upward toward the lower leg (although for a recovery move, this can enable a skier to quickly pull the CM forward when his or her weight is too far back). Te subtalar joint is a gliding joint below the ankle joint, between the talus and calcaneus bones. Tis is where side- to-side roll of the foot occurs, creating eversion and inversion. Eversion is the action of the foot rolling inward, as when you tip the outside ski of a turn onto its inside edge. Inversion is the action of the foot rolling outward, as in when you tip the inside ski of a turn onto its outside edge.
Te midtarsal joint is a gliding joint crossing the foot between the talus and calcaneus, and bones of the midfoot. It allows for small amounts of adduction (movement toward the midline of the body) and abduction (movement away from the midline of the body) of the foot. Pronation and supination are terms commonly used in reference to the posi- tion of the foot. Pronation is a movement that consists of ankle dorsiflexion combined with eversion and abduction of the foot. Supination is a movement that consists of ankle plantar flexion combined with inversion and adduction of the foot. Both pronation and supination occur when the foot is weighted.
MUSCLES
Muscles are bands of soft tissue fibers that contract and relax to stabilize or move joints. Working in groups, muscles regulate tension for performing complex movements. Muscles move joints through three types of tension: concentric, eccentric, and isometric. In concentric tension, the muscle actively flexes and the fibers shorten (contract) to overcome opposing forces and move the joint, as when the hamstring muscles concentrically create tension to flex the knee. In eccentric tension, the muscle lengthens as a result of exerting less tension or force than the outside force it is working against (such as gravity). It can act as a braking force to slow down or smooth out a movement. For example, when a mogul skier flexes the knees and hips to absorb a bump, the quadriceps and gluteal muscles (thigh and butt) eccentrically contract to slow the skier’s flexion and absorb the bump in a controlled manner. As the tension on these muscles increases, the muscle fibers elongate.
64 PSIA ALPINE TECHNICAL MANUAL
TheSnowPros.org
FIGURE 4.11: Eversion and inversion of the right foot
EVERSION
INVERSION
FIGURE 4.12: Pronation and supination of the foot
PRONATION
SUPINATION
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154