Markus D. Jakobsen

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 2.4 times/week for 12 weeks and another 52 weeks with 1.3 sessions/week [football group (FG)] and seven subjects acted as controls [control group (CG)]. For FG, fat mass (3.2 kg) and systolic blood pressure (8 mmHg) 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±0.3 h/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.

Muscle activity during leg strengthening exercise using free weights and elastic resistance: effects of ballistic vs controlled contractions

The present studys aim was to evaluate muscle activity during leg exercises using elastic vs. isoinertial resistance at different exertion and loading levels, respectively. Twenty-four women and eighteen men aged 26-67 years volunteered to participate in the experiment. Electromyographic (EMG) activity was recorded in nine muscles during a standardized forward lunge movement performed with dumbbells and elastic bands during (1) ballistic vs. controlled exertion, and (2) at low, medium and high loads (33%, 66% and 100% of 10 RM, respectively). The recorded EMG signals were normalized to MVC EMG. Knee joint angle was measured using electronic inclinometers. The following results were obtained. Loading intensity affected EMG amplitude in the order: low<medium<high loads (p<.001). Ballistic contractions always produced greater EMG activity than slow controlled contractions, and for most muscles ballistic contractions with medium load showed similar EMG amplitude as controlled contractions with high load. At flexed knee joint positions with elastic resistance, quadriceps and gluteus EMG amplitude during medium-load ballistic contractions exceeded that recorded during high-load controlled contractions. Quadriceps and gluteus EMG amplitude increased at flexed knee positions. In contrast, hamstrings EMG amplitude remained constant throughout ROM during dumbbell lunge, but increased at more extended knee joint positions during lunges using elastic resistance. Based on these results, it can be concluded that lunges performed using medium-load ballistic muscle contractions may induce similar or even higher leg muscle activity than lunges using high-load slow-speed contractions. Consequently, lunges using elastic resistance appear to be equally effective in inducing high leg muscle activity as traditional lunges using isoinertial resistance.

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 200 ms (relative RFD at 1/6 MVC: 567 ± 39 vs 353 ± 42% MVC/s), higher total lean body mass (56.9 ± 0.8 vs 52.7 ± 2.2 kg) 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.

Effect of workplace- versus home-based physical exercise on musculoskeletal pain among healthcare workers: a cluster randomized controlled trial.

OBJECTIVE Numerous studies has shown that regular physical exercise can reduce musculoskeletal pain, but the optimal setting to achieve high adherence and effectiveness remains unknown. This study investigated the effect of workplace versus home-based physical exercise on musculoskeletal pain among healthcare workers. METHODS The randomized controlled trial (RCT) comprised 200 female healthcare workers from 18 departments at 3 hospitals. Participants were randomly allocated at the cluster level to ten weeks of: (i) workplace physical exercise (WORK) performed during working hours for 5×10 minutes per week and up to 5 group-based coaching sessions on motivation for regular physical exercise, or (ii) home-based physical exercise (HOME) performed during leisure time for 5×10 minutes per week. Both groups received ergonomic counseling on patient handling and use of lifting aides. Average pain intensity (0-10 scale) in the low back and neck/shoulder was the primary outcome. RESULTS Per week, 2.2 (SD 1.1) and 1.0 (SD 1.2) training sessions were performed in WORK and HOME groups, respectively. Pain intensity, back muscle strength and use of analgesics improved more following WORK than HOME (P<0.05). Between-group differences at follow-up (WORK versus HOME) was -0.7 points for pain intensity [95% confidence interval (95% CI) -1.0- -0.3], 5.5 Nm for back muscle strength (95% CI 2.0-9.0), and -0.4 days per week for use of analgesics (95% CI -0.7- -0.2). The effect size for between-group differences in pain intensity was small (Cohens d=0.31). CONCLUSIONS Workplace physical exercise is more effective than home-based exercise in reducing musculoskeletal pain, increasing muscle strength and reducing the use of analgesics among healthcare workers.

EMG evaluation of hip adduction exercises for soccer players: implications for exercise selection in prevention and treatment of groin injuries.

Introduction Exercise programmes are used in the prevention and treatment of adductor-related groin injuries in soccer; however, there is a lack of knowledge concerning the intensity of frequently used exercises. Objective Primarily to investigate muscle activity of adductor longus during six traditional and two new hip adduction exercises. Additionally, to analyse muscle activation of gluteals and abdominals. Materials and methods 40 healthy male elite soccer players, training >5 h a week, participated in the study. Muscle activity using surface electromyography (sEMG) was measured bilaterally for the adductor longus during eight hip adduction strengthening exercises and peak EMG was normalised (nEMG) using an isometric maximal voluntary contraction (MVC) as reference. Furthermore, muscle activation of the gluteus medius, rectus abdominis and the external abdominal obliques was analysed during the exercises. Results There were large differences in peak nEMG of the adductor longus between the exercises, with values ranging from 14% to 108% nEMG (p<0.0001). There was a significant difference between legs in three of the eight exercises (35–48%, p<0.0001). The peak nEMG results for the gluteals and the abdominals showed relatively low values (5–48% nEMG, p<0.001). Conclusions Specific hip adduction exercises can be graded by exercise intensity providing athletes and therapists with the knowledge to select appropriate exercises during different phases of prevention and treatment of groin injuries. The Copenhagen Adduction and the hip adduction with an elastic band are dynamic high-intensity exercises, which can easily be performed at any training facility and could therefore be relevant to include in future prevention and treatment programmes.

Muscle Activation Strategies During Strength Training With Heavy Loading vs. Repetitions to Failure

Abstract Sundstrup, E, Jakobsen, MD, Andersen, CH, Zebis, MK, Mortensen, OS, and Andersen, LL. Muscle activation strategies during strength training with heavy loading vs. repetitions to failure. J Strength Cond Res 26(7): 1897–1903, 2012—Going to failure, or not, has probably been one of the most debated issues during the history of strength training. However, few studies have directly compared the physiological effect of failure vs. nonfailure strength training. The purpose of this study was to evaluate muscle activation strategies with electromyography (EMG) during heavy repetitions vs. repetitions to failure with lighter resistance. Fifteen healthy untrained women performed a set with heavy loading (3 repetition maximum [RM]) and a set of repetitions to failure with lower resistance (∼15 RM) during lateral raise with elastic tubing. Electromyographic amplitude and median power frequency of specific shoulder and neck muscles were analyzed, and the BORG CR10 scale was used to rate perceived loading immediately after each set of exercise. During the failure set, normalized EMG was significantly lower during the first repetition and significantly higher during the latter repetitions compared with the heavy 3-RM set (p < 0.05). Normalized EMG for the examined muscles increased throughout the set to failure in a curvilinear fashion—e.g., for the trapezius from 86 to 124% maximal voluntary contraction (p < 0.001)—and reached a plateau during the final 3–5 repetitions before failure. Median power frequency for all examined muscles decreased throughout the set to failure in a linear fashion, indicating progressively increasing fatigue. In conclusion, going to complete failure during lateral raise is not necessary to recruit the entire motor unit pool in untrained women—i.e., muscle activity reached a plateau 3–5 repetitions from failure with an elastic resistance of approximately 15 RM. Furthermore, strengthening exercises performed with elastic tubing seem to be an efficient resistance exercise and a feasible and practical alternative to traditional resistance equipment.

Effect of specific resistance training on forearm pain and work disability in industrial technicians: cluster randomised controlled trial

Objectives To determine the effect of specific resistance training on forearm pain and work disability in industrial technicians. Design and setting Two-armed cluster randomised controlled trial of 20 weeks performed at two industrial production units in Copenhagen, Denmark. Participants Working-age industrial technicians both with and without pain and disability. Interventions The training group (n=282) performed specific resistance training for the shoulder, neck and arm muscles three times a week. The control group (n=255) was advised to continue normal physical activity. Outcome All participants rated forearm pain intensity (Visual Analogue Scale, 0–100 mm) once a week (primary outcome) and replied to a questionnaire on work disability (Disability of the Arm Shoulder and Hand, 0–100) at baseline and follow-up (secondary outcome). Results Questionnaires were sent to 854 workers of which 30 (n=282) and 27 (n=255) clusters were randomised to training and control, respectively. Of these, 211 and 237 participants, respectively, responded to the follow-up questionnaire. Intention-to-treat analyses including both individuals with and without pain showed that from baseline to follow-up, pain intensity and work disability decreased more in the training group than in the control group (4–5 on a scale of 0–100, p<0.01–0.001). Among those with pain >30 mm Visual Analogue Scale at baseline (n=54), the OR for complete recovery at follow-up in the training group compared with the control group was 4.6 (95% CI 1.2 to 17.9). Among those with work disability >30 at baseline (n=113), the OR for complete recovery at follow-up in the training group compared with the control group was 6.0 (95% CI 1.8 to 19.8). Conclusion Specific resistance training of the shoulder, neck and arm reduces forearm pain and work disability among industrial technicians. Trial registration number NCT01071980.