An anterior cruciate ligament injury prevention framework: incorporating the recent evidence.

Anterior cruciate ligament (ACL) injury rates have increased by ∼50% over the last 10 years. These figures suggest that ACL focused research has not been effective in reducing injury rates among community level athletes. Training protocols designed to reduce ACL injury rates have been both effective (n = 3) and ineffective (n = 7). Although a rationale for the use of exercise to reduce ACL injuries is established, the mechanisms by which they act are relatively unknown. This article provides an injury prevention framework specific to noncontact ACL injuries and the design of prophylactic training protocols. It is also apparent that feedback within this framework is needed to determine how biomechanically relevant risk factors like peak joint loading and muscular support are influenced following training. It is by identifying these links that more effective ACL injury prevention training programs can be developed, and, in turn, lead to reduced ACL injury rates in the future.

Effects of lupin-enriched foods on body composition and cardiovascular disease risk factors: a 12-month randomized controlled weight loss trial.

BACKGROUND: Regular consumption of diets with increased protein or fibre intakes may benefit body weight and composition and cardiovascular disease risk factors. Lupin flour is a novel food ingredient high in protein and fibre. OBJECTIVE: To investigate the effects of a lupin-enriched diet, during and following energy restriction, on body weight and composition and cardiovascular disease risk factors in overweight individuals. DESIGN: Participants (n = 131) were recruited to a 12-month parallel-design trial. They were randomly assigned to consume lupin-enriched foods or matching high-carbohydrate control foods. All participants underwent 3 months of weight loss, 1 month of weight stabilization and 8 months of weight maintenance. Body weight and composition and cardiovascular disease risk factors were assessed at baseline, 4 and 12 months. RESULTS: Lupin, relative to control, did not significantly influence (mean difference (95% CI)) weight loss at 4 months (0.1 kg (-1.2, 1.4)) and 12 months (-0.6 kg (-2.0, 0.8)), maintenance of weight loss from 4 to 12 months (-0.7 kg (-1.83, 0.48)) or measures of body fat and fat-free mass. Relative to control, 24-h ambulatory systolic (-1.3 mm Hg (-2.4, -0.3), P = 0.016) and diastolic (-1.0 mm Hg (-1.9, -0.2), P = 0.021) blood pressures were lower at 12 months but not at 4 months; fasting insulin concentrations and homeostasis model assessment (HOMA) scores were significantly lower at 4 months (-1.2 mU l(-1) (-1.3, -1.1), P = 0.004 and -0.6 units (-1.0, -0.19), P = 0.004) and 12 months (-1.3 mU l(-1) (-1.4, -1.1), P < 0.001 and -0.7 units (-1.1, -0.24), P = 0.002). CONCLUSIONS: A diet higher in protein and fibre derived from lupin-enriched foods does not enhance weight loss or improve the maintenance of weight loss. However, such a diet may provide cardiovascular health benefits in terms of insulin sensitivity and blood pressure.

Effects of increasing dietary protein and fibre intake with lupin on body weight and composition and blood lipids in overweight men and women.

BACKGROUND: Lupin kernel flour (LKF) is a novel food ingredient that is high in protein and fibre. We have previously shown that partial substitution of refined wheat-derived carbohydrate in bread with protein and fibre from LKF can reduce appetite and energy intake acutely. In addition, several studies have suggested that lupin may reduce cholesterol concentrations and benefit glucose and insulin metabolism. AIM: The aim of this study was to investigate the effects on body weight and composition and blood lipids, glucose and insulin of an ad libitum LKF-enriched diet higher in dietary protein and fibre. SUBJECTS AND METHODS: A total of 88 overweight and obese men and women were recruited for a 16-week parallel-design randomized controlled trial. Participants replaced 15-20% of their usual daily energy intake with white bread (control) or LKF-enriched bread (lupin) in an ad libitum diet. Measurements of body weight and composition, and fasting blood biochemical measurements were performed at baseline and 16 weeks. The primary analysis included 74 participants (37 per group) who completed the intervention. RESULTS: At baseline, mean (+/-s.d.) body mass index and total cholesterol were 30.6+/-3.5 kg m(-2) and 5.37+/-0.94 mmol l(-1), respectively. Estimated (mean between-group difference (95% confidence interval)) protein (13.7 (2.28, 25.0) g per day) and fibre (12.5 (8.79, 16.2) g per day) intakes were higher during the intervention with lupin than with control. For lupin relative to control, the net effects on body weight (-0.4 (-1.3, 0.6) kg), fat mass (-0.5 (-1.1, 0.2) kg) and percentage (-0.5 (-1.1, 0.1)%), plasma leptin (-1.66 (-4.91, 1.59) ng ml(-1)) and adiponectin (0.20 (-0.73, 1.13) mg l(-1), as well as serum total cholesterol (-0.08 (-0.38, 0.22) mmol l(-1)), triglycerides (0.09 (-0.10, 0.21) mmol l(-1)), glucose (0.10 (-0.11, 0.30) mmol l(-1)) and insulin (0.40 (-1.20, 2.00) mU l(-1)) were not significant. CONCLUSIONS: This study does not support the proposal that an ad libitum diet enriched in LKF resulting in moderate changes in both protein and fibre intakes can benefit body weight and composition or fasting blood lipids, glucose and insulin concentrations in overweight men and women with mildly elevated total cholesterol concentrations.

Effects of a 1-year randomized controlled trial of resistance training on lower limb bone and muscle structure and function in older men.

SUMMARY: A 1-year randomized controlled trial of resistance training compared with a control group was undertaken in 143 men aged 55-80 years. Although hip bone mineral density, lean body mass, and function increased in both groups, lean body mass and function but not bone density increased more in the resistance group. INTRODUCTION: Previous studies have demonstrated a positive effect of resistance training on bone mineral density (BMD) in postmenopausal women, but the effect in men is unclear. The aim was to examine the effect of a 1-year resistance training program on bone and lean body mass in 143 men aged 55-80 years, randomized to either resistance training or active control. METHODS: Resistance exercises were selected to provide loading at the hips. Measurements were taken at 0, 6, and 12 months for BMD (whole body, hip, and spine), lean body mass, strength, and functional fitness. RESULTS: The intervention showed a significant increase in total hip BMD for both groups at 12 months (active control, 1,014-1,050 mg/cm(2); resistance, 1,045-1,054 mg/cm(2), p < 0.05) with no increased effect of resistance training compared to active control. However, compared to the active control group, the resistance group increased their lean body mass (active control, 0.1 +/- 2.1%; resistance, 1.5 +/- 2.7%, p < 0.05), fitness (active control, 4.6 +/- 11.1%; resistance, 13.0 +/- 13.4%, p < 0.05), and lower limb muscle strength (active control, 14.3 +/- 16.8%; resistance, 39.4 +/- 30.87%, p < 0.05). CONCLUSIONS: In contrast to previous findings in older women, in older men, a resistance training program does not increase hip bone mass more than walking 30 min three times a week.

MRI and clinical evaluation of collagen-covered autologous chondrocyte implantation (CACI) at two years.

We present our experience with the collagen-covered autologous chondrocyte implantation (CACI) technique. Thirty two implantations were performed in 31 patients. Clinical outcome was measured using the KOOS score and the 6-minute walk test, as well as an MRI scoring protocol (75% of patients had a complete data set for MRI follow-up) to describe the repair tissue generated by CACI. We have also correlated our MRI results with our clinical outcome. To the authors knowledge there are no comparative studies of MRI and clinical outcome following CACI in the current literature. Patients demonstrated an increased walk distance that improved significantly from 3 months to 24 months postoperatively (p<0.05). Analysis of the KOOS results demonstrated a significant (p<0.05) improvement in four of the five subscales from 3 months to 24 months after CACI, with the most substantial gains made in the first 12 months. Patients demonstrated an increased MRI outcome score over time that improved significantly from 3 months to 24 months postoperatively (p<0.05). We observed an 8% incidence of hypertrophic growth following CACI. We report one partial graft failure, defined by clinical, MRI and histological evaluation, at the one year time point. In contrast to the current literature we report no incidence of manipulation under anesthesia (MUA) following CACI. This research demonstrates that autologous chondrocytes implanted under a type I/III collagen patch regenerates a functional infill material, and as a result of this procedure, patients experienced improved knee function and MRI scores. Whilst our results indicated a statistically significant relationship between the MRI and functional outcome following CACI, MRI cannot be used as surrogate measure of functional outcome following CACI, since the degree of association was only low to moderate. That is, functional outcome following CACI cannot be predicted by the morphological MRI assessment of the repair tissue at the post-surgery time points to 24 months.

Equipment set-up among Olympic sprint and slalom kayak paddlers.

The anthropometry and equipment set-up for sprint (31 male; 11 female) and slalom (12 male; 12 female) kayak paddlers who competed at the 2000 Olympic Games in Sydney were measured in the 15 day period before competition. This paper provides normative data for equipment set-up in these sports, as well as information about differences in rigging and paddle dimensions between sprint and slalom kayak paddlers. These differences were consistent for both male and female athletes, with sprint paddlers seated higher and using longer paddles with longer, though narrower, blades (p < 0.0001). Among male sprint paddlers, only minor differences in equipment set-up were found between competitors ranked in the top 10 places compared to the rest of the field. Considering all male paddlers initially, then sprint paddlers alone, significant (p < 0.01) regression equations were developed for the prediction of foot bar distance (r2 = 0.482 and 0.589 respectively) and hand grip distance (r2 = 0.400 and 0.541 respectively). The process of fine tuning equipment set-up often requires hours of practice with subjective feedback from the athlete. The normative data presented in this paper should assist coaches with this process as their athletes evolve toward their individual optimum set-up.

Anticipatory effects on knee joint loading during running and cutting maneuvers.

PURPOSE: To determine how unanticipated performance of cutting maneuvers in sport affects the external loads applied to the knee joint and the potential risk for ligament injury. METHODS: A 50-Hz VICON motion analysis system was used to determine the lower limb kinematics of 11 healthy male subjects during running and cutting tasks performed under preplanned (PP) and unanticipated (UN) conditions. Subjects performed the UN tasks in response to a light stimulus on a target board. A kinematic model was then used in conjunction with force place data to calculate the three-dimensional loads at the knee joint. RESULTS: External flexion/extension moments at the knee joint were similar between PP and UN conditions; however, the varus/valgus and internal/external rotation moments during the UN cutting tasks were up to twice the magnitude of the moments measured during the PP condition. CONCLUSION: Cutting maneuvers performed without adequate planning may increase the risk of noncontact knee ligament injury due to the increased external varus/valgus and internal/external rotation moments applied to the knee. These results are probably due to the small amount of time to make appropriate postural adjustments before performance of the task, such as the position of the foot on the ground relative to the body center of mass. Subsequently, training for the game situation should involve drills that familiarize players with making unanticipated changes of direction. Practice sessions should also incorporate plyometrics and should focus on better interpretation of visual cues to increase the time available to preplan a movement.

External loading of the knee joint during running and cutting maneuvers.

PURPOSE: To investigate the external loads applied to the knee joint during dynamic cutting tasks and assess the potential for ligament loading. METHODS: A 50-Hz VICON motion analysis system was used to determine the lower limb kinematics of 11 healthy male subjects during running, sidestepping, and crossover cut. A kinematic model was used in conjunction with force place data to calculate the three-dimensional loads at the knee joint during stance phase. RESULTS: External flexion/extension loads at the knee joint were similar across tasks; however, the varus/valgus and internal/external rotation moments applied to the knee during sidestepping and crossover cutting were considerably larger than those measured during normal running (P < 0.05). Sidestepping tasks elicited combined loads of flexion, valgus, and internal rotation, whereas crossover cutting tasks elicited combined loads of flexion, varus, and external rotation. CONCLUSION: Compared with running, the potential for increased ligament loading during sidestepping and crossover cutting maneuvers is a result of the large increase in varus/valgus and internal/external rotation moments rather than any change in the external flexion moment. The combined external moments applied to the knee joint during stance phase of the cutting tasks are believed to place the ACL and collateral ligaments at risk of injury, particularly at knee flexion angles between 0 degrees and 40 degrees, if appropriate muscle activation strategies are not used to counter these moments.

Inertial characteristics of adolescent male body segments.

In response to the presently limited information on body segment inertial characteristics of children and adolescents this investigation estimated the mass, centre of mass and principal moments of inertia of adolescent male body segments. Significant prediction equations based on anthropometric measurements were then sought. Thirteen subjects were measured at 6-monthly intervals for 2.5 yr to provide inertial characteristics for the leg, thigh, lower trunk and upper trunk segments. These characteristics were derived using an elliptical zone modelling technique. Following a correlation analysis, significant prediction equations of segment inertial parameters were derived from five, or fewer, anthropometric measurements. For all cases, more than 84% of the variance in the dependent variable was accounted for with a maximum R2 value of 94% being recorded for the prediction of thigh segment mass. The use of these prediction equations offered accurate and convenient estimates of body segment inertial characteristics within the limitations applicable to all modelling approaches. In contrast to recent studies, these equations accommodated the current morphological status of the subject.

Radiographic study of skin displacement errors in the foot and ankle during standing.

The accuracy of skin markers for the prediction of skeletal locations in the foot and ankle was assessed using radiographs. The relationship between skin and skeletal markers was examined for three weight-bearing positions of the right lower limb: a 10° calcaneal inversion position, a neutral alignment, and a 5° calcaneal eversion position. Significant discrepanices in the respective locations of skin and skeletal markers were observed; however, it was not possible from the results of this study to recommend the use of particular landmarks in preference to the other locations employed.

Morphological characteristics of Olympic sprint canoe and kayak paddlers.

Canoe and kayak paddlers (n = 50 M & 20 F) who competed in the sprint events at the 2000 Olympic Games in Sydney were measured on a battery of 38 anthropometry dimensions prior to competition. The ensuing analysis aimed to identify common physical characteristics that provide these elite paddlers with a competitive advantage. This study demonstrated that participants in Olympic sprint paddling events can be considered homogeneous in shape and physical size; male and female paddlers have SAMs of 1.1 and 1.0 respectively. Compared to other athlete groups, the variance in stature and body mass of paddlers is generally low. Whilst sprint paddlers are not athletes with extreme proportionality profiles, they do possess unique characteristics not commonly observed in the general population. These include a lean body composition (Phantom z-scores for skinfolds range from -1.5 to -2.5 for most sites) with proportionally large upper body girths (z-scores > +1.0 for arm and chest girths), and narrow hips (for males). The morphology of elite paddlers appears to have altered during the past 25 years toward a more compact, robust physique. This trend is especially noticeable for the female competitors.

The effect of a Galeazzi fracture on the strength of pronation and supination two years after surgical treatment.

The aim of this study was to determine the effect of a Galeazzi fracture on the strength of pronation and supination at a mean of two years after surgical treatment. The strength of pronation and supination was measured in varying rotational positions of the forearm of ten male patients (mean age 38.9 years (21 to 64)) who had undergone plate fixation for a Galeazzi fracture. The stability of the distal radioulnar joint was assessed, and a clinical assessment using the quick-Disabilities of the Arm Shoulder and Hand (quickDASH) questionnaire and patient-related wrist examination (PRWE) scores was undertaken. In addition, the strength of pronation and supination was measured in a male control group of 42 healthy volunteers (mean age 21.8 years (18 to 37)). The mean absolute loss of strength of supination in the injured compared with the non-injured arm throughout all ranges of forearm rotation was 16.1 kg (sem 5.3), corresponding to a relative loss of 12.5% (95% confidence interval (CI) 3.6 to 21.4). For the strength of pronation, the mean loss was 19.1 kg (sem 4.5), corresponding to a relative loss of 27.2% (95% CI 14.2 to 40.1). Loss of strength of supination following a Galeazzi fracture correlated with poor quickDASH (p = 0.03) and PRWE scores (p < 0.01). Loss of strength of pronation (27.2%), and of supination (12.5%) in particular, after a Galeazzi fracture is associated with worse clinical scores, highlighting the importance of supination of the forearm in function of the upper limb.

Knee joint preservation with combined neutralising high tibial osteotomy (HTO) and Matrix-induced Autologous Chondrocyte Implantation (MACI) in younger patients with medial knee osteoarthritis: a case series with prospective clinical and MRI follow-up over 5 years.

PURPOSE: There is no ideal treatment for younger patients with medial knee osteoarthritis (OA) and varus malalignment. We have investigated the first case series of combined neutralising high tibial osteotomy (HTO) and Matrix-induced Autologous Chondrocyte Implantation (MACI) with MRI. Treatment goals were clinical improvement and delay of arthroplasty. METHODS: Between 2002 and 2005 18 patients (Mean age 47 years) underwent surgery. Exclusion criteria were lateral compartment and advanced patellofemoral OA. The Knee Injury and Osteoarthritis Outcome Score (KOOS), six minute walk test (6MWT) and a validated MRI score were outcome measures. RESULTS: There were significant improvements (p<0.05) in all five KOOS domains. Four were significantly maintained to 5 years. The domain "symptoms" and results in the 6MWT dropped off at 5 years. MRI results were first significantly improved (24/12) but declined at 60 months. Good quality infill was found in 33% patients at the study endpoint (n=5/15). Histological investigation of one knee demonstrated full-thickness hyaline-like cartilage (20/12). After 2 early failures and one graft detachment graft fixation was changed (Smart nails instead of sutures in 14 cases). Graft hypertrophy requiring a chondroplasty occurred once. There were no other major complications. Specific minor complications included patellar tendinitis (n=8). CONCLUSIONS: This combined procedure provides a safe treatment option for younger patients with medial knee OA and varus alignment with significant clinical improvement at 5 years. However, overall graft survival and cartilage infill were poor. Larger studies are needed to statistically verify predictors for longer term cartilage repair in these patients.

Olympic lightweight and open-class rowers possess distinctive physical and proportionality characteristics.

Rowers competing at the 2000 Olympic Games were measured for 38 anthropometric dimensions. The aim was to identify common physical characteristics that could provide a competitive advantage. The participants included 140 male open-class rowers, 69 female open-class rowers, 50 male lightweight rowers, and 14 female lightweight rowers. Body mass, stature, and sitting height were different (P < 0.01) between the open-class and lightweight rowers, as well as a comparison group of healthy young adults ("non-rowers", 42 males, 71 females), for both sexes. After scaling for stature, the open-class rowers remained proportionally heavier than the non-rowers, with greater proportional chest, waist, and thigh dimensions (P < 0.01). Rowers across all categories possessed a proportionally smaller hip girth than the non-rowers (P < 0.01), which suggested the equipment places some constraints on this dimension. Top-ranked male open-class rowers were significantly taller and heavier and had a greater sitting height (P < 0.01) than their lower-ranked counterparts. They were also more muscular in the upper body, as indicated by a larger relaxed arm girth and forearm girth (P < 0.01). For the male lightweight rowers, only proportional thigh length was greater in the best competitors (P < 0.01). In the female open-class rowers, skinfold thicknesses were lower in the more highly placed competitors (P < 0.01). In conclusion, the rowers in this sample demonstrated distinctive physical characteristics that distinguish them from non-rowers and other sports performers.

Somatotype and size of elite female basketball players.

The aim of this study was to compare the somatotype and size of elite female basketball players in terms of playing position and team performance. Anthropometry and somatotype data were collected on 168 players from 14 countries before the Women's World Basketball Championship, Australia, 1994. There were 64 guards (mean +/- s: age 25.4 +/- 3.3 years, height 1.72 +/- 0.06 m, mass 66.1 +/- 6.2 kg, somatotype = 2.9-3.9-2.6), 57 forwards (age 25.2 +/- 3.8 years, height 1.81 +/- 0.06 m, mass 73.3 +/- 5.9 kg, somatotype = 2.8-3.5-3.2) and 47 centres (age 24.1 +/- 3.1 years, height 1.90 +/- 0.06 m, mass 82.6 +/- 8.2 kg, somatotype = 3.2-3.1-3.4). Mean somatotypes by position were significantly different (F = 7.73, P < 0.01). Guards had greater mesomorphy than centres and less ectomorphy than forwards and centres. When discriminant function analysis was applied to endomorphy, mesomorphy, ectomorphy, age, height and mass, only height, mass and ectomorphy entered (Wilks' lambda = 0.351, F = 31.40, P < 0.000), 70% of the variance was accounted for, and 72% of players were correctly classified. In the four top versus four bottom teams, guards were taller and more ectomorphic, forwards were taller, with lower mesomorphy and higher ectomorphy, and centres did not differ. Thus there are some differences in somatotypes by position and team placing, but the combination of height, mass and ectomorphy provide the best differentiation by position.

Stability of human proportions through adolescent growth.

Male and female subjects (n = 125) were measured on a battery of anthropometric tests every six months for a period of five years. Using maturity status as the temporal component (pubescent assessment stages one through five), proportionality characteristics of subjects were monitored as they matured toward the adult form. Subjects were assigned to one of the Hi, Mid and Lo sub-groups based on their score at PA stage one for each of 15 proportionality characteristics. Subsequently, those in the Mid group were removed from the analysis, while male and female subjects were pooled for the final ANOVA model. The results showed that a number of variables remained stable from PA stages one through five. That is, differences between the Hi and Lo groups were maintained throughout maturation. Predominantly, these included the proportional body segment breadth measures. Proportionality characteristics of the upper limbs appeared to stabilise from mid-adolescence. However, those related to the lower limb were not stable. In other words, a significant difference for the lower limb variables at PA stage one was not maintained through stages four and five. The results raised some doubts as to the suitability of using lower limb proportions as selection criteria in talent identification programs.

Sexual dimorphism in the physiques of World Championship divers.

The aim of this study was to evaluate sexual dimorphism in male (n = 43) and female (n = 39) springboard and platform divers at the 1991 World Diving Championships in Perth, Western Australia. In addition to recording the age, height and body mass of each diver, measurements were taken of 8 skinfolds, 13 girths, 8 breadths and depths, and 11 lengths. The derived variables were somatotype, sum of 6 skinfolds (SUM6) and height-adjusted proportional z-scores. The mean (+/- s) values for the males were: age, 22.2 +/- 4.6 years; height, 171 +/- 9 cm; body mass, 66.7 +/- 10.2 kg; somatotype, 2.0-5.3-2.4 +/- 0.5-1.0-0.8; SUM6, 45.9 +/- 11.4 mm. For the females, these values were: age, 20.9 +/- 3.8 years; height, 161 +/- 6 cm; body mass, 53.7 +/- 5.5 kg; somatotype, 2.8-3.8-2.8 +/- 0.7-1.0-0.9; SUM6, 65.6 +/- 17.0 mm. The males were taller, heavier, more mesomorphic, less endomorphic and had a smaller SUM6 than the females (P < 0.01). A series of discriminant function analyses were applied to groups of variables. Wilks' lambda and the overall F-ratio were highly significant (P < 0.001), with correct classification of sex reaching 84-99%. The best combinations of variables were as follows: (1) absolute size, 3 girths + SUM6, or body mass + SUM6 + height (Wilks' lambda = 0.17-0.35); (2) relative size, 2 girths + SUM6 + body mass. Combinations of breadths and lengths, skinfolds, or somatotype components, were less successful, with 84-87% classified correctly (Wilks' lambda = 0.40-0.48). We conclude that, in addition to the expected absolute size differences, sexual dimorphism between male and female divers can be explained by differences in relative size, skinfolds and somatotype, and that these differences may have implications for coaching and selection in diving.

The elite athlete - assessing body shape, size, proportion and composition.

In the quest to optimize performance of the elite athlete the sport scientist has sought to determine the ideal physique for a given sport or event. For some sports, specific structural characteristics offer definite performance advantages; for example in rowing, in addition to height, a large arm span has been identified as important. In other sports. such as long distance running, low levels of adiposity or 'fatness' appear to be linked with faster running times. There are four areas where appraisal of the athlete's physique can provide useful information: (1) identification of talented athletes; (2) to assess and monitor the growing athlete; (3) to monitor training and performance; and (4) to determine 'race weight' in weight-category sports. As a research tool a particular method must be reliable and valid. Other considerations include how expensive the method is, if it is suitable for a field situation and if large amounts of data on a number of subjects can be collected quickly. The method should be safe for both the athlete and the tester and provide useful feedback for the athlete or coach. Anthropometry, with training is able to fulfil most of these criteria and is the most widely used method of physique assessment in sports science. Large anthropometric data bases have been collected on elite athletes at Olympic games and world championships according to a standard protocol. Kinanthropometry, which has developed from anthropometry, is concerned with measurement and evaluation of different aspects of human movement and individual variation in body shape, size, proportion and composition. For the assessment of adiposity a sum of skinfolds, usually over six sites, is most commonly used rather than percentage body fat formulae. Muscle mass can be assessed indirectly through girth and corrected girth measurements. Limb lengths and breadths are used to assess skeletal structure and proportional differences in limb size. The anthropometric methods most commonly used to describe the physique of the athlete, which appraise shape, size, proportion and composition, will be discussed.

Stability and change in children's skill.

This paper explores age-related performance variability, both within trials and between sessions, in repetitive hopping. The mean, the standard deviation (SD), and the coefficient of variation (CV) of several timing and ground-reaction-force variables of hopping were analysed by repeated-measures ANOVA for age-related effects across test sessions and foot used. Forty-five subjects in five age groups (3-4 years, 4-5 years, 6-7 years, 8-9 years, or Adult) performed self-paced, one-footed hopping on three occasions within one week. As was expected, the results showed main effects for Age in all force and time variables, with the exception of CV of medio-lateral force. No significant main effects for Feet were revealed. However, significant Feet x Session interactions were found in flight-time measures, with higher flight-time SD and lower CV for the non-preferred foot in Session 1, a reversal in Session 2, and a negligible difference in Session 3. Across sessions, decreased SD and CV for both vertical and medio-lateral force and shorter flight time indicated more efficient hopping. Overall, it was concluded that SD and CV measures were more sensitive measures of children's performance across repeated sessions than were mean scores and that the order of testing the limbs is an important consideration in experimental protocols when lateralized tasks are measured.