The effect of dance training on joint mobility,muscle flexibility,speed and agility in young cross-country skiers--a prospective controlled intervention study

We evaluated a short-term (3 months) and a long-term (8 months) effect of dance training on joint mobility and muscle flexibility of the spine, hip and ankle and on speed and agility in young cross-country skiers. Twenty elite cross-country skiers - aged 12-15 years - participated in the study. Five males and five females received dance training (intervention group) and five males and five females did not dance (reference group). Joint mobility and muscle flexibility of the spine, hip and ankle joints were measured using a goniometer, a kyphometer, a measuring tape and a ruler. Two sports-related functional tests - the slalom-test and the hurdle-test - were also performed. These measurements/tests were performed before the start of the dancing period and after 3 and 8 months. The subjects from the intervention group increased their speed with 0.3 s after 3 (P = 0.05) and 8 months (P = 0.02), respectively, when measured with the slalom-test. They also improved their speed and agility according to the hurdle-test after 3 months with 0.8 s (P = 0.000) and 8 months with 0.6 s (P = 0.01). Furthermore, they increased flexion-extension of the thoracic spine with 7.5 degrees after 3 months (P = 0.05) and with 9 degrees degrees after 8 months (P = 0.03) and lateral flexion of the spine with 0.04 m (P = 0.005) and 0.03 m (P = 0.02) after 3 and 8 months, respectively. The reference group was impaired or unchanged in the studied parameters after both 3 and 8 months. We conclude that dance training has a positive effect on speed and agility and on joint mobility and muscle flexibility in flexion-extension and lateral flexion of the spine in young cross-country skiers.     

Self-reported health, physical activity and prevalence of complaints in elite cross-country skiers and matched controls

AIM: The purpose of this study was to compare physical health, physical activity and location for possible symptoms in high school students with cross-country skiers of the same age from ski high schools. Another aim was to study back pain with regards to influence on skiing. METHODS: The subjects studied were: 92% (n=120) of all Swedish cross-country skiers at ski high schools and 68% (n=993) of regular high school students from the North part of Sweden answered a reliable questionnaire (r=1) with regards to health, physical activity and location of possible symptoms/injuries during the last 3 months. Furthermore, the skiers answered questions on possible ski related back pain. RESULTS: All skiers were active also in other sports compared with 26% of the controls and at considerably higher levels of physical effort than the controls; 92% of the skiers and 76% of the controls described themselves as healthy, meaning 'very good' or 'good' (P=0.0001); 55% of the skiers and 64% of the controls reported recent symptoms (P=0.06); 47% of the skiers reported previous or present complaints of back pain, mainly low back pain, which could be relieved by changing body position from a flexed to a more extended one while skiing, and 77% reported their back pain to disappear during rest. CONCLUSIONS: These results show the need for encouraging regular high school students to participate in sport. It also shows the importance of introducing preventative strategies regarding back pain to long-distance cross-country skiers, who are exposed to a prolonged flexed position of their back.     

Radiographic abnormalities in the thoracolumbar spine of young elite skiers

An increased frequency of radiologic abnormalities in the thoracolumbar spine has been reported among young athletes in various sports, but there are no data concerning ski sports. To evaluate the incidence of these abnormalities in young elite skiers, we compared 120 skiers younger than 17 years old (alpine skiers, ski jumpers, and Nordic cross-country skiers) with a random sample of 39 control subjects of the same age who had no history of high-performance sports participation. Standardized anteroposterior and lateral radiographs of the entire lumbar spine, the lower thoracic spine, and the upper part of the sacrum were obtained from each athlete and each control subject. Radiographs were evaluated by two independent observers for the presence and size of anterior and posterior endplate lesions and Schmorl's nodes. The elite alpine skiers and ski jumpers demonstrated a significantly higher rate of anterior endplate lesions than did the control subjects. This finding might be attributable to excessive loading and repetitive trauma of the immature spine under high velocity, especially in the forward bent posture.     

Back injuries and pain in adolescents attending a ski high school

This study compared overuse injuries, small abnormalities, and pain alone in different types of skiing and activity levels. Subjects were 45 ski high school athletes aged 15–19 years. We found the back and knees significantly more prone to activity-related injuries and pain than other body regions. Thirty subjects (67%) had low back pain on the first examination, and 17 had pain caused by overuse of the back. This was more frequent among active, young competitive boys in the cross-country skiing group, with mature height less than 99%, than among noncompetitive boys in the same group or among the alpine skiers. Neck pain was reported only by girls. Eight subjects had low back pain related to small abnormalities. The subjects were given counseling about training and physiotherapy. The 1-year follow-up found a significant reduction in back pain due to overuse injuries (from 17 to 3 subjects) and indistinct neck pain (from 10 to 2) but no reduction in pain in those with small abnormalities in the low back. Low back pain was common in young athletes, particularly in cross-country skiers. Excessively rapid progression of training and faulty technique increased back pain complaints from 36% when entering the school to 67% at the first examination. A proper evaluation and treatment of overuse injuries and accurate counseling of training types, volume, and progression reduced the low back pain problems to 29% of subjects 1 year later in spite of a maintained high activity level. A minimum entrance requirement to conditioning seems mandatory for students attending a ski high school.     

Low back pain in young female gymnasts and the effect of specific segmental muscle control exercises of the lumbar spine: a prospective controlled intervention study

Prospective controlled intervention study. To evaluate a specific segmental muscle training program of the lumbar spine in order to prevent and reduce low back pain in young female teamgym gymnasts. Teamgym is a team sport comprising three events: trampette, tumbling and floor programme. In a recent study, it was found that teamgym gymnasts practice and compete despite suffering from back pain. Specific muscle control exercises of the lumbar spine have shown good results in reducing pain intensity and functional disability levels in patients with low back pain. To our knowledge, this type of training has not been studied in an adolescent athletic population before. Fifty-one gymnasts, with and without LBP, 11–16 years old, from three top-level gymnastics team participated in the study comprising 12 weeks. Every day the gymnasts answered a questionnaire regarding low back pain. After baseline (4 weeks) the intervention group performed a specific segmental muscle training program. Twenty-four gymnasts (47%) reported low back pain during baseline. Nine gymnasts failed to answer the questionnaire every day and the following results are based on 42 gymnasts (intervention group, n = 30, and control group, n = 12). Gymnasts in the intervention group reported significantly less number of days with low back pain at completion compared to baseline (P = 0.02). Gymnasts in the control group showed no difference in terms of days with low back pain or intensity of low back pain between baseline and completion. Eight gymnasts (out of 15) with LBP in the intervention group became pain free. Specific segmental muscle control exercises of the lumbar spine may be of value in preventing and reducing low back pain in young teamgym gymnasts.     

Biological risk indicators for recurrent non-specific low back pain in adolescents

Objectives: A matched case-control study was carried out to evaluate biological risk indicators for recurrent non-specific low back pain in adolescents.

Methods: Adolescents with recurrent non-specific low back pain (symptomatic; n = 28; mean (SD) age 14.9 (0.7) years) and matched controls (asymptomatic; n = 28; age 14.9 (0.7) years) with no history of non-specific low back pain participated. Measures of stature, mass, sitting height, sexual maturity (Tanner self assessment), lateral flexion of the spine, lumbar sagittal plane mobility (modified Schöber), hip range of motion (Leighton flexometer), back and hamstring flexibility (sit and reach), and trunk muscle endurance (number of sit ups) were performed using standardised procedures with established reliability. Backward stepwise logistic regression analysis was performed, with the presence/absence of recurrent low back pain as the dependent variable and the biological measures as the independent variables.

Results: Hip range of motion, trunk muscle endurance, lumbar sagittal plane mobility, and lateral flexion of the spine were identified as significant risk indicators of recurrent low back pain (p<0.05). Follow up analysis indicated that symptomatic subjects had significantly reduced lateral flexion of the spine, lumbar sagittal plane mobility, and trunk muscle endurance (p<0.05).

Conclusions: Hip range of motion, abdominal muscle endurance, lumbar flexibility, and lateral flexion of the spine were risk indicators for recurrent non-specific low back pain in a group of adolescents. These risk indicators identify the potential for exercise as a primary or secondary prevention method.

     

Effects of flexibility training on enhancing spinal mobility in older women.

The purpose of this study was to examine the extent to which spinal flexion and extension, or spinal mobility, could be improved in a population of older adults participating in a 10 week flexibility training program. Twenty female volunteers, mean age 71.8, were randomly assigned to either the experimental group (flexibility training) or the control group (no training). Prior to the initiation of training, all subjects were tested for total spinal mobility, the combined sum of spinal flexion and extension. Subjects in the experimental group were exposed to a series of flexibility exercises, three times per week, for 20-30 minutes in duration, for a total of 10 weeks. The control group participated in an alternative exercise program with the experimental group, including walking, swimming, dance, and other locomotor activities, however, they did not receive the additional flexibility training. At the conclusion of the 10 week period, all subjects were retested for spinal mobility, using back flexion and extension measures. Results indicated a significant improvement in spinal mobility in the experimental group, and virtually no measurable change in the control group. This study suggests that specialized training in back flexibility for older adults is warranted, and that significant gains in spinal mobility can be obtained, regardless of age.     

Risk factors associated with alpine skiing injuries in children. A case-control study.

We investigated the relative contribution of four risk factors to the occurrence of injuries among alpine skiers aged 12 years and younger (3 to 12 years old; mean age, 9.43 years). The risk factors selected were deficient binding adjustment, absence of formal training, low skill level, and use of rented equipment. A group of injured skiers (N = 41) and a control group of uninjured skiers (N = 313) were recruited among young skiers at one major alpine ski center in the Quebec City, Canada, area during the 1995 to 1996 season. No significant group differences were found for mean age or sex distribution. The adjusted odds ratios for injury were 7.54 (95% confidence interval [2.57, 22.15]) for skiers in the low level of skill category relative to highly skilled skiers, 7.14 (2.59, 19.87) for skiers who rented their ski equipment compared with skiers who owned their equipment, and 2.11 (1.02, 4.33) for skiers with ill-adjusted bindings compared with skiers with better-adjusted bindings. Only formal training did not meet the 0.05 significance level for entry into the model; this is probably because of methodologic limitations. Implications of these results for the development of a prevention program aimed at young skiers are discussed.     

Is postural control affected by expertise in alpine skiing?

Objectives: This study examined the postural performance of two groups of male skiers competing at different levels and the consequences on postural control of the suppression of visual afferences by eye closure. Methods: Seven national level (NAT) skiers and 7 regional level (REG) skiers were asked to stand as still as possible on a force platform with eyes opened and closed and while wearing or not wearing their ski boots in a stable posture and in two unstable postures (in the sagittal or frontal plane). Postural performance was assessed with centre of foot pressure measurements. Results: REG and NAT skiers were similarly influenced by the absence of visual information and presented similar postural performance when tests were performed with ski boots. However, without ski boots, REG skiers displayed better postural performance than NAT skiers. Conclusions: The inferior postural performance of NAT skiers without ski boots could be a long term effect of repetitive wearing of ski boots, which impairs postural performance by restricting the range of motion of the ankle-foot complex. Since individuals with decreased postural performance are believed to be more susceptible to ankle injury than those with finer postural control, NAT skiers should benefit from specific training aimed at improving postural ability and preventing ankle injury.     

No difference in prevalence of spine and hip pain in young Elite skiers

Purpose

To investigate the prevalence between back and hip pain in young Elite skiers.

Methods

Sample group (n = 102), consisted of young Elite skiers (n = 75) and age-matched non-athletes (n = 27), all completed a three-part back and hip pain questionnaire, Oswestry Disability Index and EuroQoL to evaluate general health, activity level, back and hip pain prevalence.

Results

No significant differences were shown for lifetime prevalence of back pain in the skiers (50%) compared with controls (44%) (n.s.). Duration of back pain for the skiers showed (30%) > 1 year, whilst (46%) > 5 years. A significant difference was shown with increased Visual Analogue Scale back pain levels for skiers 5.3 (SD 3.1) compared with controls 2.4 (SD 1.9, p = 0.025). No significant differences were shown for lifetime prevalence of hip pain in skiers (21%) compared with controls (8%) (n.s.).

Conclusion

Young Elite skiers are shown not to have increased lifetime prevalence for back and hip pain compared with a non-athletic control group.

Level of evidence

II.

     

Differences in V1 and V2 ski skating techniques described by accelerometers

The aims of the study were to describe the differences between the ski skating techniques V1 and V2 and evaluate reproducibility in complex cyclic hip movements measured by accelerometers. Fourteen elite senior male cross‐country skiers rollerskied twice for 1 min (V1 and V2) at 4° inclination and 3 m/s. Tests were repeated after 20 min and again 4 months later. Five triaxial accelerometers were attached to the subject's hip (os sacrum), poles, and ski boots. Post‐processing included transforming to an approximately global coordinate system, normalization for cycle time, double integration for displacement, and revealing temporal patterns. Different acceleration patterns between techniques and large correlation coefficients (Pearson's r = 0.6–0.9) between repeated trials were seen for most parameters. In V2, the hip was lowered [?10.9 (1.2) cm], whereas in V1, the hip was elevated [4.8 (1.5) cm] during the pole thrust. In conclusion, V2 but not V1 showed similarities to double poling in the way that potential energy is gained between poling strokes and transferred to propulsion during the poling action. Elite skiers reproduce their own individual patterns. One triaxial accelerometer on the lower back can distinguish techniques and might be useful in field research as well as in providing individual feedback on daily technique training.     

Lower extremity and spine characteristics in young dancers with and without patellofemoral pain

Very little is known about patellofemoral pain syndrome (PPFS) among young dancers. Understanding the mechanism of the injury and implementing a preventative programme are important in order to minimize the risk of PFPS. The aim of the current study is to determine the extent to which factors such as lower extremity and back characteristics are common among dancers with PFPS. The study population included 271 dancers with PFPS and 271 non-injured dancers, aged 10–16 years. All dancers were screened for morphometric profile, dance discipline (h/week), anatomical anomalies (present/absent of scoliosis, genu valgus/varum, etc.), and joint range of motion (measured by goniometer at the hip, knee, ankle, foot, and spinal joints). The predicting factors for PFPS among young dancers (10–11 years old) were: hyper hip abduction (OR = 0.906) and lower back and hamstring flexibility (OR = 3.542); for adolescent dancers (12–14 years old): hyper ankle dorsiflexion (OR = 0.888), hind foot-varum (OR = 0.260), and mobility of patella (OR = 2.666); and, for pre-mature dancers (15–16 years old): scoliosis (OR = 5.209), limited ankle plantar-flexion (OR = 1.060), and limited hip internal rotation (OR = 1.063). In conclusion, extrinsic and intrinsic parameters predisposing the dancers to knee injuries should be identified by screening in early stages of dance classes.     

Maximal strength training improves work economy in trained female cross-country skiers.

PURPOSE: The present study examines the hypothesis that maximal strength training improves work economy and anaerobic threshold in trained female cross-country skiers while working on a ski ergometer. METHODS: Fifteen female cross-country skiers (17.9 +/- 0.3 yr, 166.7 +/- 1.3 cm, 60.1 +/- 1.9 kg, and 55.3 +/- 1.3 mL x kg(-1) x min(-1)) participated in the study. Eight skiers made up the high-intensity strength-trained group, and seven served as the control group. Endurance performance was tested on a specially instrumented ski ergometer. Strength training and testing simulated double poling in cross-country skiing. RESULTS: A significant (P < 0.001) improvement in double-poling economy on the ski ergometer was observed among the strength-trained group. Anaerobic threshold did not change during the experimental period for either group. After a 9-wk training period, time to exhaustion increased from 5.2 (+/-0.9) to 12.3 (+/-1.6) min (P < 0.001) and from 4.0 (+/-0.9) to 6.3 (+/-0.9) min (P < 0.01) for the strength and control group, respectively. Time to exhaustion was significantly higher (P < 0.001) for the strength group compared with the control group after training. One repetition maximum increased 14.5% (1.8) (P < 0.001) in the strength group but was unchanged in the control group. Expressed in relation to peak force at one repetition maximum, strength training resulted in a significant reduction in the relative available force employed working on the ski ergometer (P < 0.01). Time to peak force at maximal aerobic velocity on the ski ergometer was significantly reduced in the strength-training group (P < 0.01). CONCLUSIONS: It is concluded that maximal strength training in the upper-body improved the double-poling performance by improved work economy. Work economy was improved by a reduction in relative workload and time to peak force while double poling.     

Technological advances in cross-country ski equipment.

Nordic skiing has a long history dating back to at least 2500 B.C. It is not surprising then that skiing equipment has undergone many changes. Today's skis, poles, and boots use the latest in space-age synthetics including carbon and Kevlar fibers, which has resulted in an unprecedented advance in ski equipment technology, producing ultralight yet strong equipment. These changes have played an important role in bringing about an improvement in racing performance with today's skiers being able to ski a course in half the amount of time that it would have taken just 60 yr ago. Estimates indicate the change in mass of racing equipment accounts for a relatively small amount (12%) of the improvement in race performance with changes in the functional characteristics of equipment, track preparation, and training practices being responsible for the remaining 88%. In addition to improvements in ski equipment, advances are being made in developing laboratory equipment used to assess an athlete's upper body power and endurance capacities. Lab testing with an arm ergometer showed its utility when it exposed a glaring deficiency in upper body power among a group of U.S. developmental skiers. Further improvement in ski equipment and lab testing tools are expected in the future as the worldwide technological revolution continues and Olympic Teams and sports science groups continue to work cooperatively.     

The aging spine in sports

1. Masters athletes may experience low back pain from multiple sources. Masters athletes with discogenic back pain should avoid or modify sports with combined rotational and compressive forces; individuals with facet-mediated pain should avoid or modify sports with excessive extension and rotation. 2. Optimization of flexibility, strength, endurance, and core control is critical. Sports specific training, realistic goal setting, and counseling are of maximal importance. 3. Overall, the health benefits of continued sports and athletic participation outweigh the potential risks of spinal degeneration in middle-aged athletes. There is little correlation between radiographic appearance of the spine and symptoms; therefore, symptoms should serve as the primary guide when determining activity modifications. Overall, masters athletes should be encouraged to remain active and fit to enhance their quality of life and reduce the risk of cardiovascular disease.     

Low back pain in elite cross-country skiers

Low back pain is a common complaint among competitive cross-country skiers. Fifty-three top male and 34 female skiers in the age group 16–25 were interviewed with a questionnaire regarding anthropometric parameters, training variables, back pain and other injuries. The frequency of back pain was 64% in the whole group, men affected slightly more often than women. Back pain was defined as previous or present recurrent skiing correlated backache that more or less affected skiing ability. Diagonal skiing style was the most commonly back pain-inducing style, whereas no skier experienced back pain when "skating" only. The low back was the predominant location of pain. Anthropometric and training variables seemed to be of little value in predicting back pain.     

Ski boot canting adjustments affect kinematic,kinetic, and postural control measures associated with fall and injury risk

ObjectivesThe aim of this study was to investigate if and to what extent small lateral wedges inserted under the ski boot, known as canting, could impact knee kinematics/kinetics, balance, and neuromuscular activity in recreational alpine skiers in the laboratory setting.DesignExperimental, crossover study with repeated-measures analysisMethodsThirty-eight recreational skiers completed a single-leg postural balance test while wearing standardized ski boots in their unmodified state (control), and with medial and lateral canting wedges applied. Kinematics, kinetics, postural control measures, and neuromuscular activity of the lower extremity were assessed using optical motion capture, instrumented force plates, and electromyography.ResultsCanting modifications had significant impact on lower extremity kinematics and kinetics: canting wedges on the medial side of the foot significantly decreased knee valgus moments, hip internal rotation, and hip adduction. Medial canting also improved some postural control measures associated with balance quality, and reduced activation levels of the Vastus Lateralis, Biceps Femoris, and Tibialis Anterior.ConclusionsIn the laboratory setting, canting appears to be an appropriate option for improving balance in alpine skiers. Medial canting can alter skier kinematics and kinetics in ways which are consistent with mechanisms of ACL injury. Canting may also result in reduced neuromuscular effort. These changes in movement have potential to prevent lower limb injuries in alpine skiers. The findings of this study motivate future research to predict individual responses to canting treatment in a study setting more closely resembling the sports environment.     

Spinal sagittal mobility and joint laxity in young ballet dancers

The present study compares spinal configuration, spinal range of motion and joint mobility in first-year students of the Swedish Ballet School and in nondancing students of corresponding age and sex in a state school. The study comprises all the first-year (fourth grade) students (n=23) at the Swedish Ballet School: 11 boys and 12 girls. Their dance practice time was 10 h per week. Thirty-six children in the fourth grade at a state school comprised the control group. None of the controls took ballet classes or participated in organised gymnastics out of school. The neutral spine configuration in standing and the sagittal spine mobility were measured using Debrunner's kyphometer and Myrin's inclinometer. Joint laxity was measured by employing a modified form of the Contompasis method. Compared with the controls, the dancers showed a higher incidence of joint hypermobility, greater mobility of the thoracic spine, a less prominent lordosis of the lumbar spine and a less prominent kyphosis in the thoracic spine in the neutral standing position. The dancers had done little or no ballet training before entering the ballet school at the age of ten. The results agree with those of earlier studies and suggest that increased flexibility is an asset for those being selected as future ballet dancers.This study was orally presented at the First World Congress on Arts and Medicine, New York, February 1992     

Reduction of injuries in downhill skiing by use of an instructional ski-video: a prospective randomised intervention study

Despite various attempts at prevention, injury in downhill skiing continues to be a worrisome recreational problem. The purpose of this study was to test the effect of an instructional ski video on the behaviour and injuries of 763 downhill skiers. They were enrolled in two study groups, based on whether or not an instructional video had been shown in their bus on the way to a skiing resort. The video focussed on information regarding how to get started in downhill skiing and injury prevention. The outcome parameters, behaviour (binding test and adjustment), injury risk, type and consequence, were registered on the return trip 8 days later by a questionnaire. In the intervention group all outcome parameters changed significantly. The binding test was performed by 86% in the intervention group and by only 59% in the control group (P < 0.05). Adjustment of the bindings was done by 22% in the intervention group vs 14% in the control group. Regarding injury risk, 205 injuries were seen in 158 persons (20.7%) which is 26 injured skiers per 1000 skier-days and 33.6 injuries per 1000 skier-days. In the intervention group 16% of all skiers were injured vs 23% in the control group, yielding a reduction in injury risk of 30% (P < 0.05). Injuries caused by falls were seen in 12.6% in the intervention group vs 16.2% in the control group (P < 0.05). Injuries caused by collision were seen in 6% of the intervention group vs 12% in the control group (P < 0.05). The overall mean injury risk was 16 injuries per 1000 falls. Knee injuries made up 32.6% of the total. For inexperienced skiers the knee injury risk was significantly lower if the bindings had been tested (P < 0.05). Therefore, an instructional ski video can change the behaviour of downhill skiers and reduce the injury risk and consequences significantly. Received: 26 March 1997 Accepted: 20 December 1997     

Low-back pain in adolescents is associated with poor hip mobility and high body mass index

The objective of this cross-sectional study was to investigate whether body mass index (BMI) and hip mobility are associated with low-back pain (LBP) in adolescents. The study population included all adolescents in 8th and 9th grades in a rural and in an urban area in Eastern Norway. Eighty-eight adolescents participated (mean age 14.7 years), making the response rate 84%. LBP was assessed by a questionnaire answered in the classrooms as pain/discomfort in the low back during the preceding year. Body height and weight were measured, and BMI was calculated. Hip mobility was measured as active movements by a goniometer. The level of significance was set to P< or =0.05. In bivariate analysis for the whole group, LBP was associated positively with a higher than mean BMI, while LBP among boys was associated with a less than mean hip flexion, internal rotation, and hamstrings flexibility. In multiple regression analyses, adjusting for gender and well-being, LBP was associated with a higher than mean BMI, a less than mean hamstrings flexibility, and a less than mean hip flexion. The results suggest further prospective research to investigate whether poor hip mobility and high BMI may predict juvenile LBP.