The effect of leg preference on postural stability in healthy athletes.

In research regarding postural stability, leg preference is often tested and controlled for. However, leg preference may vary between tasks. As athletes are a group of interest for postural stability testing, we evaluated the effect of five leg preference tasks categorization (step up, hop, ball kick, balance, pick up) on single-leg postural stability of 16 field hockey athletes. The 'center of pressure speed' was calculated as the primary outcome variable of single-leg postural stability. Secondary variables were 'mean length of the GRF vector in the horizontal plane', 'mean length of the ankle angular velocity vector', and 'mean length of the hip angular velocity vector', as well as the separate outcomes per degree of freedom. Results showed that leg preference was inconsistent between leg preference tasks. Moreover, the primary and secondary variables yielded no significant difference between the preferred and non-preferred legs, regardless of the applied leg preference task categorization (p>0.05). The present findings do not support the usability of leg preference tasks in controlling for bias of postural stability. In conclusion, none of the applied leg preference tasks revealed a significant effect on postural stability in healthy field hockey athletes.

The impact of adherence on sports injury prevention effect estimates in randomised controlled trials: looking beyond the CONSORT statement.

OBJECTIVE: To investigate estimated outcome effects of a sports injury prevention intervention when analysed by means of a per protocol (PP) analysis approach. DESIGN: Randomised controlled trial (RCT) involving 522 athletes who sustained a lateral ankle sprain allocated to either an intervention (received a preventive programme in addition to usual care) or control group who were followed prospectively for one year. METHODS: Secondary analysis of data relating to registered ankle sprain recurrences, exposure and adherence to the allocated intervention using a PP analysis approach. RESULTS: Twenty-three percent of the RCT intervention group indicated to have fully adhered with the neuromuscular training programme. A per protocol analysis only considering fully adherent athletes and control athletes, showed a Hazard Ratio of 0.18 (95% CI: 0.07-0.43). Significantly fewer recurrent ankle sprains were found in the fully adherent group compared to the group that was not adherent (relative risk = 0.63; 95% CI: 0.43-0.99). CONCLUSIONS: A PP analysis on fully adherent athletes versus control group athletes showed that the established intervention effect was over threefold higher compared to an earlier intention-to-treat based analysis approach. This shows that outcomes of intervention studies are heavily biased by adherence to the allocated intervention.

Potential savings of a program to prevent ankle sprain recurrence: economic evaluation of a randomized controlled trial.

BACKGROUND: The most common ankle injury is the lateral ankle sprain. Dutch annual sports-related ankle sprain costs can roughly be estimated at €187,200,000. Research has shown that proprioceptive training accounts for an approximated overall 50% reduction in ankle sprain recurrence rate. HYPOTHESIS: An unsupervised proprioceptive training program to reduce the recurrence of lateral ankle sprains will reduce overall health care costs. DESIGN: Cohort study (economic analysis); Level of evidence, 2. METHODS: The study included 522 male and female athletes: 256 athletes (120 female and 136 male) in the intervention group, and 266 athletes (128 female and 138 male) in the control group. Both groups received treatment according to usual care. Athletes allocated to the intervention group received an 8-week proprioceptive training program in addition to usual care. Costs per athlete and costs per injured athlete were calculated. Costs related to ankle sprain recurrences were measured from a societal perspective using cost diaries. Bootstrapping was used to analyze the cost-effectiveness data. Follow-up was 1 year. RESULTS: Mean total costs in the intervention group were €81 (standard deviation, €134) per athlete and €114 (€325) per injured athlete. Mean overall costs in the control group were €149 (€836) per athlete and €447 (€1403) per injured athlete. Statistically significant differences in total costs were found per athlete (mean difference, -€69; 95% confidence interval, -€200 to -€2) and per injured athlete (-€332; -€741 to -€62) in favor of the intervention group. A cost-effectiveness plane showed the effect of the intervention was larger and the costs were lower in the intervention group than the control group. CONCLUSION: The use of a proprioceptive training program after usual care of an ankle sprain is cost-effective for the prevention of ankle sprain recurrences in comparison with usual care alone. In the Netherlands, an estimated annual €35.9 million in medical and lost productivity costs can be saved solely by advocating a proprioceptive training program as in the present study.

Effect of unsupervised home based proprioceptive training on recurrences of ankle sprain: randomised controlled trial.

OBJECTIVE: To evaluate the effectiveness of an unsupervised proprioceptive training programme on recurrences of ankle sprain after usual care in athletes who had sustained an acute sports related injury to the lateral ankle ligament. DESIGN: Randomised controlled trial, with one year follow-up. SETTING: Primary care. PARTICIPANTS: 522 athletes, aged 12-70, who had sustained a lateral ankle sprain up to two months before inclusion; 256 (120 female and 136 male) in the intervention group; 266 (128 female and 138 male) in the control group. INTERVENTION: Both groups received treatment according to usual care. Athletes allocated to the intervention group additionally received an eight week home based proprioceptive training programme. MAIN OUTCOME MEASURE: Self reported recurrence of ankle sprain. RESULTS: During the one year follow-up, 145 athletes reported a recurrent ankle sprain: 56 (22%) in the intervention group and 89 (33%) in the control group. Nine athletes needed to be treated to prevent one recurrence (number needed to treat). The intervention programme was associated with a 35% reduction in risk of recurrence. Cox regression analysis showed significantly fewer recurrent ankle sprains in the intervention than in the control group. This effect was found for self reported recurrent ankle sprains (relative risk 0.63, 95% confidence interval 0.45 to 0.88), recurrent ankle sprains leading to loss of sports time (0.53, 0.32 to 0.88), and recurrent ankle sprains resulting in healthcare costs or lost productivity costs (0.25, 0.12 to 0.50). No significant differences were found between medically treated athletes in the intervention group and medically treated controls. Athletes in the intervention group who were not medically treated had a significantly lower risk of recurrence than controls who were not medically treated. CONCLUSIONS: The use of a proprioceptive training programme after usual care of an ankle sprain is effective for the prevention of self reported recurrences. This proprioceptive training was specifically beneficial in athletes whose original sprain was not medically treated. TRIAL REGISTRATION: ISTRCN34177180.

Effect of sensorimotor training on morphological, neurophysiological and functional characteristics of the ankle: a critical review.

Sensorimotor training is effective in preventing ankle sprain recurrences, but the pathway through which this effect occurs is unknown. Biomechanical and neurophysiological analyses of sensorimotor training leading to functional changes of the ankle are needed to establish this pathway. This article reviews the effect of sensorimotor training on morphological, neurophysiological and functional characteristics of the ankle. A MEDLINE and CINAHL computerized literature search was conducted to search for relevant articles. A study was included if (i) the study contained research questions regarding the effect of sensorimotor training on mechanical, neurophysiological, and/or functional ankle functioning; (ii) the study dealt with subjects with a history of ankle sprain; (iii) the study contained a control group; (iv) the results contained measures of mechanical, neurophysiological or functional insufficiencies as study outcome; and (v) the study met a predefined cut-off score set for methodological quality. Results on joint position sense and muscle reaction times showed a learning effect of repeated measures and not a training effect. Decrements of postural sway after sensorimotor training were mainly attributable to a learning effect as well. Effects on muscle strength were not found. Evidence for an effect of sensorimotor training on neurophysiological, morphological and functional characteristics is limited, if present at all. Thus, the pathway of sensorimotor training remains unclear. Future studies need to focus on (i) differentiating between morphological, physiological and functional changes; (ii) larger sample sizes with a priori sample size calculations; (iii) correspondence between training and test method; (iv) using measures other than postural sway more closely linked to functional stability; and (v) using a longer follow-up period than 6 weeks.

The 2BFit study: is an unsupervised proprioceptive balance board training programme, given in addition to usual care, effective in preventing ankle sprain recurrences? Design of a randomized controlled trial.

BACKGROUND: There is strong evidence that athletes have a twofold risk for re-injury after a previous ankle sprain, especially during the first year post-injury. These ankle sprain recurrences could result in disability and lead to chronic pain or instability in 20 to 50% of these cases. When looking at the high rate of ankle sprain recurrences and the associated chronic results, ankle sprain recurrence prevention is important. OBJECTIVE: To evaluate the effect of a proprioceptive balance board training programme on ankle sprain recurrences, that was applied to individual athletes after rehabilitation and treatment by usual care. METHODS/DESIGN: This study was designed as a randomized controlled trial with a follow-up of one year. Healthy individuals between 12 and 70 years of age, who were actively participating in sports and who had sustained a lateral ankle sprain up to two months prior to inclusion, were eligible for inclusion in the study. The intervention programme was compared to usual care. The intervention programme consisted of an eight-week proprioceptive training, which started after finishing usual care and from the moment that sports participation was again possible. Outcomes were assessed at baseline and every month for 12 months. The primary outcome of this study was the incidence of recurrent ankle injuries in both groups within one year after the initial sprain. Secondary outcomes were severity and etiology of re-injury and medical care. Cost-effectiveness was evaluated from a societal perspective. A process evaluation was conducted for the intervention programme. DISCUSSION: The 2BFit trial is the first randomized controlled trial to study the effect of a non-supervised home-based proprioceptive balance board training programme in addition to usual care, on the recurrence of ankle sprains in sports. Results of this study could possibly lead to changes in practical guidelines on the treatment of ankle sprains. Results will become available in 2009. TRIAL REGISTRATION: ISTRCN34177180.

Increased hypoxic ventilatory response during 8 weeks at 3800 m altitude.

Acclimatization to chronic hypoxia (CH) increases ventilation (V(I)) and the isocapnic hypoxic ventilatory response (HVR) over 2-14 days but hypoxic desensitization blunts the HVR after years of CH. We tested for hypoxic desensitization during the first 2 months of CH by studying five normal subjects at sea level (SL) and for 8 weeks at 3800 m (CH, PI(O(2)) approximately 90 Torr). We measured the isocapnic HVR (Delta V(I)/Delta Sa(O(2)) and tested for hypoxic ventilatory decline (HVD) by stepping Sa(O(2)) to 80% after 14 min at 90%. The HVR increased significantly after 2 days and remained significantly elevated for 8 weeks of CH. HVD was similar at SL and during 8 weeks of CH. Hence, hypoxic desensitization of the HVR does not occur after only 8 weeks of hypoxia and the increased HVR during this time does not involve changes in HVD.

Persistence of the lactate paradox over 8 weeks at 3,800 m.

The arterial blood lactate [La] response to exercise increases in acute hypoxia, but returns to near the normoxic (sea level, SL) response after 2 to 5 weeks of altitude acclimatization. Recently, it has been suggested that this gradual return to the SL response in [La], known as the lactate paradox (LP), unexpectedly disappears after 8 to 9 weeks at altitude. We tested this idea by recording the [La] response to exercise every 2 weeks over 8 weeks at altitude. Five normal, fit SL-residents were studied at SL and 3,800 m (Pbar = 485 torr) in both normoxia (PIO2 = 150 torr) and hypoxia (PIO2 = 91 torr approximately air at 3,800 m). Arterial [La] and blood gas values were determined at rest and during cycle exercise at the same absolute workloads (0, 25, 50, 75, 90, and 100% of initial SL-VO2Max) and exercise duration (4, 4, 4, 2, 1.5, and 0.75 min, respectively) at each time point. [La] curves were elevated in acute hypoxia at SL (p < 0.01) and at 3,800 m fell progressively toward the SL-normoxic curve (p < 0.01). On the same days, [La] responses in acute normoxia showed essentially no changes over time and were similar to initial SL normoxic responses. We also measured arterial catecholamine levels at each load and found a close relationship to [La] over time, supporting a role for adrenergic influence on [La]. In summary, extending the time at this altitude to 8 weeks produced no evidence for reversal of the LP, consistent with prior data obtained over shorter periods of altitude residence.