Luc Janssens

Freezing in Parkinson's disease: a spatiotemporal motor disorder beyond gait.

Freezing of gait (FOG) is an incapacitating problem in Parkinsons disease that is difficult to manage therapeutically. We tested the hypothesis that impaired rhythm and amplitude control is a common mechanism of freezing which is also present during other rhythmic tasks. Therefore, we compared the occurrence and spatiotemporal profiles of freezing episodes during upper limb motion, lower limb motion, and FOG. Eleven freezers, 12 non‐freezers, and 11 controls performed a rhythmic bilateral finger movement task. The triggering effect of movement speed, amplitude, and coordination pattern was evaluated. Regression slopes and spectral analysis addressed the spatial and temporal kinematic changes inherent to freezing episodes. The FOG Questionnaire score significantly predicted severity of upper limb freezing, present in 9 freezers, and of foot freezing, present in 8 freezers. Similar to gait, small‐amplitude movements tended to trigger upper limb freezing, which was preceded by hastened movement and a strong amplitude breakdown. Upper limb freezing power spectra were broadband, including increased energy in the “freeze band” (3–8 Hz). Contrary to FOG, unilateral upper limb freezing was common and occurred mainly on the disease‐dominant side. The findings emphasize that a core motor problem underlies freezing which can affect various movement effectors. This deficit may originate on the disease‐dominant body side and interfere with amplitude and timing regulation during repetitive limb movements. These results may shift current thinking on the origins of freezing as being not exclusively a gait failure.

Peak and submaximal steady-state metabolic and cardiorespiratory responses during arm-powered and arm-trunk-powered handbike ergometry in able-bodied participants

The purpose of this study was to compare the peak and submaximal metabolic and cardiorespiratory responses during steady-state arm-powered (AP) and arm-trunk-powered (ATP) handbike ergometry. Twelve male able-bodied participants with no prior experience in handcycling completed a maximal progressive incremental test and a series of 6-minute submaximal tests at 130 W with various cadences in a custom-designed handbike ergometer that allowed a realistic simulation of AP and ATP handcycling. Peak power output, peak oxygen uptake, and peak ventilation were significantly lower, whereas peak blood lactate concentration was significantly higher during AP handcycling. Mean gross mechanical efficiency was significantly higher during AP handcycling (range 16.7 to 20.5%) compared with ATP handcycling (range 15.8 to 17.6%). These results suggest that AP handcycling is advantageous during submaximal steady-state handcycling, whereas ATP handcycling allows for a higher peak power output generation. However, it remains unclear which handbike configuration would be favorable during competition.

Prospective control abilities during visuo-manual tracking in children with 22q11.2 Deletion syndrome compared to age- and IQ-matched controls.

To examine whether children with a 22q11.2 Deletion syndrome (22q11.2DS) are able to use prospective control, 21 children with 22q11.2DS (mean age=9.6+/-1.9; mean FSIQ=73.05+/-10.2) and 21 control children (mean age=9.6+/-1.9; mean FSIQ=73.38+/-12.0) were asked to perform a visuo-manual tracking task in which they had to track a cursor rhythmically between 2 target zones. Children with 22q11.2DS performed worse than the age- and IQ-matched controls (higher absolute time and distance errors) suggesting that the 22q11.2DS group experiences an additional (syndrome specific) processing deficit that cannot be attributed to their lower intellectual abilities. The 22q11.2DS group neither the control group improved their tracking performance throughout five identical full feedback conditions of the tracking task possibly due to a slow visuo-motor adaptation process, a short span of attention and cognitive flexibility impairments. The results showed that both the 22q11.2DS group and the controls had difficulties anticipating the movement of the target (prospective control) and thus are assumed to rely more on feedback instead of on an internal representation of the movement.

Stability of Measurement Outcomes for Voluntary Task Performance in Participants With Chronic Ankle Instability and Healthy Participants

CONTEXT Acceptable measurement stability during data collection is critically important to research. To interpret differences in measurement outcomes among participants or changes within participants after an intervention program, we need to know whether the measurement is stable and consistent. OBJECTIVE To determine the within-session stability of muscle activation patterns for a voluntary postural-control task in a group of noninjured participants and a group of participants with chronic ankle instability (CAI). DESIGN Descriptive laboratory study. SETTING Musculoskeletal laboratory. PATIENTS OR OTHER PARTICIPANTS Twenty control participants (8 men, 12 women; age = 21.8 ± 2.4 years, height = 164.3 ± 13.4 cm, mass = 68.4 ± 17.9 kg) and 20 participants with CAI (12 men, 8 women; age = 21.2 ± 2.1 years, height = 176 ± 10.2 cm, mass = 71.7 ± 11.3 kg). INTERVENTION(S) Participants performed 4 barefoot standing trials, each of which included a 30-second double-legged stance followed by a 30-second single-legged stance in 3 conditions: with vision, without vision, and with vision on a balance pad. MAIN OUTCOME MEASURE(S) The activity of 7 muscles of the lower limb was measured for the stance task in the 3 different conditions for each trial. The onset of muscle activity and muscle recruitment order were determined and compared between the first and the fourth trials for both groups and for each condition. RESULTS We found no differences in the onset of muscle activity among trials for both groups or for each condition. The measurement error was 0.9 seconds at maximum for the control group and 0.12 seconds for the CAI group. In the control group, 70% to 80% of the participants used the same muscle recruitment order in both trials. In the CAI group, 75% to 90% used the same recruitment order. CONCLUSIONS Within 1 session, measurement stability for this task was acceptable for use in further research. Furthermore, no differences were found in measurement stability across conditions in the control or CAI groups.

Muscle-Activation Onset Times With Shoes and Foot Orthoses in Participants With Chronic Ankle Instability.

CONTEXT Participants with chronic ankle instability (CAI) use an altered neuromuscular strategy to shift weight from double-legged to single-legged stance. Shoes and foot orthoses may influence these muscle-activation patterns. OBJECTIVE To evaluate the influence of shoes and foot orthoses on onset times of lower extremity muscle activity in participants with CAI during the transition from double-legged to single-legged stance. DESIGN Cross-sectional study. SETTING Musculoskeletal laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 15 people (9 men, 6 women; age = 21.8 ± 3.0 years, height = 177.7 ± 9.6 cm, mass = 72.0 ± 14.6 kg) who had CAI and wore foot orthoses were recruited. INTERVENTION(S) A transition task from double-legged to single-legged stance was performed with eyes open and with eyes closed. Both limbs were tested in 4 experimental conditions: (1) barefoot (BF), (2) shoes only, (3) shoes with standard foot orthoses, and (4) shoes with custom foot orthoses (SCFO). MAIN OUTCOME MEASURE(S) The onset of activity of 9 lower extremity muscles was recorded using surface electromyography and a single force plate. RESULTS Based on a full-factorial (condition, region, limb, vision) linear model for repeated measures, we found a condition effect (F(3,91.8) = 9.39, P < .001). Differences among experimental conditions did not depend on limb or vision condition. Based on a 2-way (condition, muscle) linear model within each region (ankle, knee, hip), earlier muscle-activation onset times were observed in the SCFO than in the BF condition for the peroneus longus (P < .001), tibialis anterior (P = .003), vastus medialis obliquus (P = .04), and vastus lateralis (P = .005). Furthermore, the peroneus longus was activated earlier in the shoes-only (P = .02) and shoes-with-standard-foot-orthoses (P = .03) conditions than in the BF condition. No differences were observed for the hip muscles. CONCLUSIONS Earlier onset of muscle activity was most apparent in the SCFO condition for ankle and knee muscles but not for hip muscles during the transition from double-legged to single-legged stance. These findings might help clinicians understand how shoes and foot orthoses can influence neuromuscular control in participants with CAI.

POSTURAL STABILITY DURING THE TRANSITION FROM DOUBLE-LEG STANCE TO SINGLE-LEG STANCE IN ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTED SUBJECTS

Background Despite recent advances in rehabilitation and secondary prevention strategies after anterior cruciate ligament reconstruction (ACLR), re-injury rates remain high and long-term outcomes are often disappointing. Deficits in postural stability are shown to be important. Objective To evaluate postural stability during the transition from double-leg stance to single-leg stance in ACLR and non-injured control subjects. Design Cross-sectional (retrospective). Setting Controlled laboratory study. Participants 20 ACLR subjects (15 females, 5 males), 23.1±13.9 months after ACLR and fully returned to their pre-injury sport, and 20 non-injured control subjects (15 females, 5 males) participated in the study. Both groups were matched for age, gender, weight, height and activity level. All ACL injuries were caused by a non-contact injury mechanism. Risk factor assessment A transition task from double-leg stance to single-leg stance with eyes closed was performed while standing on a single force plate. Movement speed was standardized. Both legs of each subject were tested. Main outcome measurements Spatiotemporal center of pressure outcomes were compared between groups and between legs within the same group. Significance was set at P<.05. Results The ACLR group showed a significant increased postural sway after the new stability point during single-leg stance (P=.005). No significant different postural stability outcomes were found between legs in both groups (P>.05). Conclusions Despite the full return to sport, ACLR subjects showed a decreased ability to overcome the postural perturbation created by the transitional movement. These postural stability deficits may leave the lower extremity more vulnerable to ACL re-injury and/or other long-term problems after ACLR. Whether these deficits are a result or a pre-existing risk factor of the initial ACL injury remains unclear. The lack of bilateral differences in the ACLR group may imply that secondary prevention strategies should not only focus on the ACLR leg, but also on the non-ACLR leg.

Postural Stability During Single-Leg Stance: A Preliminary Evaluation of Noncontact Lower Extremity Injury Risk

Study Design Controlled laboratory study with a prospective cohort design. Background Postural stability deficits during single-leg stance have been reported in persons with anterior cruciate ligament (ACL) injury, ACL reconstruction, and chronic ankle instability. It remains unclear whether impaired postural stability is a consequence or cause of these injuries. Objectives To prospectively investigate whether postural stability deficits during single-leg stance predict noncontact lower extremity injuries. Methods Fifty injury-free female athletes performed a transition task from double-leg stance to single-leg stance with eyes closed. Center-of-pressure displacement, the main outcome variable, was measured during the first 3 seconds after the time to a new stability point was reached during single-leg stance. Noncontact lower extremity injuries were recorded at a 1-year follow-up. Results Six participants sustained a noncontact ACL injury or ankle sprain. Center-of-pressure displacement during the first 3 seconds after the time to a new stability point was significantly increased in the injured (P = .030) and noninjured legs (P = .009) of the injured group compared to the respective matched legs of the noninjured group. The area under the receiver operating characteristic curve (AUC) analysis revealed significant discriminative accuracy between groups for the center-of-pressure displacement during the first 3 seconds after the time to a new stability point of the injured (AUC = 0.814, P = .015) and noninjured legs (AUC = 0.897, P = .004) of the injured group compared to the matched legs of the noninjured group. Conclusion This preliminary study suggests that postural stability measurements during the single-leg stance phase of the double- to single-leg stance transition task may be a useful predictor of increased risk of noncontact lower extremity injury. Further research is indicated. Level of Evidence Prognosis, level 4. J Orthop Sports PhysTher 2016;46(8):650-657. Epub 3 Jul 2016. doi:10.2519/jospt.2016.6278.

Spectrum analysis of wireless electromyography in water and on dry land: a single case example

Recent developments in wireless capture of muscle activity signals have improved the freedom of motion and the ease of use. Nevertheless, no study has examined the quality of wireless electromyographic technology during water activities. In this study the performance of a surface electromyography (SEMG) wireless system on dry land and in water was compared. Tibialis anterior muscle activity of 1 subject while contracting against a resistance of 84 Newton (N) was measured in 2 conditions: using a wireless (KINE) system with waterproof taping on the pool deck and submerged. Analysis of the raw signal showed acceptable ratios of 37 to 44 decibel (dB) between rest activity and the force activity at 84 N in both conditions. The total spectrum analysis and short term frequency analysis showed that no filtering occurred in either of the two conditions as frequencies were picked up in the entire spectrum. Spectrum analysis of rest activity or of the force buildup showed no spikes indicating any pickup of noise. The wireless system produced clean results and submersion and as a consequence recollection from the memory of the unit did not cause additional noise. Furthermore, the wireless system provided a satisfactory signal-to-rest activity ratio of approximately 40 dB and a range of 4 millivolts (mV). The KINE EMG units provided a valid means to analyze muscle activity during swimming while permitting unrestricted movement and ease of use.

Kinematic movement strategies in primary school children with 22q11.2 Deletion Syndrome compared to age- and IQ-matched controls during visuo-manual tracking

The present study focused on the mechanism subserving the production of kinematic patterns in 21 children with 22q11.2DS (mean age=9.6+/-1.9; mean FSIQ=73.05+/-10.2) and 21 age- and IQ-matched control children (mean age=9.6+/-1.9; mean FSIQ=73.38+/-12.0) when performing a visuo-manual tracking task in which they had to track a cursor rhythmically between 2 target zones. Children with 22q11.2DS moved faster (overall) and reached their maximum velocity sooner when compared to controls. However, the number of corrective submovements to attain the target did not differ. Children with 22q11.2DS seem to adopt a young ballistic movement strategy, with a fast ballistic first movement phase, followed by a second movement phase with very little online corrections to attain the target. Children with 22q11.2DS are not able to process the incoming feedback during the second movement phase to maximize the accuracy of the ongoing movement and use this phase to prepare the following. The fact that the parietal cortex and cerebellum are involved in action prediction and internal representation and are implicated in children with 22q11.2DS provides a possible neurological basis for their problems with prospective control and tracking behavior.

LOWER EXTREMITY MUSCLE ONSET TIMES DURING THE TRANSITION FROM DOUBLE-LEG STANCE TO SINGLE-LEG STANCE IN ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTED SUBJECTS

Background Deficits in neuromuscular control are believed to increase re-injury risk after anterior cruciate ligament reconstruction (ACLR). Previous studies mainly focused on muscles at the operated knee, less on muscles around other joints of the operated and non-operated leg. Objective To evaluate lower extremity muscle onset times during the transition from double-leg stance to single-leg stance in ACLR and non-injured control subjects. Design Cross-sectional (retrospective). Setting Controlled laboratory study. Participants 20 ACLR subjects (15 females, 5 males), 23.1±13.9 months after ACLR and fully returned to their pre-injury sport, and 20 non-injured control subjects (15 females, 5 males) participated in the study. Both groups were matched for age, gender, weight, height and activity level. All ACL injuries were caused by a non-contact injury mechanism. Risk factor assessment A transition task from double-leg stance to single-leg stance with eyes closed was performed, using a single force plate and surface electromyography. Movement speed was standardized. Both legs of each subject were tested. Main outcome measurements Onset times of 10 lower extremity muscles were compared between groups and between legs within the same group. Significance was set at P<.05. Results The ACLR group showed significant delayed muscle onset times for gastrocnemius (P=0.40), peroneus longus (P=.022), vastus medialis (P=.007), gluteus medius (P=.035) and gluteus maximus (P=.001). No significant different muscle onset times were found between legs in the ACLR group (P>.05). Conclusions Despite the full return to sport, ACLR subjects showed delayed muscle onset times during the transitional movement, not only around the knee, but also around the hip and ankle of both legs. Whether these deficits are a result or a pre-existing risk factor of the initial ACL injury remains unclear. Secondary prevention strategies should focus on the whole lower kinetic chain of both legs to improve neuromuscular control after ACLR.