Very interesting question, but very generic. The simple answer is the muscles of the whole of the body. All depends from the position the object is and the weight as well as the shape. Are we talking of small of large boxes? Round or square? Are they high on another object or down on the floor? The muscles involved are not only the lower limb or the core body or the upper limb ones but also the diaphragm is involved. There is coordination of all muscles in every movement of our body and combination of activities. Hope you find all this helpful. Thanks for asking.

Thank you for the answer George.

Actually, the task that i observe is repetitive lifting square box (A4 paper box) from knuckle height level then carrying it for 2 meters distance and then put it on table at sternum height level.

What is the most active muscle for lifting, carrying and lowering task?

For the task you described, a functional task evaluation would require the weight of the box since the weight of the box would determine if the task is qualified as a task performed as an occasional task (1 - 4 times/hour, 1 - 32 times per day), frequent task (5 - 8 times/hour, 33 - 66 times/day), or constant task (12 - 60 times/hour, 67+ times/day). For occasional tasks loads of 10 - 50 lbs (4.5 -22.7 kg) are considered very light - medium; loads from 50 - 100+ lbs (22.7 - 45.4 kg) are considered medium to very heavy. For frequent tasks loads of < 0.5 kg - 11.4 kg are considered very light - medium, while loads from 11.4 - 22.7+ kg are considered medium to very heavy. Tasks classified as constant involve loads of < 0.5 kg - 4.5 kg for very light to medium; and from 4.5 kg - 9.1 kg are considered medium to very heavy.

The muscles of the trunk (primarily trunk extensors) and the muscles of the lower extremity will be used for stability and moving the box across the 2 meters. The muscles of the upper extremity (shoulder girdle, shoulder, elbow/radioulnar joint, and the wrist and hand) would be used to varying degrees to lift, hold, and lift the box to sternum level and place it in its place. No single muscle would be most active. Which muscles contribute to the specific portion of the task you intend to study will depend on the magnitude of the load, the frequency the task is completed, the velocity at which the task is completed, the height differential between where the box is lifted from to the height at which the box is placed when the task is completed (since the carrying of the box in the hands across the 2 meters does not accomplish any significant work, which could be measured and quantified accurately).

The only significant difference in muscular activity in the task described is not a difference in which muscles are active but the type of muscular activity that is taking place. The same muscles will be used whether lifting, carrying, or lowering the box. When lifting the box the muscles must overcome the effects of gravity on the box, which tends to cause it to remain at knuckle level on the table or supporting surface, this is accomplished using a concentric muscle action. When carrying the box across the floor for 2 meters, the box is basically held in a stable, static condition. The legs provide a propulsive force but the resistance to movement is at the foot/floor interface and no useful work is done to the box, therefore the muscles responsible for controlling the box and its contents are active in an isometric contraction, where the muscle produces a force exactly equal to the force of gravity to maintain control of the box while carrying it across the 2 meter space. When placing the box in its final position, the upper extremity muscles and possibly the trunk and lower extremity muscles will again produce a force greater than the resistive force provided by gravity using a concentric muscle action, just as they did when originally picking up the box. Finally when lowering the box to its final resting position, the same muscles that used a concentric muscle action to lift the box would utilize an eccentric muscle action to allow the box to be safely lowered to its final position.

So your problem is really one of adequately defining the movement or movements you are going to be studying, because the global nature of your current question is too large to provide a specific answer like you appear to be seeking.

Dear Mirta, during lifting biceps, long and short flexors of the forearm and trapezius muscle work more than that of opposite group muscles. during carrying gait muscles of trunk and lower limb works (mainly calf at ankle, quadriceps at knee and gluteal at hip, erectors at trunk work maximally). as far as upper limb concerned it all depends whether you are carrying boxes close to your body, ergonomically correct one, or away from your body. if it is close to your body trapezius and wrist flexor muscles work maximum and if it is away from your body shoulder flexor, trunk extensors and trapezius works maximally. if lowering takes plays at sternum level, it involves shoulder, elbow and wrist flexors work maximally apart from concentric contraction of calf. finally word of caution that recent expensive muscle analysis equipments, such as EMG, force platform, 3D video analysis states that  all muscle groups work during any kind of motion.

This is a very complex question and, as mentioned above, the answer  depends on multivariate factors. In the setting described in your case, the most important muscles are m. biceps bracii (both of them !).

From your description I take it that the object is starting the movement from an area that it is mid-thigh (knuckle height level), and it is lifted to mid body level (sternum height - which I take at the level of the lower part of the sternum). The subject who is lifting the object is standing and he/she is not bending the knees to pick it up neither is bending the hips or back. The weight of the object is not given but I take it that it is an empty A4 box. 

In such case the subject as he/she is not bending the core or lower limbs he initial work is done by the flexors of the arm and the upper body muscles (shoulder internal rotators and adductors mainly, as well as the dorsal muscles as trapezius), followed with the inclusion during lifting of the abdominals and the dorsal muscles. Diaphragm is involved but as the weight is negligible its involvement is too.

During the walking phase, the core muscles are active (dorsal and abdominals) as well as the flexors of the upper limbs but in balance with the extensors to keep the arm in 90 degrees of elbow flexion and the fingers and wrists in balanced position to hold the object. In addition the shoulder adductors and internal rotators are active and in balance with external rotators and upper limb dorsal muscles (stabilisers of scapula, trapezius) helping the object to be kept in position. On top of those there are the muscles of the lower limbs which are assisting with walking (talking for the whole of them, flexors, extensors, external and internal rotators and abductors as well as adductors).

During the phase in which the object is left on the bench, the flexors and adductors of the upper limbs are relaxed and the activity goes to the abductors, external rotators and extensors of the upper limbs as well as the dorsal upper body muscles.

hi

In general the muscles of the arms and particularly the front and rear upper arm muscles

Dear Mirta

It is very interesting but complex question as it depends on  multivariate factors, so you have to concentrate for specific muscles tasks (variables) and their outcome measures.

Hello,

lots of great answers here already, here are few other points to consider:

1. Unless you standardise the technique itself, answering that question will always present difference between subjects.

2. Morphological differences between subjects themselves will have a role to play in both technique utilised and muscle activity

3. Ultimately we are looking at a deadlift activity, look into research done on this Olympic lift for background for your research

4. I have to disagree on any particular muscle group being the most important. Largely, it is the antigravitarian muscles as a whole that will symbiotically perform the task.

Regards

Xavier

Thank you very much for those who answer my question. It is very great answer and useful for design my experiment.

Sincerely,

Mirta