<p>There are multiple things against this. </p>

<ol>
<li>It needs a close death experience to gain power and they need to be healed afterwards, as Dende wasn't on earth at this time and they surely don't want to eat all the beans. It would take a lot of time to regain their full strength and they could die trying of course.</li>
<li>Vegeta and Goku would never use something like that to gain power because of their pride. </li>
<li>They might have underestimated the cyborgs</li>
<li>Future Trunks was not in this timeline on that time</li>
<li>Gohan was a kid at this time and he "had to study". His mother would have never allowed him to be beaten half dead and recovered just to increase power.</li>
</ol>

<blockquote class="spoiler">
  <p> 6. Future Trunks might not be aware of this fact, since when he lived Goku and Vegeta were already dead and Gohan might never told him that.</p>
</blockquote>

<p>As Exception from 2:</p>

<blockquote class="spoiler">
  <p> Vegeta did this on Namek cause he hated Frieza, he destroyed the planet Vegeta and killed nearly all the Sajyans. (As exception of 2.)</p>
</blockquote>

<p>Those are the reasons against, it in my opinion. There might be more, and some might not be right, but I hope you can use this answer.</p>

CC BY-SA 3.0
2016-12-20T14:42:41.410Z
To add in Future Gohan probably never actually knew that. He might have gotten a power a spike when he lost his arm but never understood why. I'm pretty sure if he did there would have been no need for Trunks to travel back in the first place.
Callat
CC BY-SA 3.0
2012-12-18T15:27:31.203Z
Also, it would make the series rather dull if it were to happen that way. So the mangaka didn't do it that way :)
Madara's Ghost
CC BY-SA 3.0
2012-12-18T20:46:03.497Z
My to that answer is too long to the comment so please read this: https://gist.github.com/4331770
Hashirama Senju
CC BY-SA 3.0
2012-12-18T21:32:32.887Z
@MadaraUchiha This is the most obvious one :) but since the characters don't mind this it doesn't matter
Tartori
CC BY-SA 3.0
2012-12-18T21:34:16.150Z
@HashiramaSenju I add a coment to your github link, since my comment is to large for here. Everybody else, please be aware that there might be spoilers for you.
Tartori
CC BY-SA 3.0
2012-12-18T21:45:02.537Z
@Tartori OK, 1.So they could do it before the cell games at least.
Logically, Everything else it total guess of yours.
unless you give me hard evidence.
Hashirama Senju
CC BY-SA 3.0
2012-12-18T07:53:06.043Z
2012-12-21T15:57:42.757Z
2012-12-21T15:57:42.757Z
Tartori
<p>There was also the possibility they could have died while trying this, so it's not such a good strategy.</p>

CC BY-SA 3.0
2013-08-03T21:09:41.120Z
Come on, seriously? With dende on their side they can literally make a hole in their stomach and still live for incredibly long time, Then heal themselves.
Hashirama Senju
CC BY-SA 3.0
2013-08-02T15:26:31.120Z
2013-08-02T15:26:31.120Z
noko
<h2>First things first</h2>

<ul>
<li>Goku use in the spaceship, while going to Namek. (Seeds)</li>
<li>Vegeta ask Dende to help him with it in Namek. (Heal)</li>
<li>Gohan get power up thanks to the <a href="http://dragonball.wikia.com/wiki/Old_Kai" rel="nofollow noreferrer">Old Kai</a>. (Without getting damage, only releasing the hidden power)</li>
<li>Trunks and Goten never needed the power up (they used only the SSJ 3 form to do this)</li>
</ul>

<hr>

<h2>The Androids appearance</h2>

<blockquote>
  <p>Three years have passed since the visit by the mysterious Future
  Trunks. Goku, Piccolo and Gohan leave to go and face their destiny
  against enemies they have only heard about, but not seen. They are as
  prepared as they could be, though Piccolo wishes they had more time to
  become stronger.</p>
</blockquote>

<p>Source: <a href="http://dragonball.wikia.com/wiki/The_Androids_Appear" rel="nofollow noreferrer">The Androids Appear - Summary (1st Paragraph)</a></p>

<p>The point that need to be considerate here is: <strong>You need to train your technique not only your power (check out how boxers or others professional fighters train before a fight)</strong></p>

CC BY-SA 3.0
2012-12-21T18:44:31.123Z
There is no connection between what you said and what I wrote.
And if you follow the comments written under the Tartori answer You will see that they had more than one chance to do so.
In addition to that, By simple logic, When you are strong significantly from someone else, There is no meaning to the technique.
Hashirama Senju
CC BY-SA 3.0
2012-12-21T18:53:17.403Z
**1.** "When you are strong significantly from someone else, There is no meaning to the technique." `The idea of teaching the weak to defeat the strong is an ancient tradition in the martial arts. The art of tai chi, for instance, in its original form as a fighting style rather than a health exercise, was supposedly developed so that a weaker fighter could learn to prevail over a stronger one through intelligent tactics. `[Source](http://www.livestrong.com/article/522687-the-best-martial-arts-for-powerlifters/#ixzz2FiJqycFb) **2.** your question is about the androids appearance.
Michel Ayres
CC BY-SA 3.0
2012-12-21T18:53:40.167Z
**3.** use the [CHAT](http://chat.stackexchange.com/) for discussion/debate. **4.** My answer is about WHY they prefer to train their skills over their power. **5.** Try keep the comments inside the stackexchange sites.
Michel Ayres
CC BY-SA 3.0
2015-12-02T17:19:30.460Z
Many, many years before, when Goku and Krillin were kids and were training under Master Roshi, he told them they had reached the top of their skills, and they could only improve becoming stronger, faster and more resiliant.
Flamma
CC BY-SA 3.0
2012-12-21T18:21:22.123Z
2016-12-20T05:48:09.460Z
2016-12-20T05:48:09.460Z
Michel Ayres
<p>A Saiyajin can multiply his power if he takes great damage or is near death and is able to heal himself afterwards.</p>

<p>With that ability alone, they could rinse and repeat countless times before the first encounter with the Androids (you can't be too safe).</p>

<p>Goku and Vegeta have their pride and all, I get that. But Trunks and Gohan are much more rational (especially Future Trunks). So why didn't they do what Vegeta did on Namek with Dende for example?</p>

CC BY-SA 3.0
2013-08-02T15:52:14.033Z
plot holes yo!!
Sam I am says Reinstate Monica
<dragon-ball-series>
Why didn't the Saiyajins raise up their power energy?
# Why didn't the Saiyajins raise up their power energy?
Posted by: username_0 on 2012-12-18
A Saiyajin can multiply his power if he takes great damage or is near death and is able to heal himself afterwards.

With that ability alone, they could rinse and repeat countless times before the first encounter with the Androids (you can't be too safe).

Goku and Vegeta have their pride and all, I get that. But Trunks and Gohan are much more rational (especially Future Trunks). So why didn't they do what Vegeta did on Namek with Dende for example?
**Tags:** dragon-ball-series
> **Comments:**
> **username_1**: plot holes yo!!  
---
## 3 answers
### Answer by username_2 on 2012-12-18. Score: 16
There are multiple things against this.

1. It needs a close death experience to gain power and they need to be healed afterwards, as Dende wasn't on earth at this time and they surely don't want to eat all the beans. It would take a lot of time to regain their full strength and they could die trying of course.
2. Vegeta and Goku would never use something like that to gain power because of their pride.
3. They might have underestimated the cyborgs
4. Future Trunks was not in this timeline on that time
5. Gohan was a kid at this time and he "had to study". His mother would have never allowed him to be beaten half dead and recovered just to increase power.

> 6. Future Trunks might not be aware of this fact, since when he lived Goku and Vegeta were already dead and Gohan might never told him that.

As Exception from 2:

> Vegeta did this on Namek cause he hated Frieza, he destroyed the planet Vegeta and killed nearly all the Sajyans. (As exception of 2.)

Those are the reasons against, it in my opinion. There might be more, and some might not be right, but I hope you can use this answer.
> **Comments:**
> **username_4** (2012-12-18): Also, it would make the series rather dull if it were to happen that way. So the mangaka didn't do it that way :)  
> **username_0** (2012-12-18): My to that answer is too long to the comment so please read this: https://gist.github.com/4331770  
> **username_2** (2012-12-18): @MadaraUchiha This is the most obvious one :) but since the characters don't mind this it doesn't matter  
> **username_2** (2012-12-18): @HashiramaSenju I add a coment to your github link, since my comment is to large for here. Everybody else, please be aware that there might be spoilers for you.  
> **username_0** (2012-12-18): @Tartori OK, 1.So they could do it before the cell games at least.
Logically, Everything else it total guess of yours.
unless you give me hard evidence.  
> **username_3** (2016-12-20): To add in Future Gohan probably never actually knew that. He might have gotten a power a spike when he lost his arm but never understood why. I'm pretty sure if he did there would have been no need for Trunks to travel back in the first place.  
---
### Answer by username_5 on 2013-08-02. Score: 0
There was also the possibility they could have died while trying this, so it's not such a good strategy.
> **Comments:**
> **username_0** (2013-08-03): Come on, seriously? With dende on their side they can literally make a hole in their stomach and still live for incredibly long time, Then heal themselves.  
---
### Answer by username_6 on 2012-12-21. Score: 0
## First things first

* Goku use in the spaceship, while going to Namek. (Seeds)
* Vegeta ask Dende to help him with it in Namek. (Heal)
* Gohan get power up thanks to the [Old Kai](http://dragonball.wikia.com/wiki/Old_Kai). (Without getting damage, only releasing the hidden power)
* Trunks and Goten never needed the power up (they used only the SSJ 3 form to do this)

---

## The Androids appearance

> Three years have passed since the visit by the mysterious Future
> Trunks. Goku, Piccolo and Gohan leave to go and face their destiny
> against enemies they have only heard about, but not seen. They are as
> prepared as they could be, though Piccolo wishes they had more time to
> become stronger.

Source: [The Androids Appear - Summary (1st Paragraph)](http://dragonball.wikia.com/wiki/The_Androids_Appear)

The point that need to be considerate here is: **You need to train your technique not only your power (check out how boxers or others professional fighters train before a fight)**
> **Comments:**
> **username_0** (2012-12-21): There is no connection between what you said and what I wrote.
And if you follow the comments written under the Tartori answer You will see that they had more than one chance to do so.
In addition to that, By simple logic, When you are strong significantly from someone else, There is no meaning to the technique.  
> **username_6** (2012-12-21): **1.** "When you are strong significantly from someone else, There is no meaning to the technique." `The idea of teaching the weak to defeat the strong is an ancient tradition in the martial arts. The art of tai chi, for instance, in its original form as a fighting style rather than a health exercise, was supposedly developed so that a weaker fighter could learn to prevail over a stronger one through intelligent tactics. `[Source](http://www.livestrong.com/article/522687-the-best-martial-arts-for-powerlifters/#ixzz2FiJqycFb) **2.** your question is about the androids appearance.  
> **username_6** (2012-12-21): **3.** use the [CHAT](http://chat.stackexchange.com/) for discussion/debate. **4.** My answer is about WHY they prefer to train their skills over their power. **5.** Try keep the comments inside the stackexchange sites.  
> **username_7** (2015-12-02): Many, many years before, when Goku and Krillin were kids and were training under Master Roshi, he told them they had reached the top of their skills, and they could only improve becoming stronger, faster and more resiliant.  
---
