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Last week, Dr. John covered research on hand paddles and parachutes on sprint swimming. This week we’ll explore resistance (overload) training paired with underload training. Underload training involves assistive tools like bungee cords, fins, and fast suits. We’ve touched on this concept in other writings, but will devote this post to a closer look.

The general thinking behind pairing overload with underload is simple: Overload the muscles and they’ll adapt to that stimulus to grow stronger. Provide assistance to enable faster movements, and faster muscle firing will occur. You can be strong as an ox, but if your muscles don’t fire rapidly, you won’t achieve high velocities. Likewise, fast turnover with no strength won’t produce results either. Power is a product of strength and speed.

Literature supporting overload paired with underload looks at external forces applied to the whole body. Running parachutes, heavy baseballs or shot puts, heavy baseball bats, and running parachutes for sprinters are common examples in other sports. Swimming is unique as not only do we have external devices (power racks and parachutes), we also modify the body with fixed appendages via paddles and fins (but hopefully not those aqua aerobics web gloves!).

Why does this distinction matter? Most would agree that your overload and underload velocities should remain relatively close to your normal swim stroke. In baseball, it has been shown that 15-20% overload and underload provides an effective range for desired adaptations (Escamilla 2000). There’s no definite evidence this range applies to swimming, although some believe the original impetus to explore the 15-20% range came from unpublished Eastern Bloc research in the 60s, 70s, and 80s for a wide range of sports. It may follow that the associated stroke rates with these ranges will naturally emerge.
Timing in each phase of the stroke should be considered along with overall velocity. Most don’t have the equipment to quantify this variable, but it’s important to understand the concept qualitatively. One way to understand the importance of timing is with terrestrial gait. For example, running involves specific ranges of time spent in specific phase (support, propulsion, landing). These ranges can vary, but if the timing of any phase exceeds these ranges, a different form of gait emerges. Appendages like paddles and fins may strain the boundaries of the relative stroke phases so that overload or underload stimuli might not be stroke specific. If paddles are too large for a swimmer, they may slow down the arms without the same timing adjustments to the legs. This isn’t to suggest we’re wrong by using fins, paddles, and pull buoys. Perhaps the main benefit of these appendages is not for overload or underload, but instead for other areas such as hand position, body alignment, or hip rotation.

As an aside, fin use during rehab may alter stroke coordination so that time spent in each phase of the stroke may differ markedly from the normal stroke. The legs and hips change, but muscle timing patterns may differ. I don’t know if this has been studied formally, but it could be that for some injured swimmers, fins swimming is nothing more than kicking with arm movements only partially related to their normal stroke. Again, that’s not to say fins are without value, but we need to take a closer look at the individual to determine whether appropriate muscle timing happens with fin use (Check out Dr. John’s COR Shoulder System for optimal shoulder prevention and rehab!)

Many coaches already use combinations of overload and underload, so the concept is not new. Girold (2006) found that dryland strength and a regime of in-water resistance and assistance yielded similar improvements (both better than the control group, which used neither method), though this study only looked at the use of bands for the in-water work; not other tools. However, the in-water group had improvements in stroke rate. Even though this group did not perform better than the dryland weights group in the limited duration of the study, an athlete with a higher stroke rate after this training may have a greater “upside” if they later add strength.

Here are a few other key areas to consider:
  • Timing…Immediacy: Some teams have a pull day, a strength day, and a speed day. Others combine methods within a workout. Pulling happens most frequently among non-sprinters, but as noted above, the value in pulling may relate to neural training as much as resistance training. Research suggests that immediacy is important, so the approach most consistent with the literature is to pair overload, underload, and normal swimming (at least some of the time) within the same session (Cronin 2002).
  • Range: As noted above, a range of 15-20% above and below normal load is an effective range for sport specific training (DeRenne 1990). Stimuli outside those ranges have may limited transfer for reasons discussed above (velocity and timing). It’s obviously much harder to quantify resistance or assistance with a parachute or bungee cord than a baseball that comes marked with a number. Fortunately, qualitative assessment can be useful. Anyone who looks like they are struggling with the added weight or speed probably isn’t training the correct stimuli. 
  • Suits: Drag suits have been part of the swimming culture for years but formal study has been limited. However, one recent study showed that drag suits can improve sprint performance when used in sprint training (Dragunas 2012). I’d put this study in the category of “not enough to prove or disprove,” in part because it only studied freestyle sprints, and in part because drag suits come in many versions, from mesh suits worn nearly full time to suits with pockets for specific training. 
Generally, the use of drag suits has been substantially out of proportion to any corresponding assistance training. Enter the illegal suit. Yes, instead of sending illegal LZRs and other brands to the goodwill bin, some coaches have been using them in practice for overspeed training. Illegal racing suits complement resistance from drag suits. Logically, this strategy makes great sense, as it allows for full body coordination, unlike an appendage that only affects one part of the body.

Blending of overload and underload training is nothing new in the swimming world, but by looking closely at the factors affected by each method we can refine our use. Although optimal load ranges have not been quantified in swimming, targeting a range of 15-20% overloand and underload within the same session is consistent with the evidence to maintain velocity and timing.


  1. Dragunas, AJ, Dickey, JP, and Nolte, VW. The effect of drag suit training on 50 m freestyle performance. J Strength Cond Res 26(X): 000-000, 2012
  2. Girold S, Calmels P, Maurin D, Milhau N, Chatard JC. Assisted and resisted sprint training in swimming. J Strength Cond Res. 2006 Aug;20(3):547-54.
  3. Cronin JB, McNair PJ, Marshall RN. Is velocity-specific strength training important in improving functional performance? J Sports Med Phys Fitness. 2002 Sep;42(3):267-73.
  4. Escamilla RF, Speer KP, Fleisig GS, Barrentine SW, Andrews JR. Effects of throwing overweight and underweight baseballs on throwing velocity and accuracy. Sports Med. 2000 Apr;29(4):259-72.
  5. DeRenne C, Ho K, Blitzblau A. Effects of Weighted Implement Training on Throwing Velocity. The Journal of Applied Sport Science Research. 1990, 4, 16-19.
By Allan Phillips. Allan and his wife Katherine are heavily involved in the strength and conditioning community, for more information refer to Pike Athletics.
Dr. John Mullen, DPT, CSCS world-renowned physical therapist and strength coach.
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