Trunk muscle strength and lumbo‐pelvic kinematics in adolescent athletes: Effects of age and sex

Considering their potential relevance for low‐back pain, we investigated trunk muscle strength, sagittal lumbo‐pelvic alignment while standing and lumbo‐pelvic ratio during trunk flexion in adolescent athletes with regard to the effects of age and sex. Twenty‐two early adolescent (EA: 13‐15 years, 10 females) and 28 late adolescent (LA: 16‐19 years, 14 females) high‐level athletes (training duration more than 12 hours per week) participated in the study. We measured trunk extension and trunk flexion moments during maximum voluntary isometric contractions using a dynamometer. Further, we examined lumbo‐pelvic kinematics in the upright standing position and during forward trunk bending using two 3‐dimensional accelerometers. Using a lineal regression model in which the flexion moment from each participant was used as predictor for the corresponding extension moment, we found higher residuals (P < 0.001) in the EA compared to LA, indicating greater imbalances in the trunk muscle strength in EA. We found a higher lordosis in the upright position, greater pelvic rotation, and greater lordotic posture during the forward bending in females (P < 0.01). These age‐related imbalances and sex‐related characteristics in lumbo‐pelvic kinematics might affect the neuromuscular control of trunk stability and the magnitude of spine loading. We recommend the implementation of specific coordination and stabilization programs for muscle groups that contribute to lumbo‐pelvic kinematics and training routines that support a balanced strength development within the trunk muscles in adolescent athletes.     

Trunk muscle endurance tests: Reliability, and gender differences in athletes

Adequate trunk muscle endurance may play an important role in injury-free performance among athletes. However, reliability of tests of isometric trunk muscle endurance in common use has not been clearly established and few studies have reported normative data for athletes. This study first examined intra-rater and inter-rater reliability of the side bridge endurance test and a test of trunk flexor endurance in a group of non-athletes, then measured performance of a group of elite athletes on tests of trunk muscle endurance commonly used in the clinic. The side bridge endurance test and the trunk flexor endurance test were found to have high intra-rater and inter-rater reliability, albeit with relatively large standard error of measurement (S.E.M.) values. In contrast with previous studies of non-athletes, male athletes had equivalent holding times on the Biering–Sørensen trunk extensor endurance test to those of female athletes. However, female athletes had significantly lower holding times on the side bridge endurance tests than their male counterparts. The implication of the significant difference in endurance performance between male and female athletes in some muscle groups but not others is that testing and training of trunk muscle endurance should be ‘multidirectional’ for all athletes who aim to optimise performance and minimise injury risk.     

Trunk muscle strength and disability level of low back pain in collegiate wrestlers

INTRODUCTION/PURPOSE: Low back pain (LBP) is a frequent injury in athletes. This study examined the relationship between isokinetic trunk muscle strength and the functional disability level of chronic LBP. We particularly focused on the existence of radiological abnormalities (RA) in the lumbar region. METHODS: Subjects were 53 collegiate wrestlers. Trunk extensor and flexor muscle strength was measured at three angular velocities (60, 90, and 120degrees x s(-1)). The examined parameters for trunk muscle strength were peak torque, work, average torque, and average power. The disability level of LBP was estimated by using two questionnaires. Based on the RA evaluation with x-ray and MRI, all 53 wrestlers were assigned to two groups as the RA group (N = 35, 66%) and the non-RA group (N = 18, 34%). Correlations between trunk muscle strength and the disability level of LBP in each group were analyzed with Spearman's rank test. RESULTS: Without considering the disability level, there were 14 subjects with LBP (40%) in the RA group and 8 (44%) in the non-RA. Significantly correlated parameters with the disability level of LBP could be observed only when the subjects were restricted to the non-RA group. The correlated parameters with the two questionnaires were peak torque at 120degrees x s(-1), work at 60degrees x s(-1) and 90degrees x s(-1), and average torque at 90degrees x s(-1) and 120degrees x s(-1). There were no significantly correlated parameters in the RA group. None of the trunk flexor parameters were significantly correlated with the disability level of LBP. CONCLUSION: The relatively low strength of trunk extensors may be one of the factors related to nonspecific chronic low back pain in collegiate wrestlers.     

Evaluation of methods for normalizing muscle strength in elite and young athletes

BACKGROUND: The following equation has been most often used in order to present recorded muscle strength (F) normalised for various measures of body size (such as body mass m) Fnor = F x m(-b). Since previous studies have provided inconsistent results, the purpose of the present one was to assess the value of the exponential parameter b (b-value) that (a) provides both the normalised strength independent of body mass and (b) demonstrates the highest possible correlation between the normalised strength and standard tests of movement performance. METHODS: Thirteen groups of male and female athletes of both different age and different sport specialisation were tested for maximal isometric force of various leg muscle groups, as well as for vertical and standing long jump. RESULTS: The data obtained on most of the experimental groups suggested that the b-value close to the theoretically predicted b=0.67, but also different from b=0 and b=1, should be used for calculation of the normalised strength independent of body mass. Although the strength normalised using b=0.67 and b=1 demonstrated higher correlation with jumping performance than the non-normalised strength (i.e., b=0), the data also suggested that b>1 could provide the highest prediction of movement performance. CONCLUSIONS: Muscle strength should be calculated as force per kg(2/3) rather than as absolute force or force calculated per kg of body mass in order to assess strength independent of body size in routine testing of muscle function. However, different and probably task specific normalisation methods could be required in order to predict performance of various movement tasks by assessed muscle strength.     

Association between lower extremity muscle strength and acute ankle injury in youth team-sports athletes

ObjectivesTo investigate lower extremity muscle strength as risk factor for an acute ankle injury in youth athletes.DesignCohort study.SettingBasketball and floorball clubs.Participants188 youth (≤21) male and 174 female athletes.Main outcome measures1RM leg press, maximal concentric isokinetic quadriceps and hamstrings as well as maximal isometric hip abductor strength were measured and athletes were followed for an acute ankle injury up to three years. Cox regression models were used in statistical analyses.ResultsIn males, greater 1RM leg press and maximal quadriceps strength increased the risk of any type of acute ankle injury (Hazard ratio [HR] for 1 SD increase, 1.63 [95% CI, 1.12–2.39] and 1.43 [95% CI, 1.01–2.01], respectively). In females, greater 1RM leg press and difference between legs in hip abduction strength increased the risk of acute non-contact ankle injury (HR for 1 SD increase, 1.44 [95% CI, 1.03–2.02] and 1.44 [95% CI, 1.03–2.00], respectively). However, ROC curve analyses showed AUC:s of 0.57–0.64 indicating “fail” to “poor” combined sensitivity and specifity of these tests.ConclusionGreater strength in both sexes along with asymmetry in hip abductor strength in females increased the risk of acute ankle injury.     

Relation between isokinetic muscle strength and functional capacity in recreational athletes with chondromalacia patellae

OBJECTIVES: To investigate the effects of isokinetic exercise on pain and functional test scores of recreational athletes with chondromalacia patellae (CMP) and to examine the correlation between isokinetic parameters and functional tests or pain score. METHODS: The functional ability of 30 recreational athletes with unilateral CMP was evaluated using six different tests. Pain scores were assessed during daily activities before and after the treatment protocol. Isokinetic exercise sessions were carried out at angular velocities of 60 degrees /s (25-90 degrees range of flexion) and 180 degrees /s (full range). These sessions were repeated three times a week for six weeks. RESULTS: Quadriceps and hamstring peak torque, total work, and endurance ratios had improved significantly after the treatment, as did the functional parameters and pain scores. There was a poor correlation between the extensor endurance ratio and one leg standing test. A moderate correlation between the visual analogue scale and the extensor endurance ratio or flexion endurance ratio was also found. CONCLUSIONS: The isokinetic exercise programme used in this study had a positive effect on muscle strength, pain score, and functional ability of knees with CMP. The improvement in the functional capacity did not correlate with the isokinetic parameters.     

Effects of whole body vibration training on muscle strength and sprint performance in sprint-trained athletes

Despite the expanding use of Whole Body Vibration training among athletes, it is not known whether adding Whole Body Vibration training to the conventional training of sprint-trained athletes will improve speed-strength performance. Twenty experienced sprint-trained athletes (13 male symbol, 7 female symbol, 17-30 years old) were randomly assigned to a Whole Body Vibration group (n=10: 6 male symbol and 4 female symbol) or a Control group (n=10: 7 male symbol, 3 female symbol). During a 5-week experimental period all subjects continued their conventional training program, but the subjects of the Whole Body Vibration group additionally performed three times weekly a Whole Body Vibration training prior to their conventional training program. The Whole Body Vibration program consisted of unloaded static and dynamic leg exercises on a vibration platform (35-40 Hz, 1.7-2.5 mm, Power Plate). Pre and post isometric and dynamic (100 degrees/s) knee-extensor and -flexor strength and knee-extension velocity at fixed resistances were measured by means of a motor-driven dynamometer (Rev 9000, Technogym). Vertical jump performance was measured by means of a contact mat. Force-time characteristics of the start action were assessed using a load cell mounted on each starting block. Sprint running velocity was recorded by means of a laser system. Isometric and dynamic knee-extensor and knee-flexor strength were unaffected (p>0.05) in the Whole Body Vibration group and the Control group. As well, knee-extension velocity remained unchanged (p>0.05). The duration of the start action, the resulting start velocity, start acceleration, and sprint running velocity did not change (>0.05) in either group. In conclusion, this specific Whole Body Vibration protocol of 5 weeks had no surplus value upon the conventional training program to improve speed-strength performance in sprint-trained athletes.     

Bone mineral density in adolescent female athletes: relationship to exercise type and muscle strength

PURPOSE: This study investigated the influence of different exercise types and differences in anatomical distribution of mechanical loading patterns on bone mineral density (BMD) in elite female cyclists, runners, swimmers, triathletes, and controls (N = 15 per group). Associations between leg strength and BMD were also examined. METHODS: Areal BMD (g x cm(-2)) was assessed by duel-energy x-ray absorptiometry (DXA) (total body (TB), lumbar spine (LS), femoral neck (FN), legs, and arms). Right knee flexion and extension strength was measured using a Cybex Norm isokinetic dynamometer at 60 degrees x s(-1). RESULTS: Runners had significantly higher unadjusted TB, LS, FN, and leg BMD than controls (P < 0.05); higher TB, FN, and leg BMD than swimmers (P < 0.05); and greater leg BMD than cyclists (P < 0.05). Absolute knee extension strength was significantly (P < 0.01) correlated (0.33 < or = r < or = 0.44) with TB, FN, LS, and leg BMD for all groups combined. Weaker but still significant correlations (0.28 < or = r < or = 0.33) existed for normalized (per leg lean tissue mass) knee extension strength and all BMD sites, except FN BMD. There were no significant correlations between absolute or normalized knee flexion strength and any of the BMD variables. Absolute knee extension strength was entered as the second independent predictor for LS and leg BMD in stepwise multiple linear regression analysis (MLRA), accounting for increments of 4% and 12%, respectively, in total explained variation. CONCLUSION: We conclude that running, a weight bearing exercise, is associated with larger site-specific BMD than swimming or cycling, that the generalized anatomical distribution of loads in triathlon appears not to significantly enhance total body BMD status, and that knee extension strength is only a weak correlate and independent predictor of BMD in adolescent females.     

Jump-land characteristics and muscle strength development in young athletes: a gender comparison of 1140 athletes 9 to 17 years of age

BACKGROUND: Many authors have speculated that altered neuromuscular control and strength of the lower extremity are responsible for the gender disparity in knee ligament injury rates. HYPOTHESIS: Significant increases in normalized quadriceps and hamstrings strength and limb symmetry on single-legged hop test occur with age. No gender differences in strength occur until age 14 years, after which boys generate greater peak torques than do girls. Age and gender do not influence lower limb alignment on a drop-jump test. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: We studied the effects of age and gender in 1140 athletes, 9 to 17 years old, on muscle strength and neuromuscular control during functional activities. Isokinetic quadriceps and hamstrings strength was measured at 300 deg/s. Limb symmetry was assessed with single-legged hop tests. A video drop-jump test determined lower limb alignment in the coronal plane. RESULTS: Extension peak torques significantly increased with age; maximum strength was noted in girls at age 13 years and in boys at age 14 years (P < .001). Although maximum flexion strength occurred in boys at age 14 years (P < .001), girls had only slight increases from ages 9 to 11 years (P = not significant). Boys aged 14 to 17 years had significantly greater normalized isokinetic strength than did age-matched girls. No age or gender effects existed in limb alignment on the drop-jump test or limb symmetry on single-legged hop testing. CONCLUSION: Maximum hamstrings strength was noted in female athletes by age 11 years, compared with age 14 years in male athletes, and a distinct lower limb valgus alignment existed in the majority of all athletes on landing. The absence of a gender difference in lower limb alignment on landing suggests other factors may be responsible for the gender disparity in knee ligament injury rates.     

Nutritional aspects of women strength athletes

Strength training elicits sports related and health benefits for both men and women. Although sexual dimorphism is observed in exercise metabolism, there is little information outlining the specific nutritional needs of women strength athletes. Many women athletes restrict energy intake, specifically fat consumption, in order to modify body composition, but this nutritional practice is often counter-productive. Compared to men, women appear to be less reliant on glycogen during exercise and less responsive to carbohydrate mediated glycogen synthesis during recovery. Female strength athletes may require more protein than their sedentary and endurance training counterparts to attain positive nitrogen balance and promote protein synthesis. Therefore, women strength athletes should put less emphasis on a very high carbohydrate intake and more emphasis on quality protein and fat consumption in the context of energy balance to enhance adaptations to training and improve general health. Attention to timing of nutrient ingestion, macronutrient quality, and dietary supplementation (for example, creatine) are briefly discussed as important components of a nutritionally adequate and effective strength training diet for women.     

Trunk exercise training improves muscle size,strength, and function in older adults: A randomized controlled trial

The aim of this study was to assess the effectiveness of a multimodal exercise program to increase trunk muscle morphology and strength in older individuals, and their associated changes in functional ability. Using a single‐blinded parallel‐group randomized controlled trial design, 64 older adults (≥60 years) were randomly allocated to a 12‐week exercise program comprising walking and balance exercises with or without trunk strengthening/motor control exercises; followed by a 6‐week walking‐only program (detraining; 32 per group). Trunk muscle morphology (ultrasound imaging), strength (isokinetic dynamometer), and functional ability and balance (6‐Minute Walk Test; 30 second Chair Stand Test; Sitting and Rising Test; Berg Balance Scale, Multi‐Directional Reach Test; Timed Up and Go; Four Step Square Test) were the primary outcome measures. Sixty‐four older adults (mean [SD]; age: 69.8 [7.5] years; 59.4% female) were randomized into two exercise groups. Trunk training relative to walking‐balance training increased (mean difference [95% CI]) the size of the rectus abdominis (2.08 [1.29, 2.89] cm²), lumbar multifidus (L4/L5:0.39 [0.16, 0.61] cm; L5/S1:0.31 [0.07, 0.55] cm), and the lateral abdominal musculature (0.63 [0.40, 0.85] cm); and increased trunk flexion (29.8 [4.40, 55.31] N), extension (37.71 [15.17, 60.25] N), and lateral flexion (52.30 [36.57, 68.02] N) strength. Trunk training relative to walking‐balance training improved 30‐second Chair Stand Test (5.90 [3.39, 8.42] repetitions), Sitting and Rising Test (1.23 [0.24, 2.23] points), Forward Reach Test (4.20 [1.89, 6.51] cm), Backward Reach Test (2.42 [0.33, 4.52] cm), and Timed Up and Go Test (?0.76 [?1.40, ?0.13] seconds). Detraining led to some declines but all outcomes remained significantly improved when compared to pre‐training. These findings support the inclusion of trunk strengthening/motor control exercises as part of a multimodal exercise program for older adults.     

Dynamics of muscle strength improvement during isokinetic rehabilitation of athletes with ACL rupture and chondromalacia patellae

AIM: To assess quantitatively dynamics and extent of the increase in muscle strength during isokinetic rehabilitation. METHODS: Experimental design: daily measurements of muscle strength; detailed testing at the beginning and at the end of rehabilitation. Setting: Cybex Rehabilitation Center, Zagreb. Subjects: 44 athletes (31 m, 13 F, age 16-35), 3 injury-defined groups: athletes with ACL rupture (non-reconstructed and reconstructed) and chondromalacia patellae. Interventions: all subjects underwent isokinetic rehabilitation on Cybex Orthotron KT2 device, using individually designed protocols (extension and flexion exercises, concentric muscle contractions, 15 treatments). Measurements: monitoring of daily progress on rehabilitation device and detailed testing on diagnostic device. RESULTS: All patients showed considerable improvement. Muscle strength improved on average 141% (SD=110) in ACL-reconstructed group, 144% (SD=130) for chondromalacia patellae group and 150% (SD=74) for ACL-non-reconstructed group, comparing to initial strength. Dynamic status tested on Cybex Otrhotron diagnostic device prior and after rehabilitation strongly correlated with final progress monitored on the rehabilitation device. CONCLUSION: Isokinetic rehabilitation is a quick and effective method in treating knee injuries in athletes. Both types of objective criteria have shown significant increase in muscle strength. The improvement of muscle strength was on the average 149% (SD=101), which is about 10% daily for 15 treatments. The greatest progress, 19% per day, occurred during first five days. The athletes were able to resume their sport activities as follows: patients from chondromalacia patellae group, and most of them from the non-reconstructed ACL group were back in competition within a month, while 75% from the ACL reconstructed group came back within 3 months, and the rest of them within 5 months.     

Effect of concentric and eccentric hamstring training on sprint recovery,strength and muscle architecture in inexperienced athletes

ObjectivesTo investigate whether five-weeks of concentric (CON) or eccentric (ECC) hamstring strength training have different effects on recovery from sprint running, eccentric strength and architecture of the biceps femoris long head (BF_LH).DesignCohort study.MethodsThirty males (age, 22.8 ± 4.1 y; height, 180.1 ± 6.4 cm; weight, 85.2 ± 14.6 kg) were allocated into either a CON or ECC group, both performing nine sessions of resistance training. Prior to and immediately after the five-week intervention, each participant’s BF_LH fascicle length (FL), pennation angle (PA), muscle thickness (MT), peak isometric KF torque and Nordic eccentric strength were assessed. Post-intervention, participants performed two timed sprint sessions (10 × 80 m) 48 h apart. Blood samples and passive KF torques were collected before, immediately after, 24 h and 48 h after the first sprint session.ResultsAfter five-weeks of strength-training, fascicles lengthened in the ECC (p < 0.001; d = 2.0) and shortened in the CON group (p < 0.001; d = 0.92), while PA decreased for the ECC (p = 0.001; d = 0.52) and increased in the CON group (p < 0.001; d = 1.69). Nordic eccentric strength improved in both ECC (p < 0.001; d = 1.49) and CON (p < 0.001; d = 0.95) groups. No between-group differences were observed in peak isometric strength (p = 0.480), passive KF torques (p = 0.807), sprint performance decrements between sprint sessions (p = 0.317) and creatine kinase (p = 0.818).ConclusionsDespite inducing significant differences in BF_LH muscle architecture, there were no significant between group differences in sprint performance decrements across two sprint sessions.     

Hip strength in collegiate female athletes with patellofemoral pain

PURPOSE: Decreased hip strength has been theorized to contribute to the development of patellofemoral pain. The purpose of this study was to test for strength differences of six hip muscle groups in collegiate female athletes diagnosed with unilateral patellofemoral pain compared with the unaffected leg and noninjured sport-matched controls. METHODS: At four Division III schools, all collegiate female athletes experiencing unilateral patellofemoral pain were recruited during the 2004-2005 academic school year. The athletes were diagnosed with patellofemoral pain by sports medicine-trained family physicians or orthopedic surgeons. Hip strength of six different muscle groups was tested using a handheld dynamometer. The highest value of two trials was used, and strength values were normalized to body weight. The measurements from the injured leg were compared with the uninvolved leg and also with uninjured control subjects matched for sport. RESULTS: Thirteen athletes were diagnosed with unilateral patellofemoral pain. The injured-side hip abductor (P = 0.003) and external rotator muscle groups (P = 0.049) were significantly weaker than the noninjured sides. There were no significant differences in the other hip muscles tested. In addition, the injured legs were significantly weaker in five of the six hip muscle groups compared with the control group. CONCLUSIONS: The results of this study show that hip abductors and external rotators were significantly weaker between the injured and unaffected legs of the injured athletes. In addition, injured collegiate female athletes exhibited global hip weakness compared with age- and sport-matched asymptomatic controls. Screening for hip muscle weakness and adding strengthening exercises to the affected hip muscles may be important factors in managing female athletes with patellofemoral pain.     

Acute effects of muscle fatigue and recovery on force production and relaxation in endurance, power and strength athletes

Acute effects of fatigue produced by a maintained 60% isometric loading on force production and relaxation characteristics of the leg extensor muscles were studied in male endurance (n = 9), power (n = 6) and strength athletes (n = 9). The initial non-fatigued isometric force-time curves differed considerably (p less than 0.05-0.001) between the groups so that the times of force production were the shortest and correspondingly the maximal rate of force production the greatest in the power athletes but the longest and the smallest in the endurance athletes. The endurance time of 70.7 +/- 32.9 s at the 60% fatiguing loading was in the endurance athletes longer (p less than 0.01) than in the power (30.6 +/- 7.1 s) and strength groups (31.7 +/- 5.5 s). The present fatiguing loading resulted in all athlete groups in significant (p less than 0.05-0.001) worsening in maximal force, in the times of force production and in the maximal rates of force production and relaxation. However, this worsening in the endurance athletes in maximal force (to 92.9 +/- 7.1%) as well as in the maximal rates of force production (to 79.2 +/- 20.8%) and relaxation (to 73.1 +/- 29.2%) were significantly (p less than 0.05-0.01) smaller than the corresponding decreases in the power athletes (to 64.3 +/- 8.0%, 74.8 +/- 7.4% and to 40.9 +/- 12%, respectively) and in the strength athletes (to 65.7 +/- 7.0%, 56.7 +/- 16.0% and to 34.8 +/- 6.7%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Total rupture of pectoralis major muscle in athletes

Total rupture of the pectoralis major muscle is rare. It may follow a severe trauma or strenuous athletic exercise or performance. Five cases of total rupture of the pectoralis major muscle treated in athletes are reported. Two of them had made an extremely exerted effort in weight lifting, one was injured during a parachute landing, one was tackled in an ice hockey match, and one injured his pectoralis major muscle while pushing himself up from a swimming pool. In two cases the diagnosis was made early and in three cases 2-4 months after the injury. All of the patients were male and were treated successfully with surgery. Later they were able to exercise their sports. The weight lifters did not go on with competitive sports.