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Biomedical subjects

W van Mechelen

Publications and source records attributed to W van Mechelen.

At least 19 recordsLinked to original sources
PubMed2006

Should office workers spend fewer hours at their computer? A systematic review of the literature.

Worldwide, millions of office workers use a computer. Reports of adverse health effects due to computer use have received considerable media attention. This systematic review summarises the evidence for a relationship between the duration of work time spent using the computer and the incidence of hand-arm and neck-shoulder symptoms and disorders. Several databases were systematically searched up to 6 November 2005. Two reviewers independently selected articles that presented a risk estimate for the duration of computer use, included an outcome measure related to hand-arm or neck-shoulder symptoms or disorders, and had a longitudinal study design. The strength of the evidence was based on methodological quality and consistency of the results. Nine relevant articles were identified, of which six were rated as high quality. Moderate evidence was concluded for a positive association between the duration of mouse use and hand-arm symptoms. For this association, indications for a dose-response relationship were found. Risk estimates were in general stronger for the hand-arm region than for the neck-shoulder region, and stronger for mouse use than for total computer use and keyboard use. A pathophysiological model focusing on the overuse of muscles during computer use supports these differences. Future studies are needed to improve our understanding of safe levels of computer use by measuring the duration of computer use in a more objective way, differentiating between total computer use, mouse use and keyboard use, attaining sufficient exposure contrast, and collecting data on disability caused by symptoms.

Arm↗
PubMed2006

The effectiveness of graded activity for low back pain in occupational healthcare.

BACKGROUND: Low back pain is a common medical and social problem associated with disability and absence from work. Knowledge on effective return to work (RTW) interventions is scarce. OBJECTIVE: To determine the effectiveness of graded activity as part of a multistage RTW programme. DESIGN: Randomised controlled trial. SETTING: Occupational healthcare. SUBJECTS: 112 workers absent from work for more than eight weeks due to low back pain were randomised to either graded activity (n = 55) or usual care (n = 57). INTERVENTION: Graded activity, a physical exercise programme aimed at RTW based on operant-conditioning behavioural principles. MAIN OUTCOME MEASURES: The number of days off work until first RTW for more then 28 days, total number of days on sick leave during follow up, functional status, and severity of pain. Follow up was 26 weeks. RESULTS: Graded activity prolonged RTW. Median time until RTW was equal to the total number of days on sick leave and was 139 (IQR = 69) days in the graded activity group and 111 (IQR = 76) days in the usual care group (hazard ratio = 0.52, 95% CI 0.32 to 0.86). An interaction between a prior workplace intervention and graded activity, together with a delay in the start of the graded activity intervention, explained most of the delay in RTW (hazard ratio = 0.86, 95% CI 0.40 to 1.84 without prior intervention and 0.39, 95% CI 0.19 to 0.81 with prior intervention). Graded activity did not improve pain or functional status clinically significantly. CONCLUSIONS: Graded activity was not effective for any of the outcome measures. Different interventions combined can lead to a delay in RTW. Delay in referral to graded activity delays RTW. In implementing graded activity special attention should be paid to the structure and process of care.

Adolescent↗
PubMed2006

Long term health complaints following the Amsterdam Air Disaster in police officers and fire-fighters.

BACKGROUND: On 4 October 1992, a cargo aircraft crashed into apartment buildings in Amsterdam, the Netherlands. Fire-fighters and police officers assisted with the rescue work. OBJECTIVES: To examine the long term health complaints in rescue workers exposed to a disaster. METHODS: A historical cohort study was performed among police officers (n = 834) and fire-fighters (n = 334) who performed at least one disaster related task and reference groups of their non-exposed colleagues (n = 634 and n = 194, respectively). The main outcome measures included digestive, cardiovascular, musculoskeletal, nervous system, airway, skin, post-traumatic stress, fatigue, and general mental health complaints; haematological and biochemical laboratory values; and urinalysis outcomes. RESULTS: Police officers and fire-fighters who were professionally exposed to a disaster reported more physical and mental health complaints, compared to the reference groups. No clinically relevant statistically significant differences in laboratory outcomes were found. CONCLUSIONS: This study is the first to examine long term health complaints in a large sample of rescue workers exposed to a disaster in comparison to reference groups of non-exposed colleagues. Findings show that even in the long term, and in the absence of laboratory abnormalities, rescue workers report more health complaints.

Accidents, Aviation↗
PubMed2006

Counselling increases physical activity behaviour nine weeks after rehabilitation.

BACKGROUND: For people with disabilities, a physically active lifestyle can reduce the risk of secondary health problems and improve overall functioning. OBJECTIVES: To determine the effects of the sport stimulation programme "rehabilitation and sports" (R&S) and R&S combined with the daily physical activity promotion programme "active after rehabilitation" (AaR) on sport participation and daily physical activity behaviour nine weeks after inpatient or outpatient rehabilitation. METHODS: Subjects in four intervention rehabilitation centres were randomised to a group receiving R&S only (n = 315) or a group receiving R&S and AaR (n = 284). Subjects in six control rehabilitation centres (n = 603) received the usual care. Most common diagnoses were stroke, neurological disorders, and back disorders. Two sport and two daily physical activity outcomes were assessed with questionnaires seven weeks before and nine weeks after the end of rehabilitation. Data were analysed by intention to treat and on treatment multilevel analyses, comparing both intervention groups with the control group. RESULTS: The R&S group showed no significant change. Intention to treat analyses of the R&S+AaR group showed significant improvements in one sport (p = 0.02) and one physical activity outcome (p = 0.03). On treatment analyses in the R&S+AaR group showed significant improvements in both sport outcomes (p<0.01 and p = 0.02) and one physical activity outcome (p<0.01). CONCLUSIONS: Only the combination of R&S and AaR had increased sports participation and daily physical activity behaviour nine weeks after the end of inpatient or outpatient rehabilitation.

Activities of Daily Living↗
PubMed2006

Physical capacity in relation to low back, neck, or shoulder pain in a working population.

AIMS: To investigate the longitudinal relation between physical capacity (isokinetic lifting strength, static endurance of the back, neck, and shoulder muscles, and mobility of the spine) and low back, neck, and shoulder pain. METHODS: In this prospective cohort study, 1789 Dutch workers participated. At baseline, isokinetic lifting strength, static endurance of the back, neck, and shoulder muscles, and mobility of the spine were measured in the pain free workers, as well as potential confounders, including physical workload. Low back, neck, and shoulder pain were self-reported annually at baseline and three times during follow up. RESULTS: After adjustment for confounders, Poisson generalised estimation equations showed an increased risk of low back pain among workers in the lowest sex specific tertile of performance in the static back endurance tests compared to workers in the reference category (RR = 1.42; 95% CI 1.19 to 1.71), but this was not found for isokinetic trunk lifting strength or mobility of the spine. An increased risk of neck pain was shown for workers with low performance in tests of isokinetic neck/shoulder lifting strength (RR = 1.31; 95% CI 1.03 to 1.67) and static neck endurance (RR = 1.22; 95% CI 1.00 to 1.49). Among workers in the lowest tertiles of isokinetic neck/shoulder lifting strength or endurance of the shoulder muscles, no increased risk of shoulder pain was found. CONCLUSIONS: The findings of this study suggest that low back or neck endurance were independent predictors of low back or neck pain, respectively, and that low lifting neck/shoulder strength was an independent predictor of neck pain. No association was found between lifting trunk strength, or mobility of the spine and the risk of low back pain, nor between lifting neck/shoulder strength or endurance of the shoulder muscles and the risk of shoulder pain.

Adult↗
PubMed2005

A birth-weight questionnaire indicated that life style modifies the birth weight and metabolic syndrome relationship at age 36.

OBJECTIVE: Investigating the relationship between birth weight and the metabolic syndrome and the modifying effects of lifestyle in adults (36.5 years). STUDY DESIGN AND SETTING: 273 subjects completed a birth-weight questionnaire; waist circumference, HDL and triglyceride concentrations, blood pressure and HbA1c, physical activity and fitness, smoking status and dietary intake were measured. Risks for the metabolic syndrome and for having at least two of the components of the metabolic syndrome were calculated and the modifying effect of lifestyle factors was assessed by comparing four groups based on birth weight and a lifestyle factor. RESULTS: Birth weight was not associated with the metabolic syndrome (odds ratio OR = 0.67, 95% confidence interval CI = 0.25-1.79). Birth weight lower than the median increased the risk for having at least two components (OR = 2.28, 95% CI = 1.15-4.50). Subjects who smoked and had a birth weight lower than the median had a 6.9 times increased risk. Modification by lifestyle measured at age 36 was not observed, although effect modification using lifestyle data from 32 years was found. CONCLUSIONS: Lower birth weight increased the risk for having at least two components of the metabolic syndrome. Smoking, being less physical active or fit, have an unfavorable diet at age 32 adds to this risk.

Adult↗
PubMed2005

Changes in force, surface and motor unit EMG during post-exercise development of low frequency fatigue in vastus lateralis muscle.

We investigated the effects of low frequency fatigue (LFF) on post-exercise changes in rectified surface EMG (rsEMG) and single motor unit EMG (smuEMG) in vastus lateralis muscle (n = 9). On two experimental days the knee extensors were fatigued with a 60-s-isometric contraction (exercise) at 50% maximal force capacity (MFC). On the first day post-exercise (15 s, 3, 9, 15, 21 and 27 min) rsEMG and electrically-induced (surface stimulation) forces were investigated. SmuEMG was obtained on day two. During short ramp and hold (5 s) contractions at 50% MFC, motor unit discharges of the same units were followed over time. Post-exercise MFC and tetanic force (100 Hz stimulation) recovered to about 90% of the pre-exercise values, but recovery with 20 Hz stimulation was less complete: the 20-100 Hz force ratio (mean +/- SD) decreased from 0.65+/-0.06 (pre-exercise) to 0.56+/-0.04 at 27 min post-exercise (P<0.05), indicative of LFF. At 50% MFC, pre-exercise rsEMG (% pre-exercise maximum) and motor unit discharge rate were 51.1 +/- 12.7% and 14.1 +/- 3.7 (pulses per second; pps) respectively, 15 s post-exercise the respective values were 61.4 +/- 15.4% (P<0.05) and 13.2 +/- 5.6 pps (P>0.05). Thereafter, rsEMG (at 50% MFC) remained stable but motor unit discharge rate significantly increased to 17.7 +/- 3.9 pps 27 min post-exercise. The recruitment threshold decreased (P<0.05) from 27.7 +/- 6.6% MFC before exercise to 25.2 +/- 6.7% 27 min post-exercise. The increase in discharge rate was significantly greater than could be expected from the decrease in recruitment threshold. Thus, post-exercise LFF was compensated by increased motor unit discharge rates which could only partly be accounted for by the small decrease in motor unit recruitment threshold.

Adaptation, Physiological↗
PubMed2005

An economic evaluation of a proprioceptive balance board training programme for the prevention of ankle sprains in volleyball.

OBJECTIVES: To evaluate the cost effectiveness of a proprioceptive balance board training programme for the prevention of ankle sprains in volleyball. METHODS: A total of 116 volleyball teams participated in this study which was carried out during the 2001-2002 volleyball season. Teams were randomly allotted to an intervention group (66 teams, 628 players) or a control group (52 teams, 494 players). Intervention teams followed a prescribed balance board training programme as part of their warm up. Control teams followed their normal training routine. An ankle sprain was recorded if it occurred as a result of volleyball and caused the subject to stop volleyball activity. The injured player completed a cost diary for the duration of the ankle sprain. Analyses were performed according to the intention to treat principle. Mean direct, indirect, and total costs were calculated and were compared between the two groups. RESULTS: The total costs per player (including the intervention material) were significantly higher in the intervention group (36.99 (93.87)) than in the control group (18.94 (147.09)). The cost of preventing one ankle sprain was approximately 444.03. Sensitivity analysis showed that a proprioceptive balance board training programme aimed only at players with previous ankle sprains could be cost effective over a longer period of time. CONCLUSIONS: Positive effects of the balance board programme could only be achieved at certain costs. However, if broadly implemented, costs associated with the balance board programme would probably be lower.

Adult↗
PubMed2004

[Overweight and obesity in children and adolescents and preventative measures].

The prevalence of overweight and obesity in children is increasing rapidly. This is alarming because obesity is associated with severe chronic diseases, such as type 2 diabetes mellitus. Obesity at young age is related to obesity at adult age. Consequently, the prevention of overweight from childhood onwards is an important issue. Apart from diabetes mellitus type 2 there is an increased risk of orthopaedic complications, respiratory problems, fertility problems, cardiovascular diseases and psychosocial consequences in the form of a negative self-image, emotional and behavioural problems and depression. Environmental and behavioural factors are regarded as the most important causes of the rapid increase in the prevalence of overweight and as the most important starting points for prevention. Most prevention programmes are still in the initial stages. Prevention programmes aimed at stimulating breast feeding and daily physical activity (playing outside) and the restriction of sweetened drinks and watching TV are very promising. With such preventive measures the involvement of both the school and the parents is important.

Adolescent↗
PubMed2004

Metabolically assessed muscle fibre recruitment in brief isometric contractions at different intensities.

This study investigated the recruitment of type I, IIA and IIAX fibres after seven isometric contractions at 40, 70 and 100% maximal voluntary knee extension torque (MVC, 1 s on/1 s off). Biopsies of the vastus lateralis muscle were collected from seven subjects at rest and immediately post-exercise. Fibre fragments were dissected from the freeze-dried samples and characterized as type I, IIA and IIAX using mATPase staining. Phosphocreatine (PCr) and creatine (Cr) content were measured in the remaining part of characterized fibres. A decline in the ratio of PCr to Cr (PCr/Cr) was used as an indication of activation. The mean peak torques were, respectively, 39 (2), 72 (2) and 87 (6)% MVC. Cumulative distributions of type I and IIA fibres were significantly shifted to lower PCr/Cr ratios at all intensities (Kolmogorov-Smirnov test, P<0.05). The cumulative distribution of type IIAX fibres showed a significant leftward shift only at 87% MVC ( P<0.05). A hierarchical order of fibre activation with increasing intensity of exercise was found, with some indication of rate coding for type I and IIA fibres. Evidence for activation of type IIAX fibres was only found at 87% MVC.

Adenosine Triphosphatases↗
PubMed2004

Voluntary activation level and muscle fiber recruitment of human quadriceps during lengthening contractions.

Voluntary activation levels during lengthening, isometric, and shortening contractions (angular velocity 60 degrees/s) were investigated by using electrical stimulation of the femoral nerve (triplet, 300 Hz) superimposed on maximal efforts. Recruitment of fiber populations was investigated by using the phosphocreatine-to-creatine ratio (PCr/Cr) of single characterized muscle fibers obtained from needle biopsies at rest and immediately after a series of 10 lengthening, isometric, and shortening contractions (1 s on/1 s off). Maximal voluntary torque was significantly higher during lengthening (270 +/- 55 N.m) compared with shortening contractions (199 +/- 47 N.m, P < 0.05) but was not different from isometric contractions (252 +/- 47 N.m). Isometric torque was higher than torque during shortening (P < 0.05). Voluntary activation level during maximal attempted lengthening contractions (79 +/- 8%) was significantly lower compared with isometric (93 +/- 5%) and shortening contractions (92 +/- 3%, P < 0.05). Mean PCr/Cr values of all fibers from all subjects at rest were 2.5 +/- 0.6, 2.0 +/- 0.7, and 2.0 +/- 0.7, respectively, for type I, IIa, and IIax fibers. After 10 contractions, the mean PCr/Cr values for grouped fiber populations (regardless of fiber type) were all significantly different from rest (1.3 +/- 0.2, 0.7 +/- 0.3, and 0.8 +/- 0.6 for lengthening, isometric, and shortening contractions, respectively; P < 0.05). The cumulative distributions of individual fiber populations after either contraction mode were significantly different from rest (P < 0.05). Curves after lengthening contractions were less shifted compared with curves from isometric and shortening contractions (P < 0.05), with a smaller shift for the type IIax compared with type I fibers in the lengthening contractions. The results indicate a reduced voluntary drive during lengthening contractions. PCr/Cr values of single fibers indicated a hierarchical order of recruitment of all fiber populations during maximal attempted lengthening contractions.

Adult↗
PubMed2004

Changes in PCr/Cr ratio in single characterized muscle fibre fragments after only a few maximal voluntary contractions in humans.

AIM: This methodological study investigated the number of brief maximal voluntary isometric contractions (MVC) needed to show evidence of fibre activation, as indicated by changes in the phosphocreatine to creatine (PCr/Cr) ratio. METHODS: Subjects performed series of four, seven and/or 10 MVC (1 s on, 1 s off) of the m. quadriceps (60 degrees -flexion angle). Biopsy samples of the m. vastus lateralis were taken at rest and immediately post-exercise. Single muscle fibres were dissected from the freeze-dried samples and classified as types I, IIA or IIAX, using mATPase stainings. Fragments of characterized fibres were analysed for PCr and Cr content. Analyses of variance were performed to investigate changes in PCr/Cr per fibre group over time, followed by Bonferroni post-hoc test (P < 0.01). The fifth percentile of resting values of each fibre group was determined. RESULTS: Mean PCr/Cr ratio after four, seven and 10 MVCs were significantly lower for all fibre groups (P < 0.01). The mean decreases were 44, 64 and 76%, respectively. However, only after seven and 10 contractions PCr/Cr ratios of all, but three type I and two type IIAX fibres, individual fibres were below the fifth percentile. CONCLUSION: In very short duration exercise, involving seven brief maximal voluntary contractions, changes in the PCr/Cr ratio indicated activation of different characterized muscle fibre fragments. The results suggest that this approach may be useful for investigating the pattern of fibre type activation in exercise of very short duration.

Adult↗
PubMed2004

Once a week is not enough: effects of a widely implemented group based exercise programme for older adults; a randomised controlled trial.

OBJECTIVES: To determine the effects of gymnastics on the health related quality of life (HRQoL) and functional status of independently living people, aged 65 to 80 years. Gymnastics formed part of the More Exercise for Seniors (MBvO in Dutch) programme, a group based exercise programme for older adults in the Netherlands. It has been widely implemented since 1980. DESIGN: Randomised controlled trial with pretest and post-test measurements. INTERVENTION: The exercise programme given by experienced instructors lasted 10 weeks and was given weekly (MBvO1; n = 125, six groups) or twice weekly (MBvO2; n = 68, six groups). The control group (n = 193) was offered a health education programme. SETTING: Community dwelling of older people, with a comparatively low level of fitness as assessed with the Groningen Fitness test for the Elderly. RESULTS: No significant effects were found on the HRQoL (Vitality Plus Scale, TAAQoL, and RAND-36) and the functional status (Physical Performance Test and the Groningen Activity Restriction Scale). The MBvO2 group, with a low level of physical activity at baseline, showed the only improvement found on the Vitality Plus Scale (F = 4.53; p = 0.01). CONCLUSIONS: MBvO gymnastics once a week did not provide benefits in HRQoL and functional status after 10 weeks. However, participants with a low level of physical activity may benefit from MBvO gymnastics if they participate twice a week. To improve the health of the general public, sedentary older adults should be recruited and encouraged to combine MBvO with the health enhancing physical activity guidelines.

Activities of Daily Living↗
PubMed2004

Worksite health promotion using individual counselling and the effectiveness on sick leave; results of a randomised controlled trial.

AIMS: To investigate the effectiveness of a worksite health promotion programme by individual counselling on sick leave. METHODS: Three municipal services of Enschede, the Netherlands, participated in this trial. A total of 299 civil servants were measured at baseline and were randomised by cluster into the intervention (n = 131) or the control group (n = 168). During nine months, subjects in the intervention group received a total of seven consultations, particularly aimed at increasing their physical activity level and improving their dietary habits. Both the intervention and the control subjects received written information as to several lifestyle factors. Sick leave data regarding the nine month intervention period (from May until January) were collected from each municipal service's personnel department. In addition, sick leave data concerning the nine month period pre- and post-intervention were collected. Sick leave data were analysed using multilevel analysis. RESULTS: For both groups, the mean sick leave rate during the intervention increased compared to before the intervention. After the intervention period, the control group increased even more (from 22.9 to 27.6 days), whereas the intervention group slightly decreased (from 21.5 to 20.5 days). Median values of sick leave rate decreased for both groups. No statistically significant intervention effect was found. In both groups, the mean sick leave frequency slightly decreased over time (intervention effects were not significant). CONCLUSIONS: Results showed no significant effect of individual counselling on sick leave. Continued research investigating the effectiveness of this individual counselling programme on several health related outcomes is useful to clarify the trend observed in sick leave.

Adult↗
PubMed2004

The effectiveness of ergonomic interventions on return-to-work after low back pain; a prospective two year cohort study in six countries on low back pain patients sicklisted for 3-4 months.

AIMS: To study occurrence and effectiveness of ergonomic interventions on return-to-work applied for workers with low back pain (LBP). METHODS: A multinational cohort of 1631 workers fully sicklisted 3-4 months due to LBP (ICD-9 codes 721, 722, 724) was recruited from sickness benefit claimants databases in Denmark, Germany, Israel, Sweden, the Netherlands, and the United States. Medical, ergonomic, and other interventions, working status, and return-to-work were measured using questionnaires and interviews at three months, one and two years after the start of sickleave. Main outcome measure was time to return-to-work. Cox's proportional hazards model was used to calculate hazard ratios regarding the time to return-to-work, adjusted for prognostic factors. RESULTS: Ergonomic interventions varied considerably in occurrence between the national cohorts: 23.4% (mean) of the participants reported adaptation of the workplace, ranging from 15.0% to 30.5%. Adaptation of job tasks and adaptation of working hours was applied for 44.8% (range 41.0-59.2%) and 46.0% (range 19.9-62.9%) of the participants, respectively. Adaptation of the workplace was effective on return-to-work rate with an adjusted hazard ratio (HR) of 1.47 (95% CI 1.25 to 1.72; p < 0.0001). Adaptation of job tasks and adaptation of working hours were effective on return-to-work after a period of more than 200 days of sickleave with an adjusted HR of 1.78 (95% CI 1.42 to 2.23; p < 0.0001) and 1.41 (95% CI 1.13 to 1.76; p = 0.002), respectively. CONCLUSIONS: Results suggest that ergonomic interventions are effective on return-to-work of workers long term sicklisted due to LBP.

Absenteeism↗
PubMed2003

Voluntary drive-dependent changes in vastus lateralis motor unit firing rates during a sustained isometric contraction at 50% of maximum knee extension force.

The purpose of the present study was to relate the expected inter-subject variability in voluntary drive of the knee extensor muscles during a sustained isometric contraction to the changes in firing rates of single motor units. Voluntary activation, as established with superimposed electrical stimulation was high (range: 91-99%, n=8) during a short maximal contraction, but was lower (range: 69-100%) in most subjects at the point of force failure during a sustained (49.1+/-10.1 s) fatiguing contraction at 50% of maximum force. On a different experimental day the firing behaviour of 27 single motor units was recorded with wire electrodes in the vastus lateralis muscle, 24 of which could be monitored from the time of recruitment to the point of force failure (53.6+/-9.8 s). Motor unit firing behaviour differed considerably among subjects. During the second half of the sustained, fatiguing contraction the changes in firing rate firing rate variability of early recruited units ranged from -10% to +100% and from -50% to +160% respectively among subjects. There were significant positive linear relations between voluntary activation, on the one hand, and rectified surface electromyogram (rsEMG, r=0.82), the changes in motor unit firing rate ( r=0.49) and firing rate variability ( r=0.50) towards the point of force failure on the other. The present data suggest that differences in voluntary drive that appear among subjects during fatigue may be an important determinant of motor unit firing behaviour.

Action Potentials↗
PubMed2003

Participatory ergonomics as a return-to-work intervention: a future challenge?

BACKGROUND: Participatory ergonomics (PE) are often applied for prevention of low back pain (LBP). In this pilot-study, a PE-program is applied to the disability management of workers sick listed due to LBP. METHODS: The process, implementation, satisfaction, and barriers for implementation concerning the PE-program were analyzed quantitatively and qualitatively for 35 workers sick listed 2-6 weeks due to LBP and their ergonomists. RESULTS: Two-hundred-and-seventy ergonomic solutions were proposed to the employer. They were targeted more at work design and organization of work (58.9%) than at workplace and equipment design (38.9%). They were planned mostly on a short-term basis (74.8%). Almost half (48.9%) of the solutions for work adjustment were completely or partially implemented within 3 months after the first day of absenteeism. Most workers were satisfied about the PE-program (median score 7.8 on a 10-point scale) and reported a stimulating effect on return-to-work (66.7%). Main obstacles to implementation were technical or organizational difficulties (50.0%) and physical disabilities of the worker (44.8%). CONCLUSIONS: This study suggests that compliance, acceptance, and satisfaction related to the PE-program were good for all participants. Almost half of the proposed solutions were implemented.

Adult↗