Low-weight-high-repetitions (LWHR) programs constitute a popular group-based form of exercise for the general population, accompanied by various health benefits for the participants. However, the effect of such programs on cardiorespiratory fitness is still controversial. The aim of the current study was to examine the effects of a 3-month LWHR group exercise program vs pilates on cardiorespiratory fitness, body composition and overall health on previously inactive adult women.

This is a randomized exercise intervention study in healthy subjects (adult women-inactive). Participants will be randomly allocated in two groups: the LLHR group and the Pilates group. All assessments will be blinded to the intervention group of the participants. Both exercise programs will be performed in groups lasting for three months and performed 3 times per week. The study conformed to the principles enumerated in the Helsinki Declaration and ethical approval has been obtained by the national ethical committee.

Participants in the LLHR training will participate in a three-month, group based pre-choreographed exercise programme, consisting of three LLHR training sessions per week (in non-consecutive days). All participants will be familiar with the exercises that will be used in this intervention. Each LLHR fitness program, includes a variety of multifunction exercises (i.e. squats, lunges, chest press and chest extension, rowing, triceps extension and bicep curls) addressing all muscle groups; using barbells, dumbbells or body weight. Each session will last for 60 min (including 5 min warm up and 5 min cooldown). Exercise intensity will increase progressively once a month by adding weights to the barbells and dumbbells.

Participants in the Pilates program will be trained with the same exercise schedule for the 3-month period. Their 60 min session, will be consisted of warm-up and cool down (5 minutes each), along with static-isometric exercises addressing major muscle groups. Pilates exercises focus on breathing, concentration, control and precision. Exercise intensity progression in the Pilates program will be performed every one month by increasing the level of demanding of the exercises.

All training sessions of both the LLHR and Pilates programs will be supervised by a qualified sports scientist (one sport scientist responsible for each program) for securing training standardization. Participants in both programs will be advised to avoid taking part in any other exercise session during the intervention period.

Prior to the initiation of the study, participants will be examined by a physician for confirming their health status. According to the updated criteria, "inactive" is an individual who is performing insufficient amounts of moderate-to-vigorous physical activity (Sedentary Behaviour Research Network, 2012).

Inclusion Criteria:

• Female, inactive, able to participate in an exercise training

Exclusion Criteria:

• male gender, inability to perform the exercise training program due to musculoskeletal injury, a medication that could affect cardio-metabolic function, including anti-hypertensive, diabetic or anti-obesity drugs and inability to systematically participate in the proposed training programs according to the schedule (i.e. absence from 3 consecutive exercise sessions or missed more than 10% of total exercise sessions), psychiatric disorders.

Inactive but otherwise healthy adult women will participate in the current study.

Only with other researchers participating in the study

Participants will not be aware of the type of exercise intervention. Assessors will be blind for the group allocation of the participants