Weight training: squats can increase power and strength

Squats are one of the toughest exercises in the gym, but as James Marshall, explains, certain squat variations have much to offer power and strength athletes.Speed, acceleration and power are vital for many track and field events as well as numerous other sports. And research has shown that developing lower limb strength plays a key role in developing these attributes (1). In particular, building lower limb strength increases the muscles’ ability to exert force – required for example for exploding out of the blocks or pushing in a scrum. Speed athletes in particular can benefit from strength-building leg work such as squats because during sprinting the forces generate can exceed body weight by three or four-fold (2).

Mention squats and most people think of a simple barbell and weight exercise. However, while simple squats are undoubtedly effective, there’s plenty of good evidence that certain variations on squats may be even more effective. One of these is ‘chain squats’, where a heavy chain is added to either end of the barbell – a popular practice, particularly among American athletes. In addition to chains, lengths of elastic can also be used (one end secured to the floor) to produce a similar effect.

At the bottom of the movement, where the legs are able to generate least power (due to mechanical disadvantage), most of the chain lies on the floor, with only a small portion suspended (therefore adding minimal resistance). As the athlete rises, more and more of the chain becomes suspended, increasing the resistance on the bar. But this is matched by the muscles’ increasing efficiency – ie the muscles are made to work harder in the range of movement where they have most strength.

The net result is that muscles are worked more efficiently over a larger range of movement. Another benefit is that the athlete can power right through to the top of the movement (instead of having to slow down to risk locking out the knees), which more closely reflects the movement demands of sport generally.

The additional loading added as you rise up during a chain squat is a function of chain size. If you use half-inch chains, each suspended foot will add 7.5kgs per side. So rising up three feet will add 3 x 2 x 7.5kgs = 45kgs of extra resistance at the top of the movement compared to the bottom. With elastic, the extra resistance produced is altered by using different ‘band girths’. It’s worth adding however that these variants are tough and assume a good base level of strength conditioning; as a rule of thumb, you should be able to comfortably squat your own body weight before attempting them.

Research on chain squats

Researchers from the University of Wisconsin measured the effect of ordinary squats, chain squats and squats with elastic bands on the electrical activity in the muscles used of 11 college athletes (3). Although there were no electrical differences, the subjects commented that the chain and elastic squats felt different to perform. A possible limitation however was that the barbell weights were reduced by 10% when chains or elastic were added, when in practice, many athletes keep the same barbell weight and use chains/elastic to provide additional resistance.

In another study, resistance trained adults squatted around 60-85% of their 1-rep maximum then used resistance bands to add either 20% or 35% more resistance (4). Although there were no differences in the rate at which force was developed, when the bands were used, both peak power and peak force were significantly increased, especially when 85% of the 1-rep max load was combined with an additional 20% resistance from elastic.

Squat jumps

While weightlifting exercises such as the ‘clean and snatch’ are very effective for developing power, they require a large time investment to develop technical proficiency. However squat jumps (a squat with faster ascent and jump at the top) are easier to master and can offer similar benefits. Researchers have looked at optimal loading for squat jumps by seeing how they affect 20m sprint times.

A study examined the effects of squat jumps using loads of either 30% or 80% of 1-rep max for 8 weeks in 26 subjects and found that while both groups developed more peak power, it was the 30% 1-rep max group that increased sprint velocity and reduced sprint times; the 80% group became slower (5). Another study on strength-trained rugby league players found that squat jumps with loads of between 47 and 63% of 1-rep max were most effective in building power; below 47% was insufficient loading to generate peak power while above 63% slowed the movement down too much (6).

If you’re thinking of incorporating squat jumps into your training routine, make sure you have as a minimum a 1-rep max for squats equivalent to your body weight before you begin. Try beginning with twice weekly squat jump sessions consisting of 4 sets of 5 jumps, using 30% of your 1-rep max, Continue also with conventional strength training and when you can squat twice your body weight for 1-rep max, you can gradually increase squat jump load towards 50% of 1-rep max.

References:

1.    JSCR 19 (2), 349-357 (2005).
2.    Periodization.  T. Bompa (1999).
3.    JSCR 16(4), 547-550 (2002)
4.    JSCR 20 (2) ,268-272 (2006)
5.    JSCR 16 (1), 75-82 (2002).
6.    JSCR 15 (1), 92-97 (2001).

Original article by James Marshall
Summary by Andrew Hamilton BSc Hons MRSC ACSM