Emil Sundstrup

Muscle adaptations and performance enhancements of soccer training for untrained men

We examined the physical demands of small-sided soccer games in untrained middle-age males and muscle adaptations and performance effects over 12xa0weeks of recreational soccer training in comparison with continuous running. Thirty-eight healthy subjects (20–43xa0years) were randomized into a soccer (SO), running (RU) and control (CO) group. Two–three weekly 1-h training sessions were performed. Muscle lactate (30.1xa0±xa04.1 vs. 15.6xa0±xa03.3xa0mmol/kg d.w.), blood lactate, blood glucose and time above 90% HRmax (20xa0±xa04% vs. 1xa0±xa01%) were higher (pxa0<xa00.05) during training in SO than in RU. After 12xa0weeks of training, quadriceps muscle mass and mean muscle fibre area were 9 and 15% larger (pxa0<xa00.05) in SO, but unaltered in RU, and in SO, the fraction of FTx fibres was lowered (10.7xa0±xa01.8 vs. 17.9xa0±xa03.2%). In SO, citrate synthase activity was 10 and 14% higher (pxa0<xa00.05) after 4 and 12xa0weeks, but unaltered in RU. After 4xa0weeks VO2max and Yo-Yo IE2 performance were elevated (pxa0<xa00.05) to a similar extent in SO (7 and 37%) and RU (6 and 36%) but increased further (pxa0<xa00.05) from 4 to 12xa0weeks in SO (6 and 23%). In SO, 30-m sprint performance was improved (pxa0<xa00.05) by 0.11xa0±xa00.02xa0s. Blood lactate during running at 11xa0km/h was lowered (pxa0<xa00.05) from 0 to 4 and 4 to 12xa0weeks (2.6xa0±xa00.3 vs. 3.8xa0±xa00.6 vs. 6.1xa0±xa00.9xa0mM) and from 0 to 12xa0weeks in RU. No changes occurred for CO. In conclusion, recreational soccer organized as small-sided games stimulates both aerobic and anaerobic energy turnover and is an effective type of training leading to significant cardiovascular and muscular adaptations as well as performance enhancements throughout a 12-week training period.

Positive performance and health effects of a football training program over 12 weeks can be maintained over a 1-year period with reduced training frequency

We examined whether improvements in the performance and health profile of an intensive 12‐week football intervention could be maintained with a reduced training frequency. Seventeen healthy untrained males completed the study. Ten subjects trained 2.4u2003times/week for 12 weeks and another 52 weeks with 1.3u2003sessions/week [football group (FG)] and seven subjects acted as controls [control group (CG)]. For FG, fat mass (3.2u2003kg) and systolic blood pressure (8u2003mmHg) were lower (P<0.05) after 64 than 0 weeks, and VO2max (8%) and Yo‐Yo intermittent endurance level 2 test performance (49%) were higher (P<0.05), with no difference between 64 and 12 weeks. After 64 weeks, quadriceps muscle mass (11%), mean fiber area (10%) and citrate synthase activity (18%) were higher (P<0.05) than those at 0 weeks. Leg bone mass (3.5%) and density (2.0%) were higher (P<0.05) after 64 than 0 weeks, but not different between 12 and 0 weeks. Plantar jump force (17–18%), 30‐m sprinting velocity (1.3–3.0%) and muscle glycogen concentration (19–21%) were higher (P<0.05) and blood lactate during submaximal exercise was lower (27–72%, P<0.05) after 64 than after 12 and 0 weeks. The above‐mentioned variables were unaltered for CG. In conclusion, positive adaptations in cardiovascular fitness obtained over 12 weeks of regular recreational football training can be maintained over a 1‐year period with a reduced training frequency, with further development in musculo‐skeletal fitness.

Long-term musculoskeletal and cardiac health effects of recreational football and running for premenopausal women.

We examined long‐term musculoskeletal and cardiac adaptations elicited by recreational football (FG, n=9) and running (RG, n=10) in untrained premenopausal women in comparison with a control group (CG, n=9). Training was performed for 16 months (∼2 weekly 1‐h sessions). For FG, right and left ventricular end‐diastolic diameters were increased by 24% and 5% (P<0.05), respectively, after 16 months. Right ventricular systolic function measured by tricuspid annular plane systolic excursion (TAPSE) increased (P<0.05) in FG after 4 months and further (P<0.05) after 16 months (15% and 32%, respectively). In RG and CG, cardiac structure, E/A and TAPSE remained unchanged. For FG, whole‐body bone mineral density (BMD) was 2.3% and 1.3% higher (P<0.05) after 16 months, than after 4 and 0 months, respectively, with no changes for RG and CG. FG demonstrated substantial improvements (P<0.05) in fast (27% and 16%) and slow (16% and 17%) eccentric muscle strength and rapid force capacity (Imp30ms: 66% and 65%) after 16 months compared with 4 and 0 months, with RG improving Imp30ms by 64% and 46%. In conclusion, long‐term recreational football improved muscle function, postural balance and BMD in adult women with a potential favorable influence on the risk of falls and fractures. Moreover, football training induced consistent cardiac adaptations, which may have implications for long‐term cardiovascular health.

Recreational football training decreases risk factors for bone fractures in untrained premenopausal women

The present intervention was designed to investigate whether a 14‐week period of regular recreational association football (F) or endurance running (R) has an effect on the risk of falls and bone fractures due to gains in muscle function and volumetric bone mineral density (vBMD). Fifty healthy untrained Danish premenopausal women were randomized into two training groups (F and R) that trained 1.8±0.3 (±SD) and 1.9±0.3u2003h/week, respectively, and these groups were compared with an inactive control group (C). Jumping and dynamic muscle strength were tested and tibial vBMD was measured using peripheral quantitative computed tomography. Total vBMD in left and right tibia increased by 2.6±2.3% and 2.1±1.8% (P<0.005), respectively, in F and by 0.7±1.3% (P=0.05) and 1.1±1.5% (P<0.01), respectively, in R without any significant changes in C. Similar results were found for trabecular vBMD. In F, peak jump power increased by 3±6% (P<0.05), and hamstring strength during fast (240°/s) and slow (30°/s) contractions increased by 11±25% and 9±21%, respectively, (P<0.05) without any significant changes in R or C. In conclusion, 14 weeks of regular recreational football improved peak jump power, maximal hamstring strength and vBMD in the distal tibia, suggesting a decreased fracture risk due to stronger bones and a reduced risk of falling.

The effect of recreational soccer training and running on postural balance in untrained men

The aim of this study was to examine the effect of intense intermittent exercise performed as soccer training or interval running in comparison with continuous endurance running exercise on postural balance in young healthy untrained males. Young sedentary men were randomized to soccer training (SOC, nxa0=xa010), continuous running (RUN; nxa0=xa09), high-intensity interval running (INT; nxa0=xa07) or no training (CON; nxa0=xa09). Postural balance was evaluated pre and post 12xa0weeks of training using a 30-s single-leg stance test on a force plate (AMTI) to yield center of pressure (CoP) sway path and 1-min beam standing (Flamingo test). CoP sway length decreased by 18.2% (pxa0<xa00.01), 14.6% (pxa0<xa00.05) and 12.8% (pxa0<xa00.05) in SOC, INT and RUN, respectively. CoP sway area decreased in SOC (−30.2%; pxa0<xa00.01) and INT (−23.4%; pxa0<xa00.01) but remained unaffected in RUN. Acceleration parameters (Mean CoP acc, SD accX, SD accY) decreased in SOC only (17–19%, pxa0<xa00.05). All training groups demonstrated fewer falls (37–41%, pxa0<xa00.01) in the Flamingo test. No changes were observed in CON. Relationships (rxa0>xa00.40) were observed between pre-training values in CoP sway area versus muscle fiber area, explosive muscle strength and countermovement jump velocity. Postural control was improved in response to 12xa0weeks of soccer training and high-intensity interval running, respectively, while less-marked changes were observed following continuous running. Notably, the reduced variability in CoP acceleration after soccer training indicates that this training regimen may produce superior improvements in postural sensory-motor function.

The effect of strength training, recreational soccer and running exercise on stretch-shortening cycle muscle performance during countermovement jumping.

The purpose of the present study was to evaluate the effect of contrasting training modalities on mechanical muscle performance and neuromuscular activity during maximal SSC (stretch-shortening cycle) countermovement jumps (CMJ). Bilateral countermovement jumping, surface electromyography (EMG) and muscle fiber size (CSA) were studied in untrained individuals (n=49, 21-45 yrs) pre and post 12 weeks of progressive heavy-resistance strength training (ST, n=8), recreational soccer training (SOC, n=15), high-intensity interval running (INT, n=7), continuous running (RUN, n=9) or continuation of an inactive life-style (CON, n=10). ST displayed shortened CMJ take-off time (p<.05) and increased (p<.05) maximal CMJ jump height, peak down- and upward velocity of center of mass (COM), rate of vertical force development (RFD: ΔF(Z)/Δt), peak power production, rate of power development (RPD), mean plantar flexor EMG and peak hamstring rate of EMG rise (RER). Peak quadriceps EMG rate of rise increased in SOC (p<.05). Moreover, ST and SOC demonstrated increased quadriceps muscle fiber CSA and lean leg mass. Positive relationships (r>.70) were observed following ST between training-induced changes in CMJ SSC muscle performance, neuromuscular activity and muscle fiber CSA, respectively. ST induced a more rapid CMJ take-off phase and elevated muscle power production, indicating a more explosive-type SSC muscle performance. No effects were detected in CMJ performance after continuous running, high-intensity interval running and recreational soccer, despite an increased muscle fiber CSA and quadriceps muscle activity in SOC. Enhanced neuromuscular activity in the hip extensors (hamstrings) and plantar flexors, and increased myofiber fiber size were responsible for the enhanced CMJ SSC muscle performance with ST.

Muscle function and postural balance in lifelong trained male footballers compared with sedentary elderly men and youngsters.

The present study investigated whether elderly subjects exposed to lifelong football training have better rapid muscle force characteristics, body composition and postural stability in comparison with untrained elderly. Ten elderly men exposed to lifelong football training (FTE; 69.6 ± 1.4 years) and eight age‐matched untrained elderly men (UE; 70.5 ± 1.0 years) were studied and 49 untrained young men (UY; 32.4 ± 0.9 years) served as a reference group. FTE showed an elevated rate of force development (RFD) and impulse at 0–30, 100 and 200u2003ms (relative RFD at 1/6 MVC: 567 ± 39 vs 353 ± 42%u2003MVC/s), higher total lean body mass (56.9 ± 0.8 vs 52.7 ± 2.2u2003kg) and better postural stability (Flamingo test: 15 ± 1 vs 33 ± 2 falls) compared with UE (P<0.05), with no difference between FTE and UY. The proportion of type IIA fibers was higher and the area percentage of type IIX fibers was lower in FTE than in UE (P<0.05). Rapid muscle force characteristics and postural stability were consistently higher in elderly subjects exposed to lifelong football training, providing an enhanced ability to counteract unexpected perturbations in postural balance. The superior RFD and balance in elderly footballers were of such a magnitude that no deficit could be observed when compared with young untrained individuals.

Validity and reliability of elastic resistance bands for measuring shoulder muscle strength

Valid and reliable measurements of muscle strength are important in sport medicine. This study assesses concurrent validity and intrarater reliability (test–retest reliability) of elastic resistance bands for measuring shoulder muscle strength. Altogether, 50 healthy adults [mean age 36.0 (SD: 11.6), 29 women and 21 men] participated in testing and retesting 1–2 weeks later. The maximal elastic resistance (TheraBand) that each participant could hold for 3 s during standing bilateral shoulder abduction to 90° was converted into torque and validated against gold standard maximal voluntary isometric contraction (MVC) (Vishay force transducer) performed unilaterally while lying supine. The intrarater reliability of both tests were high; for the MVC and elastic band test, respectively, ICC(3,1) was 0.98 (95% CI: 0.97–0.99) and 0.99 (95% CI: 0.98–1.00), and measurement error was 4.8% (95% CI: 3.7–5.9) and 4.7% (95% CI: 3.1–6.2). For concurrent validity, ICC(3,1) was 0.96 (95% CI: 0.95–0.98) and measurement error was 8.1% (95% CI: 6.6–9.6), and the elastic band test explained 93% of the variance in the MVC test. However, the elastic band test produced systematically lower torque values than the MVC [56.5 (SD: 26.8) vs 66.5 (SD: 25.5) Nm, P < 0.01]. In conclusion, the test for shoulder muscle strength using elastic resistance bands has excellent validity and reliability, but produces systematically lower torque values than MVC. The reason for the lower torque values may be that the elastic band test has an initial concentric phase and is performed bilaterally and standing upright.

Factors affecting pain relief in response to physical exercise interventions among healthcare workers

The aim of this study is to identify factors associated with musculo‐skeletal pain reduction during workplace‐based or home‐based physical exercise interventions among healthcare workers. Two hundred female healthcare workers (age: 42.0, BMI: 24.1, average pain intensity: 3.1 on a scale of 0‐10) from three hospitals participated. Participants were randomly allocated at the cluster level (18 departments) to 10 weeks of (i) workplace physical exercise (WORK) performed in groups during working hours for 5 × 10 minutes per week and up to five group‐based coaching sessions on motivation for regular physical exercise, or (ii) home‐based physical exercise (HOME) performed alone during leisure‐time for 5 × 10 minutes per week. Linear mixed models accounting for cluster identified factors affecting pain reduction. On average 2.2 (SD: 1.1) and 1.0 (SD: 1.2) training sessions were performed per week in WORK and HOME, respectively. The multi‐adjusted analysis showed a significant effect on pain reduction of both training adherence (P=.04) and intervention group (P=.04) with participants in WORK experiencing greater reductions compared with HOME. Obesity at baseline was associated with better outcome. Leisure‐time exercise, daily patient transfer, age, and chronic pain did not affect the changes in pain. In conclusion, even when adjusted for training adherence, performing physical exercise at the workplace is more effective than home‐based exercise in reducing musculo‐skeletal pain in healthcare workers. Noteworthy, obese individuals may especially benefit from physical exercise interventions targeting musculo‐skeletal pain.

Regular use of medication for musculoskeletal pain and risk of long-term sickness absence: a prospective cohort study among the general working population

The aim was to determine the prospective association between use of pain medication – due to musculoskeletal pain in the low back, neck/shoulder and hand/wrist – and long‐term sickness absence.