Designing an ideal strength training program for sport in itself can be a complex process. Yet resistance training is only one component of an athlete's overall training regime, which can also include endurance training, speed training, flexibility training and skill / tactical work.
Perhaps the most important element in a total conditioning program is adequate rest and recovery, without which the body cannot adapt properly to the imposed demands.
How does strength training interact with other components of fitness? Does endurance training have a negative effect on strength and power? And does strength and power training negatively effect aerobic power or flexibility?
This article examines the integration of a sport-specific strength training plan into the total conditioning program and how any negative impact of concurrent training can be reduced.
The body adapts specifically to the demands imposed upon it. So what happens when two different modes of training that place different stresses on the body are performed concurrently?
A number of studies have examined the compatibility of simultaneous strength and endurance training (2,3,4,5). In 1980, Hickson (4) found that strength development maybe negatively effected by endurance training. Hunter and co-workers found that over a 12-week period a program of barbell squats only increased leg strength by 39%. This compared favourably to a program of squats and endurance training, which increased strength by just 24% (6).
Similar detriments to strength have been supported by other researchers (7,8). In contrast however, studies have also found that endurance training has no detrimental effect on strength development (9,10,11,12,13). Interestingly, although some of these studies found a negative effect on strength and some didn't, all agreed that concurrent strength and endurance training has no negative effect on endurance.
Strength at high velocities may be more vulnerable to endurance training than strength at slow speeds (5,7,13). This has obvious implications for power and speed performance which may be susceptible if a significant amount of endurance training is undertaken.
Kraemer and fleck (1) suggest that strength and endurance training programs with a moderate amount of volume seem to be compatible with no deleterious effects on either strength or endurance. As the volume increases to that adopted by elite athletes, detriments in strength are more likely to occur. It may be the overtraining phenomenon that is to blame rather than the incompatibility of concurrent strength and endurance training.
Beginning in the 1970's many runners avoided resistance training for fear that it resulted in a decrease in endurance performance. This was based on studies that found a reduction in mitochondrial density following a resistance training program (14).
Subsequent research has found that strength training does not reduce endurance performance (7,8,9,10,11,12) and mitochondrial density can actually increase as a result of a resistance training program (15).
There is evidence to suggest that strength training is beneficial to endurance performance (16,17,18) in non-athletes. For example, time to exhaustion in a cycle ergometer test and lactate threshold can be increased without any change in VO2max (18).
Strength training may also improve endurance performance in trained athletes. In one study on elite cyclists, 30-second sprint performance decreased with heavy endurance training. By adding resistance training to the program, sprint performance was maintained without any negative effects on endurance (19). Additionally, by substituting 32% of total endurance training in elite distance runners for strength training, 5km performance has been improved significantly (20).
In summary, substantial endurance training may be detrimental to strength and power athletes. In endurance sports, strength training applied correctly appears to have an ergogenic effect without altering VO2max.
The flexibility training section of the site discuses the effect of stretching as part of the warm up. Recent research has found that pnf stretching can hinder vertical jump performance (21). Static stretching may also be detrimental to subsequent power performance (22,23).
These post-stretch decreases in force production may be related to the inactivation of the muscles affected - more so than a change in elasticity often thought to be the cause (24). Evidence that static or pnf stretching immediately prior to power and speed events harms performance is by no means conclusive and studies have also shown it to have no negative effects. The general consensus seems to favor dynamic stretching as part of the warm up and static stretching following exercise or a training session. While the debate continues, how do the long-term adaptations associated with strength training affect flexibility?
One study measuring the effects of 11 weeks of resistance training on range of movement found that ankle dorsiflexion and shoulder rotation both increased without any flexibility training (25). Research in the elderly has found that resistance training alone can in increase performance in the sit and reach test by 13% (26).
While these increases in range of motion can be quite marked in sedentary individuals, the effect of strength conditioning on flexibility in trained individuals is less pronounced. For example, weightlifters posses average to above average flexibility in most joints (27,28,29). This would suggest that long-term physiological changes that occur through lifting weights neither significantly increase nor reduce range of motion.
For athletes, perhaps more important than the extent of flexibility is the ability to control movements within a given range of motion. For example, a martial artist may be able to kick to head height but lack any significant power or control at that joint angle. Strength training and concurrent flexibility training can help to control movements within an athlete's current range of movement (30).