The study design is a 2-arm randomized controlled trial with 6-month intervention period and follow-up at 6, 12 and 24 months among blue-color workers of Nokia City with reduced work ability and high number of musculoskeletal problems. The participants (n=190) will be randomly assigned to intervention-arm providing face-to-face Personalized Exercise Counseling combined with interactive accelerometer (PEC-arm) or a non-intervention Control-arm. The study aims at improving workability (main outcome) and reducing musculoskeletal pain by counseling and motivating the workers to increase physical activity and exercise according to self-selected modes. Exercise instructors of Nokia City are responsible for providing the face-to-face part of PEC. The Urho Kaleva Kekkonen (UKK) Institute is responsible for providing online feedback of the data collected by the interactive ExSed® accelerometer, stored and analyzed in the Cloud, from where the participants in the PEC-arm receive daily feedback thru a smart phone application. Cost-effectiveness of the PEC-intervention compared to the Control-arm in terms of quality adjusted life-years (QALY) and days of sickness absence are also investigated. The following measurements will be taken at baseline and the three follow-up timepoints: work-, health- and physical activity related factors collected by two electronic questionnaires, objective measurements of movement continuum (sleep, sedentary behavior, standing-ups, standing, light activity, moderate activity, vigorous activity) for 24/7 (RM42 research accelerometer), 3 tests of physical fitness and blood samples related to blood sugar and lipid profile.

Sick-leaves due to musculoskeletal disorders (MSDs) among municipal workers of Nokia City increased notably during the year 2017, which was noticed as increased call and burden in occupation healthcare settings. According to the disease grading statistics of early retirement, MSDs were the leading cause. Due to the afore facts Nokia City composed a novel model of co-operation between the personnel administration and exercise facilities of Nokia City: The coordinator of wellbeing (occupational nurse) now prescribes exercise referrals for patients to directly contact the sports sector for personalized exercise counseling.

The purpose of the present study is to investigate the effectiveness and cost-effectiveness of the afore described novel operations model of exercise referral in the Nokia City. Personalized Exercise Counseling (PEC) intervention guides and motivates the workers to set and achieve personal exercise/physical activity goals. The hypothesis is that the PEC improves workability (main outcome) and reduces musculoskeletal pain, and thus improves quality of life and reduces days of sickness absence. Regarding cost-effectiveness of the PEC-arm is expected to be cost-effective in terms of quality adjusted life-years (QALY) and days of sickness absence compared to the Control-arm.

The target population of the PEC-Nokia study is practical nurses, personnel of kitchen and cleaning service and janitorial service. In case that the number of participants fulfilling the inclusion criteria of these occupational groups is not adequate to reach the number needed to be randomized (n=190), other occupations may be recruited.

Sample size was calculated based on the work ability score (WAS) i.e. current work ability compared to lifetime best on numeric rating scale from 0 (completely unable to work) to 10 (work ability at its best). Thus, to detect a difference in main effects (i.e., Personalized Exercise Counselling (PEC) group vs. non-treatment group (Control) with a significance level of 0.05 and a power of 90%, the study required at least 150 participants (75 in each study-arm). For compensation of probable loss of participants to follow-up, the aim is to recruit 190 participants. We expect that there would be a minimal difference of 15% between the PEC-arm and Control-arm among those with improved WAS-score to the good level (i.e. at least 8). We expect that 5% of the participants in the Control-arm and 20% in the PEC-arm will reach the afore target. Reductions of 30% or 15mm (0-100) in intensity of musculoskeletal pain levels at neck-shoulder, lower back, and knee would meet the criteria of clinically important change.

The participants (n=190) will be randomly assigned into 6-month Personalized Exercise Counseling combined with interactive accelerometer (PEC-arm) or a non-intervention Control-arm. Statistician KT will randomly assign about 200 persons to one of the two parallel groups in a 1:1 ratio using a computer-generated procedure. The codes of the study group will be provided to the participants fulfilling the inclusion criteria, using the method of sealed envelopes, immediately after the person has given his/her written consent to participate to the well-being coordinator (specialist nurse of occupational health employed by Nokia City). Only the investigators (i.e. the research group) will be blinded to group allocation.

Electronic questionnaires have been prepared to cover the following: Work-related factors include perceived physical strain, perceived exertion after typical work day at different body sites of musculoskeletal structures and work stress; Health-related factors include perceived health, depression, sleep and recovery, quality of life and days of sickness absence; Physical activity related factors include preferred activity modes and motivation, Fear Avoidance Beliefs related to physical activity at work and leisure-time. In addition, the following physical tests will be used to measure health-related fitness: Neck-shoulder mobility for flexibility, Modified push-ups for upper body strength and trunk stability and 6 minutes' walk test for cardiorespiratory fitness in terms of distance walked and predicted maximal oxygen uptake.

Inclusion Criteria:

• Reduced workability of less than 8 in the numeric rating scale assessed by the Work Ability Scale (WAS), an item of the Work Ability Index (WAI), as "Current work ability compared with lifetime best rated on a numeric rating scale from 0 (completely unable to work) to 10 (work ability at its best)"

Exclusion Criteria:

• not likely to be albe to do one's current job two years from now assessed with Future Walk Ability (FWA) item from WAI "Do you believe that, from your health perspective, you will be able to do your current job two years from now?"' was rated with three response alternatives: unlikely (1), not certain (2) and relatively certain (3)

After the screening phase, all electronic questionnaire data will be collected in the form of pseudonymity i.e. using only the numeric identification codes. All data (results of blood samples, fitness tests, research accelerometers) will be saved and analysed using only the codes.