Vengo entrenando desde enero para dosificar el esfuerzo.

Because venir + gerundio highlights an action that started before now and has continued up to now.

• entreno = I train / I’m training in a general sense; it can describe a habit.
• estoy entrenando = I’m training right now; it focuses on the current moment.
• vengo entrenando = I’ve been training / I’ve been training for some time now; it emphasizes continuity over a period leading up to the present.

So this structure is useful when the speaker wants to show an ongoing process, not just a present activity.

Venir + gerundio is a verbal structure used to show that something has been developing progressively over time until now.

In this sentence:

• vengo = present tense of venir
• entrenando = gerund of entrenar

Together, vengo entrenando means something like:

• I’ve been training
• I’ve been coming along training
• I’ve been engaged in training over this period

Compared with other similar structures:

• estar + gerundio → action in progress now
• llevar + gerundio → duration up to now
• venir + gerundio → continuation with a sense of development over time

Because the action is understood as still continuing now.

In Spanish, when something began in the past and is still going on, the language often uses a present-tense structure:

• Vengo entrenando desde enero
• Llevo entrenando desde enero
• Entreno desde enero

All of these can refer to something that started in the past but remains true in the present.

So vengo is in the present because the speaker is talking about a process that is alive and ongoing now, not finished.

Desde gives the starting point of an action.

• desde enero = since January

It tells you when the training began.

This works very naturally with actions that continue into the present. Other examples:

• Vivo aquí desde 2020.
• Trabajo en esta empresa desde mayo.

You could also use:

• desde hace + period of time
  Example: Vengo entrenando desde hace meses.

Difference:

• desde enero = names the starting point
• desde hace meses = gives the amount of time up to now

Yes, absolutely. In fact, for many speakers in Spain, llevar + gerundio is often the more common and neutral way to express duration.

• Llevo entrenando desde enero = I’ve been training since January

Compared with vengo entrenando:

• llevo entrenando sounds very natural for simple duration
• vengo entrenando can sound a little more marked and may suggest an action that has been unfolding progressively

So both are correct, but llevo entrenando desde enero may feel more everyday in many contexts in Spain.

Entrenando is the gerund of entrenar.

How it is formed:

• verbs ending in -ar → -ando
• entrenar → entrenando

The Spanish gerund is often similar to the English -ing form, but it is not used in exactly the same way as in English.

Here it is part of a verbal expression:

• vengo entrenando

That means it is not acting like a noun; it is helping to describe the ongoing action.

Because para + infinitive usually expresses purpose or goal.

Here:

• para dosificar el esfuerzo = in order to pace/manage the effort

So the idea is: the speaker has been training since January with the aim of managing their effort better.

By contrast, por usually expresses things like:

• cause
• reason
• exchange
• movement through a place

So por dosificar would not fit well here if you want to express purpose.

Yes, it sounds natural, especially in contexts like:

• sport
• exercise
• racing
• endurance activities

Dosificar literally means something like to dose or to distribute in measured amounts, and with el esfuerzo it means:

• to pace your effort
• to manage your energy
• to avoid spending all your strength too early

So it is a fairly idiomatic and sensible collocation in sports or training language.

Because Spanish often omits subject pronouns when the verb already makes the subject clear.

• vengo already tells you the subject is yo

So:

• Vengo entrenando desde enero...
• Yo vengo entrenando desde enero...

Both are correct, but the version without yo is more normal unless the speaker wants emphasis or contrast, for example:

• Yo vengo entrenando desde enero, pero él no.

Yes. Spanish word order is flexible, especially when you want to emphasize one part of the sentence.

For example:

• Vengo entrenando desde enero para dosificar el esfuerzo.
• Desde enero vengo entrenando para dosificar el esfuerzo.

Both are correct.

Difference in focus:

• starting with Vengo entrenando emphasizes the ongoing action
• starting with Desde enero emphasizes the time frame

The meaning stays basically the same.

Usually, no, not as naturally.

In standard Spanish, especially in Spain, he entrenado is a present perfect form that tends to present the action more as a completed whole or as an experience/result connected to the present. It does not express ongoing duration as clearly as:

• vengo entrenando
• llevo entrenando
• entreno desde enero

So if you want to say the training started in January and is still continuing, he entrenado desde enero is generally not the best choice.