximal intended velocity contractions (MIVC) combined with football sessions can be considered a relevant and time-efficient practice for maintaining and improving high velocity movements in football. Flywheel (FW) resistance exercise (RE) have recently emerged with promising results on physical parameters associated with football performance. METHODS: In this randomized controlled trial over 6 weeks, 38 recreationally active male football players randomly performed RE with MIVCs two times per week as either 1) FW squats (n = 13) or 2) barbell free weight (BFW) HL squats (n = 13), where a third group served as controls (n = 12). All three groups conducted 2-3 football sessions and one friendly match a week during the intervention period. Pre- to post changes in 10-m sprint, countermovement jump (CMJ) and 1RM partial squat were assessed with univariate analyses of variance. RESULTS: The FW and BFW group equally improved their 10-m sprint time (2 and 2%, respectively, within group: both p < 0.001) and jump height (9 and 8%, respectively, within group: both p < 0.001), which was superior to the control group's change (between groups: both p < 0.001). The BFW group experienced a larger increase (46%) in maximal squat strength than the FW group (17%, between groups: p < 0.001), which both were higher than the control group's change (both p < 0.001). CONCLUSION: Squats carried out with FWs or BFWs where both are performed with MIVCs and combined with football sessions, were equally effective in improving sprint time and jump height in football players. The BFW group experienced a more than two-fold larger increase in maximal partial squat strength than the FW group in maximal partial squat strength. This presents FW RE as an alternative to BFW HL RE for improving high velocity movements in football. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04113031 (retrospectively registered, date: 02.10.2019).

Criterion validity of two physical activity and one sedentary time questionnaire against accelerometry in a large cohort of adults and older adults.

OBJECTIVES: We compared the ability of physical activity and sitting time questionnaires (PAQ) for ranking individuals versus continuous volume calculations (physical activity level (PAL), metabolic equivalents of task (MET), sitting hours) against accelerometry measured physical activity as our criterion. METHODS: Participants in a cohort from the Tromsø Study completed three questionnaires; (1) The Saltin-Grimby Physical Activity Level Scale (SGPALS) (n=4040); (2) The Physical Activity Frequency, Intensity and Duration (PAFID) questionnaire (n=5902)) calculated as MET-hours·week-1 and (3) The International Physical Activity questionnaire (IPAQ) short-form sitting question (n=4896). We validated the questionnaires against the following accelerometry (Actigraph wGT3X-BT) estimates: vector magnitude counts per minute, steps∙day-1, time (minutes·day-1) in sedentary behaviour, light physical activity, moderate and vigorous physical activity (MVPA) non-bouted and ≥10 min bouted MVPA. RESULTS: Ranking of physical activity according to the SGPALS and quartiles (Q) of MET-hours∙week-1 from the PAFID were both positively associated with accelerometry estimates of physical activity (p<0.001) but correlations with accelerometry estimates were weak (SGPALS (PAL): r=0.11 to 0.26, p<0.001) and weak-to-moderate (PAFID: r=0.39 to 0.44, p<0.01). There was 1 hour of accelerometry measured sedentary time from Q1 to Q4 in the IPAQ sitting question (p<0.001) and also weak correlations (r=0.22, p<0.01). CONCLUSION: Ranking of physical activity levels measured with PAQs appears to have higher validity than energy expenditure calculations. Self-reported sedentary time poorly reflects accelerometry measured sedentary time. These two PAQs can be used for ranking individuals into different physical activity categories supporting previous studies using these instruments when assessing associations with health outcomes.

Physical activity levels in adults and elderly from triaxial and uniaxial accelerometry. The Tromsø Study.

INTRODUCTION: Surveillance of physical activity at the population level increases the knowledge on levels and trends of physical activity, which may support public health initiatives to promote physical activity. Physical activity assessed by accelerometry is challenged by varying data processing procedures, which influences the outcome. We aimed to describe the levels and prevalence estimates of physical activity, and to examine how triaxial and uniaxial accelerometry data influences these estimates, in a large population-based cohort of Norwegian adults. METHODS: This cross-sectional study included 5918 women and men aged 40-84 years who participated in the seventh wave of the Tromsø Study (2015-16). The participants wore an ActiGraph wGT3X-BT accelerometer attached to the hip for 24 hours per day over seven consecutive days. Accelerometry variables were expressed as volume (counts·minute-1 and steps·day-1) and as minutes per day in sedentary, light physical activity and moderate and vigorous physical activity (MVPA). RESULTS: From triaxial accelerometry data, 22% (95% confidence interval (CI): 21-23%) of the participants fulfilled the current global recommendations for physical activity (≥150 minutes of MVPA per week in ≥10-minute bouts), while 70% (95% CI: 69-71%) accumulated ≥150 minutes of non-bouted MVPA per week. When analysing uniaxial data, 18% fulfilled the current recommendations (i.e. 20% difference compared with triaxial data), and 55% (95% CI: 53-56%) accumulated ≥150 minutes of non-bouted MVPA per week. We observed approximately 100 less minutes of sedentary time and 90 minutes more of light physical activity from triaxial data compared with uniaxial data (p<0.001). CONCLUSION: The prevalence estimates of sufficiently active adults and elderly are more than three times higher (22% vs. 70%) when comparing triaxial bouted and non-bouted MVPA. Physical activity estimates are highly dependent on accelerometry data processing criteria and on different definitions of physical activity recommendations, which may influence prevalence estimates and tracking of physical activity patterns over time.