John Shepherd looks the scientific evidence for electrical muscle stimulation, and whether athletes could use it not just for recovery, but for fitness gains too MORE
Running injury prevention
Think about the physical requirements of a sprinter in full flow, and its the powerful thigh muscles that invariably come to mind. But as John Shepherd explains, neglecting lower limb training not only increases the risk of injury, but also limits an athlete’s potential to maximise athletic power and injury avoidance.
The calf muscles interact with the ankle joint through a myriad of smaller muscles that stabilise and control the movement of this joint and the foot. Crucial in this lower limb soft tissue movement chain is the Achilles tendon. This band of soft tissue connects the heel bone to the calf muscles. It acts as a kind of cable that ‘pulls’ on the heel, through the action of the calf muscles, to create ankle movement. It also has a crucial shock absorption role, which can significantly contribute toward the development of the type of athletic power needed for running, jumping and agility movements (more later).
To the front of the lower legs, running over and around the shin, is further soft tissue that also stabilises and controls ankle and foot movement. This includes the muscle peroneus longus and tendons, such as the extensor hallucis longus. The foot structure contains over 100 muscles, ligaments and tendons and 24 bones. As we’ll see later, it too can contribute significantly to athletic power, balance and stability.
The action of lower legs in walking, running and sprinting
Researchers from California have spent some time analysing the role of the main lower leg muscles involved in walking (1). The team examined the individual contributions of the gastrocnemius and soleus muscles at a walking speed of 1.5 metres per second. At any instant in the gait cycle (the walking or running action), the work required by these muscles to support the body and move it forward was defined by its contribution to the trunk’s vertical and horizontal velocity, and its contribution to moving the legs forward during the swing phase of the gait cycle.
The stance phase occurs when one foot is on the ground and the other is swinging forward (the swing phase) in preparation for the next foot strike (ground contact) and ensuing stance phase. During the stance phase the body is normally held in an upright position.
For lower leg muscles, the researchers found that the gastrocnemius and soleus provided trunk support during the single-leg stance and pre-swing phases of the walking action. As the body moves forward into early single-leg stance, the muscles accelerate the trunk vertically but decelerate forward progression of the trunk. In mid-single-leg stance, the gastrocnemius delivers energy to the leg, while the soleus decelerates it.
However, these functions are reversed in the action on the trunk. In the late single-leg stance, just prior to the foot leaving the ground, both major calf muscles perform a concentric muscular contraction as they accelerate the trunk forward while decelerating the downward motion of the trunk (basically they act to prevent the ankle collapsing back to the floor). However, the soleus acts to accelerate the trunk forward, while the gastrocnemius delivers almost all its energy to accelerate the leg to initiate its swing.
The action of the lower leg muscles is very similar during running/sprinting, although the hip muscles play a far greater role in generating speed in terms of the upper legs (2). Sprinting also involves far greater impact forces than walking (up to three times body weight) even though the foot may only be in contact with the ground for around 0.8 seconds for an elite sprinter. During the foot strike, pre- and mid-stance phases, the calf muscles have to absorb this force, before contributing to pushing the athlete forward into the next stride, whilst stabilising the trunk. This is akin to walking, but with a far greater shock absorbency requirement.
It’s during the foot-strike phase of the sprinting/running action that calf muscles (and even more commonly) Achilles tendons, can be strained. Conditioning the lower limbs to accept greater eccentric strength can reduce injury potential and improve performance by increasing ‘stiffness’ (more later).
Reducing injury through lower limb strengthening
There are a multitude of exercises that can be used to strengthen the lower limbs (examples of which are given below), but how effective are they? A Norwegian study looked at how ankle and knee injuries could be reduced in teenage handball players during the 2002-03 season (4); 1,837 players were split into an intervention group and a control group. The intervention group performed exercises designed to improve awareness and control of the ankles and knees during standing, running, cutting, jumping, and landing. The exercises included those with a ball, the use of wobble boards and covered warm-up, sport technique, balance and strength. The control group continued with their normal training methods. The main results were as follows:
– For the group as a whole, 262 players (14%) were injured at least once during the season;
– The intervention group had lower risks than the control group when it came to sustaining acute knee or ankle injuries;
– The incidence of moderate and major injuries (defined as absence from play for 8 to 21 days) was also lower for the intervention group for all injury types.
The researchers concluded that, ‘the rate of acute knee and ankle injuries and all injuries to young handball players was reduced by half when players followed a structured programme designed to improve knee and ankle control during play.’
Lower limb strengthening exercises
Stand with your feet slightly beyond shoulder width apart. Swing your arms back behind your body and very slightly bend your knees. Swing your arms down, as they pass your hips jump into the air, using your calf muscles and ankles to provide most of the power. Land without undue yielding (in order to increase joint stiffness and improve eccentric force absorption) and spring immediately back into another jump.
Suggested routine: 3×10 exercises with 1-minute recovery between sets.
Eccentric calf raises
Eccentric calf raises have been identified as being as effective at combating and treating the majority of Achilles tendon injuries as other treatments, including surgery. When performing this exercise, concentrate on the lowering phase of the movement, lowering to a count of 4 and lifting to a count of 1. To gain familiarity, select a medium to heavy weight that creates fatigue after 8-10 repetitions, before progressing to heavier weights that create fatigue after 4-6 repetitions. Use a standard calf raise machine. After gaining familiarity and strength with this exercise, perform freestanding versions from a double- and then eventually from a single-leg stance, using similar loads and repetitions.
NB. Standing calf raise exercises target the gastrocnemius, while seated calf exercises hit the soleus. To fully strengthen the main calf muscles combine both exercises in your training programme.
Foot and toe strengthening exercises
To perform this exercise stand barefoot on carpet. Scrunch the toes of one foot and try to claw/pull yourself forward. Persevere, as you will be able to achieve some forward movement in time. Once mastered continue to pull yourself forward with your toes, using each foot in an alternate fashion.
Performing sprint drills/running barefoot
Olympic medallists Roger Black (400m) and Jason Gardener (4x100m) both employed barefoot training to develop greater foot and ankle strength and flexibility. You can also strengthen your feet by performing sprint drills barefoot and even by running (although the latter should be carefully progressed to). If you run barefoot, do so only over moderate distances (40-60m) and on soft grass, making sure there are no sharp objects. Distances should be only gradually increased as your lower and upper limbs become used to the higher forces that running without shoes generates. This will reduce the chances of sustaining an injury and condition the feet, ankles and legs gradually.
NB. running barefoot involves greater impact than barefoot sprint drills, hence the need for greater caution.
Barefoot high knee lift with ankle extension
Stand with your feet slightly apart. Lift the thigh of one leg to a position parallel to the ground, whilst at the same time pushing up onto the toes of the grounded foot. Claw forward with the suspended leg and then let the foot come down to the ground whilst lifting and pulling the previously grounded foot up toward your buttocks and through to perform the next stride simultaneously. You’re basically performing a slow paced running action. Coordinate your arms with your legs (opposite arm to leg). You’ll find that your feet and ankles have to work harder to control your movement and balance and are consequentially strengthened.
Suggested routine: 4x20m with a slow walk back as recovery.
John Shepherd MA is a specialist health, sport and fitness writer and a former international long jumper
1 J Biomech 2001; 34(11):1387-98
2 J Sports Sci 2001; 19(4):263-72
3 Int J Sports Med 2002; 23(2):136-41
4 Med Sci Sports Exerc 1981; 13(5):325-8
5 J Biomech 1997; 30(11-12):1081-5